Vibration after gears replaced

mlmealey · Apr 13, 2006

I have a 2001 GT and I began to notice a chatter from the rear end at low speeds while turning. I then took it to my local mechanic who advised me that the rear needed rebuilt.

He installed a used set of 3:55 gears that had less than 2k on them (seemed like the most cost effective means at the time). This corrected the low speed chatter but I began to get a vibration at high speeds, 65mph and up. The vibration would get worse the faster I went.

I took the vehicle back and the mechanic thought it would be the pinion baring. This time I purchased an entire rebuild kit and new 3:73 gears.

I got the vehicle back last evening and I have the exact same issue.

The mechanic also advised me that the front wheel barings were in need of replacement.

My question is this… Has anyone had a similar experience? Could the vibration be due to the front wheel barings and it is just coincidence that it occurred at the same time the rear end was worked on? Or is it that the gears are not setup correctly?

I do not feel the vibration in the steering wheel where I would assume that you would feel a front end issue. However I do feel the vibration on my feet and on my rear while setting in the seat.

Any advice at this point would be greatly appreciated.

Thanks,

Mossberg · Apr 13, 2006

All you probably needed was your driveshaft to be balanced or get an aluminum driveshaft.

Give Me TP · Apr 13, 2006

Sometimes the driveshaft will cause vibrations after a rear gear change, either by not being reinstalled in the the same postion it was originally or by being slightly out of balance, which will be magnified at higher rpm. The easiest check is to see if any reference marks on the drive shaft (at the pinion flange end) are lined up.

mlmealey · Apr 13, 2006

I have read several posts about gear changes and drive shaft issues that may occur. It “appears” that several individuals have fixed their issues by replacing or upgrading to an aluminum drive shaft.

If I do go this route do I also need to replace the yoke? I would also assume that I should go ahead and replace the U-Joints at the same time.

hognutz · Apr 13, 2006

I have no vibration issues with 3.73's and stock driveshaft. I think your mechanic is guessing. You can see wear. Are the parts he is replacing bad? if the same issue is there this tells me what he fixed is not the problem. a chatter in the rear end wile turning can be you clutches in you LS. you can add friction modifier for that. you should always be able to see part failure and it makes me wonder if you original parts were bad or not.

If you ujoints are good and your driveline is balaced you will not need an aluminum one. now if you would rather try a new driveshaft and fix your original so be it but people who think you have to have an aluminum one are mistaken. buying a new driveline is easier though just more expensive.

like your wheel bearings for example. they may very well be bad but you can inspect them to see if they are bad.

my .02 is find a different mechanic as his repairs are not fixing your problems.

blackfang · Apr 13, 2006

He probably did not index the driveshaft. A simple rebalance with a hoseclamp will work. I did that and it fixed the issue for about 2 years until I got an aluminum driveshaft.

Mike97gt · Apr 13, 2006

you need a new mechanic. the chattering in low speed corners is the traction lok clutch discs. there is a TSB on them. the vibration at highway speeds is most likey because this dim wit negleted to index the driveshaft.

before he has you wasting any more money you need to remove the driveshaft and turn it 90 degrees untill the vibration stops.

BlackenedSVT · Apr 14, 2006

Mossberg said:
All you probably needed was your driveshaft to be balanced or get an aluminum driveshaft.

yeah that is your vibration problem. The new gears throw off the factory calibration of the driveshaft sometimes, and it vibrates while at certain highway speeds. When i installed my 4.10s in my 98GT, i would get a vibration on the highway between 80-85mph, and it would get really violent at like 90mph. But if i went 95+ it would go away, and if i went slower it would go away.

Just need your driveshaft balanced. I think its like $100

BlackGT4.6 · Apr 14, 2006

Did they put friction modifier in it when they refilled it if not your traction lock could be shot aswell. Or the drive shaft could have not been reinstalled correctly as stated previousley.

blackfang · Apr 14, 2006

Like Mike said, rotate it 90* and keep doing that until it goes away. If it doesn't, a hose clamp on the d/s near the pinion, and rotating that will work. I dont have the diagrams from my cd rom describing the process at work, but I will post it later.

Vibration after gears replaced

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