Diablozx9

I have a 1981 Corvette (daily driver) with a lightly modified 350 (holley & intake, dual exhaust, light cam, etc). However the th350 and differential are stock. I was wondering if a higher rpm torque converter (2200 rpm?) would help my lanches (and make driving more fun) and be cheaper then a lower geared differential. anyone have experience with this?

johnt365

I just google'd the specs and it looks like your car may have a 2.87 rear gear ratio. If that is the case, you are going to be hard pressed to find any joy from a torque converter.

Here is my experience. My motor dyno'd at 270 at wheels through a TH400 and 3.08 rear. Dog. I swapped the converter to a 2800, still a dog, felt like I was riding the clutch on a standard. Installed 3.55 rear end, BINGO! White smoke from tires.

My opinion is that the converter is a lot of work. It is hard to get the best of both worlds with a 3 speed transmission. I think if you want a performance launch you gotta get the launch drive ratio as close to 10:1 as possible. 2.52 x 2.87 = 7.23. I think you would be happier with a rear swap to 3.55 or 3.73 if you can swing it. It is a compromise

Lets see what others say.

ps. post more info about your cam if you have it. That will let people know where your torque curve is.

BKbroiler

I've changed torque converters, twice, and changed rear gears, once, on my car. Changing torque converters is certainly easier and cheaper than changing gears, assuming you do the installs but send the rear out for the gear set-up, not a job for beginners.
As for which is more effective, a 2,200 stall converter won't do much. Go at least to 2,500. Mine is 3,000 and not bad for normal driving. I would do that before the rear, but your gears have to go, especially if they are 2.87. After putting the 3,000 converter in my car, I switched the rear from 3.08 to 3.73. The gear swap alone took 1/2 second off my 1/4 mile ET.

George Ries

i have a 76 with a 355 making 400 plus hp th350 trans with transco shift kit i have a tci break away converter 22 to 2400 stall 3.08 rear and it smokes the tires

George Ries

and yes im dumping the 3.08 and going to 3.55 then it should roast the tires it did anyway with the 3.08s

SuperBuickGuy

hmmm

I have a 2400 B&M stall in my avatar car - it's annoying. It doesn't create enough pressure to keep it in 3rd gear while maintaining light throttle. That said, with the cam I've got in my car; I need the high stall so it's something I live with.

If you have a stock 'vette; I'd swap lots of other things before I got to the converter. With a loose converter, you also need a better cooler because the transmission clutches will slip more on light throttle; thus, you're $250 into a project that will make your car harder to drive.

ramair_bryan

Hijack.........................Do they make a higher stall lockup converter for our 81s?..........Best of both worlds?

Diablozx9

The rear end gearing is definitly crap but, i was wondering if the higher rpm stall would help overcome the bad gearing since the engine will be spun up to the stall speed and therefore making torque.

SuperBuickGuy

Consider what you're suggesting - By putting a higher-stall converter in your car, as a rule of thumb, your torque converter produces less pressure at lower rpms, thus leaving your engine unloaded and gets you into your powerband before the clutches engage enough to move the car. With that said, it creates a tremendous amount of slippage on the clutches. With low numerical (highway gears), that slipping will be exponentially worse - thus you'll absolutely need a cooler; and you'll still have a much lower life expectancy of the TC. To give you a number, I would expect that you'd be replacing the transmission clutches in 10k miles.

The biggest killer won't be the launches, it'll be when you're tooling down the highway at 2000 rpms. The transmission will probably slip 20% or even more - that eats transmissions.

The way to help would be higher numeric rear gears - and those aren't terribly expensive if you buy a used differential.

Anyway, don't get me wrong, I'm a big believer in dialing in as much performance as you can into your car; I just would hate for you to be on here in 3 months wondering what a rebuilt transmission costs - and not expecting it. OTH, t400s are cheap to buy and really cheap to rebuild (especially if you're just doing clutches and you do it yourself).... this gives you a heads up to learn what you're going to need soon. And don't let anyone talk you out of doing it yourself, they and turbo 350s are the easiest and so popular of a transmission that there are numerous books and youtube videos on how to do it....

Diablozx9

Good advice. Thanks

George Ries

what cam do you have in your engine and what gears are you running

LastC3AZ

as suggested earlier ..... your TC should be related to the cam your running ..... thus the torque curve ...... better gearing is the best bang for the buck ..... but be careful not to go too far with your tranny .... as your cruise RPM will suffer ..... We are running a 355 with a 700R4 .... cruise at about 70 mph tachs at about 2700 rpm .... with your 300, I would bet you'll be well over 3k ...... just a thought ......

REELAV8R

Earlier this year I installed a B&M street and strip Th350 with a 2400 stall converter into a 77 L48 with 3.55 rear end and a stock motor. I did this in anticipation of upping the HP on the stock motor to 300 to 350 HP. Haven't got the engine power up yet but even with the stock motor, side pipes and a good Q-jet rebuild it performs quite well.
I did install an oil cooler for the trans in front of the radiator in anticipation of higher trans temps due to slippage and the whole setup works well. Cruising @ 65mph the rpms are about 2600, so the rest of the time the converter is slipping to some degree, but I don't really notice it.
Launches are much funner than they were before and it chirps into second each time I get on it.
Fuel economy was unchanged still get between 18 and 20 mpg when not sticking my foot to the floor.