Manuel Jeff Martin

Hello everyone i need some advice.

I just had a shop rebuild my diff, with 3.70 gears and a whole new bearing install kit from. Its pretty much a new diff. Well after 75 miles into the break in, and driving like an old lady the gears are howling inbetween 50-65mph. the shop says its not his setup thats the problem its the gears, so he say get them warranteed, like thats easy. It only whines when steady throttle is applied, i know its not set up right, but he insists his work is good and its the gears that are at fault.


I need advice. Im a college student and i just spent 1000$ dollars fixing a diff that, turns out is not fixed.

Thanks
Manuel

Tim94gt

iTrader: (2)

Did he add the friction modifier?

Manuel Jeff Martin

Yes he added the modifier.

Tim94gt

iTrader: (2)

I'd pull the cover and check the contact pattern. If the backlash and pinion depth are ok, call the gear manufacturer.

O-FiveCC

iTrader: (10)

Lot's of these gears are whining. You can read about it on LS1GTO.com

402GOAT

iTrader: (2)

who was the manufacturer of the gears?? whine is generaly typical with aftermarket gears

Jontall

The Motive gears whine a little. Another cause is the pinion depth is wrong and this is a very common problem. Shops just can't seem to set the pinion depth correctly.

409CISecondGen

iTrader: (2)

My 3.91s whine and I personally know of another guys Motive 3.91s that also whine.

SJFGTO

Some noise is common with these diffs and a lower gear ratio. Torco 85W-140 with type f modifier can lessen the noise somewhat. But if the noise is substantial it is likely because the install was not correct. If the install is not correct you need to fix it now before a wear pattern develops, then it is too late. FYI I run 4.10s and a tru trac, bone silent!

Manuel Jeff Martin

the gears are Motive and they are only 3.70...... The shop does not want to honor his work because i shift 1-3-5-6. he says short shifting like this puts more strain on the rear end?? sounds like an excuse to pocket my money after an incorrect instal. I babied this rear end, and after 75 miles it not only whines in constant throttle from 50mph-60mph, but also whines in deceleration now.

BPP

iTrader: (2)

The motives do whine a bit but it sounds like the pinion depth is off. Mine was terrible after my first install due to the installer not removing the factory pinion shim. This caused the pinion depth to be incorrect I am betting that is your issue

409CISecondGen

iTrader: (2)

That's bullshit, the car comes from the factory with a 1-4 skipshift.

silver02Z

iTrader: (19)

Sucks that he doesn't want to warranty the work

If it makes you feel any better my Aussie 3.91's whine.. I even used Torco 85w140 with type F modifier and still some noise. I'm betting mine were setup wrong also.

6PntHo

iTrader: (2)

Mine Wine just a hair. And I've got about 200 miles on mine.

SJFGTO

Pure crapploa. It is hard to tell you what to do because I can not hear it over the internet. But if the whine is more of a moderate hum, try Torco. Some noise is nomal, especially for motive gears. If it howls, that is clearly a poor install (did it howl before?) In that case have someone re-do the work before you end up with a permanent noise...or worse.

Cwarta

iTrader: (12)

Your builder is full of ****. Like said above, these cars are designed to skip shifts. I just installed 3:91`s this weekend (Aussie gears) and 100% dead silent. I am even using Lucas Gear oil, not the good Torco! Pinion depth is most likley wrong. I have 500 miles on my rear end right now and plan to swap to torco soon.

Glenn B

iTrader: (5)

OP,
as stated above, swap your fluid to Torco 85-140 with the correct amount of modifier and see if that helps. Also most people i have spoke with recommend a 500 mile break-in period.
With that said, I also just swapped gears to Motive 3.91s, and the shop I used did a super job on my diff.... BUT I still have a bit of higher pitched gear whine about 50-60 mph or so only at very light off-on throttle. Its not excessive, but i can hear it....

My setup is good, and I know that. Most aftermarket gear companies Richmond, Motive etc, admit that aftermarket gears will have increased noise as they have designed the gears to be stronger than stock and have more contact between the pinion and spur gear. Factory gears are quieter, but ultimately give up strength in the quest for NVH.

I have had 3 aftermarket gear set-ups in different cars over the years and it is not unacceptable to have some increased gear noise.
But thats the thing, we need to find out if your noise is acceptable or if the gears were in fact set up wrong and the diff should be re-setup so as your parts dont fail.
Try to be as precise as possible when you describe the rear end noise so as the members here can give you the best advice possible.

Are your gears noisy at any other time aside from 50-60 mph cruising?
I think it odd your shop so quickly dismissed looking into the issue because of "skipped shifts". That seems shady to me.
Did you have a full install kit installed with the gears?
I ask because the shops with experience with our differentials say the one important thing overlooked by many shops is the install depth of the pinion gear. The installer just uses the factory shims and tosses the new gears in on top of that assuming it will be fine, and it ISNT.
Possibly speak with the person who did your install and ask a few good questions and see what kind of answers you get.
FWIW, Motive gears have had more issues with noise than other brands of gears for these cars. Some attribute that to the very low production run #s Motive did on this application.
--Glenn

Glenn B

iTrader: (5)

This.

pctek

I dont know anymore than you proabably know about diffs, gears etc but after reading up some stuff on ls1gto.com the whine is usually because the back lash or something like that of the gears is not right. Thats why alot of goats even when brand new had the whine right away or soon after new because it wasnt setup right at the production of the diffs.

My 05 goat has 71,000 miles on it and it has the whine/howl noise just like you describe it is the oem stock one too. Adding more or less fm doesnt take it away nor does different brand of oil take that away. Its because the setup is not right. There is a link in the sitcky that contains some videos on how diff work is done.


Theres a guy on ls1gto forums that knows alot about diffs the name is " Konnie the Goat " You can ask him questions. And this website can rebuil it properly for others lookin gto have theres rebuilt to in the future.
http://www.shop.gforce1320.com/main.sc

So the diff really needs to be looked at someone that really knows how this particalur diff works and what settings to shoot for, so usually a local diff shop in town cant set it up right.... they can rebuild it no problem but thats easy or different than also setting it up right with the clearances of the gears and such.

Here is some reply messages to me when I was asking konnie the goat questions about diff related stuff. Might give you some ideas...

The spring tuning kit increases the pressure the cones exert on the carrier, making the LSD less likely to slip. It would only affect noise in turns.

As for bearings, you'd need all of them. Depending on the condition of the gears, you may need new ones to cure the whine. Dana did a horrible job building these units. 90% of the whine is the gears and bearings.

replacing the bearings is basically the same work as replacing the gears. It requires some special tools, and experience to get it right, and is not really DIY friendly.

There is a link in the sitcky that contains some videos on how diff work is done.

http://www.ls1gto.com/forums/showthread.php?t=327020

thewrench

Every rear that comes into the shop with whine is 9 times out of 10 the pinion depth being set wrong. This is an install issues and the shop should fix it.