Getting a chattering in turns from the rear end.

[Tony]

I'm getting a sound coming from my rear end. G80 w/3.73. I changed to Amsoil Sythetic 80W-90 in September and it only does it in turns. It's like a whirring sound if I could explain it best. I haven't checked the level or anything. What do you guys think. The fluid was original untouched at like 95k. It was pretty nasty. I noticed GM says to use only there fluid with the locker, which is just 80W-90 gear oil?!

[killian96ss]

Do you have a clutch type posi instead of a Gov-Loc locking rear diff?

If you have a clutch type limited slip diff then your problem makes perfect sense and you just need a bottle of limited slip additive to help prevent chattering.

If you have the Gov-Loc then something else must be wrong with your truck since these diffs do not require limited slip additive.

I have been running synthetic Redline 75W/90NS in all of my vehicles which have limited slip posi's & Gov-Loc's with absolutely no problems.

Steve

[Tony]

I thought there is only one locking rear end available for S-series? This is a '01 Sonoma Crew Cab.

I guess how do I find out what I got?

EDIT: I guess the G80 is the Eaton Gov-Loc.

This started right after I changed fluid. What should I do?

[killian96ss]

Did you buy your Crew Cab new or used?

If you bought it used there is a small possibility that the previous owner took out the Gov-Loc and replaced it with a limited slip posi.

G80 is the RPO code for the Gov-Loc and for limited slip posi's.

All 3 of my vehicles have the G80 code (2 Gov-Loc's and 1 Limited slip).

If you are certain you have a Gov-Loc then another fluid change is probably the best place to start.

I used Redline 75W/90NS in my Crew Cab for almost 90k miles with no problems and the Gov-Loc worked fine when there was enough wheel speed difference.

Did you do the last gear oil change?

If so, how much gear oil did you put back in?

Was there any water contamination?

Can you describe the noise any better?

Whirring and chattering are very different noises.

Steve

[Tony]

Did you buy your Crew Cab new or used?

If you bought it used there is a small possibility that the previous owner took out the Gov-Loc and replaced it with a limited slip posi.

G80 is the RPO code for the Gov-Loc and for limited slip posi's.

All 3 of my vehicles have the G80 code (2 Gov-Loc's and 1 Limited slip).

If you are certain you have a Gov-Loc then another fluid change is probably the best place to start.

I used Redline 75W/90NS in my Crew Cab for almost 90k miles with no problems and the Gov-Loc worked fine when there was enough wheel speed difference.

Did you do the last gear oil change?

If so, how much gear oil did you put back in?

Was there any water contamination?

Can you describe the noise any better?

Whirring and chattering are very different noises.

Steve

The truck was bought new in 2001. The fluid was untouched until about 95k. I changed the fluid back in September of '06. The fluid was a dark brown color, it was foamy but I really can't remember. I know I have pictures, but they are on my other computer.

I filled it up to the fill hole, which was about 2 qts. I used Amsoil Synthetic 80-90 gear oil. Is that good? I mean the rear end takes 80-90 right?

Like I said I thought there was only one locking differential that was available for the S-Series line. My glove box gives the RPO of G80. Is there any other way to tell if I don't have the Eaton locker.

The reason I say chattering is because I have access to GM Techline and the closest symptom they list is chattering. It's only in turns and it goes away when I give the gas (that might be because the engine is louder?). I don't feel any grinding or metal on metal contact. It's more of a whurring sound. Like a whur..whur...whur sound. Almost like a bad wheel bearing sound I guess is the best way to explain it.

[HenryJ]

I would try dumping the diff oil again and filling it with the recommended lubricant. Check the drained fluid for debris or clues.
Check for loose carrier bearings or a rough pinion bearing while you have the cover off.

[Tony]

I would try dumping the diff oil again and filling it with the recommended lubricant. Check the drained fluid for debris or clues.
Check for loose carrier bearings or a rough pinion bearing while you have the cover off.

What is the recommended lubricant?

How do I check the carrier bearings and the pinion bearing?

[HenryJ]

What is the recommended lubricant?

Sticky: GM Fluid and Lubricant Recommendations

Lubricants for rear axle :

With RPO G80 1052271 only

Without RPO G80 (open diff) 1052271 or SAE 80W-90 GL5

GM Vehicle care Axle Lubricant SAE 80W-90

*excellent axle durability

1#1052271
Gr.8.800
23 fl.oz.

"Gm axle lubricant exceeds API GL-4 requirements and has been formulated specifically for use in certian GM axles as specified. Not all products labeled GL-4 will provide satisfactory service.

