Ford p/u 1946 gearbox
 

Hi All.. my pickup jumps out of 2nd gear on over run.
Any suggestions on what causes this and how to fix it?
Regards Kevin

Re: Ford p/u 1946 gearbox
 

Welcome aboard. Your trans problem is pretty common and is probably due to wear and excessive clearances in some of the components. Get a copy of Mac Van Pelt's transmission book as a guide for inspection, repair and assembly of this model of transmission, vanpeltsales.com

Re: Ford p/u 1946 gearbox
 

"on over run" are you referring to the practice of using second gear to slow the truck down? if so that is not a good use of the trans, does the shift from 1st to 2nd cause any problem? such as scrapping of the gears. these trans have a very primative synchronizer and not really suitable for this use. also make sure the pin and the groove on the shift lever are not worn, as this will cause the problem

Re: Ford p/u 1946 gearbox
 

I've heard that slipping out of second was classed by a sloppy/worn second gear on the shaft.

Re: Ford p/u 1946 gearbox
 

There are a number of wear areas that can contribute to 2nd gear push out. When helical gears became common in the semi-synchronized 3-speed transmissions, the design had to be set up to counter the thrust loads that happen with them. Under load, they thrust one direction and under engine braking, they thrust the opposite direction. When the transmission is new, all the thrusting loads are pretty well countered but as things wear, they aren't counteracted as well. Gears wear, rotating bearings and bushings wear, synchronizer blocker rings can wear, shafts wear, and thrust bearings wear. All of this and wear in the shift tower detents can have an affect. With wear, the input shaft can wiggle around and main shaft will can move around with it. The cluster gear can move a good bit fore and aft as well as a bit of wiggle depending on where the worst of the wear may be. The second gear can woble a bit on the bushing it rides on and the syncho is going to move around a bit too if the shafts & are moving around too much. All this stuff can have an affect.

Re: Ford p/u 1946 gearbox
 

Thanks Guys.. I guess I'm going to have to pull the box out. I installed it in the early '80s and it was doing it then. As you all say it's probably worn in out in general a bit like myself. The engine is a tad tired as well and chews the oil. Fortunately they're quite easy to pull apart as I recall.
Cheers guys