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  Chicagoland MG Club:Driveline
Barney Gaylord Ring Gear Replacement
brought to you by
The MGA With An Attitude

This is one easy course in how to install a new STARTER RING GEAR on the flywheel. To all the folks who tell you it canít be done at home, go sing. You can do this. Backyard barbeque, anyone?

Having done this once, it turned out to be reasonably simple and easy. And this is another one of those ďI did it myselfĒ ego trips, because it sounds a lot more difficult than it really is. The ring gear is a really tight interference fit on the flywheel (shrink fit). To remove the ring gear, you cut about half way through gear between teeth with a hack saw, then use a cold chisel and hammer to break the gear at the cut, and it comes right off. Putting the new one on takes a bit longer, but itís also more fun. Itís party time!

Throw a back yard barbeque and invite a few friends. In this case you need to have a charcoal grill (large enough to hold the ring gear), because a gas grill has a hard time getting the temperature high enough in an expedient manner. After the food is done, and the coals are all nice and white all over, just drop the ring gear right on top of the coals and cover the grill for about 15 to 20 minutes to heat and expand the ring. Ideally you want it to turn blue, then remove it from the heat before it loses its hardness. However, itís not that big a deal if you overheat it and it starts to glow a little red.

Be sure you put it on the right way around, chamfered gear tooth ends to the rear, away from the shoulder on the flywheel for the MGA and early MGB with inertia starter, or chamfered end to the front for later MGB with pre-engage starter. Lay the flywheel flat with the flange down and the step on top. Just drop the hot ring gear onto the flywheel (with the chamfer on the teeth the right direction) and squirt some oil on it with a hand pump oil can to cool it at the right rate to get the hardness back. If you were to water quench it, it could get brittle and crack. If you allow it to air cool (slowly), it could end up fully tempered (soft), leading to accelerated wear. As it cools it shrinks to a permanent tight fit.

Have a drink and congratulate yourself on a job well done. Of course you still have to deal with that messy oil spill and the hot coals in the grill. Later when the car is back on the road you can forget about the starter jamming problems. That was the reason you wanted to do this, wasnít it?

Happy motoring,
Barney Gaylord
The MGA exercizing attitide
CMGC Warrenville Autocross - August 24, 2003

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