The Stovebolt Site Forums The Parking Lot Big Bolts rebuilding a 1941 4 speed can't find tear down pictures or info

Iam rebuilding my 4 speed slide gear transmission and can not find anything that helps with taking it apart. I have the top slide gears out but can not figure out which way the reverse gear shaft is supposed to be tapped out?? If anyone has rebuilt this transmission that has the info, I would be very thankful.

I believe your transmission is the GKT-134. I pulled mine apart last winter and I don't remember anything too complicated about it. There may be a bolt or tab on the front of the transmission that has to come out before that shaft can be tapped out. I remember having to remove a bunch of crud from mine. I don't remember having to search for that bolt or tab.

Wish I could be of more help. I searched for some pictures but I guess I didn't take any.

That's cool ill try it. So the reverse rod will just tap out right? What side would I tap on? The part that is flush with the case or the side that sticks out a little?

Later-model transmissions like the SM-318 have a drift pin that intersects a slot in the reverse idler shaft from the outside of the case. The shaft is removed by tapping the pin into the recess in the shaft, and the pin is short enough to fall all the way into the recess. It's VERY difficult to see the pin, as it's usually driven flush with the surface of the case. Do a thorough cleaning with a wire brush and solvent or you might miss it. (Assuming the older trans retains the pivot pin the same way)
Jerry

I don't have anything that goes back that far but the directions on the SM420 which is similar except it is syncrod, says to drive the pin in to the shaft like the others have posted. Then drive the shaft out front to rear.

Alright will do. I'll also post some tear down pictures for anyone that maybe doing this in the future. Thanks again.

Pictures of the tear down. http://s1139.photobucket.com/user/1...39_n_zpsbqhjye3y.jpg.html?sort=3&o=7

How are you doing with your tranny rebuild..?

I am in the same process on a 1940 model and having issues finding the proper bearings. Specifically the bearing for the front of the countershaft.... the last one at the bottom.

According to my parts manual it calls for a Hyatt 1207 for the rear and that one was easy to find but the front one Hyatt 1206 is a mystery.

First of all Hyatt no longer exists..... I was supplied with a NTN #nj206..... OD of 62mm matches but the inside needs to be 38.0mm and what I was shown was 38.45mm and is too loose it will self destroy. The bearing surface on the counter shaft calls for 38.0mm and measured at 37.94 mm

Any suggestions....?

Bob C

Hy RAC1812 and guys, according to my 1951 GM 212 catalog which covers back to 1931, the front countershaft bearing is Hyatt "C1206" GM p/n 142260. C1206 crosses to Napa p/n M1206UV $34.65, hope that helps.

Thank you sir

Off to NAPA to check them out.

Will advise.

Bob C

NAPA has nothing in stock anywhere across North America.

According to the specs listed on NAPA site the bearing is the right size..... 62mm OD x 38mm ID.

Pursuing another lead under Federal-Mogul M1206EAHL ......bearing search engine at the Bearing store got a blank no stock.... unless some old NOS is lingering around.

The usual Chev suppliers such as Obs.. and Chev of the 40s are NO STOCK but are looking for sources.... a guy in Belgium as exhausted his European contacts.

The ID dimension is the problem we can find 37.5 and 38.5 mm ID but not the specific 38.0 mm. My countershaft measures in at 37.96 allowing for some wear after 74 years. Shaft could be machined to fit tne 38.5 mm but would prefer to avoid that route.

Any leads/suggestions would be appreciated and whatever I find will be update on this thread.

Thanks

Bob C

Hy RAC1812, the SKF p/n for that bearing is C1206, or 1206TS, or F1206TS, or F-C1206TS Hope that helps.

There are some ORB 1207 Hyatts on eBay. 1206 also. What numbers are on your old bearings?

Hey Fella,s
Try this
http://locateballbearings.com
Maybe this outta should help somebody,sometime?
regards,
stevesr.

Thanks for the leads guys.

That should keep me busy for a few days.

Guys at NAPA are following up with SKF ..............

My key supplier counter clerk is away all of next week enjoying his SkiDoo. I will need his help in decoding all the prefix and suffix to the 1206 bearings.

According to the military parts manual 1941 and the engraving on the bearing it is Hyatt 1206 .... no other appendages. Each letter before or after such EHAL and YM etc. denotes a particualr application and can have minor difference in dimension.

The Hyatt 1206 has a central race which is removed for the transmission application.... the OD of that insert has to be exactly 38mm to be the right dimension...... some of the 1206 by different makers have no such insert and makes it very difficult to measure..... so I carry the counters haft with me when ever I visit suppliers.

Oddly enough the 1207 is readily available.

Next step will be to contact the various Ebay sellers and ask them to verify the OD and ID of what they are listing.

Hopefully will find some and will share the info ...

Thanks all ...now to get to work.

Bob C

Somebody with a lathe and a tool post grinder can turn a 37.5 MM ID into a 38 pretty easily. Send me one and I can do it in a couple of hours.
Jerry