OK, here's what I'm hearing:

In gear (manual trans), clutch engaged, lower RPM's coasting or decelerating under little-to-no load I'm hearing a mechanical clatter in the rear end... possible the tranny, driveline or rear diff. Sort of a marbles in a can, wrapped in a pillow sound.

Push the clutch in or take it out of gear and it goes away.

Give it some gas (put the engine/tranny under load) and it goes away.

It's pretty subtle and originally sounded sort of like a spun wheel bearing IMO... but the fact that adding gas or pushing in the clutch makes the noise disappear oviously shoots down that possibility.

Fluid in the rear diff is good as is the tranny fluid.

This truck is new to me... and the noise is subtle enough that maybe I just hadn't noticed it before. Could it be a normal noise? Or is my rear diff about to consume itself? I don't know and would appreciate any ideas from those who might have a little more insight into the tech end of things.

The rig is a '94 4Runner by the way. The only known issue is a leaky valve cover gasket as I just replaced the leaky rad. It was a piece of cake. This though, has me a little worried.

 

Does it sound more like a low rumble? I have this exact problem and I think it's the rear diff. I am guessing it's got too much slop in it. But at 400k, everything else does too. It's something I am going to have to pull out soon. Been thinking about swapping axles if I can find a used one some place.

When a bearing ate it's cage in the transmission, it had a more, gear like whine sound.

 

I may be going in an off direction here, but my brother had a bronco (not the II) and his was doing something similar and it turned out to be the rear u-joint. His was the other way 'round though- noise on the throttle, no noise coasting.

 

U-joint on its way out? When you load up a u-joint you take the slop out of it.

 

OK, so the concensus seems to be rear diff, or U-joint. A low rumble is a good way to describe the noise. Sort of like a marble rolling across a tile floor in the next room.

Other than a full tear-down... is there a way I can check either to be sure?

Replacing the rear diff... is it the internals, or do I pretty much need to do a whole rear axel? Ballpark $$$ on parts?

If it's a U-joint, how do I tell if its the part coming from the driveline, ot the rear diff thats worn?

Also... how long do I let it go if it's either one? If it's just slop in either part, it doesn't sound like a catastrophic failure is emminent. Or is it?

 

My 95 4Runner recently started making a squeeling type sound when the truck is in gear and im pulling away from a stand still and now it makes the sound you're describing when Im slowing down for a stop light in gear; if I take it out of gear it stops (manual trans), kind of a rumbling/grindind sound like something is loose underneath.

Anyways, I have the truck in the shop today and Im waiting for a phone call after they try to figure out what it is. If they end up fixing the sound coming from my truck I will post and let you know what they did and that might give you somewhere to start.

 

Feel for play in the u-joint. You can also unbolt the driveshaft and run the u-joint through it's full range of travel to feel for looseness or grittiness as it rotates. Also, you can remove the rear driveshaft and run in front wheel drive to help isolate the noise source. Rear diff comes out of the axle housing for repair. Might also be the rear axle bearings, sound from those will vary in turns, louder when the bad bearing is on the outside of the turn.

 

My first thought was ujoint but the marbles sound rules that out....

Try putting the truck on jackstand and turning the tires whilst someone listens below....

 

Ok, so I just got off the phone with the shop that is looking into the same sort of sound coming from the bottom of my truck and he seems pretty certain that its a bad rear U-joint. I am having the U-joint replaced and I'll be picking the truck up tonight.

I'll let you know if they were right. The U-joint sounds like a good place to start though.

 

Picked my 4runner up from the shop earlier tonight. After having the rear U-joints done the sound has gone. I'd try replacing those or at least inspect them to see if they are worn. I think if you get under there and try to wiggle the drive shaft, you'll notice if the u-joint is worn if there is any movement.

Goodluck!

 

$$$???

 

Cost me about $250 Canadian, which might be a bit high but I wasnt about to try and do the U-joints myself.

The sound is gone though, all I need to do now is get the 4Runner up to highway speed and make sure the driveshaft is balanced and doesnt vibrate.

 

WOW! for 250 they better have replaced those joints with OEM Toyota....glad you got it fixed!

 

Yeah, they probably arent OEM....
There might be a slight vibration coming from the drive shaft now with the new U-joint. Im going to test it on the way home from work tonight, need to get it up to at least 100 kms to see if there is any vibration. If there is a vibration I'll be taking the truck back to them and asking them to fix it.

If it does vibrate, should I make them get the shaft balanced? or should I ask them to pull that U-joint out and get an OEM U-Joint?

I cant deal with another vibrating driveshaft, my Supra had a vibrating drive shaft that no one could fix and it was the most annoying thing when driving.

 

I had all the U-joints replaced in my drive shaft not too long ago. I also have a loud thud when I load/unload the drive line at speed. I also have a lot of slop in the rear diff. Combined with the noise, I think it's warn out. The question is, can I fix it myself, or do I have to take it to a shop?

 

Its pretty unusual for a new ujoint to cause driveshaft vibration. Perhaps they accidently knocked balance weights off the driveshaft.

 

Yeah, I did some highway driving the other night to make sure there were no High speed vibrations and everything checked out.

So now onto the next thing on my list of repairs...haha