When I drive my 1983 Elky, presently I take it pretty easy, just short trips around the neighborhood. I noticed recently that when I drive in reverse, a clunk clunk noise occurs. If I back up to test this it will go clunk, clunk, clunk until I apply the brakes and put the automatic posi-traction (all stock) in drive. I have put a lot of money in the beast and don't want to have any expensive repairs done just now.
One guy suggested it might be a bad U-joint. Ideas?
Thanks,
Eric

:) Yup, that sound's like the problem all right...BUT...noise does travel so check the rear end as well...but I'm betting it's the U-Joint! :cool: "SKULL"

U joint is the first thing I would look at too. Get under the car and see if you can twist the driveline at all with the car in park. There shouldn't be any play between the differential yoke and the driveshaft. Also have you tried driving forward in low gear really slow to see if the sound shows up? 1st gear is what I mean.

Would also check my rear tranny mount for wear or failure to see if it could possibly be allowing the tranny to move up toward the floor causing an incorrect driveshaft pinion angle. Low gears like Reverse would show this up the worst.

just some ideas..

8)

I had that problem once. After talking to a few people found out it had something to do with the clutch's in the posi. All I had to do was change the fluid and go to the local Chev. dealer and get an additive for posi units.Been so long ago that don't rmember the name of the stuff but you had to get it at a dealer. Sounds like the same thing mine did about , kinda bind up and clunk in reverse. Worth a shot.

Yea I had the same problem once,,,, come to find out it was a Ranchero! 8-)

dammet, I hate when those ranchero problems sneak up on you!!!

I presume that any looseness would occur at the end of the shaft where the U joint is worn. In this case at the rear by the differential.
A friend suggested that I could replace the U joint myself, saying it is an "easy" job. My mechanical skills are minor as is my tool collection. Any comments on how to change the U joint?
Thanks,
Eric

There are some pitfalls that can be encountered when changing u-joints. If you have minimal skills and tools have a good repair shop do it. If the joints have never been replaced they will have to be pressed out. Also care must be taken not to have an end cap fall off and needle bearings drop out. If you replace them with greasable joints the fittings have to be turned correctly for a grease gun to fit.

Safety issues such as correct placement of jack/jackstands and wheel chocks are important as well. Once the u-joint is unbolted the car can roll if the e-brake isn't set or if it isn't otherwise supported/constrained.

My main concerns confirmed. This car is going to the shop. Thanks for the advice.
Eric

Some advice: Don't take the truck to a mechanic and say "change the u-joints." Instead, tell him about the clunk, clunk noise and see what he comes up with. After he tells you what he thinks, you can tell him what you think. Best of both worlds.

Good point. My mechanic runs a small independent shop and he takes it all in with a grain of salt anyway. I learned my lesson years ago, when a mechanic replaced a slipping clutch, ignored an oil leak causing the problem, and blamed me for the fact that the new clutch was gone also after about a week.
Eric

I got a similar clunk clunk, seems worse after a long drive, is when I am driving slow, so a low gear in the automatic, in forward, not reverse, and especially turning sharp turns like parking...

So I'm gonna check those rear tranny mounts and try to twist that driveline in Park and see what it gets me.

Thanks a lot!
El Camino Central continues to Rock.

I bought a new elky in 84 and after only a couple thousand miles I had a cluncking noise that ended up with the complete ring/pinion/carrier and all being replaced under warranty.

I hope that's not the case for you guys but there were some bad units produced that year for sure.

The Verdict:
I took the 83 Elky with posi rear end in hoping for a U-joint problem...
The car has 93 thousand miles on it, and a prior owner towed his fishing boat with it.
The problem had a sudden onset with the loud "clunk clunk" in reverse.
The mechanic pulled the back plate off the differential after discovering minimal play in the U joints, not sufficient to cause the problem. The splines on both axles were starting to show nicks as they were attempting to "skip". The spider gears were also nicked. Too much play in the gearing with the potential to lock up the whole differential I was told.
The best fix involves replacing all of the innards ($500) in the differential, and a newer part set up also requires replacing both axles ($300 each) The new axles have 28 rather than the 26 splines on the original posi set up and the shafts are somewhat larger. Labor would be about $250. We are looking at $1350. I asked him if he knew anybody who wanted to buy a nice El Camino , because I surely can't go that much, knowing that the car needs other things, as do most older cars periodically.
He got on the phone and located a non posi differential out of a 1981 Malibu, with axles, for $250 and would charge me $250 labor. I would want the U-joints replaced, as a precaution, as they do show some wear.
I do like my Elky, but was floored by the cost of repairs. I will go with the cheaper repair, and the mechanic assured me that he will inspect the differential before installing it, to make sure it is tight. $520 out the door with new U-joints.
So as a prior member suggested, positraction may not be the most desirable option for that year Elky.

Este, you just listed the very best incentive for doing it yourself. You get the satisfaction of doing along with the savings. Ever thought about getting your own rear end from a donor car and changing it out yourself?

Este, you just listed the very best incentive for doing it yourself. You get the satisfaction of doing along with the savings. Ever thought about getting your own rear end from a donor car and changing it out yourself?

Great idea. However, I am a trucker, sixty years old, and I simply can't do the work myself. I'll drive a few extra miles and appreciate that the cheaper alternative works for me.
We have our dreams and our realities.
Eric