Torque Converter Terminology
Eric Ruybalid
SR Performance GNeric85@webtv.net
Introduction
I noticed on a few posts the other day people were asking about the "MAX RATIO at STALL" on the box. It is listed at 142K. What this means in GM terms is " The 'K' factor is an engineering term that means the speed of one member divided by the square root of the torque on the same member." This is calculated at stall conditions. On a 298 mm torque converter you can multiply the "K" factor by 14.2574 to get the stall speed.
Converter Chart
 K Factor Approx. Stall Speed Marking 142 2024 RPM A 140 1996 RPM B 135 1925 RPM C 130 1853 RPM D 115 1639 RPM E 110 1568 RPM F 100 1425 RPM G 97 1383 RPM H 89 1269 RPM J 85 1211 RPM K

If you look at the tag that is usually on the bottom of the torque converter, there is a code with 2 letters, 1 number, 1 letter. The first letter is the application, 200-4R's use a C, the second letter is the "K" factor, the number is the clutch type, capacity & travel in degrees, and the fourth digit (optional) refers to the cover style, number of mounting lugs and method of welding the lugs.

Cover Style: optional code

4th digit: A = Open cover (no converter clutch) 3 lugs with one weld per lug. (gas)
B = Open cover (no converter clutch) 3 lugs with three welds per lug. (diesel)
C = Converter clutch type, 3 lugs with one weld per lug. (gas)
D = Converter clutch type, 3 lugs with 180 degree weld on each lug. (diesel)
E = Converter clutch type, 6 lugs with 180 degree weld on each lug. (diesel)
F = Converter clutch type, 3 lugs, 245 mm style lug.

For the 298 mm torque converters 4-digit code tag...explaned as follows.

1st digit= application
2nd digit= "K" factor (K x 14.2574)
3rd digit= clutch type
4th digit= cover type

APPLICATION:

B = 250 and 350 transmission,
C = 200/200-4R, 325-4L & pre 85 700-R4
D = 85 and later 700-R4 with 30 spline input

"K" FACTOR: A= 142 = 2024 rpm
B = 140 = 1996 rpm
C = 135 = 1925 rpm
D = 130 = 1853 rpm
E = 115 = 1639 rpm
F = 110 = 1568 rpm
G = 100 = 1425 rpm
H = 97 = 1383 rpm
J = 89 = 1269 rpm
K = 85 = 1211 rpm

CLUTCH TYPE: 0 = no clutch
1 = 300 ft/lb 43 degrees travel
2 = 240 ft/lb 46 degrees travel
3 = 290 ft/lb 44 degrees travel *
4 = 160 ft/lb 37 degrees travel
5 = 220 ft/lb 35 degrees travel
6 = 195 ft/lb 42 degrees travel
7 = 195 ft/lb 30 degrees travel *
8 = 300 ft/lb 44 degrees travel
9 = 290 ft/lb 44 degrees travel #
A = 300 ft/lb 29 degrees travel
B = 300 ft/lb 44 degrees travel
C = 330 ft/lb 28 degrees travel

* poppet valve
# static open poppet valve which is normally open and closes during acceleration.

COVER STYLE:

A = Open cover (no converter clutch) 3 lugs with one weld per lug (gas)
B = Open cover (no converter clutch) 3 lugs with three welds per lug (diesel)
C = Converter clutch type, 3 lugs with one weld per lug (gas)
D = Converter clutch type, 3 lugs with 180 degree weld on each lug (diesel)
E = Converter clutch type, 6 lugs with 180 degree weld on each lug (diesel)
F = Converter clutch type, 3 lugs, 245 mm style lug.

Last updated: