MTFCA Forum

I found this in my transmission screen. I am assuming I am going to have to
pull the engine and repair the tranny.
What gear did it come from?

Dave, I'm NO expert, but that looks like a lug out of the clutch drum that holds the clutch discs in place. If that is what it really is, there may be more cracked and ready to break as well. Take it real easy on the clutch when you drive it.

I hope a more knowledgeable T person can confirm or deny my assessment.

Good Luck

I'm going to venture to say it is starter bendix tooth.

That is a disc lug from the brake drum.

I jumped in prior to seeing the size - I regress.

Best guess: a tooth off the driven gear or a triple gear.
Viewable thru the inspection cover. May need a mirror or endoscope.

I compared it to a triple gear, the middle gear on a triple gear I think is a match.
Wrong profile for the gears on the drums. The gears on the drum are much wider.

Richard, could I be that lucky?

I agree with John, triple gear tooth from one of the earlier 3 piece gears.

Allan from down under.

Probably a pull the transmission repair. However? What are the chances that it has been hiding in the engine for decades from a previous rework?

You should be able to inspect all the triple gears with the help of a friend.
Put the rear end on stands. Remove the hogshead cover. Begin in high gear so that the drums do not change relative positions. Drain the oil and allow to drip for maybe an hour to remove most of the oil from the gears and flywheel.
Looking through the hogshead cover hole, rotate the engine and put a chalk mark on each triple gear. Closely (as closely as you can through that small opening?) inspect that visible side of every gear as it goes by. After all three triple gears have been marked and checked? Set the E brake, have friend rotate the engine enough for each triple gear to turn about a quarter of a turn. Put back into high gear. Rotate engine and closely inspect that quarter of each triple gear. Repeat. Again set brake, turn engine enough that triple gears twist about a quarter turn, and again inspect. Then repeat again.
If one of your triple gears has lost a tooth? You should be able to see it by carefully inspecting a quarter turn of the gears at a time.
Remember. In high gear, the transmission drums are locked together and the triple gears do not rotate on the flywheel. With the E brake locked, the clutch is disengaged, and the drums and the triple gears rotate in a predictable relationship. Marking the gears with harmless chalk makes it so that you can keep track of what areas you have seen and how much the triple gears have rotated in relation to the flywheel.

If that broken tooth came out of your engine, and is confirmed by size and cut to have been a triple gear tooth, but none of your triple gears are broken? There is a very good chance that tooth could have been hiding somewhere in the engine from a long time before.

When I rework an engine, I clean and carefully inspect for hiding debris. I have removed many hiding pieces from from blocks, pans, and especially flywheel magnetos. In spite of that, I once had a part of a broken bolt show up when changing the oil. Whether it was stuck in the pan's drain, or I missed it on one of the flywheel magnets? I will never know. I spent nearly two hours checking for every possible bolt the piece could have come from, and all of them were intact and good condition. I closed up the engine, crossed my fingers and never had a problem from it.


For whatever it is worth? Not being able to inspect that tooth up close and personal or compare it side by side with examples of the various gear teeth inside a model T makes it difficult to be certain what it is from. However, it does appear to me to be from one of the earlier riveted style triple gears. If your T has the later triple gears with thinner gears and this tooth is therefore too long? It may not be necessary to spend a lot of time looking for its source?
Inside of a standard model T engine only has a few gears with teeth that a tooth could come from. Starter Bendix and flywheel gears (doesn't look like those?). Timing gears (check size?)? Triple gears, early or later? Or transmission drum gears? Those, if you have spares handy? Carefully compare size, cut, and profile to make sure the tooth may or cannot be from any of the three drums!
There were a few after-market oddities like speedometer drives that put an additional gears inside a T engine. But that is pretty unlikely. Far more likely could be some errant broken bit dropped into the engine at some time in the past hundred years? One of my past model Ts surprised me with a metal piece that had nothing to do with a model T. Someone before I had the car must have dropped it into the engine.

Wayne

It was a brand new engine 4-5 years ago, but I have driven it from Milwaukee to Detroit twice, so it has gotten a work out.

Thank you for the advice. I will have to find a model t owner to help me look thru the hogshead at the triple gears.

Well well. Would you look at that. Out comes the engine. Good thing I just purchased an engine hoist.

From what I see of those two mating parts, there is something missing.

Looks like you know what you will be doing for a few Fall and Winter months?

An observation. firstly, the missing tooth there doesn't appear to match the tooth you found?
Secondly, there appears to be discoloration on the gear where the tooth broke off. I would speculate that this gear had cracked years ago, the tooth broke off and went through the gears, breaking off another one somewhere?
Doesn't change anything. The engine has to come out, be largely taken apart to remove and completely disassemble the transmission to rebuild it.

Carefully clean everything. Try to do an accounting of teeth and other things to make sure you have all significant pieces removed before final assembly. As I mentioned earlier. broken bits do like to find their way onto the magneto magnets and stay there to shake out sometimes years later. You don't want to have a future day ruined by a revisit by a broken gear tooth!

Looking at the pictures , I can see that the triple gear itself is flaking and should of been changed out for a better example or new ones installed.
Anytime you can see metal being removed from gear tooth itself it's setting itself up for this to happen.
Most likely the low speed/reverse and drive gear are also marginalized from amount of wear.
As others have mentioned a thorough cleaning and inspection is definitely needed.

Drained the oil. Nothing there. Wonder what is on the inspection cover. Will know soon enough.

It appears the broken piece fits exactly to the original gear. Tranny is taken apart and will be inspected. Engine looks fine. All triple gears have evidence that this break might have occurred some time ago. Question is, should all the triple gears be replaced?

I've re-built many T engine/transmissions and dismantled many for parts, I have never come across a triple gear that had broken a piece off.

I rarely trash model T parts. And I like the early style triple gears if they look good. The truth is, that you cannot always tell if a gear has been compromised or not. So any gear you use may have been damaged in this way regardless of how good it looks.
Yes, you should trash all three triple gears as pieces of the broken gear likely ran through them. Closely inspect the drum gears for any signs of damage also.

I agree with Wayne, replace all three gears, from the same set if you can get them. I'd also stick with the earlier 3 piece gears. There wider teeth spread the load better than the later one piece gears with the narrower teeth. Plus your drum shafts have been running the wider gears, so bedding in will likely be less noisy. If you re-bush replacement gears, check that the rivets are tight before installing new bushes.

Allan from down under.