Below is T-5 info copied from:

https://www.thirdgen.org/newdesign/t...ulations.shtml

1987 5-sp Warner Gear
LB8 4.03 2.37 1.50 1.00 .76
LG4 2.95 1.94 1.34 1.00 .63
LB9 2.95 1.94 1.34 1.00 .63
LB9 2.95 1.94 1.34 1.00 .73

Were both NWC and WC used in 1987 for the LB9? Is the latter WC? If so, why were both used? Norwood vs. Van Nuys? Running change during model year, and if so, approx. when in model year?

Thanks

 

Maybe just a mid year transmission change. My guess is that the early 87's built in 86 and early 87 got the NWC T-5, while the later ones built mid to late 87 got the WC T-5.

 

They did change from the 1st design to the 2nd design during the 87 model year; but that has nothing to do with the 5th gear ratio change. Those gears are interchangeable.

I would expect the gear selection to have been related to a package along the lines of G92... the higher-performance .73 is what was used in alot of the more optioned cars over the years such as L69s, 1LEs, etc. LG4 cars, TBI cars, and other lesser drive line optioned cars got the gas-mileage gear.

 

Investigated my car a bit and compared to TGO tranmissions list and 5Speed.com info.

Found I have the following in a 1987 G92 Van Nuys IROC built Jan 1987:

2.95
1.94
1.34
1.00
0.63

Verified 1st and 5th gears by test drive and using calculators on TGO.

Transmission tag is 1352-157. Interesting thing is that 5Speed.com lists it as:

GMC 1986 V8 F Cars .9 V8 LG4-LG9

Not sure what the .9 means or the LG9. Maybe it was suppose to be LB9. Also, 1986 is the year in a Jan 87 built car. I suppose old parts were used up first. Overall was fun excercise.

Am now curious which plants used which transmissions in the 1987 model year, and when changeovers were made from 1986 to 1987 to 1988 T-5 models. There were so many running changes in the T-5 that no one may ever know.