What is required to swap a 3.42 to a 3.73?

adrenalnjunky · Post by **adrenalnjunky** » Sat Aug 23, 2003 3:02 pm

I'm wanting to know if all I need to do is swap out the rear end gears to a 3.73 ring and pinion? Or do I have to go into the transfer case as well??

Anyone know if your rear ends are the 8.5 inch rear?

If that's all it needs, how much would you estimate it would cost for parts?

Post by **HenryJ** » Sat Aug 23, 2003 3:25 pm

adrenalnjunky wrote:I'm wanting to know if all I need to do is swap out the rear end gears to a 3.73 ring and pinion?

Don't forget the front end too if we are talking 4x4 here.

Or do I have to go into the transfer case as well??

No

Anyone know if your rear ends are the 8.5 inch rear?

The Zr2 has the 8.5" ours are 7.625" rear.

If that's all it needs, how much would you estimate it would cost for parts?

Hobie did it he will have a pretty good idea.

adrenalnjunky · Post by **adrenalnjunky** » Sat Aug 23, 2003 8:24 pm

Sweet -- thanks.

Another question -- would I be better off looking around for a donor Zr2 rear end? That way I could get the 3.73, locker, and the 3.73 front out of it too.

quickbiker · Post by **quickbiker** » Sat Aug 23, 2003 10:12 pm

As far as I know, the ZR2's have identical diff's, front and rear. I know the 8.5's are on the fulls size trucks.

Post by **HenryJ** » Sun Aug 24, 2003 4:23 am

quickbiker wrote:As far as I know, the ZR2's have identical diff's, front and rear. I know the 8.5's are on the fulls size trucks.

Nope, the ZR2 got the bigger 8.5" rear diff. and it is wider, of course.

adrenalnjunky wrote:-- would I be better off looking around for a donor Zr2 rear end? That way I could get the 3.73, locker, and the 3.73 front out of it too.

That would be an option, but they are going to be a bit harder to find for a while.

You will want a newer one so that it has the disc rear brakes. There will also have to be some modifications done.

The right hand shock is on the wrong side of the axle, for our truck.

quickbiker · Post by **quickbiker** » Sun Aug 24, 2003 5:10 am

And do the ZR2's have the same front diff?

adrenalnjunky · Post by **adrenalnjunky** » Sun Aug 24, 2003 6:55 am

I just watched a ZR2 rear axle, with 3.73, full disc brakes, locker, etc. go on Ebay for $400 -- but can you imagine the shipping?

The ZR2 rear axle is wider too correct? That way you wouldnt need spacers to get that widetrack stance.

quickbiker · Post by **quickbiker** » Sun Aug 24, 2003 9:15 am

If I swapped axle, it would probably be a d44, cause you can get anything for those axles. I would like the Detroit E-locker, posi and locker in one. Kewl

Another ? Has anyone ever tried the Detroit C-Locker? They make it for our diffs. It would seem alot less harsh than the ez locker and it locks solid!

adrenalnjunky · Post by **adrenalnjunky** » Mon Aug 25, 2003 7:38 am

For economical reasons, could I swap the whole rear end to the 3.73 with a package like this

Posi + 3.73 Package

And hold off on the front until I can get an upgrade for the front Diff? I understand that running in 4wd wouldn't be a good idea, but I could hold off for a few months in that situation.

Conman · Post by **Conman** » Mon Aug 25, 2003 7:57 am

adrenalnjunky wrote:For economical reasons, could I swap the whole rear end to the 3.73 with a package like this

Posi + 3.73 Package

And hold off on the front until I can get an upgrade for the front Diff? I understand that running in 4wd wouldn't be a good idea, but I could hold off for a few months in that situation.

that ebay says you can get a higher gear as well. If you did this, I would just go out at get the 4.10 if you plan on bigger tires. But if your not planning on bigger tires, I would just live without LSD and gears IMHO.

Con

adrenalnjunky · Post by **adrenalnjunky** » Mon Aug 25, 2003 10:49 am

Well --- here's my predicament:

I plan on the basic BL + Daystars + Torsion crank. From what I understand I'll have problems fitting a 31 x 10.50 x 15 under it with just those mods.

If I could fit the 31 with little rubbing on inner fenders, I'd stop there. ( and break out the BFH to take care of the rubbing.)

I want a 31 on the truck, but if I have to go with asuspension lift as well to get anything bigger than a 30 to fit right, I'll probably put a 33 on if I have to get the TM lift, or the Superlift 6 inch becomes a reality.

See--one thing leads to another -- I'm kinda hoping with the BL on I can get the 31's to fit and I'll stop there. If they don't fit then I'll go with a 30 and probably keep my 3.42's and not worry about gearing at all.

a2b · Post by **a2b** » Mon Aug 25, 2003 10:29 pm

wait until you the lift and bigger tires are a reality. then put lower gears in. and if you TM it and bl it, you will have 32's or 33's on. if they are 33" SSR's, then they are really 34's.....point is...just wait.

and 31's with 4.10's is freakin awesome. i love going up hills in overdrive and not have to down shift on the freeway. 4.10's and 33's will be alright. the gas mileage does seem to be the same as with 31's and 3.42's.....but now i have the power that i lacked before.

and if its a street truck, stay with a LS. its easier on it. also, dont waste your time looking for other rear ends. the zr2 is not a straight bolt on. wont work without custom fab work.

to do the gear swap will cost a grand. and its a big pain in the caboose to do the front end. so yes, you can do the rear and then do the front. the rear will be the cheaper of the 2.

if you are happy with the 3.42's and 30's...i would just stick with that. the bigger tire you go the faster you will wear stuff out on your truck

adrenalnjunky · Post by **adrenalnjunky** » Tue Aug 26, 2003 6:18 am

Ahh that blows ---

I ralllly want to go with the 31's when I perform all of the upgrades. I was parked next to a buddies Tacoma with 31's on it and was thinking that tire size would be exactly what I want for a stance on mine.

