what to do tranny wise.

Hey guys, I am looking for some advice. I have a 1955 caddy that is getting a frame off restoration. I have the original 331 and tranny. I bought a 390 with matching tranny. I know the motor is good but am not sure of the tranny. I also have a tranny out of a 1979 caddy that has been sitting in my dads garage for the last 18 years. It came out of his car before we scrapped it. It was rebuilt with a life time warrenty on it, thats why I keep it. Should I hook nit up to the 390 via adapter plate ? Install the matching tranny to the 390 and see how it is? I will be using this car as a 2nd driver. I wanted more power and performance out of mill. Please give me some thoughts on this.Thanks,G.L.

 

What is the '79 transmission? TH350, or TH 400? If it were mine and I were to go to the trouble and expense of adapting a modern automatic, I'd look for an automatic overdrive.

 

its a th400 , I was wonderin if I should go with a 700. Its just that th400 is already here.

 

Sell the 400 to a drag racer who needs the strength, but not the overdrive. Then use the profit to help offset the cost of upgrading to a 700-R4.

The 700 has a steeper 1st gear (3.06, I think) that'll help get your heavy Caddy off the line, and the 0.7 overdrive will increase highway mileage, typically by ~20%. That's something to think about if you're driving it regularly.

Hope this helps.
-Gary