I’m getting asked a lot about why I’m not converting my ’76 Trans-Am to a five or six speed manual – such as the ones made by Tremec – rather than a Super T-10 four speed.
I know – I know!
The Tremec has overdrive, which makes driving an old muscle car with an aggressive final drive ratio (3.90 in the case of my car) much more pleasant as well as much less hard – on the engine – because the overdrive gearing dramatically cuts engine RPM in top gear, allowing even an old muscle car with 3.90 rear gears to cruise at 70 with the engine RPMs well under 3,000 RPM – just like a modern performance car. This is how my car behaved with the 2004R four speed overdrive automatic it had until about a month ago, when I decided to replace it with a manual for no good reason – other than I felt the need for that third pedal like most men feel the need for female companionship.
It really adds to the experience.
Anyhow, why a four speed manual – with no overdrive?
Well, the number one reason why – for me – is that I want that ’70s muscle car experience. Part of that experience was not having overdrive. It’s how those cars were made – and it wasn’t so bad. Not having the overdrive is only inconvenient if you drive on the highway a lot – and I don’t, so it’s not an issue for me. I might replace the 3.90 rear gears with 3.23 gears, which would result in a car that’s versatile enough for occasional highway hops and still runs like a raped ape from a dead stop to the next stop light. I know because I used to own another ’76 TA with the 455 and four speed combo and these cars all came with 3.23 rear gears. The engine wasn’t exactly fast-idling at 70 but at 60-ish, in fourth, it was running around 2,700 RPM and that’s reasonable. Top speed was only around 120 – but so what? How often – realistically, on the street – can one drive faster than 120?
Another part of the experience was the sound made by those ’70s four speed manuals. The gear whine (listen to the videos embedded with this article) is something lacking in most modern performance cars with manuals. It has been dialed out – or the insulation is better. Regardless, I like that gear whine sound as much as I like the sound of an old ’70s V8 with a hot flat tappet cam and a big four barrel carb. Combine those elements and you have something modern performance cars lack. Certainly, they are quicker. That has become a blinkered focal point that excludes the other aspects that made driving a ’70s performance car something intangibly more fun than driving a modern performance car.
Zero to 60 and top speed are not everything. If they were everything, then electric cars are vastly superior to muscle cars, including the modern ones. And yet, almost no one who loves old muscle cars likes electric cars, no matter how quick they are. This is fascinating – because it is revelatory.
I also want to use “stock” – that is, factory – parts because I don’t want to Frankenstein my car. It’s also much easier to put everything together when you are using the parts that were all meant to go together.
The goal here is to replicate in every detail how the car would have been made by Pontiac. This also helps me cut down on the cost of the conversion, because the stock parts are less expensive, especially as regards the Super T-10. It will cost me about half the cost of a Tremec – and that’s not a small thing, either.
I just finished installing the new flywheel and pilot bearing. I have the 11 inch clutch and pressure plate on order. Next comes the bellhousing and I can hook up the linkages. Then it’s just the T-10 and the factory stock Hurst shifter (the big lift, money-wise).
The day is getting closer!
. . .
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I have a ‘72 LeMans Sport with a 455, turbo 400 and 3:31 rear end gears. That combination if fine for local driving and once in a while highway driving. When I bought it, a long time ago, it had 3:73 gears and they were a little too steep for the 455. I think if you switch your gears out to 3:23, you’ll be very happy with that combination.
Hi Neil,
Yup! My old Trans-Am (another ’76) had the 455/4-speed and 3:23 combo. It was a great driver.
The Super T-10 in my 67 Chevelle isn’t that loud. It sounds like the 2nd TA in the first video. You can get custom ratios for the T-10 that will give you similar ratios as an overdrive set up. But that will probably will eat into any cost savings.
The new to me 85 Corvette’s is quiet. That Doug Nash 4 + 3 is a Super T-10 with the overdrive attached. The plan was to go to a 5 or 6 speed after the new motor was done, but now I might just keep it.
Generally speaking, I deplore restomods. Take this one as a random example:
https://tinyurl.com/3tey79pk
Its modern custom wheels and low-profile tires are joltingly out of place on a vintage vehicle. And so, probably, are its entire drivetrain and suspension. I wouldn’t pay five fiat dollahs for this tastelessly mongrelized contraption. Indeed, I’d probably accuse the owner of violating his state’s abortion law, earning myself a punch in the face from the insulted clown.
But — an overdrive transmission versus a factory-stock direct-drive transmission is a more subtle question. A real bad memory of my 1968 GTO, with its 400 cubic-inch V8 and four-on-the-floor, is the vibration and noise from excessive engine revs at high speed in 4th gear. It was seriously annoying on highway trips. A 5th overdrive gear would’ve tamped down that ruckus.
Probably I would lean toward the Tremec on your Firebird. But your idea of replacing the 3.90 differential with a 3.23 ratio is the equivalent of an 0.83 overdrive gear. Or a 3.08 differential would be like a 0.79 overdrive.
Borg Warner used to make separate overdrive units, the R10 and R11, which attached to the back of a three-speed manual transmission in the 1960s. Their gear ratios were 0.70 and 0.72, respectively. But this is a bit far-fetched, and probably it wouldn’t bolt up to your four-speed trans anyway.
Either way, you can’t go wrong. But pleeeeeeze, just leave them OEM ‘rims’ alone!
I got me ten forward gears and a Georgia overdrive
I’m takin’ little white pills, and my eyes are open wide
I just passed a Jimmy and a White
I been a-passin’ everything in sight
Six days on the road and I’m a-gonna make it home tonight
— Dave Dudley, Six Days on the Road
My ’63 327 Fuelie ‘vette roadster had the Muncie 4 speed. Top down, going through the gears. Visceral high! Loved it.
I feel ya: Some 20 years ago, I converted my 1968 Olds Delta 88’s 455 from a 2 barrel and single exhaust to a 4 barrel and dual exhaust—using factory parts, like a Quadrajet and dual exhaust manifolds.
Doing so meant a lot less “Dr. Frankenstein” work than if I tried using, say, a Demon 4-barrel and headers. Cheaper, too.
No need to defend your position. It’s your car, you know what you want.
Opinions are like a**holes, everyone has one.
To this day I can still hear the whine of the 4 speed muncie and the moan of the quadrajet 4 barrel of my long departed 72
formula 400 bird. Thanks for the memories Eric.
Absolutely, Peter!
More coming!
Mine had 4.1 rear gears, so much fun!
The “How fast will it go” crowd used to annoy me when they found out I had a “race car”. A 1.6 Miata won’t go much faster than your Great Pumpkin but, it’s not about “how fast” it’s all about the experience. Something those who haven’t experienced it cannot fathom.
Maybe someday they will understand.
I’ve got a Chevy with a 454 and a TH400 in it. I drove it about 1,000 miles last year. It gets about 12.5 miles to the gallon if I don’t floor it much. Funny thing is I do floor it regularly. I considered converting it to an overdrive automatic but the amount of gas that would be saved would have taken over twenty years to pay for itself.
Since this is the year my Camaro will be back on the road the other Chevy will probably only see 500 miles and the Camaro the rest of my cruise in driving. The Camaro has a tune port 350 and a M20 with 3.31 gears. In its case also negligible savings if I put a Tremek in.