MTFCA Forum

I bought this car knowing there was zero compression. I could see/feel the gear on the generator did not turn when hand cranking the engine. The pistons move freely. I felt that it was the timing gear and sure enough it was sitting there with very few teeth along the back edge of the gear. What are some of the things that come to mind that would destroy the fiber gear? I plan to replace the gear with an aluminum gear. Before I try to start the engine I will lift the rear end, put the trans in high and hand crank the engine. Hopefully I won't have any binding or locking in the drive train. Any other suggestions? Do these fiber gears just give up and fall apart? The son of the previous owner seemed to remember that the car was running and stopped quickly. Dick C.

Over the past 45 years I have heard many horror stories of fiber gears failing yet I have used one in the coupe for at least thirty years with no problems. I suspect all fiber gears and their usage conditions are not all equal.

1. Most confirmed failures were in the early 2000s, whereas mine was manufactured in the 1980s. Could it be different materials?

2. Lee Pierce noticed failures mostly occurred on cars with generators and suggested the generator gear wasn’t running true and worked the fiber gear to an early failure.

Both ideas seem feasible so who knows?
Meanwhile my old coupe runs just fine though I periodically inspect it through the oil filler cap just to make sure. Having said this, it will probably failure on my fourth tour of the year in Spokane. No concern, I carry a spare.

No concern, I carry a spare.

I hope it's not another fiber gear.


Maybe they're not all the same, but I don't aim to ever gamble on another one.

I think this one dates back to the seventies or earlier.


Dick, your gear was in a 1925 car but it wasn't a 1925 gear. The original was steel.

I've pulled three motors down the last few years with fiber gears and one gear looked new the others were toast. Get a good quality gear.

I agree with NOT using the fiber gear. My question is: is this a natural occurrence or should I look for other things that would case me a problem with a metal gear? I am aware that the generator gear could have caused the problem but given I install a metal gear would there still be as much of a concern? The car has an alternator (12 volt) which will be replaced by a 6 volt generator.

There are/were two types of fibre gears. Tony's, being as old as it is, is likely to be a laminated fibre gear. These are far superior to the stuff available today, these being made from macerated fibre, ie. chopped fibre glued together in some kind of mix. They are like chalk and cheese as far as strength/durability goes.

Allan from down under.

As I understand, the fiber gear was supposed to be quieter than a metal gear.... but they don’t last for long.
I was a little guy when the gear let go on our way to east of Columbus to the family reunion.
Coasted into a driveway just past the 4way stop in Homerville. A town where if you sneeze driving through, you missed it.
The old man tore it down in the driveway and found the gear stripped, walked back into “town”
and found a general store where a fellow said there was a barn nearby. His grandfather had a T he had kept in the barn. Pop got a ride to the barn and found a cam gear in the dirt floor of the barn !!
About 3-4 hours and we were back on the road.
There’s still a spare under the backseat.

At least a T is not an interference engine that bends all the valves when the timing goes haywire.

What caused it to go bad?

Age, and a generator set to 10A or a generator that was just slapped on with no concern for setting the proper backlash.

There are also nylon timing gears too that had issues.

When you do install the new timing gear, be sure to check the clearance to the generator gear. I had to add an extra gasket to the generator mount to get the spacing correct.

Allan wrote: ↑

Sat Jun 19, 2021 8:19 am

There are/were two types of fibre gears. Tony's, being as old as it is, is likely to be a laminated fibre gear. These are far superior to the stuff available today, these being made from macerated fibre, ie. chopped fibre glued together in some kind of mix. They are like chalk and cheese as far as strength/durability goes.

Allan from down under.

Macerated gears are made up from short chopped up fiber with binder added and compressed to make the gear. Laminated are made out of layers of fabric that binder is added and compressed to make gear. I don't know if all Model A's used the Laminated gears from the factory or not, I think they did, and if so, at some point both the T's and A's have had lower cost macerated gears installed. Both T and A can suffer the same fate, stripped teeth(macerated). While the condition of the generator gear and crank gear in the Model T along with spacing of the generator gear to cam gear may come into play, that would not explain why when the macerated gear is used in the Model A, it suffers the same fate at some point.
You will note the mottled surface of the stripped gear shown above, that is a pretty good indicator of being a macerated gear. Laminated gears generally have an even colored surface and may show signs of the fabric weave in less compressed areas.