i wouldnt think it would be the crank if it only changes with vehicle speed not engine speed

 

I experience something very similar around 65-70, i'll be watching this thread. Mine is also an m6..

 

Pilot bushing?

 

i also failed to mention that the vibration does not change a bit from in gear to out of gear or from one gear to another

 

I have the exact same problem and my car keeps eating up the rear tailshaft bushing in the transmission. Pull the tail housing off and have the bushing replaced it it should get rid of your vibration. Problem is, my car keeps eating up the tailshaft bushing and I cant figure out why, brand new trans. I've had my problem since I installed my 9", poly motor mounts, and UMI adjustable torque arm and UMI torque arm relocation bracket. I absolutely hate it and I cannot even tune my car yet because I have a feeling the thing is going to blow up on the dyno when they run it through 4th gear up to 130mph. I havent had the car over 100mph in a year and a half and I'm about to give up. I was told to talk to MADMAN this weekend, so I am going to give him a call on monday.

 

i take mine up over 100 daily. it does get less after about 100-110.

 

oh mine seems to get worse and worse so I dont want to push it to the point where something just blows up, although maybe that will be good because then I'll know what the problem is haha.

 

yea u gotta point there. how hard is the bushing to get 2? lemme guess. you have to unbolt the torque arm and pull out the driveshaft obviously. how involved is it once you get the tailshaft housing off?

 

You have to pull the tailshaft housing off the transmission, which is easier done with the trans out of the car, but can be done with it in the car.

 

what about after you get it off?

 

Have to take it to a machine shop and have the pushing pressed out and the new one pressed in. Im not sure if you can do it on your own or not

 

Normally or in most cases, if the driveshaft is at fault, the vibration will get worse the faster you go & never get better untill you slow down, so i would have to rule out the driveshaft, & possibly the pinion angle too, but you should still check it, at 1st. i was going to say pinion angle seeing it gets worse NOT under a load (letting off the gas), because once you start excellerating, your rearend starts pitching up "decreasing pinion angle", when you let off (no load) your pinion angle increases, but that still should'nt make it less the faster you go, it should in reality, increase the vibration the faster you go.

 

Hey bro I feel your pain. I have the same problem with mine. At 75-85 mph on decel it feels like the trans wants to sit in my lap. However on acceleration no problem what so ever. Once I get my blazer ready for the road I am gonna tear down the T56 on the TA and replace that bushing. The issue we are experiencing is definitely not pinion angle. There is suppose to be a bad *** bushing on the market and as soon as I get the blazer done I'll let you know how the bushing did for it. Hang in there man!

 

No man it only makes the racket on decel not while you are going slower. It almost sounds like the was if isnt set right on the pinion and makes that grubbling sound on decel attributed to someone doing a shitty job setting up pinion preload.

 

Hey man Im drunk but hav e you checked the tires? Out of balance tires can cause hell if everything checks out!

 

Never mind! LOL!

 

Radial separation or bent axle.

 

I have the exact same problem i still have not fixed it yet im 100% it's the driveshaft bushing in the t56, it first occurred when i snapped my driveshaft like a beer can. I ordered the timken 5200 and i'll be pulling the tailhousing off with the transmission still in the car this weekend hopefully

 

I'd go with Jimmard's diagnosis based on aother thread I've been following for a bit.

https://ls1tech.com/forums/gears-axl...nsmission.html

Take it easy
Brewski

 

Same problem here. Assuming it's the tail shaft bushing, would damage to the yolk be possible?