Gears & Axles - anybody run 3.90s in an M6 car with 10 bolt??




mvvette97
05-26-2009, 11:08 PM
I currently have 4.10s but they have some noise. I just installed several sets of 3.73s for some people and they all came out quiet as stock. I was thinking maybe I would go to a 3.73 since they are easier to get quiet "for me anyway" but after having 4.10s I'm afraid I may not like them. I think a 3.90 would be a nice gear but I don't know anybody that run them. What do you guys think of the 3.90?


01ssreda4
05-26-2009, 11:47 PM
i have set up several 4.10s using the factory shims removed from the 3.42s pinion with great success. perfectly quiet. they were Motive's btw.

mvvette97
05-27-2009, 12:11 AM
i have set up several 4.10s using the factory shims removed from the 3.42s pinion with great success. perfectly quiet. they were Motive's btw.
what motive gear were they? the street gear in the blue box or the performance gear in the orange yellow box?


01ssreda4
05-27-2009, 10:45 AM
what motive gear were they? the street gear in the blue box or the performance gear in the orange yellow box?

the 4.10s i have done have been the Motive stock in the blue box. The 3.73s in my car are the Motive Performance in the orange box. All have been super quiet so far. I initially try the factory shim first. It seems to set back lash a little on the tight side like .006. I mocked it up with old hollowed out bearings that are slip fits and do a wipe pattern and it always so far has turned out great. then on final assembly with new bearings i check the backlash and wipe pattern again and they look good so i roll with it. Every one has been quiet.

FirstLSx
05-27-2009, 08:18 PM
I have Motive 3.90's. They have some whine on deceleration, but are perfectly quiet on acceleration.

I've heard both sides of the story, starting to wonder if the whine is because of the installer.

mvvette97
05-29-2009, 01:10 AM
I have Motive 3.90's. They have some whine on deceleration, but are perfectly quiet on acceleration.

I've heard both sides of the story, starting to wonder if the whine is because of the installer.I have had several people tell me the 3.90s won't work in the 10 bolt because the ring gear is too big, so is this not true?

ryansm1
05-29-2009, 02:07 AM
I have had several people tell me the 3.90s won't work in the 10 bolt because the ring gear is too big, so is this not true?

It will fit if you buy the correct size ring gear. Speed Inc. and Texas Speed both sell 3.90s for the 10-bolt; I'm sure other sponsors do as well.

I have Motive 3.90's. They have some whine on deceleration, but are perfectly quiet on acceleration.

I've heard both sides of the story, starting to wonder if the whine is because of the installer.

Insufficient pinion preload would cause whine on coast. You could try tightening the pinion nut a bit and see if it gets better.

I agree that the whine has more to do with the install than the gear set. I installed "thick" 4.10s from US Gear (aka Strange) in mine and they were just as quiet as the 2.73s they replaced, which were also very quiet. I had read that the thick gears should have been noisy, and that the 4.10s were noisier than the higher gears, but I have no complaints.

If you measure the backlash, preload, and make sure your wipe patterns are good, the gears should be quiet. If you abuse the gears, they will probably start making noise. I missed a shift at WOT one day and got some nasty wheel hop, and now my gears whine a bit on "drive." :emb:

2002_z28_m6
05-29-2009, 07:23 AM
My cousin ran some 3.90 gears in his M6 SS. They were a nice gear and he was happy. They were motives and were pretty quiet. He said they made a slight noise but I drove the car and didnt hear anything.

mvvette97
05-29-2009, 08:05 AM
Ok are you sayin there are two different ring gear sizes for the 3.90 or just as long as the 3.90 is for the 7.5 10 bolt it will fit? I just noticed that the 3.90 is a 43 tooth ring compared to the 41 on the 4.10

PAGregSS
05-29-2009, 08:51 AM
I think the different size is due to the different size carriers. Make sure that you get the gear for the series carrier that is in your car as the ring gear thickness is different between a 3 series and 4 series carrier.

mvvette97
05-29-2009, 11:57 AM
I would assume mine is a 3 series since mine had 3.42 correct?

ryansm1
05-29-2009, 12:10 PM
I would assume mine is a 3 series since mine had 3.42 correct?

Yes. The F-bodies came stock with either a 2-series (with 2.73s) or a 3-series carrier (everything else). The 2-series carriers require a "thick" ring gear.

Also, the variation in the teeth on the ring gear is how you get the gear ratio. A set of 4.10s has a 41-tooth ring gear and a 10-tooth pinion, 41/10=4.1. Read the sticky at the top of this forum for more information. The series refers to the carrier, and the 7.5in refers to the ring gear diameter, I believe.