I'm planning on putting a 390 Caddy in an upcoming project. I want to connect it to a 9 inch Ford with a 2.88:1 ratio. Which choice would be better for a ******, TH400 or 200-4R? The engine will be basically stock and the vehicle will simply be a cruiser. Thanks.
with 2.88 rear gears an overdrive transmission as in the 200-r4 won't do you much good a th400 is not an overdrive , the final ratio in high is 1:1
don't get me wrong , an overdrive is a good thing...if you have 3.50-3.90 gears in the rear end. that's easy to do with a 9 inch ford
If you want a modern day trans I would go with the 400. But if you want to go back to the day, if it were me, I would use the good ole dual range hydro. But that's me. 1 vote for the TH400. OBTW: Good luck in finding one that bolts up to the 390. If I remember correct the 64 version of the 400 or the 65-67 400's are the only ones that Cadillac used and might bolt up to the 390. The 200 4r is a BOP/CHEVY bolt pattern and you will definitely need an adapter setup.
I've got a Transdapt CAD to chevy auto adapter, so that will simplify it. I've got a TH400 available too, just needs a rebuild. I have the original hydramatic that came with the 390. Works fine, but I just wanted something a little more modern.
2.88 is realy high. If you want to go modern, you might entertain the idea of atleast a 3.25 ratio (more if it was me)with a modern overdrive ******. How big a tire are you running?
I vote 200r4. The first gear is lower to help get the car moving with high gear ratios. You can't really go wrong with either though.
If the dual range works, you may as well run it. With the 4 speeds and the 2.88 gear it should get fairly decent gas milage. And they're a blast to drive, for whatever reason, of all the automatic trans cars I've driven a Pontiac with a 389 and the dual-coupling Hydramatic was the most fun.
I'll most likely be running a 235/70R15 rear tire and a 195/60R15 on the front. Haven't decided for sure yet.
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