Having the rear end out of my car right now, I made the mistake of checking some things over.
I measured the square hole in the back of the transmission where the U-joint plugs in (the 3321 driving plate) and found that it's worn a bit. The flats are smooth, and there's no evident step at the front of the bore. It's just oversize compared to the original blueprint dimension. The effect would be that there is more slop between transmission and U-joint than when new.
My question is: How much is too much ? Does anybody worry about clearance at that connection ? Specifically, my driving plate is 0.895 across flats. The blueprint dimension is supposed to be 0.875/0.877.
Do the transmission rebuilding pro's out there ever replace driving plates due to excess wear ?
Thanks in advance,
I replaced the one in my 1910 due to excessive wear in the square hole. There was noticeable movement with the ujoint in place. More than I was comfortable with. I wouldn't do it without considering the steps to insure the new piece fits well with the 4th main, is balanced with the brake drum and the tail shaft has little or no run out.
I did notice an improvement on shifting from low to high. Its smoother than before.
Try inserting the ujoint and check the movement. You'll know if it is excessive.
In the past, some of the reproduction U-joints measured oversize in the front section - one of them might be a good fit in your oversize square hole.
Has anyone tried to shim there as a temporary fix?
If so, did it hold up for any substantial use?
I would guess that shim, even hard shim, would wear away eventually and fragments would get into the 4th main bearing or u-joint, or both.
I kind of think that the repro joints are tight at the corners. In other words, the corners are not chamfered heavily enough, or in still other words, the dimension across the corners is too large, while the dimension across the flats is o.k. I could be wrong though. It's happened before.
That does sound like a lot of slop. Have you actually held the u-joint up there and wobbled it around to see how much movement it can really make? Aside from vibration, it could cause early u-joint wear & failure.
Jerry, you are correct, most of the dimensional problem is at the corners, but even after fully chamfering the corners on the reproduction U-joint that is now on my Ebay Ruckstell, I had to do some grinding on each of the flats to get it to fit inside a spare OEM drive plate that I bought just for fit-checking.
So at least one of them was oversize at the flats and I happened to be the unlucky person who got it.
Yes, a batch was made incorrectly a few years ago that had .0015" over size flats instead of under, making them .003" out of spec.
A shim, at best, is a temporary fix. But not necessarily a bad one. I can't remember which one, but I put a steel shim in one of my Ts, and drove it for years that way. I never had a problem with it. That was after I had found a couple in Ts that had apparently been run long and hard, and were still working okay. I would not recommend using brass or other soft metal shims in that location.
I use paint/rattle can metal. Readily available, cheap, and tough stuff.
Be conscious of centering. Check for cracks or uneven wear inside the transmission. Shim to a near snug slip fit. Grease heavily. Remember, this a TEMPORARY fix. Don't count on more than about 10.000 miles from it.
The primary purpose of the shim in this place is to reduce looseness and hammering between two metal parts. A secondary purpose is as a sacrificial wear material. Both slow the self destruction of the two original parts, and therefore extend the useful life of them.
As always. Perfect fitting new or original parts is a much better way to go.
Drive carefully, and enjoy, W2
Richard & Jerry : Yes, I inserted a nice condition U-joint into the back of the transmission. I can feel slight movement. It doesn't seem alarmingly loose to me. But that's why I'm asking. I'm not sure what "alarmingly" feels like in this application.
Further information that may be of interest: The reason that I have the rear end out is to permanently remove a cast iron Warford. There was no U-joint between the Warford and the planetary. That means the input shaft of the Warford was undersize to insert into the planetary. There were shims on the Warford input shaft to make a better fit. The shims looked brand new and were exactly the same size as the front of a U-joint. So it looked like the shims had been a success, although I don't know how many miles they had been driven. I have only put about 200 miles on the car in the time I've had it, and it came to me with the Warford installed. There was no discernible clunk or rattle on shifting or braking.
The bore of the driving plate feels perfectly smooth and I can't feel any wear step where the end of the Warford input shaft was riding in the driving plate.
Of interest to me is that none of the catalogs show replacement driving plates, either repro or original. And I have seen no dire warnings about inspecting for loose U-joints. I'm not trying to justify leaving the driving plate alone, but surely we would hear more on this subject if it were a known problem.
One other thing of interest: The fit of the Ford U-joint into the back of the Warford is exactly the same dimension as the Warford-to-planetary fit. Based on comparisons of the two square shaft fits I had assumed that they were normal. That is, until I checked the blueprint dimension on the driving plate and saw that it was oversize.
Just for comparison, my ujoint would rock back and forth about 1/16". Combined with the fact I was experiencing a somewhat clunky shift from low to high made me decide to switch it out. I have to admit, my shifts are smoother now.
Thank you for that number, Richard. I'll re-check mine in the morning to give you a comparison. But my feeling right now is that it's only a fraction of the 1/16" that you describe.
OK Richard. I plugged the U-joint into the back of the transmission this morning to compare the "rock back and forth" to what you saw on your car.
It's hard to be sure, but I'd say that mine is only 1/4 to 1/2 of the play you observed. You can definitely see the motion, but I'm not sure how I'd measure it.
The car shifts OK. At least I think it does. This is the only T I've ever driven and I've only ever ridden in a couple of others.
Based on input so far, my thinking is to leave it as-is unless somebody else comes forth with more information indicating an impending failure. Any additional input will be welcome. This car is hardly a Montana 500 candidate, and is only driven 5 or 10 miles per year.
If the engine and transmission were out for overhaul, a better driving plate would definitely be on the list of parts to replace.
I agree. Its a lot of trouble to change things out and recreate the same alignment and balance. You might consider a better ujoint for a closer fit. I see some have used shims with success. I personally wouldn't go that route, but it is another option.