MTFCA Forum

This is the first model t I’ve ever been around. I’m learning! Been a tractor mechanic 40 plus years. In rebuilding engine and transmission, I decided to change the ring gear . Old one is questionable and I’m only doing this once. New ring gear fits loose on flywheel. Should it fit tight along with the the brass magnet screws to hold it?

The ring gear is not a press fit. The fit varies from a drop on & tap. I would describe as snug. The brass magnet screws do all the holding.

This new ring gear is loose on the flywheel. I’m afraid that over time the screws will loosen from stretching and then break!

The flywheel may have been run with a loose ring gear. It might be helpful to get everything perfectly clean, then apply LocTite to the flywheel rim and ring gear ID, then install.

Welcome to the Model T world! While you have the engine apart BE SURE to install a rewound magneto ring. Also make sure the oil funnel fits flush and away from the flywheel.

Setting the mag /transmission clearance can be a bit tricky. When doing it be sure to try to get the same clearance all the way around. Shims work for that. When assembling the transmission to the engine you will probably do it on a engine stand in vertical position.

When turning the engine to horizontal position check the mag clearance again. Remember there may be a slight sag caused by the transmission weight. That’s often overlooked. That can be corrected by adding shims to compensate for it. Good luck and as in any old engine there are some things that’s unique in putting them together! Model T’s are no exception!

Thanks for the replies. Cat makes a bearing lock liquid that I may use. Every ring gear I ever installed needed to be heated to install and cooled to a really tight fit, nothing else held it.

Ford went to the heat to install type when the Model A came out.
If yours is really loose, might get a better flywheel. There are loads of them out there.

garyl wrote: ↑

Tue Nov 29, 2022 1:55 pm

Thanks for the replies. Cat makes a bearing lock liquid that I may use. Every ring gear I ever installed needed to be heated to install and cooled to a really tight fit, nothing else held it.

Thats what I figured you were thinking. (shrink fit wise) A drop on fit is not out of the ordinary. More slop than that would concern me also. I would not want any side movement when installed. These gears are of new manufacture & may not be made to the proper dimensions. I have been using up old, replacement inventory & have not installed todays, newest batch. (you know, the ones with the WRONG thread size)

The first ring gear/flywheel sets had counter bored holes & hollow pins to help secure the ring to the flywheel every 90 degrees. The magnet screws went thru the center of these hollow pins. This didnt last long. The extra cost must have been deemed unnecessary. Failure of all the screws is pretty rare, unless one re-used old, marginal screws.

If you are overly concerned & have the capability, pinning the ring gear as originally done would make for a fool proof attachment. I recently salvaged a late flywheel that had the ring gear brazed to the flywheel in 4 places.

Mark Gregush wrote: ↑

Tue Nov 29, 2022 2:04 pm

Ford went to the heat to install type when the Model A came out.
If yours is really loose, might get a better flywheel. There are loads of them out there.

The problem might be in the tolerance of the ring gear. Another flywheel may make no difference. If you look carefully where the ring gear fits, you will be able to see any wear from running loose.

In reply to your fear of the screws coming loose, once you have the screws tight, they will protrude just a bit from the ring gear. You need to slightly peen them to prevent them from backing out. They don't need to be mashed like a rivet, just distorted enough to make removal difficult.

On drop on ring gears, and there was a bad batch mad several years ago, I have just drilled and taped in 4 spacings, 1/2 in ring gear and fly wheel, and fitted locktite grub screws. that takes any worry away from extra stress on the brass screws.