4bolt rear rebuild question

[bubba_zenetti]

Hi all,

My rear end is starting to make all sorts of noise. I suspect the bearings are starting to go as they are making a whining sound. It would also seem that there is some slop in the rear as well. with the car parked. i can reach under it and twist the driveshaft about 1" or about 15 degrees of rotaion before it stops.

How much slop is normal on this vehicle? Also, where can one get a rear end rebuilt kit or am I stuck going to satan for it? Is there a VFAQ describing the rebuild procedure anywhere?

Thanks!

 

[AWDRulz]

hey ive been in the same situation like you for months now,ive been gettng crazy quotes from shops i take it too.Anyone here can help with rearend rebuilds?Mine has the lsd.thanks

 

[Jon Lane]

Bump. My 2G rear is going out too. Where do you racers get cheap replacements?

 

[4pistons]

Before you guys blame the rear end for slop in the driveshaft check all the u-joints. There's three of them. If they are all worn even a little bit it adds up to a lot of slop.

Rick - '91 GSX

 

[DSM90AWD]

It's hard to pinpoint the exact cause of the axial freeplay in a driveshaft as worn u-joints, lobro joint, carrier bearings / mounting bushings and the rear itself will have a cumulative impact in your test.

The best way to check just the rear, is to jack the car up with the parking brake set. Rotate the DS as far clockwise as you can and mark both the pinion and seal. Now rotate as far as you can counter-clockwise and again mark these two points.

Measure the distance btw the marks. 7mm is the service limit on the 1Gs rear.

FYI.. rebuilding a DSM rear is big$$$$ and few shops will do it (local shop quoted me >$1K for parts only).

You're better off either living with the slop or buying a used one that you can look over yourself and test for excessive lash.

FYI.. I replaced both Carrier Bearings, the CB rubber mounting bushings and two u-joints (yoke and rear flange) and most of my slop was cured

 

[4pistons]

I replaced both Carrier Bearings, the CB rubber mounting bushings and two u-joints (yoke and rear flange) and most of my slop was cured

That was my point exactly! It's far more likely, though not impossible, that those are the parts causing the slop. It's WAYYYYYY cheaper to replace those than the whole rear diff only then to find out you STILL didn't solve the problem.

Rick - '91 GSX

 

[J92EGSX]

The carrier bearing will not cause any slop in the drive train, the most likely cause if all the u joints are ok is the spider gears and the side gears in the carrier assembly, if you have been launching your car hard this is most likely the problem.

Josh
1992 GSX
ASE Certified In Drivetrain

 

[DSM90AWD]

The carrier bearing will not cause any slop in the drive train

Josh
1992 GSX
ASE Certified In Drivetrain

The carrier bearings support the driveshaft and "dampens" radial play. If the DS was a one-piece unit (well would not need CBs ) I would agree with your statement. But the DSM's are three piece units (four including the yoke) with three u-joints and a lobro joint. When these go bad you sure as hell will get slop in the drivetrain. I may not be an ASE Tech, but I've owned my AWD since it was born and have personally seen the effects of worn carrier bearings and the changes when replaced.

Not to say the rear itself is blameless.. just that any play there gets magnified many times over when other parts go bad.

Search on "Rear Thump" for more details.

 

[Jon Lane]

My car doesn't have rear end thump, but it did develop a consistent howl at just over 50mph, regardless of throttle position. I assume its the rear gear lash, and if that's out, I'd like to just rebuild the thing. The old girl's at 107k mi and the rest of the drivetrain is getting replaced this year anyway.

Does anyone know where there's a list of part numbers for 2G LSD rears and/or best place to get em? I just picked up a clutch master cylinder from NOPI for about half of what I expected to spend so I'm hoping there's a similar deal out there on rear end parts...

 

[DSM90AWD]

My car doesn't have rear end thump, but it did develop a consistent howl at just over 50mph, regardless of throttle position. I assume its the rear gear lash, and if that's out, I'd like to just rebuild the thing. The old girl's at 107k mi and the rest of the drivetrain is getting replaced this year anyway.

Does anyone know where there's a list of part numbers for 2G LSD rears and/or best place to get em? I just picked up a clutch master cylinder from NOPI for about half of what I expected to spend so I'm hoping there's a similar deal out there on rear end parts...

Sure it's not a bad lobro? When the boot tears can make a bunch of noise. Rear end noise is more like a humming/whining that increases in pitch with speed.

I warn you, very expensive to rebuild. I 've heard that Buschur has done some in past for ~$500, but is just for re-shimming the pinion. Taking to a local drivetrain shop will cost you 2x that (if not more).

 

[Jon Lane]

Sure it's not a bad lobro? When the boot tears can make a bunch of noise. Rear end noise is more like a humming/whining that increases in pitch with speed.

I warn you, very expensive to rebuild. I 've heard that Buschur has done some in past for ~$500, but is just for re-shimming the pinion. Taking to a local drivetrain shop will cost you 2x that (if not more).

I hope you're right. It just sounded like gear whine. Going to have to crawl under there and see...

 

[pianoman]

We did my cousins, u-joints, along with the CB's and there was still a whine when decelerating between 3,000 and 2500rpms.So that would mean the rear-end is bad correct?

Also you'll know if the CB's are bad cause the driveshaft can/will hit the bottom of the car under hard acceleration.

 

[4pistons]

there was still a whine when decelerating between 3,000 and 2500rpms.So that would mean the rear-end is bad correct

No, not necessarily. It could be a wheel bearing, a dragging brake pad, an imbalance in the driveshaft, or in the clutch/flywheel. It could be any of the xfer case or tranny bearings too.

It is very rare for a rear end to go bad if there's oil in it. If the bearings and gears are soaking in a pool of gear lube it's hard to wear them out.

Rick - '91 GSX

 

[DSM90AWD]

We did my cousins, u-joints, along with the CB's and there was still a whine when decelerating between 3,000 and 2500rpms.So that would mean the rear-end is bad correct?

Check your rear's lash as I explained above. If within spec and no other anomolies (silver fluid, metal particles), I would not worry about it. I've had rear gear wine to some extent in many a car (84 SVO, 68 Firebird and my Talon), and all ran fine.

Also you'll know if the CB's are bad cause the driveshaft can/will hit the bottom of the car under hard acceleration.

I found that bad u-joints will kill CBs. I had to buy the same rear CB 1.5years later after finding out my rearmost u-joint was bad causing sever vibrations (that the CB abosrbed so was not noticible).

 

[GritsnGravy]

I rebuilt my 4-bolt rear end. It was cheap! I just got shims though. If you need new bearings, it shouldn't be that more expensive. Don't take it to a shop! They charge a lot of $$ for that. Just go to you local Mitsu dealer and order new bearings and shims. The hardest part of the rebuild is the shimming. Also, I almost forgot, get new rear seal.
Paul