Towing in D or 3 ? Sustained high RPM operation question.

2kwik4u · Post by **2kwik4u** » Thu Apr 05, 2007 8:17 am

I'm sure some of you read in the other thread I'm buying a boat. It's a 2.5hr drive from the sellers location home. I'm also already planning a few weekend trips to both TN, and NC this summer. That brings me to a towing question.

For the trip home without a tranny cooler I'll definitely be in 3rd the entire time. I don't want to chance hurting the trans to save a few bucks in gas. However I'm slightly concerned about running the engine at 3k rpm for extended periods of time. I'm curious if anyone else does this, and if there are some precautions I should be taking? I already run full synthetic oil, so I'm not terribly worried about oil temps (however I'm considering an oil cooler for the future). I've heard of oil drain back issues with the larger motors (mainly the 350, however the 4.3 has the same design).

Anyone else see a problem (aside from mileage) with running the engine at 3k rpm for a few hours? Of course the first 1/2 of the trip is country back road so that will be a bit slower, but once on the highway, 65 cruising speed is pretty slow, especially considering the state speed limit has just been raised to 70.

Post by **HenryJ** » Thu Apr 05, 2007 3:42 pm

65 is not slow, 55 is not slow, 45 might be a little slow.

I don't think you will have problems running in 3 for extended periods. That is the manufacturers recommendation.
3000 rpm is not all that fast with a 5600 rpm redline.
A few mods and on level ground I could even see going to OD at times.

You will know more after this trip.

Think about an auxiliary cooler, servos and pin, programmer, brakes if you have them, etc.

2kwik4u · Post by **2kwik4u** » Thu Apr 05, 2007 4:16 pm

I checked the owners manual tonight, and it didn't mention anything about towing in 3rd.....I'll double check in the morning though to be sure I didn't miss anything. I'm still going to tow in 3rd regardless since I think we know more about preserving the transmission than the owners manual, I'm just curios why it doesn't mention this there?

Future mods include but are not limited to eFan, MSD, pulleys, TransGo HD2 shift kit, and Custom EFILive tune (mostly to enable tow/haul mode) and catback....I already have the K&N FIPK (although I expect it to break anyday now

). I figured the auxillerry tranny cooler and guage were a given. Brake mods will be limited to better pads I think. I like the rear disc, and dual piston fronts that are on there now.

Were you referring to an auxilary oil cooler or trans cooler? or both?

Post by **HenryJ** » Thu Apr 05, 2007 4:25 pm

GM owners manual wrote:If you have an automatic transmission, you can use THIRD (3) (or as you need to a lower gear) when towing a trailer. Operating your vehicle in THIRD (3) when towing a trailer will minimize heat buildup and extend the life of your transmission.

If your trailer weighs more than 1000 lbs. (450 kg) loaded, then it needs its own brakes--and they must be adequate.

F9K9 · Post by **F9K9** » Thu Apr 05, 2007 5:29 pm

This issue came up before and I am sure that we can relocate it but, the owner's manual recommends different things for different yrs. Let me recheck my '02 driver's manual.

My '02 online GM Link manual recommends towing in "D" but, I wouldn't follow that. A little more money spent on gas and saving a tranny is well worth it IMO.

Snoman002 · Post by **Snoman002** » Thu Apr 05, 2007 5:33 pm

I would not worry about it.

The oil drain back should not be a problem, I have only ever heard of that in a race motor running near redline, 3k is nowhere near those RPM's.

If you do anything before you leave I would think that a tranny temp guage would be the best. Sure a tranny cooler would be better in the end, but with the temp guage it should be an easy install and will at least warn you of an impending problem.

Post by **HenryJ** » Thu Apr 05, 2007 5:33 pm

You could also argue the decreased transmission holding pressure at lower rpm , lugging an engine with a locked converter in OD, weak OD gears, and rumor has it that there may be a lack of lubrication issue when pulling hard in overdrive.

