Transmission Pilot Bearing Spacer
 

I am rebuilding my transmission by installing all new bearings. I have new shafts with o-ring grooves to eliminate oil leakage out the rear of the tranny. I had the end of the Transmission Main Drive Shaft built up with weld and turned to 0.668" diameter.I selected the best gears I could find that appear to be in very good condition with no pitting. I am using Les Andrews instruction book for assembling the transmission. He states that the Transmission Pilot Bearing Spacer should be replaced if it show any signs of wear. I am sure that the spacer is worn, but I did not purchase a new one when I ordered the new bearings, gaskets, etc. I have access to a machine shop so I can easily make a new one rather than wait for a new one. Does anyone knoiw what the thickness of a new spacer should be? The one I removed is 0.090" thick. Is there a maximum thickness it should be? Thanks in advance for any responses. Also, is there anything else I should do to insure a good running transmission (short of buying a new one)? Don/WI

Re: Transmission Pilot Bearing Spacer
 

I do not have the dimension of the spacer around anywhere. But if you measure the diameter of the round stock from the outer side to the shaft side, there is usually no wear there. The face that rides against the bearing takes the wear. So compare that cross section diameter to the one of the non bearing cross section and you should have it. Be sure your shaft is the later one, and not the early one that took no spacer.

One thing to check is cluster end play to the case. Lately I have run across a few where the case thrust surface was worn so the cluster had about 100 thousanths end play. That's too much, and the cluster will bang back and forth. I had a custom thrust washer machined to give it .004 to .008 end play (same as a V8). Also check that your second/third slider fits the main shaft snugly enough to slide down slowly when the shaft is stood up and oiled with 600.. The looser the fit, the greater the odds it will pop out of gear on a hill in second gear.

The condition of the shift rail detents, the spring and plunger are also important, as is the selector ball, and the groove it fits into.

Re: Transmission Pilot Bearing Spacer
 

I am not sure that welding up the bearing surface of the main shaft is a good idea. The surface is supposed to be hard. There is an article available that explains how to machine it down and press a new race on. It actually takes two races in series. The article appeared in the 1985 July/August publication of the Restorer, page 13. It is a copy right document, so I cannot post it here.

You can obtain the races from Action Bearing in Boston, e-mail [email protected]. Phone 800-225-4587. The part number is IR-812, $6 each, you need two.
The race ID is .500-.4996, OD .7493-7488. "Turn the shaft down to .5005 and press on both the races. When you turn the shaft down stay approx 1/8" away from the shoulder and don't machine it square at the shoulder. Leave a small radius" Quoting from the article.

The front spacer on the main shaft comes in two variations. The early version has an intregral spacer that looks like a thick flat washer. I don't believe you can replace those. I have never seen a need to do so. The later version looks like a small round key ring and are usually worn flat in the front and should always be replaced. You can get them from Bratton. Part number 10270, $1.65 and easy to replace.

The very front of the input shaft has a diameter that should fit with a nice sliding fit into the pilot bearing in the flywheel. Quite often they are found worn and grooved. These can also be repaired by machining them down and pressing on a race that will fit into the bearing. I don't have info on the race, but you can send your shaft out for repair. The price is reasonable. Contact Jim's Automotive Services in Costa Mesa, CA 714-546-2969. Jim Nichols -owner. You might able to get a suitable race from Boston bearing if you can figure the dimensions.

Go onto the Orange County Model A club's web site. www.ocmafc.com. On the left of the home page there is a menu, scroll to "tech articles" and click. It will bring up a number of tech articles. At the very top is my name, click on it and it will bring up all my articles. There are several about the transmission. You are welcome to download and use any as you like.

Henry set some transmission traps for the next 100 years of Model A enthusiasts. So be sure you learn about all the traps. The changes that were made are very subtle, but if you are not aware it can ruin your day. They are all found in my articles.

Tom Endy