Why did this transmission fail?

I rebuilt a ford 4 speed for a 63 industrial. After 25 hours of use it failed while backing up with a load of gravel in the bucket. Going very slowly just after picking up the bucket, one wheel started to slip, I hit that brake. That's when it failed. Taking it apart the reverse idler gear lost 4 or so teeth. The lost teeth caused some damage to 2nd gear too.

Here is a pic of the damage.

I am in need of the tractor, but want to get to the bottom of what the problem was (is). Is this from having the clearance too loose or too tight? Or ? I know you really can't tell from a picture, but any ideas or experience you may have will be more valuable that what I have.

Thanks!
jb

Could this be it?

I put everything back into the case, with all the shim packs at they were when it failed. The countershaft was nice, turned easily and had no felt slop front to back or side to side.

The main cluster is another story. It has .070 to .10 front to back slop. That's just by eye as I slide it back and forth. I can't imagine that "I" missed that. I remember setting it and double checking it. However, loose it is. My thought is that one of the bearing cups wasn't all the way down at the time of initial assembly and under load it seated, leaving way too much slop.

So, to verify, will that much slop allow gears to jump and break, or is there some deeper issue that was messed up, too?

Thanks!
jb

Well, my eye seems to be out of calibration! I put a dial indicator on the end of the output shaft and it is "only" 0.045" end play.

I've got new mainshaft 2nd, countershaft 2nd and reverse on the way. About $220 total with 2 gaskets. Not too bad.

Any words of wisdom on doing it right this time?

jb

Here is a pic of the teeth that were pulled out of the case. They came from the reverse gear.

One (and I assUme the first one to break) was broken in pieces. My guess is that it broke off, munched around in between mainshaft 2nd and countershaft 2nd (just to pizza me off!). The other 2 teeth look pretty pristene, my uneducated guess is that they were forcefully tossed to the bottom of the case before they could munch up anything.

Would more closeups help any? Easy to get!

Thanks!

Oh, I don't think I slammed on the brakes. I had just picked up a bucket of spoils and was going backwards. The tires were in a little hollow from where they slipped going into the pile. One started slipping, so I put on the brake. Can't say as I recall it being a harsh sudden engagement, but then again memory of traumatic events is always suspect!

jb

Dunno what happened. Could be a backlash problem, or a preload problem. If I understand from a previous post, you replaced some gears before? Did you replace all intermeshing gears in that set? If you replaced a mainshaft gear, then you would replace the corresponding countershaft gear. Beyond that, if these were just old gears, I wonder if 40+ years of use didn't just add up at that particular moment? Some days, sh!t happens. Sometimes we do everything right, and there's still a disaster. Dunno. I know for sure that it won't be cheap to fix. I went through a Ford 8x8 synchro a year ago this past winter, and if I recall, I was into it for 2 grand for one synchro and seals/gaskets. Nothing is cheap. HTH.

Rod

Yeah, the reverse gear was replaced, the countershaft, the main 2nd, countershaft 2nd and a few more.

Don't be sorry for being blunt. I am pretty dern sure "I" am the guy that screwed up. No blame shifting or story spinning.

What I don't know is what I missed or messed up on the first go round. I am no smarter now than then and would probably make the same mistake again and again. Don't want that!

The book only lists preload using a pull scale. It is set with the addition of steel shims to the end caps. I thought it was done right, but obviously not. Is it likely, given the damage, it was too loose?

jb