Post by **Walt** » Thu Apr 05, 2007 5:57 pm

I usually tow in 3rd when pulling a heavy trailer, and most of my driving is above 65mph. Never had any problems here, except the extremely poor fuel economy.

2kwik4u · Post by **2kwik4u** » Fri Apr 06, 2007 2:57 am

Thanks for the reassurance fellas.....The guys on the boat boards are saying the same thing. Guess I'm just not used to having this sized motor spin that high for that long. My 2.2 4cyl in the Xtreme runs 3k rpm at 75mph in 5th, but thats a much smaller motor.....Guess I'm worried over nothing.

a2b · Post by **a2b** » Fri Apr 06, 2007 3:45 am

if you are towing, on most setups, sometimes 70mph isnt all that safe. i see guys all the time, that hook up a camper and then jam over to the fast lane and hammer on it like they do on the way to work. here in CA, if you are towing a trailer, the speed limit 55mph. thats it. so i have gotten use to just cruisin at 60 and calling it good. i can stop fast, it handles easy in tough traffic, or tough wind...and my tow rig likes it.

oh, and 3rd gear is fine a 3k

20Blazer00 · Post by **20Blazer00** » Fri Apr 06, 2007 9:35 pm

Well I see something that was not discussed. If you look at the stated transmission ratios for a GM 4spd Auto w/Overdrive you will see that third gear is rated as 1:1 and 4th is 0.7:1 (30% OD). So towing with third gear should not be a problem...plus towing also depends on your differential gearing, 4.10's would make towing easier in 4th but gas mileage would be affected...

border man · Post by **border man** » Sat Apr 07, 2007 2:30 am

a2b wrote: here in CA, if you are towing a trailer, the speed limit is 55mph. thats it.

Tell me 'bout it, I got a nice $398.00 ticket north of Redding, CA two years ago while pulling a small trailer doing 70MPH.

Grunto · Post by **Grunto** » Sat Apr 07, 2007 10:59 am

Towing should be done in 3rd, or D.

2kwik4u · Post by **2kwik4u** » Tue Apr 10, 2007 6:03 am

Grunto wrote:Towing should be done in 3rd, or D.

UM....D=4th 3=3rd.

I think you mean all towing should be done in "3".....As most cars come with OD, D, 2, 1.....ours has D, 3, 2, 1.....I've made the same mistake in the past when asking similar questions.

ace · Post by **ace** » Sun Apr 15, 2007 5:50 am

I tow a pretty heavy camper for our trucks. It weighs 3100 pounds plus gear and people. I bring a lot of gear too. I always tow in 3rd. My rpms do sound high when towing but if I put in D then it can't handle the slight inclines and it switches back and forth plus you don't have any power. Keeping it 3rd does alright. 65 mph is pretty fast towing. I have the 3.42 gears which stinks for towing but I was told their really is much difference between the 3.42 and 3.73 to pay a 1000 bucks. 4.10's would be nice but probably not everyday. Changing my exhaust helped a lot with the towing. More power!

Swbari00 · Post by **Swbari00** » Sun Apr 15, 2007 11:30 am

I thought all of the ZR5's had 3.73 gears.

F9K9 · Post by **F9K9** » Sun Apr 15, 2007 11:47 am

Swbari00 wrote:I thought all of the ZR5's had 3.73 gears.

Afraid not. You need to check out your label inside your dash compartment.

Swbari00 · Post by **Swbari00** » Sun Apr 15, 2007 12:19 pm

Well i know mine has them, thats why I thought all of the ZR5's did.

F9K9 · Post by **F9K9** » Sun Apr 15, 2007 12:27 pm

Swbari00 wrote:Well i know mine has them, thats why I thought all of the ZR5's did.

I have them on my '02 but Top_Sgt had an '04 without them and a bunch of stuff that was standard on mine.

ace · Post by **ace** » Sun Apr 15, 2007 2:30 pm

I'm sure my zr5 has the 3.42's. I also didn't have the G80 until I added it too.

