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well 1st and second are smooth, in 3rd now with the car on stands i can feel a vibe at 35mph, i can feel this with my hand on the car, it comes and goes when i change rpms it will stop at certain speeds and rpms, then it will come back. At around 45 to 55 i dont feel it, the it starts to show up around 80. i dont see anything moving out of the ordinary. i measured the rear from side to side and the rear is 3/8" more to the passing side. if that matters or not., how bent would the rear housing have to be to cause this, or would it? i looked at the harmonic balancer and it doesnt even look like its moving, so i dont think theres an issue there, and the motor doesnt even look like its running thats how smooth it looks. if it was something thats not in or near the rear would it still cause only the rear ujoint to go bad. if it was something from the transmission tail shaft forward would it try to eat the front ujoint and not the rear. Im thinking its something in the back end cause it only eats the rear ujoint

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Since you've changed most everything I would have to
start looking at the engine. Since it comes and goes
its a frequency thats multipling. Most of the time
if its a problem with something thats on a centerline
such as a trans(all the items are balanced to a
centerline)the problem only gets worse with the higher
rpm, not coming and going. The engine can run into
frequecy issues, coming and going. I wish you could
un-bolt the converter and run the engine by itself
just to eliminate things. Dont be so sure about the
engine or trans taking out the front U-joint and
the rearend being the cause for rear U-joint failure,
cars do alot of funny things when something is going
in and out of frequency and can transmit it to
strange places

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when i had the motor redone 2yrs ago which just reringing it and new rod, main and cam bearing and oil pump, the motor was smooth as glass, which it feels now, when i put my hand on the car and can feel the vibes i dont feel it near the motor only from the door back i feel it, thats where its the strongest. i was holding my hands on the motor at 35 mph with rags and felt no vibes but when i walked around the side of the car and put my hand on the driver side rocker panel thats where i can feel it

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I want to know how in the hell you can put your hand on the motor at 35 mph......must have a long arm.

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ROFLAMO i had the car on jack stands in the garage and my wife was in the car

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I see where you used three different driveshafts but did you have any one of them balanced by a machine shop?

are you absolutly sure the U joint fit's the rear yoke, had one on a car once that the U joint was a little narrower that the tab's in the yoke that center the U joint, and it was to one side more than the other and threw it off balance.

did you witness the rotation of the driveshaft when you had it on the stand's to make sure it was running true, I think total runout is supposed to be .010-.015 across the length of it.

that's all I can think of right now.

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U-joints are phased right????

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U-joints are phased right????

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not sure what that means

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Meaning that each is lined up with the other, instead
of being clocked a little wrong.... but you have
had 3 different d-shafts in it so I would say that
you have eliminated that(still just guessing)

How bad of a viration is it at 80mph and what does
that translate to in rpm at the engine... its a
rpm issue and not a speed thing. I'm sure that if
you changed gears in the rear that the speed of the
vibration would change so its all about rpm of any
given component

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did you check the front & rear wheels?
balanced or bent rim if seen cause it also at different tspeeds.

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I'm thinking you have hit it right on Mike..

If he has changed gear ratios, but the vibration stays at 80mph, than it should be easier to narrow it down..


Chris..

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U-joints are phased right????

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not sure what that means

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Meaning that each is lined up with the other, instead
of being clocked a little wrong.... but you have
had 3 different d-shafts in it so I would say that
you have eliminated that(still just guessing)

How bad of a viration is it at 80mph and what does
that translate to in rpm at the engine... its a
rpm issue and not a speed thing. I'm sure that if
you changed gears in the rear that the speed of the
vibration would change so its all about rpm of any
given component

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I'm thinking you have hit it right on Mike..

If he has changed gear ratios, but the vibration stays at 80mph, than it should be easier to narrow it down..


Chris..

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when i put the 3.23's in, the vibes were at about 110 mph, it just moved farther away

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This all relates back to a rpm, do you know what
the rpm's were for the 110 speed and the rpm's for
the 80 speed, does it corrilate to the difference
in gear ratio where the d-shaft is turning the same rpm?

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I'm thinking you have hit it right on Mike..

If he has changed gear ratios, but the vibration stays at 80mph, than it should be easier to narrow it down..


Chris..

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when i put the 3.23's in, the vibes were at about 110 mph, it just moved farther away

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This all relates back to a rpm, do you know what
the rpm's were for the 110 speed and the rpm's for
the 80 speed, does it corrilate to the difference
in gear ratio where the d-shaft is turning the same rpm?

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i cant remeber the rpms with the 3.23's , i'll get a better number with the 4.30s next time i take it out. but since i still have the vibes with both the 430s and the 323s, wouldnt that eliminate the gears?

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Without thinking much, that tells me that IF the
2 ratio's have the same d-shaft rpm then the problem
is the d-shaft forward, eliminating the rear end
and its compotents

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i think i agree with ya there, the only other part that i didnt change was the flex plate. it is a b&m externally balanced pc. i didnt see any cracks and it didnt look to be bent. the converter holes lined up perfect also

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the first time the tranny was apart was over the winter and after that is when they started, the front drum was wiped out, so now i have another new one in there and still now change

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I have a question now. Are you saying the problem started after the trans was put back together with a new front drum?

If so maybe the drum is bad and out of balance