I just installed a set of FMS 410's in my 04 GT and now have a thumping sound when I decellerate or coast.The thumping slows down along with the speed,but goes away when I'm on the gas.There's no howl or whine whatsoever.The pinion depth was spot on with the original shim, and I set the backlash at .010.
I pulled the cover and rechecked the backlash and it was still fine.
I wasn't real happy with the way the Trac-loc was acting, but I had another one on the shelf so I put that in along with a new set of carrier bearing,and filled it again with Royal Purple.While in there I also rechecked the pinion depth and preload but they were just like I set them.The car only has 20,000 miles on it but I checked the u-joints and wheel bearings but they are fine.I jacked it up and ran it but by myself I couldn't really pinpoint the noise but if I remove the wheels the noise goes away.
I've been under the car hitting around hoping to find something loose but no luck.This was my first 8.8but I've done plenty of other R&P's but this one has me stumped.

 

I think I may have a defective set of gears.I opened it back up, still couldn't find anything.I left the driveshaft hooked up and started rolling the axles by hand when I noticed a clunk or hard spot.I marked the axles and found that the noise happened in the same place everytime,so I'm guessing there may be a bad tooth on the ring gear.If it was the pinion with would do it 4 times a rotation.Does this make sense? I may put the 3.27's back in tonight just to see what will happen.I am getting pretty good at tearing down.I get alittle Quicker each time I do it.

 

im sorry, but that thread title just sounds so damn wrong. [&:][&:][&:]

 

i think you have a defective gear
i set up gears for my job almost everyday and i have no idea what would make this happen
but somebody else might so wait afew and see if someone chimes in

 

I've got a chance to get a set of Motives this weekend, so I think I'll put them in and see what happens.Hey Murdoc, I glad you liked the title.I didn't think about it until you said something.I wonder how many people lookedat thisfor the wrong reason.

 

When I had my 4.10s installed, they couldnt only get either the accel or decel right. I told them to redo it and it turned out it was a deffective set of gears.

 

Hey Guys, Just an update.I just put in the Motives and drove it and it's all good.No clunking or gear whine so I think I've got it.Now I need to learn how to drive it all over again, but that's the fun part!Thanks for all the help!!

 

Please stick to o/t if you have nothing to offer in the tech sections!![&:][&:][&:]