Driveline Vibration

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Jmac81d

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Hi guys, new to this site and new to Mopars, I have a 70 340 Duster with a 340/727/8.75 rear. At speeds above 30mph I get a very bad drive line vibration. I got underneath and looked for play in the u joints, they seemed fine but I found a lot of play (.187 in play) where the drive shaft slides into the transmission. So I have the following questions.
-Can the tailshaft bushing be replaced without the transmission being pulled.
-Could it be possible that the drive shaft is to short?
-How much of the yoke should project into the transmission?
-How long is a stock drive shaft for this car?
-What is normal for play between the spline and yoke?

Great web site, Thanks for your help in advance...... Jack

ps: This car was a four speed converted to the auto, could that be a factor?
 
When I swapped from a 904 to a 727 in my 73 scamp I was getting a vibration above 40 mph. I noticed that the 727 didnt have the counter weight on the tailshaft and the 904 did. The weight off a 904 wont work on a 727 so I had to look in 3 junkyards untill I found one, no more vibration.
Just something you might wanna look into.
 
Thanks for the reply, I looked at my transmission and did not see a tailshaft counter weight. Is the tailshaft weight standard equipment on all automatics?

I will look into getting one right away.....Thanks, Jack
 
Jack, I'm not sure what the exact lenght measurement would be for your driveshaft. As far as the spline into the transmission question is concerned, if the spline is inserted fully into the rear of the tranny, then pulled back approximately 3/4" to 1 1/4" you should be in the ballpark. If there's any more play than this, it could very well cause your vibration problem. And welcome to the board and the world of A Bodies. :)
 
360scamp said:
When I swapped from a 904 to a 727 in my 73 scamp I was getting a vibration above 40 mph. I noticed that the 727 didnt have the counter weight on the tailshaft and the 904 did. The weight off a 904 wont work on a 727 so I had to look in 3 junkyards untill I found one, no more vibration.
Just something you might wanna look into.
Click to expand...


what was your vibration like?
 
Thanks for the warm welcome......The vibration comes on strong between 35 and 40mph, will not go away until I slow down below 30. Vibration is driveline and or transmission. U joints are fine, weights are in place, pinion nut is tight, stock driveshaft has about 1.25 inch of clearance before yoke bottoms out into transmission. 4deg. of pinion angle in the right direction.
Tailshaft weight is not installed. Drive shaft looks straight when run up on jack stands. No leakage around tailshaft seal that would indicate a bad bearing.
What else could it be? Should I have the drive shaft balanced anyway?
Thanks for your help, Jack
 
Jack there are a couple of things you can try to determine if the vibration is in the driveshaft or not. The first thing I would do is remove the shaft at the rear end, turn it 180*, test drive and see if the vibration frequency/speed/dynamics change any compared to now.
Another old timer trick is to put a couple of hose clamps on the driveshaft and keep moving the heads of the clamps around to see if the vibration changes or not. Start with the clamp heads on opposite sides of the driveshaft, then progressively move then toward each other to see if there's any change. Cheap man's balancing act, so to speak. :) Good luck.
 
The vibration I would get would come on at 37-40 mph and get worse the faster I went and it would shake the whole car when slowing down.
I had a new custom driveshaft made and ballanced and was still getting the vibration after taking it back to the driveline guy twice and after I checked the pinion angle 3 times, got new tires, had the wheels and tires ballanced, ect..
I was just about to pull the tranny and have it rebuilt when I noticed the old 904 I pulled out had the weight on the tailshaft and the 727 didnt. I tryed to swap them but the 904 holes wouldnt line up. i found one off a truck in a junkyard and the vibration went away.
I don think that it is standard equipment, when I was looking for one only about 10% of the cars/vans/trucks I looked under had them and most of them were 904's.
If anyone knows what cars they came on and why some have them and some dont I would be interested in finding out.
 
hmmm...i checke dmy pinion angle too, and had the tires balanced...and the driveshaft is a new one from whoever supplies Mancini. Mine is a slow vibration, at 45-55, and then it is like a super high frequency from there on up, but mine doesn't do it all the time.
if you make a sound like a bee, that is like the vibration i get at 55+
 
I am thinking it is not just one thing that is causing the problem but a combination all working togeather to give me the shakes.
Since I do not have the tail shaft damper installed, I am going that route along with the gear clamp balance method. I have already located the proper damper for a 727, I will try it out and see what happens.
Thanks, Jack
 
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