Problems with new gears

[blackfire93]

I just got my car back from the shop. I had the guy put motive 3.73's in. I drove the car for a little way and noticed a little whine. It wasn't too bad. After the rear end warms up it starts to get worse. Then, when it's warm, the gears will make a grinding noise like they are rubbing against each other real hard. I took it back to him and he put more limited slip additive in. It helped the turning problem a little but didn't fix it completely. They also still whine when I'm driving. Then last night I got it up to about 85 and the car will start to shake. I called him and we're going for a drive tonight so that he can figure out what he needs to do with it. What do you guys think???

[N20LT4Bird]

You probably have at least 2 problems. The whine is usually due to improper backlash between the gears.....or possibly improper pre-load on the pinion bearings. The vibration could be a driveshaft balance issue. Often times, when switching to a numerically higher gear ratio, a driveshaft balance issue will become noticeable because the shaft is spinning faster at a lower speed. So you may have had it before, but went un-noticed. Does this mechanic specialize in driveline repair? This is usually a specialty area......and if he doesnt do rearend work on a regular basis, he may have set the backlash , or preload, or both improperly, which is not a good thing.

[Joe 1320]

You probably have at least 2 problems. The whine is usually due to improper backlash between the gears.....or possibly improper pre-load on the pinion bearings. The vibration could be a driveshaft balance issue. Often times, when switching to a numerically higher gear ratio, a driveshaft balance issue will become noticeable because the shaft is spinning faster at a lower speed. So you may have had it before, but went un-noticed. Does this mechanic specialize in driveline repair? This is usually a specialty area......and if he doesnt do rearend work on a regular basis, he may have set the backlash , or preload, or both improperly, which is not a good thing.

I second that. Often times though simply increasing the gear speed creates additional noise (slight) that you just have to live with. Sounds like it's more like what was already described though. Driveshaft imbalance is a common problem with these cars, there was even a factory TSB about the problem. Eventually it led to a change of design.

[markd79ta]

manual or auto?

[fastTa]

Yep, pinion depth/baclklash, footprint, and preload on the pinion bearings and even possibly carrier bearings.

GM Motives, if installed correctly should be very quiet. But, like everyone mentioned, your drivertrain from the drivetrain will be turning higher revolutions than it previously was at the same speeds.

I would get it on a lift and put it in gear and have someone hold the loud petal down just a little to get the drivetrain spinning and listen closely to where the "whine" is originating from.

Did you install a new complete bearing kit with the ring and pinion? What type of crush sleeve did he use?

[dochidalgo]

Add information:
Driveshaft Tech Service Bulletin

http://www.ws6.com/shaft.htm

Aluminium drive shafts
1LE.....P/N 10085375
LS1.....P/N 12564003...automatic tranny

Good luck
Dochidalgo

[blackfire93]

it's an auto.

I had him put the solid crush sleeve in and he put brand new bearings and everything in. (besides the wheels bearings)

[93/96 f-body]

related problem

Just so happens i used the same gears in my 96ss but 3.42 gears.Mine are quiet but i have the same problem at 85 +.Took the car back they told me it was the drive shaft. Took to a local shop and they said it was barely off in the middle but shouldn't have any affect.They added the weight to be safe but it wasn't the problem.I went back again and they told me i drove it 500miles and if the rear was going to fail it would have already.Way to throw some bs around! I was about ready to strangle the poor guy at the counter.We went round and round and the car been sitting and since the rebuild and about two years i still only have 1,000 miles on the rear.I know for a fact something is reloaded to tight it takes to hands to rotate the drive shaft with the car jacked up!Told them that and the gave me a bs about the breaks dragging!He told me when i picked the car up the first time the gears made noise after they first lashed them and they called one of their vendors and the set it up to their specs. He said the carrier reloaded tight we had to hammer it into place!This came out of his mouth and when i told him it was binding and repeated his exact words he just looked at me and said i'm the middle man talk to the owner of cousre who was never around when i showed up.Pissed me off could have spent not much more on a whole aftermarket set and put in myself and it would have been bullet proof.Let me know what you find out.I don't know of anyone in my area that just does rears i'm scared to dish out money again to have it fixed.Just picked up a 93 with 3.73 gears in it and it works perfect.Thinking about swapping rears and selling the 93.Good luck.Don't give up like i did make them stand behind thier work of refund the install money and fine someone qualified.

[N20LT4Bird]

I don't know of anyone in my area that just does rears .

Generally, you will want to take it to a transmission / driveline shop. If you build trannys then you know how to set up a set of gears......

[93/96 f-body]

rear

yeah thats what i thought.I took my car to the local tranny shop and still have this problem.

[markd79ta]

The reason that I asked about the transmission type is that the gears will often pronounce other problems with your car. Before I installed my gears, I had a very slight vibration at speeds over a 100mph...not a enough for me to give it a second thought. Well, after the gear install, I have vibration at 70mph. A brand new SLP drive shaft made little to no difference. The driveline shop that did my gears said it was the output shaft in the t56. Since the problem was present before the gear install, I tend to believe this. My 4.10s make very little noise considering they are 4.10s in a 7.5" carrier. Anyhow, the tranny is coming out this winter for a bearing and synchro refresh...I guess we will find out then.

[blackfire93]

I took it back to him and he put even more limited slip differential fluid in it. The binding noise has stopped. I might have heard it once or twice since then. It still whines a little at 45mph. The car shakes the worst at 90mph. For a while I thought that it might have just been the loud exhaust but I got it up to that speed and put it in neutral and it was still shaking. It doesn't shake as much at 110mph. I asked the mechanic about it and he said that the driveshaft should be in balance and that maybe I should have the balance of the tires checked. I know he knows a little bit of what he's doing because he builds circle track cars and told me that he has installed gears on many different cars. He used to be a mechanic at the local Chevy dealership. I guess I can live with a little whine at 45. You can kind of hear it 20-45 but it's worst at 45.

[jerrysta]

I had a similar problem with my gears after install. My speedo was already off so I was unsure of the speed. Fred said it was around 77. Anyhow, I had mad z28 reprogram the cpu becaue it felt like some limiter was kicking in but I have yet to test it. I have my fingers crossed!! I'll let you know as this could help with your second problem. As far as the noise, mine have been quiet so I can't help you there!

[blackfire93]

I took the gears back a few times and we added some more limited slip additive but it kept making the binding noise on the turns at slow speeds. Finally he decided to pop the cover and see if there was anything wrong inside. He refilled it with normal differential fluid (instead of the sythetic which is what he put in there the first time) and added the limited slip additive to it. Anyway, it fixed the problem. No more grinding, binding, rubbing, and whining noises when turning and only a small whine at 45 mph but very unnoticable. I guess the synthetic fluid and the limited slip additive don't work together very well.

[Joe K. 99 Zeee!!]

Some synthetic differential oil doesn't require the limited slip additive. I'm running redline in mine and it specificaly said you don't need to add it.