2kwik4u · Post by **2kwik4u** » Tue Apr 17, 2007 3:43 am

Well,

It was much to to-do about nothing. Went down there yesterday afternoon to pickup the boat. Aside from having to use 4wd to get out of the guys gravel covered road subdivision (Super steep drive in gravel), everything went well.

I found on the ramp that my emergency brake isn't nearly as strong as I thought. The was able to pull the truck backwards with the pedal all the way to the floor. I put it in park and it held, but I hate that clunk when it took it out of park. I'm going to guess that I either need some new rear pads, or those rear caliper pins need greased so BOTH pads can apply. I'll tear into this weekend.

Once the boat was out of the water, and we starting making the trip home I found the truck did pretty decent. Towing in 3rd is didn't really like the 45-55 range. Medium to large hills (for this area) forced the TC to unlock to maintain speed, and it dropped to second once on a large hill. No big deal though, it maintained speed just fine. On the expressway it did great. Ran 65-70mph all the way home in 3rd. 2800-3000 rpm the whole way. With the cruise set at 65 and turning 2800rpm it never unlocked the converter even on the largest hill coming up I-65. I'm sure if I get into the hills of NC on TN it will be another story, but so far it's looking great.

I do think that I'll be moving to the eFan and larger capacity radiator here very soon. The temps held fine last night, however the ambient temp was only ~55 degrees or so. I can imagine that running the A/C in the hotter months this summer will present some problems. Especially considering the hassles I had with it last summer when sitting in traffic.

At any rate, it did better than I expected, and I've been worried over nothing.

Oh yea, and some pics

http://picasaweb.google.com/2kwik4u/BoatPics

WVHogRider · Post by **WVHogRider** » Tue Apr 17, 2007 6:58 am

The pics all showed as the red X's for me. Can't view them.

As for the parking brake, lubing the caliper slide pins will do nothing besides allow the disk brake assembly work properly.

Not sure if you knew this or not. If you did know, ignore the remainder of the message.

The parking brake is inside the drum section of the rotor. Our trucks have a rotor/drum combo in the rear. We have a set of disc pads and also a horseshoe shaped parking brake pad. The drum portion is our parking brake. You may just need to adjust the tension on you parking brake cable, which the adjuster is located under the driver side door. Just tighten the bolt/screw assembly a little. I'd also check the parking brake pad for remaining life. Remove the rear wheel, disk brake assembly,and rotor. This allows you to get at the parking brake assembly. There is also an adjustment point between the tips of the horseshoe parking brake pad.

2kwik4u · Post by **2kwik4u** » Tue Apr 17, 2007 8:31 am

Thanks for the tip.

The GF seems to think I overuse the parking brake (Is everytime the trucks in park too much?) Any idea if I'm actually using it too much?

I'll tear into it tonight. I don't have much else going on anyway

killian96ss · Post by **killian96ss** » Tue Apr 17, 2007 9:36 am

2kwik4u wrote:The GF seems to think I overuse the parking brake (Is everytime the trucks in park too much?) Any idea if I'm actually using it too much?

You can't use it too much.

It is a good idea to always engage the parking brake to avoid breaking the parking pawl inside the tranny.

If that pawl breaks your vehicle can roll away.

It really doesn't take much to snap that small piece of metal.

Steve

2kwik4u · Post by **2kwik4u** » Tue Apr 17, 2007 10:57 am

Yea, I DESPISE that huge "clunk" that you get when you park an auto on a hill and don't use the parking break. I typically put the truck in neutral, set the brake, release the normal brakes to check for roll (how I found it wasn't holding), then put in park and shut off engine. She thinks I'm paranoid, I think I'm being cautious with my $15k truck.

Even moreso when I have my $10k boat hooked to the back of it!

killian96ss · Post by **killian96ss** » Tue Apr 17, 2007 12:32 pm

2kwik4u wrote:Yea, I DESPISE that huge "clunk" that you get when you park an auto on a hill and don't use the parking break.

That huge clunk is torque lock and it is cause by the parking pawl being released under a lot of pressure.

