What is this?
 

I feel stupid asking but what is this? Thanks.

Re: What is this?
 

its an underdrive for AA trucks

Re: What is this?
 

I jumped the gun I think cas3 has got it right.

Re: What is this?
 

Thanks. I thought that it was some kind of overdrive. I found a matching picture on an AA truck. Any applications for a shortened driveshaft hot rod set up?

Re: What is this?
 

its underdrive, not overdrive. more reduction for the poor little car motor in a big truck loaded to the max and trying to get up a big hill

Re: What is this?
 

I am unfamiliar with these; do they shift manually (NO synchromesh)?

Re: What is this?
 

i have never been inside of one, but i would guess due to the era built they are of the sliding gear type, and not synchronized.

Re: What is this?
 

Here's one taken apart.

Re: What is this?
 

Looks like it kind'a works like an "In/out" box. Kind'a like you start-out in underdrive if you're gonna need it, then just shift 'out' of U/D when you've topped the hill. What a contraption! DD


https://www.fordbarn.com/forum/attac...4&d=1590254617

Re: What is this?
 

It's just a two speed planetary transmission.

Re: What is this?
 

Run it backwards!:D

Re: What is this?
 

Seriously I was going to ask this. Why no? I'm just knee jerking. :)

Re: What is this?
 

There was a 6cyl stovebolt in NC back in the 50s that was legendary for speed that had one of these in backwards.

Re: What is this?
 

I wonder what it cost when new??

Re: What is this?
 

April 15, 1928 parts book shows $50.00.

Re: What is this?
 

That would have been high dollar, close to 10% the price of a car!