SM 420 popping out of fourth

[64RELIC]

I'v had my 64' for 20 years and never had any issues with my transmission shifting or noises.
A few weeks ago I pulled the engine to have the flywheel resurfaced, I could no longer stand the chattering when you slowly let the clutch out, funny what you put up with for years.
The machine shop took 11
thousands off there seemed to be like three darker hot spots but no cracks so it cleaned up nice.
The clutch wasn't worn out but seemed dark and possibly oil fouled so I got a new one.
The pressure plate seemed fine it still had the original swirl marks on so I cleaned it well and just touch sanded it a little.
The pilot bearing in the crank looked okay but I didn't measure it, just a little dab of grease.
The cast iron front over the output shaft, not sure what that's called, I pressed in a new seal and made a gasket to where it bolts to the transmission, there was no gasket there when I took it off. It seemed to have some sealant but no gasket.
So everything cleaned and put back together ready for a ride. Forward reverse in the driveway super smooth clutch action, I'm so thrilled. Get out on the road second gear fine third then fourth pops out of gear, leave my hand on it still pops out, it only stays in if I really hold down on the shifter. That's never happed before. I go in the house and sulk.
Next day with hope and enthusiasm I loosened (a little) the two crossbar bolts, the four trans to bell housing bolts and the six engine to bell housing bolts and rocked the truck back and fourth a bunch of times in the driveway thinking there is some kind of binding or alinement issue. Then short ride on the road pops out of 4th. Go back in the house sulk and write long winded forum post.
Hoping some one has heard of this before. Thanks, Jim

[64RELIC]

Smooth operator

[Short 3/4]

Never heard of this either, but I think I would focus on the shifter and the spring, etc in the top plate hole it goes into. You had to take that apart to get the tranny out, so could be something as simple as the cap or that cover thing that slides around being backwards or jammed up somehow. Sounds like it’s not going fully into gear.

Anyway, that’s where I would start,
Good luck, and let us know what you find

[64RELIC]

Thanks Short, I'll have a look up top. I didn't have the trans out but I did have it jammed up to the floor to get a better angle for pulling the motor.

[SkinnyG]

Back in my apprenticeship days, I was taught that popping out of "direct" is an input shaft alignment issue. No personal experience, I just remember all of it.

Maybe there is a way to check that the bellhousing is true to the motor? Dial indicator on a magnetic base, maybe?

[Short 3/4]

Sorry, misread your first post, just assumed you dropped the trans to get to the flywheel. Since you didn’t take the shifter apart I take back my original comments.

If I’m (finally) reading it right, you resealed the extension that covers the trans input shaft ( what the throw out rides on)? If that’s the case then Skinny is probably right about an input shaft problem. You might want to recheck your work on that. At least it will be easier this time to leave the bell housing and engine in place, and just drop the transmission. Also way easier to check the transmission on your bench instead of on your back!

[scottofksu]

Originally Posted by SkinnyG

Back in my apprenticeship days, I was taught that popping out of "direct" is an input shaft alignment issue. No personal experience, I just remember all of it.

Maybe there is a way to check that the bellhousing is true to the motor? Dial indicator on a magnetic base, maybe?

I was thinking similarly (i.e., index/alignment issue)...

Here's a video on the indexing process:
https://www.youtube.com/watch?v=riay1R38wQo

[64RELIC]

Originally Posted by SkinnyG

Back in my apprenticeship days, I was taught that popping out of "direct" is an input shaft alignment issue. No personal experience, I just remember all of it.

Maybe there is a way to check that the bell housing is true to the motor? Dial indicator on a magnetic base, maybe?

The bell housing to motor has these big locating pins on each side so the bolts are not really doing the alignment, there is no adjustment there

[64RELIC]

I watched that indexing video, interesting I didn't know that was a thing.Seemingly in the video he had a new block and a new bell housing, but in my case the stuff has been mated up for 60 years and probably know each other well by now. The only thing I changed is I cut and put a gasket on that cast iron front input shaft cover. That thing what ever it's called has a pretty close tolerance to the bell housing and that probably sets where the housing is in relation to the transmission. I should have cleaned that up with a new seal and gasket WITHOUT unbolting the trans from the bell housing. and loosing that
alignment. Also I need to find what the inside diameter of the pilot bushing should be. It's funny how much I think about this stuff when you wake up at 2:00 am

[Short 3/4]

Check out page 7-24 of the 63 Factory Service Manual. If you don’t have one you need one. The part that you’re talking about is called the ‘Clutch gear Bearing Retainer’ and there is no gasket between it and the gearbox case. A gasket would probably mess with the alignment of the transmission in relation to that part, and thus the bell housing. If that part is properly installed and aligned on the transmission then it should be able to be bolted up to any bell housing and engine without any problems.

[scottofksu]

Originally Posted by 64RELIC

The bell housing to motor has these big locating pins on each side so the bolts are not really doing the alignment, there is no adjustment there

They sell offset dowels for those to adjust the index. Measure and then install the proper dowel offset in any direction to adjust the index. That said and has recently been added, the gasket that was installed could be throwing you off. These things are measured in the hundreds and thousands.

Good Luck and hang in there! The day when this beast runs flawlessly is just around the corner!