Steve

Grunto · Post by **Grunto** » Wed Apr 18, 2007 6:30 pm

2kwik4u wrote:
Grunto wrote:Towing should be done in 3rd, or D.
UM....D=4th 3=3rd.

I think you mean all towing should be done in "3".....As most cars come with OD, D, 2, 1.....ours has D, 3, 2, 1.....I've made the same mistake in the past when asking similar questions.

Mine is OD, 3, 2, 1. But its just an extended cab and it's ten years old now.

I dont know as much about post '98 trucks.

And yeah I said D because of what you mentioned about other vehicles. I think most if not all the full size trucks I work with in the Summer to haul boats around have OD, D, 2, 1.

bluecrew · Post by **bluecrew** » Thu May 31, 2007 4:58 pm

i can tell you this the guy that built my trans in my 97 z71 said the trans is desighned to run in od he said ford has od off switch thgis guy built trans for gm so hes very knowledgable guy but he says these trans need some work to last from fact his name is scott give him a call 904 382 8162

killian96ss · Post by **killian96ss** » Thu May 31, 2007 5:37 pm

bluecrew wrote:the guy that built my trans in my 97 z71 said the trans is desighned to run in od

What trans do you have in your Silverado (4L60E or 4L80E) and do you also have the tow/haul mode on your shifter?

Yes the trans can handle towing in OD, but if the weight of what your towing is on the high side you may experience torque converter cycling/flaring especially on hilly terrain which does wear out parts like the TC clutch, lock up solenoid, 3/4 clutch pack, etc.

There are upgrades to help combat these problems like larger 4th gear servos, additional clutches in the 3/4 pack, increases in line pressure, PCM modifications that allows higher or lower rpms before lock up occurs, etc.

Steve

bluecrew · Post by **bluecrew** » Thu May 31, 2007 6:34 pm

4l60e no tow haul swith i wish my crew had the switch

2kwik4u · Post by **2kwik4u** » Fri Jun 01, 2007 3:28 am

I've been towing the boat in 3rd. It's ~4k lbs with gear, and fuel (estimated, I still need to get it weighed). The crew does a decent job. Just enough truck there to tow it, not enough to set any land speed records, but it will maintain 65mph on the expressway without unlocking the converter. If/When I get a custom tune, I'll have the Tow/Haul mode enabled on it, and report back again on how it works out. Until then I won't be towing in drive/4th. It simply locks/unlocks the converter way to much to be even remotely a good idea.

I did tow a small aluminum utility trailer the other night with a Polaris 6x6 on it. It towed fine in D/4th without locking/unlocking all the time. I bet total weight was only in the 1,500lb range though. Not much worse than 4-250lb guys in the truck.

kwalsh · Post by **kwalsh** » Fri Jun 01, 2007 4:49 am

I have frequently towed around 3000lbs with my CC. I always keep it in 3rd. I haven't had any problems and the majority of the trips have been around 3 hours.

I did notice that the engine temp. would rise into the danger zone on occassion but I solved that issue with the extra capacity radiator, Jet T-stat. I added the aux trans cooler too.

2kwik4u · Post by **2kwik4u** » Fri Jun 01, 2007 5:19 am

I found last weekend while towing the boat with 3 other people in the truck through some hilly backroads that I couldn't run the A/C while towing in those conditions. It would slowly climb past the 210* mark which is where I foreced everyone to just deal with the windows being down. I'm guessing I'll need to get the upgraded radiator as well. However I'm going to try other options first, as thats a semi-pricey one IMO.