*excellent axle durability
*Compatible with limited slip fiction modifiers
*Compatable with seals/elastomers"

Contains : Petroleum oil (gear oil) - CAS 64742-65-0

[killian96ss]

You probably have the Gov-Loc and one simple way to tell without taking the cover off again is to raise both rear wheels off the ground, make sure the e-brake is off, then spin one tire by hand while someone holds the other tire. The locking pin in the Gov-Loc should engage causing both tires to spin.

I have tried this numerous times and it always works as long as you spin one tire 100-200 rpm faster than the other one.

As far as the right gear oil, the 80W90 you are using is correct oil.

To be honest it really doesn't matter if you use regular oil or synthetic oil.

Neither one will cause chattering in a Gov-Loc.

Steve

[HenryJ]

Synthetic is not the recommended fluid. Some have had luck switching to synth. Some have had problems. The additives in Amsoil have been an issue for a friend locally.
The Eaton Govloc DOES have clutches. If the additives inhibit the friction needed, chattering can occur.

The locking differential consists of the following components:



Differential Carrier

Locking Differential Spider

2 Clutch Disc Sets

Locking Differential Side Gear

Locking Differential Clutch Disc Guide

Differential Side Gear Shim

Locking Differential Governor

Latching Bracket

Cam Plate

Eaton's G80 locker Information/Video

G80 Locking Rear FAQ. How it works.

Eaton Gov-Lo(c)k. It's a hybrid design that incorporates elements from the traditional limited slip (also called a "posi" or "positraction") and a traditional "mechanical locker" (brand names like "Detroit" or "Lock Right").

The way it's supposed to work is that when one wheel slips (spins faster than the other wheel on the axle), clutches in the differential are engaged. The clutches trigger a mechanical system that solidly locks the two axles together, preventing one wheel from spinning faster than the other. The Gov-Lock system will disengage the locking mechanism when torque is no longer applied to the pinion (the part of the rear diff that is connected to the driveshaft).

The Gov-Lok differs from traditional mechanical lockers in a couple of important ways (I'll use a Detroit Locker as an example of a traditional mechanical locker):

Detroits are always locked, they unlock when torque is applied by a wheel being spun faster by the road (i.e. your outside wheel tracking on a turn causes the diff to unlock, and the engine applies power to the inside wheel)

Gov-Loks are always unlocked, and the outside wheel on a turn is the powered wheel

Detroits do not need to sense wheelspin, because they are already locked - they only sense when the road is making a wheel spin faster, and then they unlock (usually with a BANG)

Gov-Loks must sense wheelspin (by the clutch mechanism) and lock when one wheel has gone faster than the other (the threshold for locking is set higher than normally occurs in a turn).

Detroits will instantly cause a vehicle to slide sideways when on an icy side incline

Gov-Loks will let one wheel spin, then engage the locking mechanism, causing the vehicle to slide sideways on an icy side incline (audio imitation: whiiiiirrrrr, BANG, sideways sliiiiiiiide)

Is one better than the other? Not necessarily.

Detroits can cause funny handling characteristics on short wheelbase vehicles (reference the inside wheel being driven on a turn). Gov-Loks have a tendency to engage harshly, causing slides and unexpected wheelspin on both rear tires. Gov-Loks also exhibit a tendency to self-destruct when a lot of torque is applied to the locking mechanism. (Imagine the force of a 31" wheel/tire quickly spinning up to 30 mph and then the locking mechanism trying to engage the other axle/wheel/tire which might be barely moving and on a high-traction surface). The extreme situation like this is when you're 3-wheeling to get over an obstacle.

You can sometimes modulate the locking action of the Gov-Lok by applying the brakes gently when you're spinning a single wheel (this is also a trick you can do with a limited slip differential). It sometimes makes the engagement of the locking mechanism less harsh. My advice is to not floor the gas when you don't have both wheels on similar surfaces -- you'll be less likely to have any of the"bad" locker characteristics bite you in the butt.

-- Submitted By Chuck Conway

[Tony]

What is the recommended lubricant?

Sticky: GM Fluid and Lubricant Recommendations

I know I've checked my owners manual, and GM Techline. They both say to use the GM stuff. What I don't get is from searching posts here and other S-10 sites is people use other brands and have no problems. And from I can gather the GM stuff is just regular 80w-90 gear oil?

You probably have the Gov-Loc and one simple way to tell without taking the cover off again is to raise both rear wheels off the ground, make sure the e-brake is off, then spin one tire by hand while someone holds the other tire. The locking pin in the Gov-Loc should engage causing both tires to spin.

