car sounds like an unbalanced washing machine

[derbyD]

1973 Automatic 240z started making a sound like an unbalanced washing machine only when the car is under load. One of the passengers said it sounds like a dyeing jet engine. I have jacked up the rear and put blocks under the rear to get the rear wheels off the ground. The wheels spin smooth. When the car is in neutral and you spin the rear wheels that causes the drive line to spin unless I hold it and stop it from spinning. If I allow the drive line to spin I hear an uneasy clunking noise coming from the tail end of the tranny. When parked on a slight incline about 10 degrees the car rolls down hill when in park. We just had a mechanic replace the rear bushings, drive line u-joints, neutral safety switch and he adjusted the shifter and linkage so it would line up better in relation to the letters on the shifter selector assembly inside the car. I have 2 main questions: 1) what would you guess the problem with the car is and 2) would you think the mechanic may have caused the problem?

[siteunseen]

If it rolls in PARK I would think it's adjusted the wrong way, no offense to your mechanic.

I take that back! and you should too.

Edited February 2, 2014 by siteunseen

[Mark Maras]

After making sure the car is safely supported, with trans. in neutral & the hand brake off, crawl under the car and grab the drive line just behind the front yoke and push & pull on it in all directions, rotate it & do it again. If you see ANY movement other than rotational you're looking at the problem. Example. Changing u-joints, a while back, I lost one of the new c-clips so I used one of the old ones not noticing that it was a bit thinner than the new one.It allowed the u-joint to shift sideways with a barely perceptable movement. I didn't discover this until I took the car for a trial run to admire my expertise. The car felt and sounded like there was an 800 lb. bumblebee in the car. I think that your movement will be more obvious. As far as the mechanic causing it? You know what he worked on. Mark in Portland

[derbyD]

Thank you both your your help. I did put the car up on blocks and push/pull on the drive line yoke itself. The yoke does move side to side & up/down just a little bit but I dont think it should move at all. The drive shaft does not move in n out at all. Mark you statement of "sounded like there was an 800 lb. bumblebee in the car" describes the sound very well. Siteunseen, I have left the mechanic a message to call me so I can take it back to him. Thank you both.

[djwarner]

Back in the early 1970 I bought a 510 wagon with one of the first Japanese automatic transmission in the US. While tooling down I10 at 80 MPH near Winslow AZ with 11,994 miles on the clock, I heard a loud bang and violent vibration began. Fortunately, I was just coming up to the exit and pulled off to a gas station. Up on a lift, the mechanic took the front end of the drive shaft and wobbled it around in a nice circle. Pulled the drive shaft and the sleeve bearing in the rear end housing slipped out with it. A half moon shaped chip had broken off the bearing and lodged between the bearing and spline. This spun the bearing in the aluminum housing and taken out the rear seal.

The mechanic proudly explained there was a Datsun dealer in town, the local John Deere dealer, and the owner's son did the service work. On the way into town, I found that less the chip, I could accelerate up past 55 and ease off the throttle the vibration would stop until I slowed below 45.

At 11,998 miles on a 12,000 mile warranty, the owner's son explained that he had never seen an automatic transmission, let alone one on a Datsun. He asked which way I was going and suggested I try to drive it back to selling dealership in Delaware or at least further east to a larger city. I got a letter explaining the failure had occurred while under warranty, and bought 4 quarts of transmission fluid.

Headed east. The interstate was still under construction then and I was repeatedly dumped onto service roads dropping my speed below the 45 MPH trip point. Got as far as Dallas before it gave out. But because the transmission was new to the US, there were no parts available. After a week in Dallas, the regional Datsun rep told the dealer to pull the parts from a new car.

Funny thing is that I had waited to buy the wagon until the Japanese transmissions were available because the Borg Warner units used previously had a poor reliability reputation. What I didn't know was that the Japanese unit was the Borg Warner design made under license.

Edited February 3, 2014 by djwarner

[Mark Maras]

derbyD

It should be easy now to determine the cause. Even a tiny amount of movement in the front u-joint will sound terrible. djwarner has made a good point. Anything wrong in the tail-shaft housing will give you the same symptoms. Have you determined which it is. Is it possible the mech. did the same dumb thing as me and used an old retainer clip allowing a tiny bit of movement? Mark in Portland