A couple of weeks ago I started hearing a rattling sound, usually while accelerating (when engine is under load).

With the recent posts about timing chains and "bag of spoons" sound, I thought it was my chain tensioners going out.

It's been getting worse, and the more I listen for it, the more I think it's coming from the rear of the vehicle instead of the front.

Today while cruising down a street, the rattling started, so I put the trans in neutral and killed the engine while the 4Runner was rolling -- rattling continued. Pretty clear sign that it isn't the timing chain.

I pulled it into my garage and slid underneath it looking for a loose u-joint. I grabbed the driveshaft and shook it in every direction but there was no movement.

Then I rotated it and it moved a decent amount (4Runner flat on floor, parking brake engaged). What's the nominal amount of slop here?

Another thing.. I drained the axle (it was full) and put a magnet in the stream to see if any metal shavings came out -- nada.

 

Ujoint - guaranteed. Probably (90%) the rearmost one.

You need to pry on it to see the slop in the ujoint.

The slop you are seeing (rotationally) is the backlash in the gears (both the R&P and the spiders). It can be quite a bit if you have a locker.

 

ok, well, I'll swap out both of them since I'm gonna be popping the driveshaft out.

Any gotchas to this? I've done u-joints before, but it was back before about half of yotatech membership was born.

I'm assuming the typical c-clamp and socket trick will work.

 

done. I bought the u-joints (toyota parts) and ran it down to a shop to have them rebuild the driveshaft.

$88 well spent for the labor.

Oddly enough, the one by the differential was ok, but the one up by the transfer case was shot -- "the bearings were ground to dust," said the shop owner.