VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 1941 coupe popping out of 3rd gear

Hi,
while worrying if my engine would make a 230mi long trip but it was actually the transmission which started making problems.

After about 2 hours driving it started popping out of 3rd gear. It happens on the freeway, so high speed and under load eg driving uphill. After driving uphill when I lift the throttle, I can push gear lever down again. It slowly pushes the lever towards neutral until it completely pops out.
It has the standard 3 on the tree with torque tube. Engine is the stock 216. I had this problem before and took the tranny out and replaced the two bearing on the main shaft. I noticed that the bearings are a bit sloppy in the hole. I thought the problem was gone but after 2 hours driving it appeared again. It seems to get worse as the tranny get warmer.

Any ideas?

I read something on vcca about putting a shim between bottom of tranny and bell housing, but no further details were mentioned (eg on how thick ).

Please let me know if you have any ideas.

Thanks
Jrom

Your description fits in with gearbox to engine misalignment. You said you had the box out and replaced some bearings was this to correct this problem or a different issue??
The alignment may be at any corner and may be any thickness and will be trial and error to sort out. A grain of sand between the gearbox and bell housing or bell housing and block can cause it or it maybe that the bell housing has bent.
Tony

If the vacuum shift is still hooked up it could cause the problem.....due to an adjustment.

Spend some time doing a Google search on this and searching this forum. While it does not happen "to all of them", it does occur often enough that there are solutions.

I think I even have an older post about installing a shim behind the input shaft to keep things tighter than when it left the factory. I just can't find it right now.

When I was going through the mechanics program in the late 70s, one of the troubleshooting questions dealt with this very scenario. As a general rule when the needle bearings, or the bore between the pilot shaft and the main shaft get sloppy it will pop out of high gear. Some careful measuring and parts research will be needed. Probably need to replace the clutch pilot bearing in the back of the crankshaft if you have not done so already. I have also slightly deepened the shifting fork detent hole in the side cover. Usually it is just a spring loaded ball bearing.

Keep the forum posted as to your efforts and solution(s). It will ultimately help someone else with the same problem.

Art

In most cases that I have found, the fit of the front gear to the transmission input shaft is the problem. If the input shaft gear or the front gear are worn with any taper eventually they will be forced apart. It is most often after alternating between accelerating (power applied) and decelerating. Closely looking at the gears for any taper will identify if that is the problem.

Will a Muncie sm420 fit into a 1941 coupe? Has anyone seen this being done? I see them for sale regularly here in Europe often with the torque tube connection. I'm hoping it is a direct fit since I saw a 3spd pickup with torque tube being converted to sm420 with torque tube. Original 3 speed transmissions are impossible to find here.