Jumping out of second gear

[Ryan_M]

My recently rebuilt transmission has roughly 1400 miles on it. Yesterday, it started popping out of second during downshifts and deceleration. I know this is the typical first sign of bad synchros. When I rebuilt, I used parts which I have since learned stand a good chance of being inferior foreign made junk.

As the result of a previous thread, I bought an NOS synchro unit to have on the shelf. Even though I have these parts, I'm not thrilled to have to pull the tranny and rebuild right now. A few questions:

1. Am I going to do any additional harm driving it as-is this summer, even if I have to occasionally hold it in second gear?

2. Could the problem possibly be due to worn poppet balls/springs? I never changed those out during the rebuild. If those are the culprit they'd be a lot easier to deal with right now. Is it possible tell by visual inspection if they are shot?

3. Any other suggested "easy" fixes or am I only avoiding the inevitable task? I've read a few posts about horseshoe shaped shims that were available years back that might help. Any other suggestions?

I'd much rather tear things apart in the winter than have to rip into it this time of year.

[bretto]

It could be the 2nd gear.  The teeth on the gear that mate up with the synchro hub get rounded and shortened and during deceleration, the 2nd gear is actually pushed away from the hub due to the torque forces and will pop out.  During acceleration, its the opposite, it's being pulled into it the hub.  That's why some have added shims to make up for the wear and keep it held in closer to the hub.  I think it's a bandaid to get getting new parts.

[Carls_jeep]

It could also be to much end play in the gear assembly. Did you set the end play when you rebuilt the tranny? If not that may have caused it to wear and start jumping out of gear.

[Ryan_M]

It could also be to much end play in the gear assembly. Did you set the end play when you rebuilt the tranny? If not that may have caused it to wear and start jumping out of gear.

I don't think I paid close enough attention to the end play as I should have during the rebuild and that could very well be the root of the problem.

I checked/tightened all the tranny related bolts this morning and a couple of them moved a 1/2 turn or so. Doesn't seem that would cause the problem but I went for a drive tonight and couldn't get it to jump out of gear. I doubt I'm going to be so lucky that it's healed itself but I'll drive a little more before ripping it apart.

[Carls_jeep]

You can wait until winter if you only drive it in good weather.

[garage gnome]

I've got to rebuild the tranny in my '49 because of this same problem. It is fine up hill or under a load, but not coasting on compression.