01ssreda4

iTrader: (96)

What I would do is pull the tail and do a bushing and seal. Someone even makes a wide bushing for more support. They aren't too tricky to replace and can be done in the garage if you're patient. You will lose your trans fluid when you pull the tail off.

BMR Tech2

iTrader: (5)

Has the driveshaft been modified in anyway? Cut and lengthened, shortened etc? U-joints being out of phase on the shaft will cause a constant vibration similar to what you are describing

C Murda

iTrader: (24)

any idea on where to get these? is it only a bushing or are there any rear bearing on the tailshaft too? i think i saw a bronze "no walk" bushing on Tick performance's site

the DS was made specifically for use with a 9" which i do have. i even just recently bought a brand new PST DS and im still having the same issues. "out of phase" would mean that basically the DS would be twisted right? at least thats the only way i can think of how it would be out of phase... either way new DS and same problem. i wish one of you guys could be here and actually feel it for your self. it is definitely center line and comes with speed of the DS (im running 4.11s so spinning that shaft to 150mph plus is serious RPMS!) the more i feel it it seems like its coming from the front end of the DS to or maybe thats all in my head but it truly feels that way to me and makes sense seeing as i can feel it all very harshly in the shifter and it will vibrate all along the trans tunnel.

i guess the next step would be to try replacing this bushing in the tail shaft... i mean its not too expensive and what other options do i even have?

01ssreda4

iTrader: (96)

Yeah it may have been tick's bushing, the buddy bought it and brought it over. I just installed it, they are brass so they are very soft and easily damaged. But, no there is no bearing, the bushing cradles the outside of the splined smooth section of the driveshaft and has slotted lubrication holes for trans fluid to get in. They are a wearable item obviously. IIRC the tail of the T56 can be sealed with RTV so you'll need the bushing and rear seal and trans fluid to complete the job.

C Murda

iTrader: (24)

im not having any leak issues that im aware of which is the ONLY thing that makes me think maybe my current bushing is fine? my trans was also the top of the line package stage 5b from sixspeedsinc (t56rebuilds) back when they were in good business. trans has been flawless but im unaware of what rear bushing they may have used in this...?? what would you say is a better part for me a factory bushing or the brass no walk one???

01ssreda4

iTrader: (96)

I'm really not sure. I'm not promising it will fix your issue but ya gotta start somewhere.

BMR Tech2

iTrader: (5)

The u-joint phase would be easy to see. I'm sure a company like PST knows to build a shaft with them in line. Basically just look to make sure the u-joint caps that attach to the driveshaft are perfectly in line.

As for the tailshaft bushing that is a very real possibility as well. It would not necessarily leak because there is a seal that rides on the shaft past the bushing. It should have some fluid coming past the bushing to lubricate it and the seal catches it from flowing out. It may be worth while to pop that tailshaft off and take a look at it. It should fit freely, but not loosely if that makes sense.

C Murda

iTrader: (24)

ok so i finally installed a new tail shaft bushing (rockland no walk) used the appropriate tool to remove old one and installed the new one just fine. i did freeze the new bushing to help aid in installing and it went in nice and tight with no puckering into the oil galleys also applied some red thread locker to the outside of the bushing (couldnt find loctite 609 ANYWHERE i swear NO ONE carries loctite **** at stores unless its super glue) anyways the DS slipped on fine no play anymore brought the car up to speed the odd vibration was still there... slightly less violent to begin with but once up to 115mph+ it felt the same it did before....

now after searching through threads about vibrations and people doing their rear bushing i came across this one thread talking about how the 5/6 gears can come loose on the shaft which will cause a serious vibration that is felt through the transmission (a lot like mine). im coming to this conclusion that THAT may be my problem... what upsets me is the fact that my transmission is top of the line built and i dont know what parts they used as they are now out of business so i dont want to downgrade and buy stock internals...also this now brings me to thinking what could have caused this and im wondering if its the harshness of my locker on the street as with the slamming back and forth of the DS i could see that brutal beating maybe walking a gear or gears off loose on the shafts they seat on??

01ssreda4

iTrader: (96)

5/6 is in the tail and easy to service.

Bob@BruteSpeed

iTrader: (16)

That very well may be the root of your problem. I'll get back to you on a new yoke for your first driveshaft. Thanks. Bob

C Murda

iTrader: (24)

is there any type of write up to do just those gears?? does it require disassembling the entire transmission?
thanks Bob. appreciate everything

01ssreda4

iTrader: (96)

No, they are in the tail and only require tailshaft removal.

99 Black Bird T/A

iTrader: (4)

Just a wild thought. Was the drive shaft out of the car while the motor work was done?

A friend of mine's car developed a vibration which was fixed by flipping the drive shaft around. Apparently when the clutch was replaced and the rear end swapped, the driveshaft also got flipped around and had to be flipped back to get rid of the nasty vibration.

1 FMF

iTrader: (1)

especially for when the car is at speed then you take your foot off the gas.
there's no load, in fact it's in the opposite direction so the rear will want to rotate downward. if you have an aftermarket tq arm those things are beefy and with a poly tq arm bushing there is not going to be any deflection... maybe under a launch from a dead stop with 400+ hp but at steady highway speed 60-100 mph no way. if there was then all the f-body's when new would have had vibes driving 80+mph on the highway, and mine at least when new for the first 10k miles was smooth as can be.

with a different rear axle installed you have to measure the horizontal drive line angle which is dependent on you centering the rear axle via adjustable panhard bar. my oem driveshaft is 40" ujoint center to center. so length in X direction (front to rear) of 40" with rear is off center by 1" in Y direction = 1.4°. compound that with an out of phase of -1° to -2° in the vertical direction = definite vibe!
I know the driveshaft with an s60 is shorter, i assume the same with a moser axle because it's bigger than the oem 7.5" rear, so the rear being off more than 1/2" will be causing a vibe, and would bet $1 that's your problem.
put a 1/2" space between your two fingers, then tell me you can visually tell that difference when looking at the rear of the car standing 10 feet away.
a centered rear is not that it looks centered visually, but a straight line exists from the front engine center of the engine crank through center of transmission slip yoke, extended down to the rear axle pinion you center. once that straight line exists with the car sitting suspension loaded, then you adjust the tq arm to set the vertical measurement so the front/rear ujoints have 0° phase difference, or in my opinion at most -0.1° (axle downward 1/10 of a degree) to account for any deflection under load when at high speed on the highway.

everything above assuming drive shaft itself is not out of balance,
and i always wondered about the carrier and differential being a balanced rotating assembly.
best of luck.

shepss217

iTrader: (5)

01ssreda4

iTrader: (96)

I would try the balancer!

Bob@BruteSpeed

iTrader: (16)

I agree, I have seen it to be the problem before. Bob

FirebirdStud

iTrader: (5)

Did you ever fix this? I have driveline vibrations as well that is driving me nuts.

Phillipm

iTrader: (2)

Old thread, but to the OP, did this ever get fixed. Sounds very similar to what I’m dealing with...