i read an article in GMHTP about knowing what a true stall speed of a TC is to leave it in second.


so i tried it and i got 400 more RPMs then when i have it in D.

why is this and is there any benefit as far as lowering ET?

 

I belive the second gear theory for finding the true stall speed of a converter is achieved by launching your car from second gear. From the way I read your post you could be doing this or power braking im not sure. But you need to launch from 2nd gear from a dead stop. I dont know if it matters if you stall it up before leaving or not though.

 

Assuming you are talking about "2nd gear start":
There are two basic factors that will raise stall speed. Either raise input torque or raise rolling resistance (such as a higher gear or added weight). Going to a higher gear will raise stall and when you put the car into second, you are raising the gear after the converter. Following the same principal, and much more well known, if you switch from 2.73s to 3.73s, your converter will stall lower.

 

fuddle... gonna make converters for t-400 ls1 cars?

 

The stall speed of a converter is rated with the car locked in 3rd gear as it is a 1 to 1 ratio thru the transmission (this is the highest work load that the converter can be subject to), this can not be done with the 4l60-e with out special controls you must use second gear, is the highest gear you have to work with and the brakes are not asked to hold as much input torque so tire slip is not an issue.
Mass of the car or truck will not change the true stall of the converter only the rate it achieves flash stall.
Some high powered cars with Nos or superchargers on slippery tracks will go faster
with the second gear leave as it will soften the hit to the tire and allow the converter to use the STR for a longer time, making up for the gear ratio loss

 

thx guys.

 

We do make a line of great converters which bolt directly between the LS1 and the TH400. Give me a call, and we can help you out.

 

so is this saying it's better to launch in 2nd gear at the track? wont it be in first gear until the car gets moving anyway?

 

well if you have "second gear start" then the car will actually start out in 2nd gear from what I remember reading.

 

1999's do not have second gear start.

It is better to buy good tires and launch in first gear, then to use second gear start.

Second gear start might be an option on the street for someone with a lot of power mods, 3.73s, and street tires. Launcing a 2.73 car in second gear will be slooooow.

 

that makes sense, thanks