Loud Grinding from tranny?driveshaft?

[funguseater]

Hey all

I was out driving up a pretty rough logging road when suddenly I hit a rock and the car jumped into 4x4. It had no problems going back into 2wd but after that bump a very load grinding sound started. I crawled under the car and noticed that some bolts holding the drive shaft up were loose. I tightened them up and now I have no noise except when the car goes over bumps or rough road, then the noise comes back. The tranny still shifts great through gears and the car drives fine on flat roads, but I fear potholes. Any Ideas what could be causing this part time rattle/grind.

Any help appreciated.... DAVE

[splatterdog]

Could be the hanger bearing on the rear driveshaft. Just did my first one on my 85 this last winter.

You can use a screwdriver butted up against your ear and held to the part in question as a stethoscope while the car is jacked up and everything is rotating. Make sure the car won't fall on you while listening and stay clear of rotating parts....

[Petros]

sounds like something got bent, a sheet metal part, that is rubbing against the drive shaft. Jack up the car good and solid, and crawl under it and just inspect it carefully. Try and find the place where it was impacted. You might notice something near or touching the driveshaft, u-joint or some other moving part. likely you can just bend or pound it back to regain the clearance.

Also check the dust sheild on the front disks, and the brake backer plates on the rear. I bent one once on a CRX when I lowered the car to the garage floor, wheels off, because I needed the jack stands for another project. Did not think I harmed anything, but a front dust sheild got bent. It sounded REALLY bad when I got the CRX running again, grinding, grinding, grinding. Easy fix.

look for the simple solutions first.

[funguseater]

Splatterdog

Yeah, that bearing was barely bolted on when I checked it. I'll have to crawl under tomorrow and check again for any bent shielding and listen to the noise. Thanks Petros I forgot that dust shield, I think its still there...

[takza]

Could be the hanger bearing on the rear driveshaft. Just did my first one on my 85 this last winter.

You can use a screwdriver butted up against your ear and held to the part in question as a stethoscope while the car is jacked up and everything is rotating. Make sure the car won't fall on you while listening and stay clear of rotating parts....

Safer thing is to use a length of vac tubing? Something solid transmits sound real well...but you'd look silly with a screwdriver stuck halfway into your ear?

[splatterdog]

You can use a screwdriver butted up against your ear and held to the part in question as a stethoscope while the car is jacked up and everything is rotating. Make sure the car won't fall on you while listening and stay clear of rotating parts....

Safer thing is to use a length of vac tubing? Something solid transmits sound real well...but you'd look silly with a screwdriver stuck halfway into your ear?

This was for checking a hanger bearing. Not a moving u-joint. Good luck getting a large screwdriver handle halfway into your ear too. Ideally you would use a mechanics stethoscope. Not everyone has one of those, even though they can be found for less than $10. Just about everyone has a screwdriver set though. Even a broomhandle could be used so you don't even need to get under the car.

As with any rotating part situation, caution is advised.

[funguseater]

Damn, the noise only occurs in bumpy conditions so I cannot check where its coming from. Did change tranny fluid today to check for metal and there was some but not too much, the fluid was blackish at rear when draining and the fluid at the front was silver(eeeks). Anyway I will probably take it to a mech for an inspection then I'll have a better idea. Thanks for the help guys, I still think its that drive-shaft hanger but we shall see.