I`m ready to install a rebuilt engine in my `24 Touring---in aligning the u-joint, found that NO pin was installed on the differential side of the u-joint.I`ve been running this car for years with no apparent problem---how neccessary is this pin? Thanks for any input--Paul
The pined U-joint actually controls the depth of gear mesh on the differential. Unless you are using the modern bearings,it should be there.
I don't know how necessary it is, but my TT didn't have one either. Still doesn't with no ill effects that I can see.
As Uncle Jack said, the U-joint controls the thrust for the ring and pinion gears unless your car has one of the modern driveshaft bearings, so it does serve a purpose. I believe that the thrust on the TT d/s is taken care of at the differential end, so the pin doesn't seem to be necessary in that application.
If the regular T car chassis has the stock pinion bearing, the pin really should be there to control pinion gear depth. If the pin is missing, the pinion gear will have a tendency to kind of float around between zero clearance and the full clearance allowed by the thrust bearing while running which will result in premature wear issues.
Now if your regular T car chassis has a modern pinion bearing setup such as the one sold by Fun Projects, then it may appear as though it is not necessary to have the pin installed in the u-joint because the modern pinion bearing controls pinion depth in both directions, but the u-joint still should be pinned to the drive shaft to eliminate the slight forward and back floating of the u-joint which can cause premature wear.
The TT truck chassis worm drive rear axle and drive shaft is an entirely different situation, but still needs the pin in the u-joint. The worm gear that is attached to the drive shaft has ball thrust bearings front and rear to control thrust in both directions within the rear axle. This eliminates the use of the back of the U-joint as a thrust surface in TT drive lines. Even though it does not appear to need the pin to control thrust, just like the car, the pin really should be installed to keep the u-joint from floating forward and back & wearing prematurely.
Please forgive me, but I don't get it. Sure, with the pin installed, you have essentially made the driveshaft one with the female end of the u-joint. However, doesn't the whole drive shaft assembly still float due to the fact that the male end is not pinned to the transmission output. I don't see how pinning one end of it while not pinning the other end has any effect on the pinion bearing.
The part that was left out is that with the "stock" setup the pin in the ujoint of course locks the Ujoint to the drive shaft but also the back surface of the ujoint rides on the front face of the upper drive shaft bushing and that is what locks pinion from further rearward movement. With the stock setup you need to very carefully set the endplay of the driveshaft/pinion gear assembly to prevent the pinion from moving rearward. This is accomplished by carefully facing off the front of the driveshaft upper bushing using a facing tool. The ideal endplay is about .004 but with the Fun Projects kit as mentioned here, the movement of the driveshaft is locked at zero endplay by the lower drive shaft bearing assembly and this would seem to make the ujoint pin unnecessary - not so but for another reason - read on.
NOW - having stated that the modern drive shaft bearing assembly locks the drive shaft and pinion gear into position with or without the u-joint pin in place - I want to point out that it is very necessary to still have that pin installed and the reason is that the knuckle of the ujoint should remain concentric with the center of the ball housing. If the ujoint slides forward or back while you are driving and then suddenly the rear wheel(s) drop in a hole, the ball will make a sudden pivot and if the ujoint is not concentric, it will be caught in a bind and need to "squirt" quickly forward or backward with some real force. Think about it. You do not want or need that to happen. It can cause severe wear on the parts of the ujoint and also the back end of the transmission tail shaft. Normal sliding in and out of the transmission tail shaft will indeed cause some wear there but it is not dangerous nor will it bind up if excessive but if the ujoint can slid up and down it may be returned to its "correct" position with a major slam of force if it happens to have slid into the opposite position from the direction it suddenly needs to move to as a result of the rear end pivoting up or down.
Pin the ujoint!
Let there be light.... OK. Now I understand. Thanks, John.
I believe it was John Regan who originally taught me about the U-Joint issue and I'm glad he posted about it here. He describes the issue very well.
There are a couple other tips I can mention here.
1) Don't heat up the pin to help you rivet over the ends. The heat will make it more prone to breakage. It is much more effective to rivet the pin over cold.
