vibrations ugh. what do you guys think?

[73restomod]

To check the angle on the trans/motor you'll need to place the angle finder on the oil pan rail. If the pinion is 5 down the trans needs to be set at 5 degrees up, which is so high I doubt there is room in the trans tunnel to do it without some sort of interference. I would stick a 2.5 degree wedge under the leaf spring pads, to bring the pinion angle around 2-3 degrees down. If the pinion u-joint and the slip-yoke u-joint are not at the same angle it results in them running out of phase, causing all manner of nasty vibrations.

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[calicuda70]

73restomod  thanks for the advice im hopefully gunna check that this weekend kinda hoping that its something like that i know just from eyeball my tranny cant be 5 up so im hopefully on the right track with it

[calicuda70]

well guys got home yesterday and just for ****s and gigs i took the shim from the rearend and fliped it so it was pointing the rearend up 5 degree instead of down what a difference so i got the ramps today it will be going up on al for fours and setting thranny angle with shims what angle should the tranny be at 0 or pos1 degree or more what ya think? cuz i know its wrong that the rear is up 5 now

thanks james

[73restomod]

My service manual, shows a picture of a level bubble, for setting the angle. Chrysler used a special tool that bolted to the engine oil pan rail (manual) or the trans oil pan (auto). It was really just a hands free bubble level. It shows that the bubble was past the first rear line slightly, which would indicate that at ride height the trans tailshaft is just above level. It goes on to explain that the second line to the rear is the acceptable maximum up angle and that it is a half degree more than the first line. I did some digging and found out that the transmissions ideal angle is 1.5 up +/-. 5 degree. Also according to the manual a 3/16 shim is worth roughly a quarter degree.

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[73restomod]

The reason behind this was because, from the factory, our cars sat nose high. Engineers reckoned that having our driveshaft parallel to the road surface would reduce unwelcome harmonics and vibration while cruising.

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[calicuda70]

well i shimmed the tranny up some about 2 washers and that seemed to do the trick amazed me. then come to find out in the 70 challenger service manual this was a common issue back then they even say to shim the tranny if its not at the right angle and to think i thought the big owl yellow book was crap haha thanks for all the input guys!

james

[1970 RT Challenger 1970]

Good Vibrations now!

[barracuda7199]

You are running the b&m flexplate with the half moon cutout and a counterweighted torque converter? The b&m flexplate makes where you need a non counter weighted converter which in my opinion is the way to go.

[calicuda70]

ok so what you guys think it was completly gone after shimming the tranny and then i drive it into work today and it starts to vibrate again not as bad but a lil lighter should i shim the rearend down now? so damn mad and lost in what to do!

[cwestra]

ok so what you guys think it was completly gone after shimming the tranny and then i drive it into work today and it starts to vibrate again not as bad but a lil lighter should i shim the rearend down now? so damn mad and lost in what to do!

I feel your pain.  I have been struggling with a very similar problem on my '70 Cuda for a couple of years now.  Mine starts to kick in around 65 mph and gets pretty nasty if I keep pushing it.  The funny thing is that I can usually get it to go away if I push the clutch in and let it out very slowly while at higher speeds.  I can't explain it but something happens when I do that.  Something must move.  Mine appears to be related to vehicle speed, as I am unable to produce it in any gear other than 4th.  When I push the clutch in I feel it hard in the pedal until I release is slowly.  I believe it is isolated to somewhere between the rear universal and input shaft of my trans. and it's translating through these components to the pedal.  Not noticeable around town but very frustrating on road trips, I know.

Anyway, I've been following this thread closely hoping you'd find a solution.  It was certainly encouraging when you adjusted your angle and got good results.  In fact, that's what I'm in the process of experimenting with right now on mine.  We could have the same problem or maybe something completely different.  Anyway, hope you find the solution.  If I come across anything that might benifit you I'll certainly let you know.  Good luck.