86 Bronco II, 2.9. 5 spd 4wd

With my limited knowledge, the loud clunk I am hearing when I accelerate, accompanied by a sqeeking suggests something amiss with the differential. The vehicle has always stuttered and surged a bit in the lower gears. There is some leakage where the drive shaft meets the rear axle. Is that enough information for someone to suggest a diagnosis?

Adair

 

I'd be checkin the Ujoints first as that is the common problem.

 

I would also check the fluid level in the rear since your losing some, but U joints are the first thing that came to my mind too..

 

some leakage where the drivehaft meets the rear axle sounds like a leaking pinion seal. A leaking seal by itself shouldn't cause those issues, unless the pinion bearing is shot, too. May need to replace the pinion bearing.
However, I too, would start with the driveshaft. Recognize that your '86 may still have its stock CV style driveshaft. Several possible symptoms of the CV joints failing. The first one I noticed was a "clicking" similar to the noise a FWD car makes in a turn when it's CV joints are failing (they are the same kind of CV joint). After that, mine starting vibrating on acceleration really bad. Felt for all the world like the clutch was chattering, when it was really the CV joint. Like a fool, I waited until my CV boot tore before replacing the driveshaft.

 

Thanks for the input. I hope the problem lies in the u joints, because I can tackle that myself. I have conventional universal joints, not the cv type. I will jack the rear end up and see if I can feel any play in the assembly. That is about the only way I might be able to tell if there is a problem in the u joint. Have you any more input on zeroing in on this? Should I go with heavier duty u joints? The u joints are a cheap repair for what I feared was a larger problem. Thank you all for the replies.

Adair

 

There really isn't a heavy duty u-joint you can buy and not really worth it unless it is lifted. I would just but the stock replacement ones. Just grab the driveshaft and turn listening and feeling for play. Check your end caps that is usually the first place. You really need to look at them closely sometimes as they can be reall buggers. You can also take it for a drive and then feel how hot they are maybe they just need grease. When and if you replace make sure you get U-Joints with greasable fittings. It's not a hard job just finnicky if they won't comeout.

 

I seem to have the exact same thing wrong with my 84.... in first and second gears while accellerating i have a loud squeek followed by a clunk when letting of the gas or shifting gears

checked for leakage and is in the same place you described.... keep in touch with what happens for i need to fix mine as well

 

I was looking at my machine today, and I could turn the driveshaft about 3/8- 1/2", but the play does not seem to be in the u-joints, but in the transfer case. How much play should there be in there?

Adair

 

originally i thought the sound was coming from the transfer case... ive been familar in the past on blown u joints (in a diff truck) and it doesnt seem to be the same noise

man i wish i knew what it was before i really mess somthing up

 

Check for a broken tranny mount also as that noise will telegraph through the drivelne. Thats about normal back lash on the trans to drive shaft. Try blocking one whell and have some one turn the other full range of back lash and listen real carefully from underneath.

 

any other ideas???

 

You can also check shocks and bushings. The original suspension bushings are rubber and have more than likely deteriorated and will cause the squeak. The clunk could be suspension hop due to deteriorated shocks. Test for the shocks by just push down a couple of times and see if it keeps going up and down after you release. If you know they've been on for over 20,000 miles they are due to be replaced

 

Well,

I brought the thing in to the shop this weekend and it seems I need a new rear end. They can rebuild it for 1700, but I think I'll scrounge for a used rear end. Should be able to do the repair for under 1000. If I had a space to work I would love to tackle it myself, but I think this one is beyond me.

Cheers all, I'll post when we dissasemble the old one and find out exactly what went wrong.

A.

 

Well,

I wound up swapping out the rear end myself with a salvaged one. It seems to have done the job, though I am still able to induce some surging at low RPMs. The loud "clunk" has been replaced by a quiet "clank", but only when I try. Good enough for me for a $175 repair. The squeeking was eliminated with some grease in the driveshaft.

Adair

 

Glad to hear things are better.