Chev 4, 4 speed truck gearbox

[Vintageben]

Ok I may well be about to ask a silly question but so what ! I'm wondering if it is possible to make a Chev 4 4 speed truck gearbox into a overdrive I know it will probably require gears being cut etc. Has anyone done this thanks for any help

[alsfarms]

Don't know your plan goal or need.  It would be much easier to swap the box for a Borg/Warner T-5 transmission.  That would give you four speeds and 5th being overdrive.  A direct answer to your question, with enough money you can do anything.  I wouldn't want to invest to convert a 4 speed box into a three speed with 4th being overdrive.  The above mentioned swap is a much more feasible and reliable option.

Al

[Vintageben]

Thanks for the reply I was hoping to keep in era with a overdrive would love a Johnson overdrive but I don't think that will become a reality. Was hoping to cruise at 50-55 mph but with less revs. Thanks again I will keep thinking about it

[alsfarms]

You should consider a "mid-ship" mounted overdrive unit.  Several modifications are available.  I have collected several Laycock OD units as they are a good type to modify into a mid-ship OD unit and are reliable .  That way you can keep your vintage transmission and yet when you are on the road, select your OD for a better gear for cruising.

Al

[hiwheeler]

Hi ,

 If its a Chev 4 truck then only 1928 has 4 wheel brakes. I can tell you from experience that a 1927 Chev 4 truck with and overdrive and 1929 Crown wheel and pinion rear end ratio and 3 port head is very hard to stop with two wheel rear brakes at 55 mph plus. So becareful what you wish for.

 regards Dave