My Jet T-stat will be here today (180*), I put an electric fan on last night, and I have a tranny cooler in my hands to install this weekend. I'm hoping I can keep some of the trans heat OUT of the radiator with the tranny cooler. Despite common/accepted practice I'll be putting it AFTER the stock cooler. I want the trans temps as low as possible. The lower the temps are, the less heat that will go into the radiator IMO.

kwalsh · Post by **kwalsh** » Fri Jun 01, 2007 5:38 am

The swap to the Trans Pro extra capacity radiator cost me around $175.....radiator ~$150, fresh Antifreeze & replaced one hose ~25

2kwik4u · Post by **2kwik4u** » Fri Jun 01, 2007 5:55 am

Thats not nearly as bad as I expected. I thought I read somewhere that the radiator itself was near $250?!?! Guess I read wrong!

killian96ss · Post by **killian96ss** » Fri Jun 01, 2007 7:07 am

2kwik4u wrote:Despite common/accepted practice I'll be putting it AFTER the stock cooler. I want the trans temps as low as possible. The lower the temps are, the less heat that will go into the radiator IMO.

I'm guessing that you already know why the tranny cooler is tied into the radiator, but if not there is a reason why.

The transmission needs to have the fluid temp regulated and not just cooled as much as possible.

If you install the add on cooler after the factory cooler the trans will run too cold which is not a good idea.

This is why GM runs the tranny fluid into a regulated (water to oil) cooler instead of a remote cooler.

The only problem with this design is that the water to oil cooler can't remove the added heat from towing.

A remote cooler should always be mounted before the stock water to oil cooler to remove the excess heat.

The stock cooler will then return the transmission fluid to the proper operating temperature before it re-enters the transmission.

I can assure you that none of this is just my opinion, but rather a well known fact that these transmissions need a minimum operating temperature to work properly and efficiently.

If you add an e-fan, low temp t-stat, and a larger radiator (which I see your currently working on) then you your coolant will be even colder than stock wich will make the idea of running the remote cooler after the stock cooler even worse.

In the end I'm sure you will do what you want to do, but I always feel it is a good idea to try to explain why things are designed a certain way just in case you didn't already know.

Steve

2kwik4u · Post by **2kwik4u** » Fri Jun 01, 2007 7:54 am

Yea, I've read that several times, and from several different places. I totally accept the theory, and the idea, however I don't think it's ideal in performance oriented applications where heavy loading is the norm not the exception. Heavy loading in my case is a 4k lb trailer with a boat on it, averaging ~3 trips to the lake a week now for a month and a half.

I've been around the Sy/Ty world long enough to see guys wreak havoc on a built 700R4, simply by not getting them enough cooling. A boost launch will take a trans from 180* temps to over 235* temps in less than 10 seconds of sitting on the line building boost. I can only imagine what the I-65 hill (little over 5 miles long at 4% grade I think) does to that same trans design, when placed in front of a 4klb boat. Jeremy broke 3 transmission in 3 months in his drive for the fastest stock turbo truck. He ran his from the trans to the stock cooler, then through the external. Jeff had one on his Typhoon before he blew the motor a few years back. Tranny temps were in the 180* range with the cooler placed AFTER the stock radiator cooler. I don't have a gauge yet, however I'm expecting similar results from my 60E when I do get a gauge (soon).

In the end this is really personal preference as to which theory you subscribe to. I think ideally one would want a thermostat controlled valve inline on the external. If it would divert fluid through the external once it reached a good operating temp, that would work the best, however thats both complex and expensive. I have seen this setup implemented on an SVT Contour that was used for autocross........I don't think the difference in transmission life in the before and after debate will be measured in years, but perhaps months when compared to each other. So long as there is additional cooling over the stock setup, I think we can both agree that it's an improved system, and will add to the overall life. Both are a compromise between low temps, and regulated temps.

Ive made the below post to the owner of PrimeGears (Well respected 700R4 builder for the Sy/Ty market) to see what his thoughts are on it. I'll let you guys know what he says. I'll also take a look at the routing on a buddies Tahoe that came with an external cooler from the factory to get a good idea of how it's setup, and the (assumed) intentions of GM on this debate.

Mikey's post to PrimeGears wrote:George, I have another trans question that is not Sy/Ty related, however is an interesting one and perhaps some good theory to discuss here.

I'm putting a transmission cooler on my 2004 ZR5. The general consensus on the CrewCab boards is that it should go BEFORE the stock cooler. The idea being that the stock cooler will regulate the temperature back to a "normal" range before putting it back in the trans. The consensus around here seems to be that AFTER the stock cooler is the best place to put it. The idea on after, is that the external will lower the temps further, and produce the lowest temps possible.

