I have a 89 B2 2.9Lwith the weak A4LD. The OD input gear basket splines stripped and trashed the whole OD unit. I have since "upgraded" with the 4.0L A4ld tranny. Hopefully no more problems with it.

The question I have is, since the A4ld is a C3 with the OD put on the front, I am wondering if I can lockup the OD unit so I can use it as a 3 speed for a swamp buggy I am building(OD not needed or ever used). I know the band controls the OD function, but the books(ASTG) and others don't really tell me what the center clutch(of the OD unit) function does and the oneway clutch(OD unit).

What I want to do is weld up the input shaft to OD input basket(its stripped out) and gears to the output of the OD unit and fit it back in. Also lock out the 3-4 shift and probly the T/C control in the valvebody. Basically making a longer input shaft to the rest of the trans.

Any thoughs on this? Before I waste some MIG wire on this venture....
I am trying to use up what I have laying around and save $$

 

Do you know how a 'sun' gear works in a 'planetary' gearset? The input shaft turns the 'basket' through the flat plate with the 'fingers' that fit into notches in the lip of the 'basket'. The splines are passing a lot of torque (all of it...) through 1/8" or less of metal. *I* would weld the input shaft to the flat plate, and the one that I fixed, the shop welded the plate to the basket. I was gonna turn the plate over, figuring it would work with the 'unused' side of the fingers. He said for $20, he could get it welded to the basket, and it would never EVER need to be fiddled with again. It was a 4.0 A* extended van that had pulled horse trailers... and lasted 180k before dying. New clutches/steels and seals, used input shaft (twisted splines), and PBT. It worked.
Back to the sun gear, you have to figure out where the torque is being transferred in OD and straight through. Take out the OD parts, and weld it up to be the equivalent of straight through. I don't have it in front of me (it's in CA now, and who knows where), so can't tell you what to weld. Should work fine. But you may get codes depending on OD and TC lockup functions...
tom

 

That little plate that hooks into the sun gear to clutch basket is what I think that failed, trashing the OD unit. Not sure if the valvebody caused it to fail as when it went down I was slowing down from 60mph to turn off the road when it dropped out of OD to 3rd, it acted like 2 gears were engaged nearly stalling engine and sliding rear tires before the planetary gear basket splines stripped out! Then nothing.... I 1st though the torque converted output hub stripped again, but once out I found what really happened.

For some reason I can't post pictures in the forums, but have made a gallery under my handle that shows what parts I want to weld together. On one picture you can see the stripped splines in the planetary gear basket and the carnage of that star plate grinding up the inside of the basket.

Did you have to do anything with the valvebody to keep it from going into OD?

 

Whoa. Stop. I did not say I welded one up, just that it would make sense that it would work. I *had* the plate welded to the 'basket', a plate that had good splines to mesh with the input shaft. The 'plate' *should* be a lot thicker than it is to handle the torque it carries.
What things are involved depend on how your overdrive is engaged. Some have an electric switch on the dash/column/shift lever, some move the valve body from (d) to D to disengage OD. If you have a manual, and put it into OD with the stuff locked up, it would try to apply the servo to clamp the band around the drum. If the band/serve parts were not there, it would be a flood of fluid trying to apply the servo. If you welded (tig/mig) the servo piston to the servo bore, it could not apply the band that is sitting on the workbench, and it would not make any difference as the gears would remain engaged as before *I THINK*. If electronic, a solenoid would be engaged rather than valve body, but the same deal with the servo piston/band, and band strut.
Does that make sense to you?
tom