Gearbox bushings Question.

Are the bushing in the gears to be a slip fit, interferance fir or a press fit?

Layshaft third, second gear mainshaft, and on the threaded end of the sleeve gear(forth main) can be slipped in and out of position.

Although they seem to be in very good condition, this concerns me, particularly on the sleeve gear.

Chime in at your leasure.

pvisseriii said:

Are the bushing in the gears to be a slip fit, interferance fir or a press fit?

Layshaft third, second gear mainshaft, and on the threaded end of the sleeve gear(forth main) can be slipped in and out of position.

Although they seem to be in very good condition, this concerns me, particularly on the sleeve gear.

Click to expand...

Layshaft 3rd, and mainshaft 2nd. should both be a sliding fit.

The sleeve gear bushes (and layshaft 1st.) should at least be a press fit. A groove and circlip was added to the sleeve gear, first at the outer clutch end for '74, and then later at both ends) I believe one remedy is to Loctite the bush in position.

Thanks LAB, that'll do it.

I used Permatex sleeve retainer on my sleeve gear bushes. I left the rest a smooth slide fit.

Dave
69S

I agree with L.A.B. and DogT. I did this when I rebuilt my current gearbox; and it works like butter. When I stripped it, all the bushings that were supposed to be a sliding fit ... where not. Now they are, as well as the others being press fit as they should. Make sure you have the layshaft roller bearing upgrade too; UBER critical ... Cheers.

Good stuff guys. I'm getting into my gearbox on my restore sometime soon. Does anyone have actual clearance figures for the slide fit between bushing and shaft? As in .001-.002?

Here's a recent forum post on this very subject I asked about too.
Buy two first cog bushes as they get a lot of use and are the thinnest and 1st to wear and can allow jumping out of 1st when in gear but not loaded by drag or power much, whoohoo. Proper reaming by machinist tools is best way to fit. in a dozen years I've yet to read/hear a single success of any Loctite holding any bearing or bush in engine or gear box stable once actually run. Put a new or used extra 3rd bush on the sleeve/main shaft to keep two bushes near the ends where it matters most.

bush-reaming-amc-gearbox-t7941.html?hilit=bush%20reaming

On my 850 Mark II the 4th gear main had a circlip on the gear side. I had it machined to except a clip on the other side. I had to add a shorten bushing to get them to fit the full inside. One of the first questions I asked myself was what bushings do what ? L.A.B. answered that question.I made a copy of that answer and taped in all my manauls. Maybe Fred Eaton could add to his technical articles as well. Phil