Just finished installing the 4.10 10 bolt in the firebird. The car has pretty close to full suspension in back (torque arm, LCA's, panhard rod, springs, etc). The transmission has a mild shift kit. After installing the rearend, I took the car for a test drive. Every hard shift would cause a loud bang from underneath. I'm wondering if it's a broken tranny mount (the tranny mount was replaced not that long ago, and it didn't show any signs of it shifting sloppy with the old rear), if I need an adjustable torque arm, etc. Any ideas are welcome.

Throwing in a picture, just incase it'll help:

 

take some pinion angle out of it and see if it gets better.check the mount while youre under there

 

I am having the same problem, my torque arm actually bent and came out of its "bracket" though. The torque arm basicly is sandwiched in between two pieces of metal with rubber in them. It connects to the tail shaft of the transmission and then connects to your rear. When changing your rear it may have slid out of that "bracket" on the transmission. There is nothing except the rubber to hold it in if you pull back on it. The torque arm keeps your rear diff from moving up and down. If you get under your car you will probably see that it is no longer connected to your transmission. Just pull the bracket off undo the two bolts that sandwich it together put it on the torque arm and reconnect the bracket to the tranny. When you move the torque arm up and down it will move your rear diff which will cause the tires to move so be carefull when putting it back into the bracket.

 

In my experience that sounds like the tranny mount...

 

Yeah, that's what my tranny mount sounded like too. Just in case it is the torque arm (crossing my fingers for ya that it isn't!) there is a mfr out there that makes one that attaches to the tranny crossmember, & takes the stress off the tailshaft... (I want to say it's Spohn, but I'm not 100% on that... )

 

Thanks for all the replies guys! Just to add something in here... The torque arm is a BMR, is new and is still solidly attached (we just put it in). Will check the trans mount, hopefully that solves things. Thanks!

 

Make sure to buy a polyurethane tranny mount instead of the stock rubber one.

 

ok i was aboust to ask if you got a relocated torque arm, because i belive witht he SPohn Torque arm that bolts to the frame instead of the transmission you actually have to bend the floor board up slightly. but since you have the BMR and its mounted to the stock position it is prolly a trans mount.

 

I love my solid mount!

 

I have a clunk too. No difference with the rubber mount or poly trans mount. I just hated the vibrations with poly mount, and I have tried 2.

Maybe I will look at that Torque arm....

 

A bad trans mount on my Jimmy caused a thump on the floor pan going over rough bumps.The extra weight of the transfer case did minimize this to some degree.I replaced the mout and problem solved.