handyandy

Hi all,

I have a few questions about rebuilding my rear end. I have a constant whine from the rear end that increases with speed, long story short it was originally much worse under load, so I checked the ring gear backlash and it was tight, re-shimmed it into spec, put in new fluid and put it all back together, but now the whine is just more constant.

I see Rock Auto has some differential rebuild kits for a good price that seem to include all new bearings and seals. I guess my main question is, if I'm going to take this apart once more and get rid of the noise once and for all, what all should I buy? Should I be ordering:
- new axles?
- new ring and pinion gears?

Or should I be treating these as only order on an as-needed basis? And are there specs that I would go by to decide if I need new ones? When I took the rear end apart initially to set the backlash, I pulled the axles and didn't notice anything obviously wrong with them. There were no deep grooves or sharp edges, just maybe light wearing where they sat on the bearings. But again, I'm not sure if this is a situation where a tiny amount of wear means a lot, and I should just get new axles to be sure, or is there some amount of wear I can measure that's still 'within spec'?

Same goes for ring and pinion gears - I didn't see what looked like any excessive or abnormal wear on the gears, but they were lashed too tight. I just bought the car so I'm not sure how long it had been like that. Is this a case of 'only replace them if they're broken', or I should just replace to be on the safe side? Overall the price difference isn't huge, but at the same time I don't want to throw money at it that's not necessary.

FirstYrLS1Z

iTrader: (4)

Since you're 6M,GM little 7.5/7.625 10 bolts don't do well behind an M6. What brand were the 4.10s' when you had the cover off ? You said tight,what WAS the lash ?
Axle bearings per your description sound OK. Replacement axles(new) are aftermarket only and some are crap.
Did you take any pics of the ring gear wear pattern and of the axles' bearing surfaces ?
97 would have had an Auburn 'posi',did you add the 'limited slip' additive ?
What tires on the rear ?

handyandy

Yeah I understand the 10-bolt is a weak point and will likely die at some point, but at the same time it will cost me like $200-$300 in parts to rebuild this rear end and eliminate the noise versus $2000-$3000 for a new rear end. I will likely end up upgrading the rear end at some point down the line, but for now the car is just a cruiser / weekend car that doesn't see any track time, and I'd rather do a rebuild now and enjoy the car this summer, and then reevaluate the rear end over the winter.

Not sure on the brand of the 4.10's, never thought to look. From what I remember lash was around 0.003-0.004, and spec was 0.006-0.010. After I re-shimmed I was measuring around 0.008-0.009". No pics of any of the surfaces just because I didn't think of it at the time, and everything looked "normal" to me. The bearing surfaces on the axles looked smooth and shiny, but no big divots or grooves. I used Royal Purple gear oil that has 'limited slip' additive already in it according to the bottle, and also says to not add more. Also from searching online others seemed to have used it with success so I figured it was fine to use. Would not having the correct additive cause a whining/humming noise that's constant and increases with speed? I thought at worst it just affect the engagement of the Posi. And tires are stock 275 wide Kumho Ecsta of some kind (can't remember exact model). They are a 'high performance summer tire', but not exactly the stickiest / grippiest in terms of launching.

If the aftermarket axles are hit or miss and might be junk, is there a way to machine / rebuild mine? Or a measurement I can take once it's apart to determine if they are still within tolerance to use with new bearings? I see some have "repair bearings", which I'm assuming are made slightly smaller to work with slightly worn parts?

FirstYrLS1Z

iTrader: (4)

Yes,the additive is only for the function of the Auburns' cone clutches. Is the Royal Purple a 'synthetic' ? There are many threads here to NOT use synthetic gear oil,I believe Auburn also states to NOT use synthetic. Use regular gear lube and a bottle of the GM additive.
Axles are case hardened. New axles and new bearings are loose anyway,much looser than a 'slip fit'. They're not tight like wheel bearings. The axles ride on them and the lube in the rear end housing provide a continuous bath of lube.
Axle repair bearings are an assembly in which the bearings are shifted outward so a newer/previously not used part of the axle rides in the bearing. Many horror stories of using them. Difficult to get the c-clips in upon re-assembly and IMPOSSIBLE to get the c-clips out if rear end work is needed again.

1st pic,I'll reuse it by hand polishing/cleaning the surface with fine emery paper. 2nd pic,too far gone to reuse.

handyandy

OK, thanks for the info - from what I remember mine were definitely closer to Pic 1, but I'll confirm once I take it apart.

What about the ring and pinion gears? Should I consider replacing those while I'm in there, or are they also fine as long as there's no obvious large amount of wear?

FirstYrLS1Z

iTrader: (4)

Check for 'play/wobble' up/down left/right of the pinion in its' bearings. If there's wobble,could be the pinion nut needs tightening(huge amount of torque required) to get the bearing play reduced OR wobble could indicate bearings are shot. If when turning the pinion by hand,does if feel smooth or rough/gritty. If no usual wear on the teeth,they should be fine.
Have you ever worked on rear ends before ?

01ssreda4

iTrader: (96)

Id buy Motive blue box gears, install kit 308tk, and reset all tolerances.

Nice centered pattern.
Backlash around 6-7.
20 in/pds on the pinion
35-40 pinion and carrier combined.
Easy driving for 250 miles.
Gear oil swap and send it.
It'll last a long time.

handyandy

Thanks for the tips. Is there a way to check for wear on the gear teeth, or you're just visually looking for some uneven wear patterns? I haven't done much work on rear ends before, but I pulled it apart myself in the winter to check and set the backlash and change the fluid. Just basically pulled stuff apart and put it back together to see how it all worked. It's not a daily driver so I'm not worried about taking my time with it, and I'd rather do the work myself slowly and learn than pay someone else to do it.

handyandy

Thanks! Is that what gears you're using? Are they just a well-made aftermarket, or are they an improvement in terms of strength?

01ssreda4

iTrader: (96)

Motive blue box are stock replacement gears. Known to be very easy to setup and very quiet. I run orange box "performance" in mine, and Ive always gotten a little whine at 50mph. I should note i NEVER break them in properly and I should.