Sloppy slip yokes

[CurtDawg510]

i have my 70 duster, 360,4speed,8 3/4
Its fun, and scoots along pretty good for a street car i drive around... but i cant get rid of my dam slip yoke vibration

The vibration get noticable around 60mph and gets nothing but worse.... any gear, clutch in, neutral, it dont matter.... at 80-85 its shakin the shifter bad, and im waiting fot the driveshaft to catapult mein the air!!!

So i have replaced the tailshaft extension housing bushing, no change, and the old one still looked new...and i have bought two PTI? Slip yokes from summit racing, and thoz all seemed to be looser than the old 70s mopar yoke.... and vibration was real bad, i could even shake driveshaft and watch the seal move around... i dont kno how it never leaked...
Now im running a spicer 1350 yoke that fits better than any of them yet, but i can still shake the driveshaft and it still shakes the car goin down the highway

Anyone got any ideas? Im stuck??
It be nice if someone made tight fitting slip yokes... if i gotta rebuild this tranny just to put in a better output shaft, im goin with 5 or 6 speed

 

[rustycowll69]

have you checked the driveshaft between centerse in a lathe? If you don't have access to a lathe, try spinning the shafts in some v-blocks. You probably shouldn't have more than 0.010" runout.

 

[fishy68]

You would be amazed how loose a yoke will feel with just .005-.008" clearance. I'd have the driveshaft spun and checked for balance. Most likely you'll find it's out of balance causing the vibration

 

[RustyRatRod]

Is that like sloppy seconds?

 

[j par]

My first thought was pinion angle.

 

[fishy68]

My first thought was pinion angle.

That'll do it too

 

[rustycowll69]

My first thought was pinion angle.

my first thought was insufficient slip yoke engagement in the back of the transmission. I don't think you should have more than 3/4" of slip yoke hanging out from completely bottomed out. Sometimes when swapping engines, transmissions, rear axles people get a little careless or too frugal trying to make a driveshaft they have work, instead of getting the correct length, or having a custom driveshaft made for them.

 

[j par]

Personally I always have a custom Driveline and U-joints made and balanced for all the obvious reasons. Besides it's in my opinion they're reasonably affordable for what you get, but like you are pointing out about mixing parts and sometimes that's where a pinion angle can get out sometimes also. My first clue was a 360 didn't come in a 1970 duster I don't think?

my first thought was insufficient slip yoke engagement in the back of the transmission. I don't think you should have more than 3/4" of slip yoke hanging out from completely bottomed out. Sometimes when swapping engines, transmissions, rear axles people get a little careless or too frugal trying to make a driveshaft they have work, instead of getting the correct length, or having a custom driveshaft made for them.

 

[Tooljunkie]

First year of 360 (70 or 71) was internally balanced. After that they were externally balanced.
I jus repowered a 59 regent, 400/727
Had a vibration just like you described. I had shaft shortened, too short, found another and tried again,and shimmed pinion down and transmission up. Almost zero vibration
During shortening process, machinist pointed out how crooked yokes were,using test bars. When he was done it was dead true and square. No balance issue.