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Was just sent a 37 Super Eight. Trans was stuck in two gears simultaneously--that part is now OK for the moment, but now the car is in permanent second gear. I surmise from what I have seen with the cover off that the second gear synchro ring has brazed itself to the mating cone. The shifting dog is plainly in neutral so it must be driving through the cone--or? Any thoughts or observations? I have not played with one of these before and really didn't want to get into a major project.

Hi Ross:

If you look in the 33-36 parts book (same trans) you can get an idea of what is happening.

Once the sychro yoke moves forward and the dog clutch engages the yolk pops back; the blocker ring should then be free from the hub. I suppose if there is not enough end play a lock up situation could happen. You should be able to visually establish end play of the blocker ring.

If you look in the manual there is a procedure for setting the shim size via measuring the yoke travel. It's around 9/64 to 10/64+ inches.

If there is end play of the blocker ring then the intermediate speed bearing has broken apart and locked up.
This would allow two gears at once without any interlock.

So this case is a teardown. You will need to buy shim stock to cut you own shims. Also, the procedure in the manual assumes worn parts are replaced, so if the blocker rings and gears are worn the process becomes very judgmental and artful. I used to get into long arguments with belligerents who didn't believe that great care and judgment is required to properly set up one of those old transmissions. Which is one reason I prefer to work with the engineers here in Detroit rather than old car maniacs.

I've heard someone made up new blocker rings and that may be a help.

Best wishes, and remember that is a hand built transmission.

Thanks for the info.

Worked on a rebuilt trans that was doing this and found Factory Spacers were missing/left out. Maybe the this '37 trans was rebuilt by the same guy.

HINT:Theres Peel-Away Shim Packs u can get from McMaster that r close to orig sizes that give u a variation of thickness. You have to mach. the ID out.

mcmaster.com/#standard-shims/=y7fneg

The synchro yoke had waaaaay too much travel, but that was not the failure mode. The synchros ae still ok. The roller bearing at the juncture of the input shaft and the mainshaft had disintegrated into a very effective locking device. I had to drive the two shafts apart. The nose of the mainshaft is ruined. Have not stumbled across why this happened yet.

Glad you found the problem, but like you wondering why. Those transmissions are so incredibly overbuilt they will often outlive several engine jobs. Did it still have an adequate amount of gear oil in it?

After years of not needing it I just sold my spare trans to Steve Babinsky and I know he has quite a few others so he may be a possible source for parts.