I'm having a strange problemo with my truck. I'm getting this really crazy clicking sound on acceleration. At first I thought it was a valve or lifter, so I pulled over, gave the motor a quick redneck tuneup, and couldn't find anything or replicate it. I've since been able to replicate the problem, and its not motor related. Its definitely "click click click click" and not "clunk clunk clunk"

If I modulate the throttle, I can get this clicking to come and go as I apply throttle. It matches speed with the drive-line, not the motor. So at 15 mph, its super slow, and at 60 its almost a buzz. It is easier to replicate as speed increases. It also clicks a little when I'm slowing down, and almost always does it when I take off.

I'm almost positive its coming from the rear of the truck. It almost sounds like somebody spinning a ratchet. I checked the u-joints, but realized after i checked them that I park on a hill (doh!) so they would be taut no matter what. I bought new u-joints to install if they check badly tomorrow.

I'll also be checking/changing the diff fluid tomorrow. Think it could be a rear bearing? It primarily occurs on acceleration though.

As a side note, my trans mount is SHOT!!! I went to check the front u-joint, and lifted the trans up a half inch. I know that could give me a clunk like a bad u-joint, but would that possibly give me clicking?

Thanks for any input.

 

I could see your trans mount as being the culprit of an occasionally clunk or vibration, but not a "ratchet"-like clicking that increases with speed. I would be looking at that rear diff. Any chance its something easy like a mudflap on a tire?

 

I already made absolutely sure that nothing can be touching the driveshaft or rear wheels. No mudflaps for me. As for the trans mount, I guess i must have just been superhumanly frustratedly strong yesterday, since it doesn't seem as bad today. To visually inspect it, it looks fairly new, and it doesn't seems to move as much as i thought.

As for today's update, I was 0.5qt low on gear oil, which made no difference to the sound. Also, my U-joints seem to have zero play.

However, I do still suspect that it could be U-joints. I had somebody drive the truck back and forth while I looked under it, and I noticed that in reverse, it makes much more of a squishy squeaky sound. Its also gotten much more consistent in the 60 or so miles I've driven since it started making the noise. It does it almost constantly now.

 

have you tried greasing your u-joints?

 

I was not able to grease my u-joints since there was no grease fitting. I believe the rear one was a factory u-joint, as it had a strap across it that my service manual refers to as production only.

The problem is solved. It was indeed the rear u-joint. It had somehow rusted solid, instead of failing in the usual way and getting loose. I pulled the driveshaft today and brought it up to my mechanic, had the new u-joint pressed in, re-installed it, and was on my merry way.