I have tried this numerous times and it always works as long as you spin one tire 100-200 rpm faster than the other one.

As far as the right gear oil, the 80W90 you are using is correct oil.

To be honest it really doesn't matter if you use regular oil or synthetic oil.

Neither one will cause chattering in a Gov-Loc.

Steve

I've read some of your posts about synthetics and right now I'm just trying to get as much MPG out of this thing. I know they are far superior. What do you recommend I should use? Maybe I'll try switching brands.

This weekend I'm going to change the front and rear diffs (front's never been touched); and the transfer case.

I was just going to use the Amsoil again since I have alot of it left over, and then some Royal Purple synthetic ATF for the transfer case.

What does everyone think? Any tips or tricks for filling these things back up? I had a hell of a time getting fluid back into the rear diff. When I first did it and that was with a suction gun, which I will never use again.

[Tony]

Ohh I also get a whine that gets louder with speed. I only hear it when my foot is on the gas. I want to say its from the rear but I've never been sure.

I also get a vibration in the floorboard from about 10-20 miles and hour, don't know if thats normal also.

[Tony]

Pics added:

This was from when I changed it in September.

image

image

image



100k limit for images. link't oversized-HJ

[HenryJ]

Ohh I also get a whine that gets louder with speed. I only hear it when my foot is on the gas. I want to say its from the rear but I've never been sure.

I also get a vibration in the floorboard from about 10-20 miles and hour, don't know if thats normal also.

That sound more like a bad bearing. Check for roughness or loose bearings. Pictures are hard to tell for sure, but I don't see anything too alarming.

[killian96ss]

The pictures you posted show that you definitely had some water in there when you changed the fluid.

It is hard to say how much if any damage has occurred from the water being in there so long.

Make sure your rear diff vent line is in a place where water can't easily get in.

Some of the CC's had there vent line mounted between the cab and the bed which is not a good location for obvious reasons.

If you want to stick with synthetics I would use Redline 75W/90NS for the front and rear diffs.

You could try Amsoil again if you have a lot left over, but if that was your problem then you would only be wasting your time.

You could also just use whatever Amsoil oil you have left in the front diff (no locker-open diff) and try Redline in the rear.

The Royal Purple synthetic ATF will work just fine in the t-case.

The whining noise you are hearing could be several things like a bad alternator bearing, transmission pump, rear diff carrier bearing or pinion bearings (as HenryJ pointed out).

The vibration is a bit puzzling since you say it only happens from 10-20 mph.

Steve

[Tony]

Ohh I also get a whine that gets louder with speed. I only hear it when my foot is on the gas. I want to say its from the rear but I've never been sure.

I also get a vibration in the floorboard from about 10-20 miles and hour, don't know if thats normal also.

That sound more like a bad bearing. Check for roughness or loose bearings. Pictures are hard to tell for sure, but I don't see anything too alarming.

When you say bearing like a wheel bearing? I know they are somewhat common right?

The pictures you posted show that you definitely had some water in there when you changed the fluid.

It is hard to say how much if any damage has occurred from the water being in there so long.

Make sure your rear diff vent line is in a place where water can't easily get in.

Some of the CC's had there vent line mounted between the cab and the bed which is not a good location for obvious reasons.

If you want to stick with synthetics I would use Redline 75W/90NS for the front and rear diffs.

You could try Amsoil again if you have a lot left over, but if that was your problem then you would only be wasting your time.

You could also just use whatever Amsoil oil you have left in the front diff (no locker-open diff) and try Redline in the rear.

The Royal Purple synthetic ATF will work just fine in the t-case.

The whining noise you are hearing could be several things like a bad alternator bearing, transmission pump, rear diff carrier bearing or pinion bearings (as HenryJ pointed out).

The vibration is a bit puzzling since you say it only happens from 10-20 mph.

Steve

How the hell did water get in there? My vent line is under the bed? I mean this thing has never been off road.

Well as for everything else I'm going to take everything one step at a time. It's not worth getting overwhelmed and trying to figure everything out at once.

Like I said before what's the best way to fill these things up. Especially the front.

[killian96ss]

How the hell did water get in there? My vent line is under the bed? I mean this thing has never been off road.

Water has a way of finding its way into places that seem unlikely.

I like to replace the factory vent line caps with actual filters for better protection.

You can also place foam around the vent line caps to help prevent water intrusion.

That chocolate colored stuff in the pictures is definitely water mixed with gear oil.

Like I said before what's the best way to fill these things up. Especially the front.

On the front and rear diff just fill them until the fluid starts coming back out of the fill hole.