Do you have an opinion on this? Is it better to have regulated temps that are slightly higher, or are we searching for the lowest temps possible?

kwalsh · Post by **kwalsh** » Fri Jun 01, 2007 7:57 am

Rockauto.com has the Proliance radiator for $148

2kwik4u · Post by **2kwik4u** » Fri Jun 01, 2007 10:49 am

Here's the response from George at Prime Gears

George wrote:If it's a 60e, it just dumps back into the pan. The fluid will "normalize" in the pan.I would run it to the stock cooler first. The liquid to liquid cooler will be MUCH more efficient than the liquid to air. Notice how small the stock coolers are and how big the aftermarket coolers are. Then once the liquid to liquid cooler gets it down a little, then run it to the liquid to air cooler to drop it another 20-30 degrees. It won't shock a 60e. Then pan will be warm from trans operation and the case will be warm from operation so there again will be some warming once it gets back.

Couple of really good points in there I think.

killian96ss · Post by **killian96ss** » Fri Jun 01, 2007 12:04 pm

2kwik4u wrote:I totally accept the theory, and the idea, however I don't think it's ideal in performance oriented applications where heavy loading is the norm not the exception. Heavy loading in my case is a 4k lb trailer with a boat on it

I've been around the Sy/Ty world long enough to see guys wreak havoc on a built 700R4, simply by not getting them enough cooling. A boost launch will take a trans from 180* temps to over 235* temps in less than 10 seconds of sitting on the line building boost.

In the end this is really personal preference as to which theory you subscribe to.

A boosted 6 cylinder running low 1/4 mile times in an AWD Sy/Ty has completely different requirements for maximum transmission performance versus a non boosted CC used for towing.

Both need adequate cooling but in very different ways.

You can't just assume that what works best for a 1/4 mile vehicle is the same for a daily driver.

The trans in a 1/4 mile vehicle needs to be very consistent and run as cool as possible to do so, but the trans in daily driven CC needs to be reliable in every day driving, traffic, towing etc., which is why GM uses a regulated water to oil cooler.

My SS has a factory external trans cooler that is combined with a factory water to oil cooler in the radiator and it is set up so that the fluid runs through the external cooler first and then the water to oil cooler after.

This is done to maintain the proper transmission operating temperature and to aid in warming up the trans fluid after start up.

These trannies need regulated fluid temperature and fast warm up for proper operation.

This is a proven factory design and not theory in any way.

It is not good for an automatic tranny to have fluid that is too cold.

BTW, George from Prime Gears has it backwards in a couple of ways.

An external oil cooler is way more efficient at removing heat than the stock water to oil cooler.

The water in you radiator is 160* to 220* while air flowing over the cooling tubes on an external oil cooler is much cooler.

Do you really think that in a side to side comparison that the water to oil cooler will drops the temps better or faster than the air to oil cooler?

Why does he think GM routes the tranny fluid through the factory external coolers before the water to oil cooler?

Does George really believe that the thin sheet metal pan holds enough heat to properly regulate "normalize" transmission fluid temps?

Ask him why he is right and all the GM transmission engineers are wrong?

If we were talking about high hp drag vehicles then yes some of the points being made would hold true, but we are NOT talking about 1/4 mile vehicles here, we are talking about daily drivers.

Personally I trust the GM engineers since they designed and thoroughly tested these transmissions to know what works best for them.

I think I've said way too much here

and it was probably pointless anyway.

Steve

2kwik4u · Post by **2kwik4u** » Sat Jun 02, 2007 4:22 am

Not pointless, but I can see we are headed towards an agree to disagree point......

In all reality it's not a right/wrong scenario, it's a preference based scenario.

