The Stovebolt Site Forums The Shop Area Driveline Difficulty to rebuild 3 speed transmission?

I think that if you are comfortable rebuilding your engine, you can tackle the transmission. But, you knowledge will be limited to service and rebuild manuals that will guide in the rebuild process for a factory fresh transmission. But, here is my take on the original 3-speed box and especially worn parts that you may think are ok to reuse: The transmissions used by GM (I think Muncie...cant remember) have tendency to want to jump out of third gear. My transmission rebuild specialists knew the cause and the solution that I am having a hard time remembering (I think I posted about it awhile ago...maybe try searching). Anyway, the solution is to machine a grove into one of the gears.

So, my vote is find a specialist to do the work and talk about the jumping out of third gear issue whether yours does it now or not.

Edit: Found my old post...here is what I said:

I dropped off my '52 Muncie three speed transmission at a local transmission rebuild shop that has been around for years. The first thing he said was "Light Duty Muncie"...never heard it described that way. I went on to tell the shop owner that I did not know the condition of the transmission, but I wanted it gone through, refreshed and made like new. He warned that the syncro drums (I think this is the part that wears and causes transmission to pop out of third etc.) were no longer available, but cold probably fix it up regardless due to his extensive used parts inventory. I also mentioned about the infamous "popping out of third gear" issue that many have experienced. He said he has a solution that will prevent that problem from ever occuring in the future. He basically cuts an indent in the third gear teeth (part that engages third gear syncro drum) and a corresponding grove in the syncro drum splines close to the end of the splines. The theory is that the amount of spline left between the grove and end of spline engages in indent and prevents the gear from disengaging until the load is release upon depressing clutch. He assured no noise or notchy feeling is evident after the modification and that the gears will not fail.