Thread: Transmission Strength?

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I have a friend who is getting ready to invest a good deal of money into a Muscle car project. At this point, it looks like he is going to go for a 68-72 Nova. Just waiting for his '69 Firebird to sell.

The engine is already in the works, and is going to be a 475CI big block, which is estimated to output about 570 horsepower. The question we have is regarding the transmission.

First of all, this is going to be a weekend car, absolutely no daily driver. This car will have to be able to make trips on the highway to the neighboring city (25 miles or so off) and an overdrive would be great, assuming there is a good transmission that can take the heat.

Orginally, we had planned to put in a TH400. Not only is the price right, but it is relatively easy to find one that will survive that kind of power. What transmissions can we look at that have an overdrive that will best withstand this type of power?

I have looked at 700R4s and 4L60s and 4L80s, but don't really know which are better. I've been using TH-350s much, and my knowledge is somewhat limited to that style transmission. I've also heard some talk of 200-4Rs, they seem to have a good reputation.

--Cliffnotes--

What is the best OD transmission to handle 570 Horsepower?
Must be able to take some racing, and be able to sustain a 50 mile highway drive.

Thanks in advance,
Rob

IMO the best tranny to handle the horsepressure isn't an automatic. I really like the TKO 600's. Techinspector introduced me to them a few years back, I tried a couple of them and really like them..... You can pick your gear ratios and "tune" the gearing to the engine's power charachteristics, and when you go out cruizin' that OD 5th gear really cuts the rev's.

If he has to stick with an automatic and has to have an overdrive, then it takes some bucks but the 700's and 4L's can be built to take it, just takes a fairly fat wallet to get them to live and perform well.....

I don't buy in on the old "you can't be consistent with a 5 speed" argument either. With the right clutch and the same burnout and staging routine EVERY PASS YOU MAKE the consistency will come. The pro stock boys can run within a few hundredths every pass, even with an automatic you still have to move the handle or punch the air shifter at the same RPM every pass, pulling the handle isn't all that much more complicated......

The problem will be that with it being a racer, you'll have poor driveability anyway. Might not get anything out of it under about 3k revs. So with an auto you'll need a high stall converter, and the nice OD you want won't get you anywhere because it won't engage the OD-clutch under about 80 mph or something. Running low revs with a high stall TC makes serious heat and doesn't move a vehicle in a specially nice way because of the slip you get across the TC. A well built 700-R4 would get you there (plan on about 2k for the trans), but a stick is the way to go in my opinion (but get a good clutch).
If you do stay automatic, I would go for the 700-R4 because it has a lower first gear than the 200-4R, so it will get you off the line quicker and it weighs a good deal less than the 4L80, and weight is an issue in every racer. The 4L60 is basically the same as the 700-R4, but it's controlled over the ECU of the engine, which you probably won't be running, I guess.
That's as always just me thinking loud...
Greetings from across the lake,
Max

With the kind of HP you're talking about the GM 200r won't do it as they max out at about 400hp. In general a TH400 will handled up to about 900 hp, and a 700 will take up to 575hp as will a 4L60. The 4L80 will handled 1000hp but will definitely need the computer electronics. If you want an overdrive but not a stick, you could go for a Gear Vendors Under/Over Drive unit. They will handle up to 1200hp or more. You could even add one to a manual trans. They are a little pricey at about $2500-3000 but you can move them from one car to another if you desire.

Regardless of the unit chosen, make sure you get it from a reputable tranny company with a written warranty. Things can go very wrong even with the best products, but when you are spending the kind of money you need to spend to match up this kind of hp to the rear wheels, make sure you are covered.