AA underdrive used as an overdrive?

hi, can anyone tell me, if using a AA underdrive unit, fitted the other way round, it will work as a overdrive? ive just picked one up at a swapmeet, after been told it works, but cant find info on it working, seems to be a few threads suggesting it could work! does anyone have the answer?

 

is that a yes or a no then?

 

I would be worried it would be way overdriven, i suppose you could count the input turns vs the output turns to get a rough ratio, also if the gears are helicle(sp?)cut they may be very noisy if powered backwards (Like the noise heard when backing up quickly in a lot of cars)

 

Now are you saying the unit is AA as in advanced adapters or are you saying AA as in 2 ton model a truck?

 

I think he is talking about using an AA Ford underdrive. These were used in the early 28 AA's that used the car transmission to give the 1.5 ton trucks an additional gear for pulling. I read somewhere that people have turned them around and they can be used as an overdrive but I have never seen it done.

 

flatford39 you are correct, its a underdrive unit from a 28 AA truck! sorry for the confusion... i was told the same as you have read, but im unable to find some one that has carried out the conversion. there are a few threads on here discussing it but ive not found one yet that can confirm it.

 

Mechanically it should work,,,good idea, maybe ,,,, Check over on the FORD BARN

 

I'd like to see pictures of it, what does it have for inputs and outputs?

 

This has been mentioned on Ford Barn Model A section...I don't know if it has been detailed out.

 

ive just bumped a thread on there, but still no real detail, as to it working or not.

 

im still hoping someone on here has more info on this conversion and has missed this thread

 

I'm bumping this thread up and adding some pictures of one of these units. I may end up buying the doodlebug it currently resides in. It appears to be a 28 AA.

If I end up buying it, I will be very interested in any specific info on converting to an overdrive but if I don't get it I'll try to figure it out myself and take pictures.

I'm not quite sure how just flipping the whole unit around would work as far as mating to the transmission and to a torque tube. This one has the flanged front to the trans and an open drive out.

 

Yes it will work. My dad has one done like this in a late 31 PU. Its quite noisy and not always a smooth shift to O/D but to answer your question, yes. He bought the truck with it already in but looks like it is just a matter of engineering it into the torque tube and mounting a lever to accuate it.

 

Good to know. Any chance you have/can get any pictures of your dad's setup?

 

We live about 200 miles apart but next time I'm at his place I will take some pics of it

 

Digging this back up again. I'm hoping Spring cleaning dumps one of these units on the market up my way again (since I've missed out on the last two I saw).

@Tiny, did you ever get those pictures?

 

I don't know about your UD, I know you can put a manual transmission in turned around backward behind your other transmission and use it for an OD. That is a very old school trick for cars that need to go very fast.

here is a thought, you could put an airplane gear in it and use the UD as a UD.

 

i started this thread 3 years ago now... the project got sold on, never did find out if it would work or not for sure!

 

Yeah, @porknbeaner, that's along the lines of what a lot of the Doodlebugs in the Northeast have only they just have two gearboxes inline to go super slow.

I'm still trying to get a hold of one of these units, @sqweaka, so I'm just going to hijack your thread a little

I'd love to pull this conversion off on something. I'm not sure I'm brave enough to see if it will hold together behind my 8ba build up or not though.

 

Try posting over on the AA thread.

 

Sounds like a cool idea. I'd be concerned that there may be thrust washers or thrust bearings that were designed to be thrust in one direction and you'd be thrusting them in the opposite direction. Seems easy enough to investigate and potentially cure.

 

If I ever get my hands on one I'm going to document it as best I can. Most of what I've come up with in years of searching is rumors and vague instructions with no pictures.

 

I've got one sitting in the shed, maybe I'll have to dig it out and have a look. Bought it for the same reason you guys are talking about, something to try some day. Haven't got around to it yet though..

 

Well then @Carter, take and post some pictures when you do!

 

Will do @patmanta!

 

Sorry I have not gotten pics for you. My dad has been very sick so all my time has been spent with him at the hospital, not in his shop. I promise I will take some pics next time i'm at his place. His poor truck hasn't been driven in like 9 months. I need to take it out for a spin next time I'm at his place. I try to take pics then. It may be a while though

 

Egad Tiny, I'm so sorry to hear that.

 

I brought this one home with a pile of parts the other day.

 

jk, do you have plans for it?

 

Joe. No I don't. It is heavy and I really don't want to ship it. It is located in Central NY 13355. $75.00 and it's yours. Come and get it.