So I guess my 2 questions are-- how bad will 31's and 3.42's be, and can I fit the 31's with little mods with just the BL and shackles and Tbar cranks?

Hobbie--check your PM's.

a2b · Post by **a2b** » Tue Aug 26, 2003 8:07 am

alot of us here are running 31's with the bl and tbar. its quite common.

3.42's and 31's arent too bad at all. but now that i am used to the 4.10's, i hate 3.42's gears.

Justin · Post by **Justin** » Wed Aug 27, 2003 4:59 am

I just found out I have 3.42 and I have 31" tires. It's nice on flat and sloping down highway sections but as soon as a slight incline comes, it downshifts to 3rd and pushed 2500 rpm. Don't plan on passing anyone including a big rig going uphill. It's funy how 50000 lbs. passes me sometimes

I plan on keeping the truck for another 2 years until 60k or so (so 10k is still on warranty) so im not sure to add much more...If you are in the same situiation, i guess its personal preference and a matter of how much money you have

a2b · Post by **a2b** » Wed Aug 27, 2003 7:39 am

Justin wrote:I just found out I have 3.42 and I have 31" tires. It's nice on flat and sloping down highway sections but as soon as a slight incline comes, it downshifts to 3rd and pushed 2500 rpm. Don't plan on passing anyone including a big rig going uphill. It's funy how 50000 lbs. passes me sometimes I plan on keeping the truck for another 2 years until 60k or so (so 10k is still on warranty) so im not sure to add much more...If you are in the same situiation, i guess its personal preference and a matter of how much money you have

no wonder you were saying that 3.73's werent enough for 31's....cuz you had 3.42's

adrenalnjunky · Post by **adrenalnjunky** » Wed Aug 27, 2003 7:50 am

that's why I plan on going to 3.73's at least -- I want to get the 31's on first--if I'm happy with the height then I may just go to 3.73 -- If I feel I want to lift suspension and go with 33's then I'll drop to 4.10's.

I know how to do the rear end, what all is involved in swapping the front Diff? Same setup just on the other end of the truck?

Dragonmaster · Post by **Dragonmaster** » Wed Aug 27, 2003 10:04 am

basically the same excepthe the case is split front to back vs side to side. The front diff has to come out in order to swap gears. While you can do it in your driveway I would suggest using a lift if you can as you have to take the cv shafts out and then drop the pumpkin.

adrenalnjunky · Post by **adrenalnjunky** » Wed Aug 27, 2003 12:26 pm

Sorry for all the questions, so it's the same 7.625 10 bolt setup that goes in the back?

Is there a locker in the front, or do I need to add a locker to both?

Post by **HenryJ** » Wed Aug 27, 2003 1:23 pm

adrenalnjunky wrote:Sorry for all the questions, so it's the same 7.625 10 bolt setup that goes in the back?

I don't remember for sure (brain fade) but I'm thinking that the front is 7.25" ring gear? I'm pretty sure that is what it is.

It is definitely a different setup than the rear, assembly wise, there is no "cover" to enable easy disassembly. You have to remove parts from either side starting at the wheel and working to the center

(not for amateurs)

Is there a locker in the front, or do I need to add a locker to both?

Nope and not a real good idea on this IFS, IMO

One more thing, IMO the 3.73 / 29" tire combo is the ideal final ratio. For 31" tires 4.10 is a close to that as possible , (ie. ideal, IMO)

If you are going to do gears and 31" tires go with the 4.10's.

a2b · Post by **a2b** » Wed Aug 27, 2003 2:34 pm

no, DO NOT PUT A LOCKER IN THE FRONT!!!!

NTXCrew · Post by **NTXCrew** » Wed Aug 27, 2003 5:30 pm

a2b wrote:no, DO NOT PUT A LOCKER IN THE FRONT!!!!

why?

a2b · Post by **a2b** » Wed Aug 27, 2003 5:56 pm

NTXCrew wrote:
a2b wrote:no, DO NOT PUT A LOCKER IN THE FRONT!!!!

why?

our front ends are WEAK

they cant even come close to doing handling a locker.

a person about a year or so ago tried it. he didnt even put a locker in, he put a LS in.

after one trail, he blew his diff to peices

if you want a locked IFS rig, do a custom swap to the full ton IFS. that thing is strong!

NTXCrew · Post by **NTXCrew** » Wed Aug 27, 2003 6:06 pm

a2b wrote:
NTXCrew wrote:
a2b wrote:no, DO NOT PUT A LOCKER IN THE FRONT!!!!

why?

our front ends are WEAK

they cant even come close to doing handling a locker.

a person about a year or so ago tried it. he didnt even put a locker in, he put a LS in.

after one trail, he blew his diff to peices

if you want a locked IFS rig, do a custom swap to the full ton IFS. that thing is strong!

oh

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What is required to swap a 3.42 to a 3.73?

What is required to swap a 3.42 to a 3.73?

Re: What is required to swap a 3.42 to a 3.73?