Auxiliary Transmission

[BLACKWATERFORGE]

Has anyone put an auxiliary transmission in their truck?
I just purchased a Watson under/direct/overdrive.

[cdeal28078]

So it is either an under and an overdrive? Oh man, I would love to have one of those! Shouldn't be too hard to hook up by looking at it either. Great find!
clint

[BLACKWATERFORGE]

Yes it is 50% under, direct and 25% over

[Donnie]

Yes it is 50% under, direct and 25% over

Hi, Do you know what this unit was originally used in? ... NICE FIND........ Donnie

[BLACKWATERFORGE]

I don't know what it was in.
Perhaps a F-500 Ford or a GMC from the 50's or 60's.
I am looking for a shifter.

[cdeal28078]

Yes it is 50% under, direct and 25% over

That is great! 25% over is pretty good really. Don't want more than that or you will bog the engine. I think an AOD is 28% over but not sure. I never got any mileage with an AOD and a 351W as it was lugging and I didn't have a high enough ratio. Good luck with it. Sure wish I had one like that
clint

[Donnie]

Going by the name of Blackwater Forge, I don't think that you will have any problem of making a shifter or any thing else that you need, ----BUT, if you ever decide that you want to sell it.............please put me on your list ...........Donnie

[38Snubnose]

I think that the underdrive and overdrive ratios previously posted are incorrect. In order to calculate a percentage you must start with a number called the "Base". The direct drive is allways the base. If 3 turns of the input shaft results in 2 turns on the output shaft, that is the underdrive. If 3 turns on the input shaft results in 4 turns of the output shaft, that is the overdrive. We all know that in direct, 3 turns of the input shaft will result in 3 turns on the output shaft. Then by having the output shaft turning 1 revolution less in underdrive, this is a 33% reduction gear because 3 is the BASE and 1 is 33% of 3. Conversley by having the output shaft turning 1 revolution more in overdrive, this is a 33% overdrive because 3 is the BASE and 1 is is still 33% of 3.

Don't allways believe everything that you read. Do the math yourself if you want everything to work out as planned.

[Donnie]

As near as I can tell these were used in F500 & up trucks...I never thought about using one in a pickup... I don't see why you can't, you will have to fabricate a remote shifter...Should not me too hard to do.. Have you pulled the cover to check for worn parts as these were used pretty hard..
On another note if you ever decide to sell it.........I'd like a shot at it, would work nice in my dodge 400 chassis, 10,000 gross..
Good luck with your shifter, I would go thru it before cutting shafts & fabbing all the parts.. Make sure that the gears are GOOD, the bearings are not hard to locate.............Donnie

[fmartin_gila1]

There was a thread about the Aux trans back in January. From what I can remember, your pics look like the Spicer 5831 models. Search for my posts and you should find that thread. They were used during the 50s & 60s. As long as the gears are good, you should be able to get bearings from any bearing house. All the remote shifters used for the various light duty and heavy duty units were the same so big truck wrecking yards should have a shifter assy. Even the COE big trucks had two trans back in the day so be sure to look at them. The remote shifter was a simple unit that had two rails and a shifter stick and you had to fabricate linkage to the Aux box utilizing solid rods with clevis setups on each end.

Fred