I had 3.90 Motive gears installed in my 05 GT (Automatic) a few months ago.

It has this rather annoying whine at roughly 55 mph. If I go faster or slower the whine is much less. It also whines when I deaccelerate at roughly that speed.

I don't remember the stock gears making so much noise.

Is this normal or is it an installation issue?

Should I go back to the shop and have them adjust it ?

How do you know if it's the gears or the installation that's at fault ?

I heard good things about Motive gears so that's what I chose. Other than the noise it works perfectly.

 

Sounds to me like an installation issue.

 

If you recall my earlier posts, I had issues with Motive 4.10's whirring and a pronounced sonic disturbance at 55 to 60 mph. I took the car back to shop and they warrantied the gear and replaced. The whirring was less noticable but the loud "groaning" sound was still there, just not as bad, and seemed to get quieter as I put more miles on the car.

In the end I swapped the stock 3.31 back in it. On an interesting note, I still get the "groaning", but now it's at 75 to 80mph vs. 55 to 60. Something to do with my rear end and the gear just made it happen earlier in the mph range.

Good luck
Chris

 

sounds like the ring and pinion are not alligned properly IMO..

 

Hmmm, perhaps this noise is normal at a certain speed for most gears.

 

My 4.10s are perfectly quiet - no change from factory 3.31s.

 

My stock gears started whining like that a little while ago. Dealer visit this Wed-Thur and they're installing the axle damper kit (on order) as per a TSB. They said if that doesn't fix it, I'm on my own as it's been modified via Eibach's, LCAs and panhard and they feel the normally inherent noise in the driveline is being treansmitted more readily into the cabin now. Also had them check my pinion angle and it's +.5 but I don't think that's a contributing factor as far as the whine around 50-60.

 

may be it reaches this "harmonic" point where it resonates at a certain speed.