2) If you have any slop in your u-joint to drive shaft connection, it is very possible that it can work harden your pin and cause the pin to break. Good insurance to minimize trouble if this happens is to find some original #2578 u-joint pin plugs. Most of the original ones I have seen are lightly dished on the inside to match the curvature of the inside of the torque tube. If the plugs are level with the inside of the tube, then in the event that one end of the pin might break in the future, the pin still will stay roughly in position and does not get torn up by hitting against a higher, square reproduction plug end.
I just installed the pin---can`t seem to get you guys to cut me any slack....(made one with a slight taper on the lathe)Thanks to all for your comments!----Paul
My Dad told me there was a reason Henry put pins and cotters in everything. Most of them will be behind you on the road if you don't.
Thanks John - I was confused too but thanks to your explanation, I now "GET IT"!
Lord knows, there are lots of things I don't understand about Model T's, but accordingly, I try to go by this personal "rule of thumb":
If Henry Ford was thorough and relentless in anything, it was always looking for ways to save $$$ on building Model T's, and I always feel that if a part, no matter how insignificant, was not needed, he would have eliminated it. If he did not see fit to eliminate it, I don't either! Fifteen million U-joint pins would have added up to a lot of $$$ saved if he thought he could get away with it!
Oh, and I guess I should have said that it would have been even more of a $$$ savings if ol' Henry could have eliminated the machining time and equipment to drill fifteen million holes for that U-joint pin too,......but he didn't spare that expense either!
Without that pin, when wear occurs on the ring gear and pinion, the pinion will slide back and forth and the ball bearing thrust washer for the pinion will becom discombublated with evential damage!
When I disassembled the rear end in our 26 I found that the heads of the three bolts that hold the differentianl housing together was half gone, they were no longer a hex headed bold. There was no pin in the universal joint.
Need to note that the thrust washers were gone. Prior to disassembly I checked for the axles for end play and thought I was good, my only reason to tear it done was to replace an axle due to a broken key way. But I found a lot more. I contributed this to the pin being missing.
There are no forces to drive the pinion gear into the ring gear. Under load either engine pulling, or braking the forces will try to push the pinion away from the ring gear. The pin keeps the driveshaft assembly together, but if theres play between the U -joint recess and the drive shaft, then a tight fitting pin will try to transmit the torque and fail. I install them on the driveshaft when I rebuild them , but usually when I take a rear axle down, they are sheared. I don't think the pin is necessary.
There has always been a group of leave-the-pin-out guys. Reed Welsch was one of them.
The theory being that a floating U-joint will easily find the center or axis of the driveshaft ball joint as the rear axle moves up and down.
i know, when the front driveshaft bushing is trimmed correctly and the pin is in the U-joint axis will be lined up with the ball joint center.
I'm all for using the u-joint pin, but I sure wish they had a head on one side, so you didn't have to try to keep the dang thang centered while trying to rivet both ends!
The easy way is to place a bolt into one of the threaded holes to support the end of the rivet when banging it with the punch. Thread in the bolt until its against the rivet end, with the rivet spaced correctly in the U-joint.
Forget what size threads there for the access bolts, but maybe its the brake shoe bolt? Someone will correct me!
Anyway that is the best method I have found.
A long time ago an old T mechanic showed me a trick on installing the U-Joint pin. Place the pin half way in a vise and smack it with a heavy hammer just enough to bend the pin slightly in the center. Now drive the pin home in the u-joint and it will never move if the drive shaft to U-joint mate is tight. No need to peen the ends of the pin. I have done this on every running T that I have and have never had one move. Your mileage may vary!
Pre-peen the pin on one end, install pin into u-joint, thread a fan shaft pivot bolt into hole and against peened pin and flop D.S over so fan bolt is against floor, bench vise, etc., use punch to peen other end.
I confess I just use my lathe and make a pin with a head on it out of some 12L14 steel rod that is slightly larger O.D. than the pin. I machine the pin to fit fairly tight to the ujoint hole and then drive it in and flip the Drive Shaft housing over and slide the hole plug hole over a punch held vertical in my vise. I then just peen the other end with a punch wile the vise held punch acts as a buck for the other end of the pin. Works for me.
12L14 must make a pin that peens over real nice!