1970 Challenger , 360, 727 , 8 3/4

When going down the road , bad vibration at 45mph
and up. When putting in neutral , almost all goes away. Engine in neutral is very smooth. (all rpm's)

Trans is rebuilt, with weighted torque converter.
New trans mount. Drive shaft is balanced and new u-joints.

When unbolting driveshaft and pushing completely into trans , how much space should be at rear u-joint and rear yoke?

How can I tell if it is in the Rear end itself, bent axle, or if it is inside the trans??

Please help, Thanks Mike

What are your driveline angles?

Its been awhile since I checked them, If I recall it is 1 1/2 degrees down on rear end and 1 1/2 degrees up on trans. Not entirely sure but thats what I recall

This car was an original slant six/ 904, Converted over to a 360, 727, everything new (everything)

When accelerating it is really bad. Feels like a tremor starting at the firewall and traveling under the console the whole way back to the rear

Vibration gets better when slowing down

Sounds like incorrect pinion angle.

After the swap was it OK then it developed? W the trans mount/bolts good I'd open up the ujoints & check for any needle problems/looseness anywhere.

Are the balance weights missing from the torque converter? Check the U-joints to see if they are centered in the yokes, if they are not they will bind and cause a bad vibration.

All u-joints are new, but I rechecked them, all needles are good , and u-joints are greased.

torque converter does have the weight on

when you disconnect the driveshaft and push completely in how much distance to the rear yoke?

Mike has it vibrated like this ever since the swap? My money is still on the driveshaft (angles/ujoints). On my 65 dart 318/904 I used a driveshaft that was too short and the yoke did not engage the tranny splines enough (way more than 3/4") and you could feel the play of the yoke on the splines as you slid it in and it vibrated mostly on decell but nothing like yours is. I found the correct shaft that was less than an inch longer & that solved it

Checked pinion angles with suspension loaded
as driving down road

Drive shaft angle is -2 degrees down towards rear

output shaft of trans is at 0 degrees

Rear end at flange is -3 degrees.



What is needed, do I have to lift the trans?
or change the rear end?

It has been there ever since the swap.

I had the tires road force balanced

I've seen the weights come of the torque.
check and see if the u joints stayed centered may a clip is off??

I had a similar problem with similar symptoms on my Challenger. Turns out that my brand new, and supposedly balanced driveshaft wasn't balanced at all...

weights are still on the torque,

What about the readings for the pinion angle