When I shift into gear from park or neutral at idle, about 500 to 600 rpm, there is a loud metallic clunk and the car jumps forward/backward. Any suggestions...

 

motor mounts, tranny mount, loose pinion nut, universal joints are some things to check.

 

The "jumping" may be more noticable now with whatever is causing the play in the drivetrain. The most likely problem is a universal on the drive shaft. With the car on a level surface (no kidding, MUST BE LEVEL) put the rear end in the air, and with the front wheels chocked, and the car securely supported on jack stands, carefully reach under and twist the drive shaft there should be no play what so ever in the joints.

 

How much movement is allowed in the universal joints and how do I check the trans mount? Thanks

 

Universals, ZERO play. Easiest way to check the trans mount is to jack up on it from under the car. It should not move. Of course don't try to jack up the whole car, that will destroy it if it is not already. just lift a little it also should not move.

 

The front joint has a very small amount of movement and I can move the trans by myself. I will replace them both...thank you.

 

I have a 4x4 truck w/240k on it and have done my share of u-joints over the years. Some quick advice for you. Lubed-for Life joints arent, or they wouldnt sell replacements! The joints from Autozone and Napa have been crap for me. Cheap Chinese ****. Try to find a Spicer brand U-joint. They have been the only ones that last for me. Mabe the truck guys will have some other favorites. Good luck!

 

I like spicer u joints myself. I've never had a problem with the Napa stuff either, but then again I've never had a truck with terribly high mileage on it either.

 

Both joints and the trans mount have been changed and the noise is still there! I did notice that with the driveshaft out, the noise is no longer there when shifting into gear. Something in the rearend? Backlash perhaps?

 

You should be able to rotate the pinion a little. If you can move it from side to side, then you'll need to replace the pinion bearing at least. I would pull the diff cover and take a look at what comes out with the fluid. After that, meassure the backlash.

If the R+P have been replaced, it could be that whoever did it did not set it up properly. Could also be the side gears are worn out inside the carrier.

 

sometimes, this happens also, the bolts come loose that hold the pinion snubber on above the yoke, where the drive shaft bolts up to the rear. its that metal plate w/ the rubber nose on the top of it. ive had it happen alot on my cars the bolts break sometimes too if youve been hammering on it real hard, move the plate, if it moves then try tightening it down,

 

I checked the R&P backlash today and it is within specs, but I did notice that the diff pinion gears and side gears move around too. There is also movement where the axles are splined to the side gears. When I rotate the driveshaft by hand in the direction of reverse, I can hear the clunk, but much quieter. Is it possible there is a pinion or related parts problem? Thanks.