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Discussion Starter #1
So I installed a New FRPP 3.73 unit and then I got this weird wobble sound (cant really be felt in the car, only heard) But it only does it when Im coasting. If I just barely touch the gas, it stops. And the rearend doesn't whine or make any other weird noises either.

Thinking it may be the u-joints, I replaced the driveshaft with a Dynotech shaft from dennis. Also wanted it to lessen the vibrations over 80mph. And the wobble is still there.

Then, just to eliminate all other things. I got the car aligned today because I knew it was off. And the wobble is still there. And it is for sure, coming from the back of the car. Dont know if its the rearend, or something else.

So anyone else have this problem or know what to do now?
 

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I just got 3.73's and mine is doing the same. Anyone know what it is?????
 

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Don't call me a Newbie
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397 Posts
I just purchased one of the FRPP units from a guy in Florida, via eBay. It is a brand new FRPP unit and arrived in perfect shape. It'll be a while before it goes in, as I need to gather a few more drivetrain goodies (and a chip), first.

I have a couple of questions, if you guys don't mind:
  1. Did you add the recommended Friction Modifier (M-19546-A) when you filled up the new unit?
  2. Where did you get the unit from?
    [/list=1] Not trying to be nosey, just wanting to see if there is a common thread...and if I have anything to be worried about down the road. :D
 

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ever since I got the new transmission in, I have had the same sound. Its only when you let off the gas at like 70mph or higher.

I'm thinking a couple things myself, but haven't tried to fix it yet. Could be worn IRS bushings because the pinion angle might be off.

Also, maybe the monkeys at the transmission shop didn't index the shaft properly or torque the bolts properly on the driveshaft.

interesting stuff.

I planned to solve my problem with a new FRPP 3.73 rear, and a new MMX Driveshaft, and new poly IRS Bushings.
 

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The Parts Guy
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I had the exact same vibration, which would disappear if my foot was barely on the throttle at highway speeds. First I replaced the front diff mounts with polyurethane ones, which really didn't change much at all. Then I had the driveshaft dynamically (spin) balanced, and I haven't had a vibration since. Well worth the $70 (included new U-joints).

-Rod
 
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