Torque converter slippage

[Chevy Dave]

I am using the Spicer Transmission Ratio RPM Calculator recommended on our forum. Does anyone know how many rpms a Turbo 400 looses at 60 mph?

[Scott S.]

Hi Dave...

Are you asking how much horsepower is being lost through an automatic transmission ???

From what I've found, a th400 looses 44 horses and a th350 looses 36. 

According to Team Chevelle, a "non lock up" th400 torque converter looses between 3%-8% of the rpms, which can be adjusted through the modulator. 

Anything more is a sign of wear. 

Scott.

[Chevy Dave]

I used the formula and my rpm and mph read very close to what they should be, so I guess my slipage is very little.

Thanks for the reply. 

[Jason72]

Converter slip is calculated by engine rpm compared to input shaft rpm. It’s easy to compare on newer transmissions with input shaft speed sensors but in the case of a th400 the easiest would be compare engine rpm to drive shaft rpm in 3rd gear. This is typically done at wide open throttle 

it can only be adjusted by changing the angles of the fins inside of the torque converter 

Edited September 12, 2024 by Jason72

[Scott S.]

Thanks Jason....

I reread the article and found that the modulator only compensates for band slippage.