My finishing thought is that if GM engineers are always correct then why do we modify any point on our vehicles? Surely they must know the best way to do everything, at least that seems to be the consistant thought around here. I tend not to agree with that. As a Mechanical Engineer myself, I know that life is full of compromises. I will bet dollars to donuts that the choice to regulate the trans temps is based more on reliability and fewer warranty claims than it is on maximum performance. Much like alot of other items on the truck (the stock clutch fan for example).

The end result is that the engineers simply can not take into account all the ranges of use that people will put a particular vehicle through. They make it as good as possible to cover as many bases as possible, and "let 'er rip".

Post by **HenryJ** » Sat Jun 02, 2007 5:13 am

I would swear that I posted a rather lengthy reply to this thread. I am a little confused as to what happened to it?

I don't think "George" has run a rig on a daily basis with a transmission temperature gauge. His opinions would be drastically different , if that were the case.

The in tank "cooler" is more of a heater than a cooler. Have you noticed that your transmission will not lock the converter until it reaches a minimum operating temperature? In mine the gauge reads 73 degrees. Then it functions normally.
Steve is right. You need to attain operating temperature quickly and then maintain it. The engine builds heat faster than the transmission. The engine can assist in warming the fluid to operating temperature.

"All I want to do is keep it cool!" Then bypass the stock cooler and run externally only. Mount it is such a way that it does not impede the flow to the radiator. Maybe even mount a fan for the cooler. That is how to do it for a drag racer. Retaining the stock cooler as a preheater is a good idea for a dragracer too. Cold is not always best. Control is best.

George has some strange ideas. Shocking a transmission with cold fluid? Heating from the pan or case?

the heat is developed elsewhere. It does mix in the pan, but that is about all I agree with in that statement. Efficient dissipation of heat. The conduction of liquid to liquid may be good, but for heavens sake skip the middle man. We are trying to get the heat to the air. liquid to -->liquid to -->air is not the best. Liquid to -->air is more efficient. That quote is third hand information and the context may be somewhat blurred. I don't want to beat him up for what someone else has quoted. If he wants to come here and debate we can do that for sure.

I put little faith in "engineers". Cheap, easy and will get it past warranty seem to be the rules. I really don't think they put all the thought into anything. We would like to think so, but standard practice is usually the course taken. Nothing is really new. It has all been done before.

OK, back on track- I have yet to see transmission temperature meet or exceed the engine temperature. Originally my thoughts were to cool the fluid before the interface with the engines coolant to reduce engine operating temperatures and the radiators efficiency. That is blown away by the fact that the transmission always runs cooler.
George has the wrong idea. Running through the in tank cooler would only serve to heat the fluid before entering the external cooler.

The best way to connect is using the lower connection to the in tank cooler. Run the fluid from the transmission to the external engine cooler, from there through the in tank stock cooler and back to the transmission.

2kwik4u · Post by **2kwik4u** » Sun Jun 03, 2007 7:43 am

Well regardless of which line I tap, I've bumped into a small issue....The fitting that came in the "kit" from Yank (Cooler came from a friend who bought a yank convertor for his truck, and they tossed the cooler in for free) doesn't fit

Anyone happen to know the size of the fitting that goes into the radiator from the transmission?!?!

I'll post some pics I took tomorrow. The cooler is HUGE. Damn near 1/2 the size of the radiator (although not that thick). I had to take the hood latch bracket off to get it to fit

Post by **HenryJ** » Sun Jun 03, 2007 4:49 pm

HenryJ wrote:...I have yet to see transmission temperature meet or exceed the engine temperature...

I tested the limits today. I was able to get the transmission temperature to exceed the engine temperature.
It was over 100° today. I pushed the truck hard while towing the boat. Pulling hills, using overdrive, running the AC.
I was able to get the transmission temperature to a maximum of 238°. Engine temperature reached 225°. Beyond 180° and up to around 200° the temperatures were neck and neck.
Turning off the AC and easing up on the throttle things cooled right down. The transmission took a little longer to cool than the engine. I can not say that OD or third ran cooler. I really didn't experiment with that.
If I were pushing these limits all the time, I would mount the cooler elsewhere and likely bypass the stock "cooler". Better yet, I would probably go fullsize and never look back as the engine would not be working as hard and the mileage would likely be better.