Some say to fill the diff until you are about 3/8" from the bottom of the fill hole, however filling the diff up another 3/8" will only help keep the wheel bearings better lubricated.

Steve

[HenryJ]

When you say bearing like a wheel bearing? I know they are somewhat common right?...

Actually I have replaced more pinion bearings than anything. The carrier bearings would run a close second.

Be sure to rule out a dry u-joint. They top the list for failures back there.

[Tony]

On the front and rear diff just fill them until the fluid starts coming back out of the fill hole.

Some say to fill the diff until you are about 3/8" from the bottom of the fill hole, however filling the diff up another 3/8" will only help keep the wheel bearings better lubricated.

Steve

I'm talking about not how far to fill them to, but how to get the fluid in there. There isn't much room for the bottle there. At least the Amsoil bottles are just oil sized bottles.

Also, since when are wheel bearings lubricated by differential fluid? The fronts aren't but maybe the rear are?

When you say bearing like a wheel bearing? I know they are somewhat common right?...

Actually I have replaced more pinion bearings than anything. The carrier bearings would run a close second.

Be sure to rule out a dry u-joint. They top the list for failures back there.

What do you mean dry u-joint? There isn't a grease fitting back there is there?

Are carrier bearings and pinion bearings in the differential itself?

[HenryJ]

... how to get the fluid in there. There isn't much room for the bottle there. At least the Amsoil bottles are just oil sized bottles.

Try a 6" long piece of clear tubing attached to the bottle. I have an old bottle left over from some tire goop that works really well. There are also cheap plastic pumps and quart jugs that will do the job.

What do you mean dry u-joint? There isn't a grease fitting back there is there?

Nope. They are supposed to be sealed and lubricated for life. The life of the u-joint. Not the life of the truck.

Are carrier bearings and pinion bearings in the differential itself?

Yes.

[JaVeRo]

The newer full size trucks with the G80 locker use a synthetic oil in the rear axle. It is made by Texaco for GM (Texaco 2276) but I have not found it as a Texaco product.

I believe the part# for the GM Synthetic is 12378261 if I am reading my notes right. I don't know if it is recommended for the S10. Take plenty of money with you if you go to buy some.

James

[killian96ss]

Synthetic gear oil works just fine with the Gov-Loc, and it provides far superior protection than the regular oil.

Another benefit is increased gas mileage.

I have never heard of any problems using synthetic oil with these lockers.

Steve

[Tony]

Update: Pulled off the rear diff. cover and there was some milkyness to the fluid, bearings seem to be tight, but the locker wouldn't lock. Manually engaged the locker and after one turn of the tires it unlocked itself. There is slight rust on everything inside the diff. The vent hose does come up between the cab and the bed that will be relocated soon.

Also pulled the driveshaft, installed new u-joints, and changed the transfer case fluid.

[Tony]

Another update: I drove the car, brake torqued it and the locker kicked in but real late.

Ohh and the rear end is still making the whining it always has been making.

I think I need to take it to a drivetrain shop.

[quickbiker]

Yea, looks like it's been suck'n mud.

[killian96ss]

the rear end is still making the whining it always has been making.

Are you positive it's the rear end?

With all the water contamination problems caused by that vent tube it seems like GM should be replacing damaged lockers, gears and bearings at no charge even if you are out of factory warranty.

Keep us updated on the cause of the whining noise.

Steve

[quickbiker]

My torque converter problem started out as a whining noise that lasted months and then ended up a loud chattering noise. I originally thought is was my rear axle.

[killian96ss]

My torque converter problem started out as a whining noise that lasted months and then ended up a loud chattering noise. I originally thought is was my rear axle.

The torque converter in my 88 S10 Blazer 4x4 made the same noise before I replaced the trans and converter.

Steve

[quickbiker]

I guess your tranny was contaminated? Did you have any shavings or bits on the magnet?

[Tony]

the rear end is still making the whining it always has been making.

Are you positive it's the rear end?

With all the water contamination problems caused by that vent tube it seems like GM should be replacing damaged lockers, gears and bearings at no charge even if you are out of factory warranty.

Keep us updated on the cause of the whining noise.

Steve

I really don't want the hassle/headache of trying to get GM to pay for this. You should see my bed and how they only cover rust "holes".

So yeah, I'm going to take it to the rear end shop sometime.

[F9K9]

Tony, check out Document ID# 1548738 and show it to your dealer. You might get it all done correctly and for free.

[Tony]

I guess I'm going to talk to my folks tonight about this. See what my dad thinks. He is an attorney. He might just pay for it out of pocket.

Family site. Watch the language-HJ