Quote:
Originally Posted by Talkwrench
I'll do another post on rebuilding the gearbox as despite all things being good and measurements ok , it was still popping out of second..  |
That problem is one that is not easy to fix (or absolutely know that you have it fixed). Charlie NY and I are of the same opinion that you want to have the best quality main shaft possible - with as little bearing surface wear on the front as possible (I found new main shafts - which are hard to come by these days). I test fit my main shafts with the front input shaft (with the caged bearing) - to find the tightest combination I can find (least deflection). Basically I put the front input in my lathe, add the mainshaft and caged bearing and then use a dial indicator to measure the max deflection as I wiggle the back on the main shaft. (Note - the lathe is NOT turned on!)
The other two things that seem to help are to re-bush 2nd gear with a very precision fit onto the main shaft - such that you can install it by hand, but it still has a bit of drag on it as you spin it. Make sure you have the correct "end play clearance" - on the tighter side of the assembled main shaft, 2nd gear and synchro assembly.
Lastly, add hard stops to the shifter top - such that when you shift to second, you prevent the shift fork from over-traveling past where it should. I've done all these things (and made my own cluster shaft) on my last two 39 transmissions . . . and they have stayed in gear in 2nd, even on heavy RPMs and wind-downs as such. If you need any more info, just PM me.