I have a clunking from my, what sounds like either the tranny or the rear end, whenever I shift into reverse and somtimes when I'm slowing down to a stop. Any ideas, maybe driveshaft? Anything would help, thanks.

 

Does it happen if you accelerate, or deccelerate? Like just alittle after you let off the gas or put it on? If its a consistent clunk when you do either of those, I would guess its the backlash in your rear.

 

I would take a quick look at the rear drive shaft u-joints, and see if there is any unwanted play.

Also what you can do is to put the truck up on a lift with someone in the drivers seat. Have the person shift into and out of gear while someone is looking under the truck so they can pinpoint the location of the sound.

 

It happens mainly when deccelerating and putting it in to reverse and drive. What exactly do you mean by backlash?

 

Backlash is like slop in your rearend. When you accelerate, it clunks becasue it is catching up.. And when you decel, it clunks because its hitting the opposite way.. If you don't experience a consistent clunk either way, then thats probably not it.
Check your tranny mount too. I thought that was my problem at first.

 

I'm not absoultley positve, but your truck may have a two peice drive shaft, inner and outer shaft. Had one on my work truck, and it did that clunking sound when I drove slow from time to time. Took it to the dealership, and they said that some drive shafts have a inner core, and it will break loose, and when it does, makes that clunking sound. Just an idea.

 

Thanks for all the replys, I was thinking tranny mounts as well too, I just have to get under the truck and see whats going on, its just been raining like crazy here so im a tad bit reluctant at the moment, but thanks again.

 

The clunk is usually easily fixed by greasing the slip-shaft where the two pieces of the rear drive shaft come together.

I have to grease mine like every 5K miles or so.......first you drop the drive shaft.....you can get by with just removing the four bolts that hold the shaft to the rear end, but mark the two half's of the shaft first, so you put it back in the same spot. Then you need to cut off the clamps holding the boot on and slide the shaft apart. I usually clean it up a bit then give it a coat of some good quality grease. Dont forget to burp the boot of air and clamp it back on with two zip ties.

Give it a try.....I would bet it cures most of your "clunk".....and if it dont.....well I has to get done time to time anyhow.....so.

 

My '90 does the same thing. I got under it with the tranny in neutral and spun the drive shaft by hand. There was no play in the u-joints or slip yoke but I could see it was turning almost a third of a complete revolution inside the differential before stopping. This told me it was (or is) the backlash in my rear-end. I think it can be adjusted by shimming the pinion (anybody know if this can be done ?), but I'm not sure. Might have to change the gear/pinion set.

 

I had a sudden clunking from my d-shaft one day and then, she dropped out on me. Im just lucky the 4wd worked to drive it home. My problem was two things 1) the u-joints all needed to be repaced 2) the yoke was not the correct way. The guys that rebuilt it for me said that it was 90* truned the wrong way. It was like this when I obtained the truck so IM not sure why it was liek this, but since the rebuild its been great.

 

What rear do you have re_fill? 9" rears are adjusted by tightening or loosening a pair of adjustments that pull or push the case together. I think shims just change where the teeth contact each other..I don't think its his backlash if it only clunks when he puts it in reverse or when he is slowing down. But who knows...

 

Well here I go being dumb, but I believe it is the standard 8.8 on the 1990 Bronco. Mine clunks when you change from forward to reverse, and vice versa, and it clunks when the tranny changes gears, but only at low speeds. When I punch it to pass someone, no clunk, but when it shifts by itself particularlry at low speed (less than 40mph) it clunks, but not all the time (?????????) There is a lot of play in the diff, like I said, and when I checked the fluid, the magnetic plug had a lot of "non" oil stuck to it. I figured it was worn gear (metallic). The gears are case hardened, and once the "case" is worn, they will deteriorate rapidly. So am I completely confused, can I adjust the lash, or do I change the gear set?

 

greybullit

sorry for piping into your thread, but I think we have the same problem. good luck with yours!

 

I don't know if your actual problem is backlash re_fill. But I don't know a whole lot about rear ends or tranny's. I will describe to the best of my ability what my confirmed (by two specialized mechanics) backlash problem is.... I will be driving at any speed, throttle in any position (exept no throttle). If I let off abruptly it will clunk... Then on the other side of that... If I am moving with no throttle, and I give it gas, it will clunk. This doesn't happen at all between shifts.

 

My '95 is doing the same thing, Random clunking when starting out slowly or just before coming to a stop. Doesn't happen all the time, though. I will climb under and check this weekend...