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I have to replace the output shaft bearing in '41 1/2 ton PU (AK) 3 speed transmission and my mechanic says that we will need a special flat wrench to remove the Bearing Retaining Nut. According to my shop manual it says we need a J-112 wrench.
I have looked and can't find one on the web. Where or what should I be looking for?

you may have to fabricate one yourself.

What size wrench?

Many bicycle repair wrenches are very thin - like 1/8" or less.

Ah yes, the famous GM J- tools. A lot of the factory manuals have pictures of the specialty J- tools. See if you can locate a factory manual for your year truck. You can then use that picture to fabricate your own tool. Make sure you get back to us when you get this done with pictures of your tool. Make sure that you stamp "J-112" on it.

Haven't seen a J-112 but a J-933 is the correct wrench for the post-war 3sp clutch (input) shaft. I just tried it on a 1940 trans and the fit is the same. Look at the pics. 1/8" thick and 1-5/8" jaws. I think the bend in the handle is probably irrelevant, but it does make for better balance. May be why you can't find a 112, it was probably superceded by the 933.
Need a press. It's a press fit.
Make sure you re-stake the nut when you put it back on.
Make sure the snap ring fits the recess... may have to use the old snap ring. I did.

How did you clean up those gears, Jethro?

That gear is a worn out one I use as a tool to line-up the clutch installation and the bearing race welded to the other end is used as a driver for installing the rear axle seals.
I put a new clutch shaft in my 3sp. It was jumping out of 3rd.

Find a 1 1/2" open end wrench at a pawn shop or a flea market, and spend some quality time with an angle grinder to thin it down, then adjust the opening to fit the flats on the nut.
Jerry

Jerry, just getting some 1/8" flat stock would result in a smaller pile of steel dust from the grinder. I've made a couple wrenches from flat stock, although mine was 1/4" thick for a fan clutch.

Buy a wrench that's already 1/8" thick, like the one pictured, and grind the jaws to the desired size.

Ron,

I will add my $.02 worth in here to offer another "alternative" tool.

First, a check of various Chevrolet Master Parts and Accessories Catalogs, starting with the 1929-41 Book, indicates that the "bearing retaining nut with oil slinger" is GM# 591150.

Second, a check of GM# 591150 through GMPartswiki shows that the same part number was used in all the early (1937-50) standard 3-speeds, the SM318 3-speeds, as well as later Muncie (1963-74) 4-speeds. Same part number across all these transmissions, checked through the various Parts Books through the 1979 edition.

That being said, it should be safe to assume that a more recent "wrench" for removing said retaining nut w/slinger for the Muncie's should take the place of the original J-112 removal tool.

Jethro's "J-933" wrench would work, if you could find one. Here is a link (not mine) to an Inexpensive wrench designed to do the job for Muncie's and should work just fine for your 3-speed. No fabrication or modification involved and readily available.

Let us know what you figure out and what may or may not have worked.

Dan

So is this wrench I have, from an auction "treasure box" lot that I've never identified, one of these J tools?

The jaws are 1 11/16 at the opening and 1 9/16 at the bottom of the straight parts. The small end appears to be 9/16.

John, yours may be a knock-off of a GM special tool. If it was genuine, it would have markings like the ones on Jethro's above.

Kevin... could very well be -- no markings on it. And it doesn't look all that old. I had thought it was a tool for a router chuck or something.

Thin wrenches. Like Bonney wrenches.

Looks just like a wrench that came with a bicycle. The large side was for adjusting/removing the bearings on the crank.

I made the Input Shaft Wrench from 1/8” flat stock. I welded two pieces together as I didn’t have any plate wide enough. Crude but effective.