4+3 transmission tutorial request

[Gusaroo]

I have been shopping for an manual overdrive tranny and I see quite a few of these corvette transmissions. Usually refered to as Doug Nash 4+3 or 4+2.

Can someone give me their opinion of these transmissions? I am looking for something to go behind a stock 454...
thx

[Jimi G]

The Doug Nash is basically a T10 4 speed with a automatic overdrive on the back of it. They can be a pain in the butt, and they are expensive, for the money you spend on it you can almost get a TKO600 5 speed. I see alot of them with the automatic part completely burnt up, and that is the most expensive part of them.

[OldSub]

What he said.

But if you are seeing lots of them and can get a good one real cheap you might try it. I've thought about it for one of my projects.

With the OD locked out its just like driving a 4-speed. The Corvette automatic-OD is tuned for fuel economy not drivability. In its stock configuration its never in OD in 1st, but probably will be when you hit second. If it isn't the spread is quite a closer, and your shifting may not seem real smooth.

I'd want to change that behavior so its only in OD when in 4th, perhaps by putting a switch on it.

[cook67]

I've rebuilt many of these they were designed wrong there is a side loaded roller bearing that always fails so even if you get a good one it will fail you also need to run a cooler for the overdrive unit its basicly a 2 speed automatic most corvette owners who have them replace them with 6 speeds if they are going to keep the car.