My ae82 w/dohc and 5 speed manual is having transmission output shaft bearing problems. What is the the difference between the sohc and dohc transmissions? Aside from availability.

Check the gear ratios, that would be the biggest difference. Other than that, depending on year, either a C50 or C52 would be used. My '87 AE82s had the C52 trans in them and they were both DOHC. If you are concerned with strength and longevity you could look at any corolla with a 4/7A engine but research the ratios, the 7A would have a lower ratio to work with the 7A's torque and could kill your performance. If you already have the SOHC trans the ribbing would be different between the 50and 52, I don't remember the obvious differences. But if it's what ya got run it, it'll do the job. If you really want to get better performance look for a C56 from a 20v AE101 with an LSD or a 6 speed from a blacktop 20v from an AE111.
Sorry for the hot air.

Thanks for the info. Looking at photos of other transmissions, the six-speeds look as if the starter is on the opposite side from mine. The photos of the SOHC transmissions look the same in the bell housing, but the the crossover charts say they won't fit. The one I have, that's sick, is a c52. Nobody around here has anything I can look at and put my hands on. Truly, if I'm going to have an old Toyota, I ought to live on the West coast.

The six speed has the starter on the intake side, but all you nee is a backing plate from a late '90s 4 or 7A and the starter from same. It's actually better having the starter on the "cold" side of the engine.
If you are looking for a trans from a wrecking yard Celicas came with an 'A' series engine in some models and would have the 'C' series trans as well.
IF you do happen to go 6 speed bee sure to get the shifter assy. and axles as well to simplify installation.

So, I got a used 5 speed from an "FX16". Not. It apparently came from a Nova, and the gear ratios are not suited to the 4age. It works, and I might get 78 mpg on the Interstate, but that's not what I want from the car. I really don't know how to research the transmissions, and could use some help from somebody who could explain it to me in small words.

All right- back to interchanges. Looking at pictures of 6 speed transmissions, what I can see of the intermediate housing (bell housing) looks quite similar to my 5 speed, with the exception of the starter on the intake side of the engine.

Questions: will the six speed transmission bolt up to the five speed bell housing? If not, can I put my starter in the place on the six speed bell housing that looks like the starter location on the five speed bell housing? Is the difference between the five and six speeds adding an overdrive gear? i.e. does it have the same close ratio box I want with a higher ratio gear added on top? Will the shifter cables for the five speed work with the six speed box? I know the shifter itself won't.

And last- where in the wilds of the Eastern United States do I find these things? I see the six speed transmissions occasionally on Ebay, but getting everything else to make it go seems impossible here. The West coast seems to the place to be for these parts.