I searched and nothing seems to exactly apply. When I start the motor and shift into 1st I get a dull thump/clunk after an instant. I think the clutch drags and takes up slack. Shifting then into reverse I get the same thud. A shade tree mech says I have pinion shaft bearings going out but I can't trust him. He won't do the work so there is that angle.

How do I trouble shoot this?

Thanks,

John

 

This COULD be a few things. The pinion shaft bearings like your mechanic said / a failing u-joint / excessive backlash in the differential gears (ring and pinion). Possibly other things. I would get the rear wheels off the ground and jack stand the truck safely. Then I would check for play back and forth / up and down when turning and moving the driveshaft by hand (transmission in neutral). If any of the failures I mentioned above are taking place, it should show up right then.

 

I know I have a u-joint issue: Starting out I will hear a sharp PING and tghe drive shaft rings. My experience tells me that a joint has end to end play and when torqued the joint slides inside the roller bearings to stop and hit like a small hammer. Been doing that for a couple years. I know a joint will find center after it gets spinning so I haven't bothered.

I will get under it and twist/torque all the joints and see if any have play. Then I will do what you have4 suggested. I didn't think about trying to move the pinion shaft by hand. Rotating a single rear wheel while the other is on the ground should show up play in the entire drive line. You have b een a great help and once it drys out here for a day I will try all that.

 

Just don't let that u-joint get too bad. If it cuts into the bearing cup, that can snap in half and the driveshaft can come out... not fun (more like a scary carnival ride). Anyway, best of luck when it dries out! :)

 

Thanks

 

I don't understand......u joints aren't expensive, why put it off for a couple years?

 

I have had that problem before. It doesn't hurt anything but is annoying. All u-joints must have a little slck/clearance to allow the joint to find center after first rotating Finding true center keeps the shaft from vibrating.

I have all three joints in a box for a couple years but never found the opportunity. I am 75 and I don't work on my cars like I used to but do care. And when I need service I sometimes go to a shop. Living on a med disability retirement I keep the shop visits to a min.

Here in Eugene it rains for weeks or months on end so you can easily forget about a small problem.

Thanks for all your comments.

 

I hope I am still able to work on my truck when I'm 75! :)

 

No ****!!!!! I understand now.... but come to think of it @75 yrs old he probably doesn't drive the trk much anyway, so a couple years could be very little use....

 

10 to 15 K miles per year. I love my truck. Thanks guys.

 

Damn, I see u still drive a lot!!! in that case I'd say that's a lot of driving on sloppy joints....

 

Not to mention sloppy driving.