U-Joint Thrashings

[RhinoB1]

Ihave an 81 and before I had the rearend rebuilt, it kept trashing the right side outer ujoints, (halfshaft came off outer flange AT SPEED 3 different times before I had it rebuilt.) So, when it was rebuilt, replaced both inner flanges and right side outer flange, half shafts brand new . That worked great for about Half a mile till camshaft broke destroying engine. Anyway, got new engine and drove about 1500 miles on it and rear end was now squatting and took to get aligned. While doing alignment, mechanic noticed inner left side u joint was bad. Had them replace it and worked good for about 30 miles. I replaced again this weekend and lasted about 5 miles this time, (luckily no repeat of half shaft space shuttle launch). I don't really think that ujoint type or mounting strap type is the problem, it would trash all of them if it was. Any Ideas on what could be the problem? Thanks, Ryan

 

[69MyWay]

Ryan,

You could have one of several problems.

First, you side yokes may be heavily worn and allowing movement that is prematurely wearing out the U joint.

Also, the actual half shaft may be damaged where the U joints go in so that it never centers all the way, and has enough wiggle room to eventually blow the bearing cap.

Your best bet at this point is to pull both half shafts. Take them to the local driveshaft cutting/balancing company and have them checked out.

Then, check your side yokes for excessive play. If they will slide in and out of the diff, you have a problem. That usually requires pulling the diff, and forcing the old ones out. What happens is they chew up the inner clip and press on the pinion pin. They mushroom out on the inside. I have seen where a fellow has to take a small dremel or grinder to the back of the yoke to get them to slide back out of the diff.

 

[RhinoB1]

Well, thanks, but that doesn't help much. Like I said, half shafts are brand new, and there is no excessive play in yokes since they are reconditioned and bought when I did the rear end.

 

[69MyWay]

Sorry, I meant to be more specific about it being a progressive problem, now it is happening all over again.

When you say "rebuilt/reconditioned" what does that mean? I am aware of many shops and individuals that will over look some things.

If those side yokes got damaged/out of round, etc. from the first series of failures, then the condition continues to compound regardless of the replacement. Now your replacement half shafts may also be damaged....were they new or used replacements?

Sorry I can't pin point your exact problem for you any easier, but no doubt you have a serious misalignment in that rear assembly.

Other than a bad wheel bearing assembly, or trailing arm assembly that has a bad bushing, getting off center, I don't know what else to tell you.

 

[RhinoB1]

I think it is more than likely a bad trailing arm bushing and am going to start there, if you can suggest whether the bearing or bushing one or the other is more likely to be the cause I would appreciate the input.

 

[69MyWay]

jack the car up and grab the back wheels. See how much movement you have.

There should be very little, and certainly no clunking when you grab one way or the other.

The wheel bearings on the rear are a pain and can be expensive to have serviced. Just do a search here on trailing arms/rear wheel bearings.

 

[RhinoB1]

last time I had it in the air with a good u joint in it, there was no more than very little endplay on the wheel bearings. I did some more thinking and looking at the rear trailing arm and pretty much figured out that if the front bushing on the arm is bad, it would allow for side to side travel of the arm from that pivot point. The other factor, rolling the tire, brings into play the fact that it would want to travel to the outside coupled with the already strong factor of load that the bushing would be supporting part of the weight of the car. This combination would place the excessive load to the inside ujoint. Took me a while to figure out but just had to do a few calculations. Asked here on this board cause I thought some one might have had this problem before and already figured it out. I was wondering what you meant by the wheel bearings being a pain, I did them last fall and it only took like an hour and a half??? thanks for the info, Ryan

 

[69MyWay]

last time I had it in the air with a good u joint in it, there was no more than very little endplay on the wheel bearings. I did some more thinking and looking at the rear trailing arm and pretty much figured out that if the front bushing on the arm is bad, it would allow for side to side travel of the arm from that pivot point. The other factor, rolling the tire, brings into play the fact that it would want to travel to the outside coupled with the already strong factor of load that the bushing would be supporting part of the weight of the car. This combination would place the excessive load to the inside ujoint. Took me a while to figure out but just had to do a few calculations. Asked here on this board cause I thought some one might have had this problem before and already figured it out. I was wondering what you meant by the wheel bearings being a pain, I did them last fall and it only took like an hour and a half??? thanks for the info, Ryan

WOW! You did the REAR bearings in an hour in a half??? Schweeeet! That would be a record in my book. Most people won't even attempt them, much less knock them out in less than an entire day of messing around.

Many people try them without the special knocking and mounting tools. Not only that, most cases, the old shock mount and other bolts are so frozen, you spend half the day trying to get access to them.

What is your trick?

Yep, if your rear is walking out, you would be putting a load on the U joints because they are not "slip" shafts, and would feel th bind.

 

[RhinoB1]

No trick really but now I am assuming you probably mean that doing it with hand tools takes awhile. With basic air tools, an $80 press, and just putting the rear on jack stands it is not to bad at all. All you do is loosen outer halfshaft retainers while car still on ground, jack up, put jack stand under frame, lower, place jack on springmount, jack up, disconnect, disconnect strut rod outer, with wheel already off Take out trailing arm bolt, and then it only takes about 10 to 15 minutes to thoroughly clean and replace bearing and races and pack them. pretty much just as easy to put back together as when taking apart, not really anything that gives you problems lining up. I have worked on vehicles for about 10 years and aircraft for about 4 years . Have an associate degree in Auto from local vo tech, Associate in Auto from UTI (otherwise known as Hot Rod U, what a joke), and a BS in Aeronautical Science From KSU. My experience probably cuts the time down a lot too. Not trying to say I am a know it all here, just thought you wouldn't think I was just being some B S 'r about how long it took me. I obviously don't know everything or I wouldn't be asking questions on here Anyway, thanks for the help and I'll let you know how it turns out, Ryan

 

[69MyWay]

Having the right tools makes all the difference.

I think the thing that bugs me the most about the rear is setting up the back lash. I ordered a kit from VAN STEEL with shims and new tubes. It took me several combos on a dummy shaft to get it right. Still not sure if it is right, but once you put that final torque on it, it is pretty much a done deal.

My buddy has his axles turned down for slip fit. He ran his race car that way and now his street vette.