The Stovebolt Site Forums The Shop Area Driveline 3 speed u-joint question

The u-joint on my 47 GMC 3 speed seems a little sloppy. The two ends that bolt on are sloppy on the shafts they cover. The other two shafts are solid but these two have what I feel is too much play. I had two other brand new u-joint repair kits that I checked. One from Carters and one from who knows where but sealed in a package. Both of those were sloppy as well albeit only half as much. Is this supposed to be this way? I would think there should be a fairly tight tolerance?

The u-joint on my '51 was what you'd call "flat worn out" when I disassembled everything. I got a replacement kit from The Filling Station and it had what I'd call reasonable clearance. Not real tight though.
Here are before and after pictures.

It's interesting to see that virtually all the wear is in the hole, not much, if any on the cross. Why not make bronze bushings to replace the worn pieces? Any good machinist with a lathe, a press, and the right size chucking reamer should be able to do that.

Jerry, I think you just found a new product line. I can send you one to get started on right away?! You will sell these like hotcakes....and Kevin, thank you for the reply and pictures. It helps. As a follow up question to this topic, how would I measure clearance for a small diameter hole like this? and what should the tolerance be?

I'd suggest using a narrow piece of steel shim stock like a field-expedient feeler gauge- - - - -maybe a strip about 1/8" wide, for instance. I think I'd look for maybe a maximum of .010" or a bit more?
Jerry

I've got to take my u-joint apart to install the engine soon. I can measure the pins and bushings for you. I don't think there's 0.010" clearance on it, but I'll have to measure.

So I pulled the u-joint off today and measured the pin and bushing. This u-joint has just 100 miles on it, and there's a tiny bit of scuffing on the pin and corresponding bore. As you can see by the picture, there isn't a polished finish on the pins (or the bushings). What I got for measurements is that pins are a nominal 0.68" and there's about 5 thousandths clearance. As opposed to modern u-joints, these are definitely not precision parts.

Thank you Kevin. I agree, not exactly precision parts. I was able to obtain some measuring implements today. I have .683 on my pins and .687 on the bushings. They do wiggle when they are just held on and not bolted down. A machinist friend of mine felt that while it was not ideal, with the film of gear oil it should be okay to run. Crossing my fingers and paying close attention in the future. Thanks for confirming we are in the same ballpark.

I agree, not a very stout design. There is a bit of movement, but hopefully the oil film takes care of it. My truck had evidence that the u-joint had completely failed, gouging the inside of the torque tube ball. I have the original gouged up ball, another I got from a stovebolter, and another NOS ball housing that I put on the truck. I'll keep my fingers crossed that the u-joint doesn't blow up, but it should outlast me. Maybe inspect every few thousand miles.

It looks like there's enough material in those yokes to retro-fit them with Torrington needle bearings, and grind the OD of the cross to whatever clearance you'd want.
Jerry

I had thought about that. It's just a matter of finding the right size bearing. The yokes could be machined for a stop on the outer end to secure the bearings, although a press fit should suffice.

How about a thin retainer plate bolted over the outside, like the 18 wheeler U joints use? Even if the yoke had to be milled down a few thousandths to keep the width the same as original? That would also retain some lubricant in the needle bearings better.
Jerry

I looked at a site for torrington bearings and the cage has to be a press fit, so really no retainer would be needed. The ball is supposed to be partly full of lubricant, so keeping bearings lubed shouldn't be an issue. I don't think it's something I'd be tackling, as I don't have the machine tools to do it. I did see that a 17mm bearing would be a good fit on the pins, but don't know about in the yoke. The 17mm bearings have a cage about an inch in OD.
One fly in the ointment is the groove in the pins (see the pic above) that extends about half the length and might tend to eat up the rollers. I'm sure a roller wouldn't like coming to an abrupt edge.

Those bearings seem loose when I hold them in my hand. That can be deceiving though. They are supposed to have a lot of end play In them.
What you need to feel for is radial play. When the u-joint is held firmly while in a straight line, you can feel any radial play while turning it back and forth in your hands. It's up to you how much play is acceptable on a used one. I don't want much at all given how much work it is to tear down the torque ball assembly.