I usually don't like to post the same message on two boards but I am at my wits end and need a lot help.

Thanks All!

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Below is a copy of the message posted on the Tech/Gen. Eng forum:

A few months after I finished my auto to T5 tranny swap my Bird developed a very bad vibration. It starts at about 60mph, peaks at 65 and stops at 70mph. The car is pretty smooth everywhere else, faster and slower.

I asked this question a while ago ( https://www.thirdgen.org/messgboard/...ML/012643.html ) and got a few good responses.

I tried adjusting the pinion angle with shims to raise and lower the tranny. This did not improve the vibes and it might have made it worse.

If I jack up the car and run it up to speed on blocks, with or with out wheels, the vibes are still there.

I have tried two different driveshafts, both with new U-joints and had no change.

If I put it in neutral or push in the clutch or shut the engine off the vibes do not go away until the car drops below 60 or I run into a tree because the wheel is locked . So the engine speed is not important.

The car has new motor and tranny mounts.

The tranny was rebuilt (new bearings and syncros) and had no problems immediately after the install.

Sorry for the long post but I am going nuts and I would like to drive my car again!!

Thanks in advance!

Dale

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1986 FireBird
2.8L MPFI
1/2 CAI
Gutted Cat, No muffler
Was 700-R4 --> Now T5
**** Great cars aren't bought, they're built ****

[This message has been edited by 86Chicken (edited November 04, 2001).]

 

My first guess is the driveshaft but you saud you tried two. Maybe bent axles? I don't know, just a suggestion

 

i had something like the same problem on my 85 2.8 t-5 camaro and my bell housing was cracked just maybe something to look at. otherwise it sounds like it is in the rear end. just my thoughts

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83 z28 400sbc 85 v6 88 v6

 

Well, I checked the axles according to directions stated in the earlier post and never got any feedback on the measurements.

As far as the bellhousing being cracked, How big does the crack need to be? If it is pretty big I think I would have noticed but maybe not. I just had the tranny out about a month ago to dink with the clutch and did not see anything far out of the ordinary.

This weekend I was planning to try to run the car on blocks w/o the driveshaft to maybe elimintate the tranny. I am concerned that w/o a load the vibes may not be present. Any thoughts on this??

Any other ideas??

Dale