2kwik4u · Post by **2kwik4u** » Mon Jun 04, 2007 3:14 am

I thought I had read in another thread where you had exceeded the coolant temp fairly easily.

Good info to have if nothing else.

I too am considering a fullsize. It's being a tough job for me to decide how long I want to keep this boat. Just a few more upgrades, and I'll be doing fine with CC pulling it for many years I think, however if I'm going to move to a 22' or 24' boat in the near future, I'd be better off to trade the ZR5 for a 1500 at least, and possibly a 2500 with a deisel......Who knows, This season is going to be with this boat and truck though.

2kwik4u · Post by **2kwik4u** » Mon Jun 04, 2007 4:17 am

Got a pic of the cooler uploaded. It's fairly large. Seemed alot bigger in person (isn't that how it alwasys works out?)

Trans Cooler Almost Installed

Camper · Post by **Camper** » Tue Jun 05, 2007 9:01 am

I tow a 4500 pound KZ Jag 20J travel trailer with my 2002. No trans cooler or any other modifications. Owners manual says it'll tow 5000 pounds as is and it does. Have been towing regularily for the last 75000 miles with this truck. Half the miles on this truck are with a travel trailer. I just got back from a week long trip to Orlando. About a 2000 mile round trip with no problems. Keep it around 65 MPH in 3rd at about 3,000 RPM down hill and on flats. Shifts to second and does about 4,200 RPM pulling longer hills on the freeway. I do keep to the factory maintenance schedule.

F9K9 · Post by **F9K9** » Tue Jun 05, 2007 1:10 pm

Welcome aboard Camper

That's the kind of info, I like to hear!

Any connection with Wright-Patterson? I had an extended stop in Dayton. Was there several years growing up and then after the service and with college

Camper · Post by **Camper** » Tue Jun 05, 2007 3:27 pm

I was stationed at Wright-Patterson back in 1979. Retired from the Air Force and moved back here a few years ago. This is a good central location to travel the United States from.

2kwik4u · Post by **2kwik4u** » Thu Jun 07, 2007 3:46 am

Transmission cooler is in

I'm not terribly enthused about using hose clamps on it, however for the price I can't really complain. The cooler, lines, clamps, and mounting hardware was given to me for free. The fittings were ~$25 total. SO I have VERY little money tied up in it. If I ever have problems with the clamps though, I'll be converting to stainless braided lines. I'll be keeping my eyes on it for a few weeks to see how it does. Took me two trips to the fitting store to get it right, as well as about 45 minutes of chasing a "clip nut" that fell into the core support and disappeared.

It'll be a week or two before I can get a datalogger on it to see what the temps have dropped to. I have a log from when it was stock to compare, however I'm sure the ambient weather will effect it slightly.

[url=hhttp://picasaweb.google.com/2kwik4u/ZR5TransmissionCooler]Trans cooler pictures can be found here[/url]

*edit* Link updated 1-29-08

Donnie · Post by **Donnie** » Fri Sep 21, 2007 5:55 pm

I tow a boat, two , three times a week, have towed as far as 300 miles, not a problem , of course, not hilly here, and I tow with respect to my boat, my truck and others on the road..I also don't want to burn all my green backs on gas, so I go slower when I tow..
I have a factory tow package, what ever that means, I do have 3.42 gears which helps with my mileage....some.....at the ramp, 4 wheel drive insures a clean no spin pull out..
I tow a 17ft Key West boat with a 90 hp motor, alum trailer, and 14 in tires.
Oh yes, if I wanted to tow more, I would have bought a vehical more in line to what I wanted to tow...sorry, I love my S10 but for towing large items, its not the best, does mine fine, but , then thats for me..

S-10CREWCAB.NET

Towing in D or 3 ? Sustained high RPM operation question.

Towing in D or 3 ? Sustained high RPM operation question.

These trucks tow fine

towing