Drive Shaft Rear U-Joint Question

[MGD72Monte]

The following shows the yoke and rear universal joint from my Monte, with the tabs which retain the bearing caps circled.

 

 

These are photos of each tab.

 

 

Below is a shot with the two parts together with the arrow indicating the location of a gap of approx 1.5 mm or 1/16" between the tab and the bearing cap.

 

I changed the yoke straps after I found I could move the driveshaft back and forth by hand. I also changed the universal joint. However there is still a gap. Is that normal or should the universal joint fit perfectly snug? If it should, can I take a hammer to those tabs to bend them inwards?

 

Thanks

[Leghome]

I personally would NOT bend those tabs. Cast Iron breaks easily. I am sure someone will have an answer as I have never ran across that problem.

[stangeba]

That is a great question but one I can't answer, sorry. I do remember one time one needle bearing slipped sideways and got pinned the wrong way under the cap and the U-Joint still fit in the yolk. I had a vibration that led me to finding this needle. If I was going to try to remember, I think I too had more slop in that area than I thought there should be. I remember thinking, "how do I center this U-Joint" and if I didn't have it centered, would it cause a vibration. Or it could be the junk "made in China" parts that just are not made correctly.

Bruce

[Andy's Auto]

I do know one thing, th U Joint should fit very snug as the tabs are what centers the shaft. Chevy used two styles of yokes. One, like yours uses no snap rings and is "self centering". The other requires the caps to holds a C Clip and uses two straps and four bolts, and the other uses the U bolts threaded for 5/6-18 nots and lock washers.

 

I believe either your yoke is worn or the U joint is wrong. But there are only two joints Chevy ever used on an A body. A 3310 and a 354PM. Like Bruce said, it it is not perfectly centered, it will vibrate.

[72MC]

Sometimes the joint is so snug it can be a pain to seat it properly in that pinion yoke. IMHO, I would get a new yoke. - Dave

[Sam (Bones)]

 

get a new yolk

[Mo's70MCs]

I may be out of place here, although even though the yoke has been questioned. I'd be inclined to question the u-joint first..not to take anything away from all the master mechanics here. First: without properly measuring the yoke for its dimensions, why would you say it's worn. Secondly: the U-joint dimensions are crucial here, and we haven't seen much of it. Or a P# for that matter. Thirdly: That yoke shows very little signs of wear? Looking at the overall picture and I'm not an expert, that u-joint seems funny looking to me, on the inside where the grease seals are at? Did the old u-joint show the same gap?

[72MC]

Rod, you raise very valid points about the the joint.

 

The joint may have the same play in the driveshaft. After pressing the joint into the driveshaft, how easy was it to install one of the retaining clips. In my experience, it too should be snug against the U joint cap. If it slipped right into position with "to good to be true" ease, I would use a feeler gauge and check for unwanted clearance between the cap and retainer.

 

New U joints always seem to be a literal hair longer than they should be. When installing NEW joints to a yoke or driveshaft, it seems the caps need that little extra effort to get them to seat properly. It's almost like the seal is pushing the cap outward since it is new. After they have been seated, used, removed, and reused, that over snuggness is gone and they should slip right into the seat. Still a snug fit but not that new snug fit.

 

That being said, I would still get a new yoke. I have replaced a good number of 30 plus year old pinion yokes and though they may appear still "good to go", it's small insurance to just purchase a good quality replacement, JM2C. - Dave

[MGD72Monte]

Thanks a lot for your input guys. To try and rule out a faulty U-Joint, I brought the yoke to the local parts store and tried the fit of two new U-joints, one regular one and one heavy duty. The heavy duty one was the "snugger" of the two, probably because it is already greased. Even thought I was able to slide it in relatively snuggly, if I press the caps inwards, I can generate about 1mm of space, a little bit less than the current joint. Anyway, until I see the difference with another yoke, I won't be able to conclusively say either way. I will probably change it so I'm looking to get my hands on another yoke. The local junkyards are long depleated of 70s and 80s vehicles. There are a few 90s, including trucks.

 

Where can I get compatibility info on what will fit? The junk yard says their computer system doesn't go back that far.

 

Thanks again

[Mo's70MCs]

OPGI Sit Down!! Try Leo.

[Montemedic]

A good transmission or driveshaft shop could assist you with this.

[wallaby]

This is a good question. I don't have a difinitive answer, but I've been thinking about it. I know when installing the press-in half of the joint into the driveshaft, you press the joint hard against the c-clip, then turn the shaft over and press it hard again in the other direction against the c-clip. The end result is both caps are as far out as possible and the u-joint has a bit of "float" and is not bound up when done.

There is no real bearing surface at the ends of the u-joint cross shafts; they shouldn't be tight against the ends of the caps. The question is how much end play is acceptable?

I tried to do some searching for this question about lateral play and got varied answers...most seemed to think that the caps should be tight against the ears and lateral movement should be nill. Others felt .010 or less.

I guess the real answer will have to come from a driveline expert.

[Sam (Bones)]

when installed in the car, using a dial indicator, lateral run-out should be under .010, preferably less, any movement of the u-joint cap in the yolk is not acceptable, I've had to center many u-joints because of vibration, by centering...I mean adjusting by either a press or a brass BFH

 

I have centered a u-joint on a worn yolk, then tightened the straps and tack-welded it, had no issues, but never on a customers car, only my own

[Mikstudie]

Try a different brand of u-joint.

[Monteman1971]

I have the same issue.... Typically the universal joint is the same length for both sides but in our case one side is longer than the other. This is something that GM did..there is nothing wrong with what you have. A good(real)parts guy will be able to get you the right joint. I got mine from my local NAPA because the parts guy there was old school and had seen this before. I wish I saved the box but I installed mine a few years ago.

 

 

Steve

[stangeba]

"but in our case one side is longer than the other"

Our case = ? Steve, could you elaborate? I would like to learn more.

Thanks, Bruce

[Monteman1971]

Bruce....see MGD72Monte's pictures. The universal joint is not fitting snug in the rear pinion because the rear pinion mounting surface is widder then that of the drive shaft.

 

Therefore he needs a universal joint that is not symetrical on both sides. One side of the joint is longer than the other. Although typically uncommon there are those that have this, mine included.

 

Steve

[bobsmc]

steve,

its called a combination joint .

i needed one when i used a bop rear end in my monte for a few years.

any driveshaft repair co. should know what he needs.

 

bob

[Monteman1971]

Thanks Bob...it even has a name! Mine was the first one that I saw like this....and I know it's from the factory because all my dates, codes and numbers match on my car. I bought it from the 2nd owner who got it in 1974 and had stored it since 1982 until I bought it in 2007.

 

Steve

[Steve Trout]

Did the old u-joint fit snug in those tabs. Let's start there