3 speed gear box - tear down

mikeob1 · Dec 27, 2009

I finally got around to pulling the 3 speed apart that was sitting in my backyard waiting to go in the 1969 project I am doing.

I'm trying to figure out if this 3 speed is junk or rebuildable.

The gears inside look OK. A couple things concerned me. The input shaft to the transmission is a little wobbly and has some sign of the previous owner welding. This transmission was attached to a Chevy 235. I'm wondering if the PO did some mods to make the Chevy engine mating work.

I am looking around trying to find the PDF file I had of the 3 speed FSM with specs so I can continue disassembly and measurement taking.

Does anyone have the FSM I'm thinking of?

Any thoughts on determining if this piece is yard art, or rebuildable?

mikeob1 · Dec 27, 2009

One more pic

output side

inkpot · Dec 27, 2009

Howdy! Nose cone on the input side has been customized, so I would just replace it to go back to OEM setup. Have you just considered going to a 4 speed instead? Offers a bit nicer driveability and a fully syncronized first gear. John

mikeob1 · Dec 27, 2009

You are right on saying a 4 speed upgrade would be better. I was going to run this 3 speed, transfer case, and driveshafts for the time being if it is runnable just because it's what i pulled out of the rig. I already have the 3 speed bell housing on the 2f motor sitting in there. But if you know of a 4 speed set up local, i might be interested

. Or if you know anyone that has a 3 speed boat anchor in their garage and wants me to take it off their hands, that would work too.

mikeob1 · Dec 30, 2009

step 1 - remove bearing retainer

So you can see this bearing retainer had it's diameter ground down and some ground allen head screws were in place. This particular transmission was attached to an 1950's era Chevy 235.

mikeob1 · Dec 30, 2009

Step 2 - drift the shift fork out

Using a long drift, pound the shift fork shaft out the front. By "front" i mean toward the motor if the transmission were hooked up. Watch for the two balls and springs. My balls fell into the transmission case...uhhh. You will want a magnet handy.

The reverse idler shaft was also ready to come out. So I did it. it just pushes out the back and then you can find a million needle bearings with your magnet.

mikeob1 · Dec 30, 2009

Reverse Idler Shaft out

yep close to a million.

mikeob1 · Dec 30, 2009

step 3 - drift counter shaft towards the rear.

use a long drift as long as the box to tap the counter shaft from the front until it comes out the back. When you remove your drift, there counter shaft will fall into the bottom of the case out of the way. It stays there until you remove the input shaft and output shaft.

I was able to remove the retaining clip on the output shaft bearing, then tap the end of the output shaft to release the input shaft. Then pound the output shaft out the back.

All three shafts came out in this step.

So again, counter shaft toward the back...then rear clip on ouput shaft bearing...then forward on the output shaft...input shaft is free...then output shaft toward the rear, then output shaft, then rear bearing, then output shaft is free. It is easier than it sounds.

step 3 pound out counter shaft and removed retainer ring on output shaft and remove input shaft.webp

mikeob1 · Dec 30, 2009

Inspection time

The reverse idler is ground down pretty good. Not unexpected because the first gear is also the ider and they aren't syncronized gears. Both are intended to shift only when the output shaft is not moving. This is about the simplest type of gear meshing. The big sucker just gets pushed up and down the output shaft.

The bearing retainer seal is also junk. The second and third gear and the dog collar and syncros all look good. Also the shift fork for 2/3 gear had some heat marks in it like it got pretty hot at some point.