The 1990 model year featured a few exciting changes for the GMT400 Platform. The SS 454 package (RPO B4U) was released, combining the sport package with a host of performance upgrades including the L19 454 big block, 3.73 9.5″ rear differential, TH400 transmission, and suspension/steering upgrades. This package was only available in shortbed, regular cab pickups. 1990 also market the first year of the new composite headlamps on certain trim levels. SUV’s were still not available in the new platform.
Here you will find specifications and information for 1990 model year Chevrolet and GMC full-size trucks.
This includes engine ratings, drivetrain specs, and chassis dimensions.
Looking for GM official tow ratings? Tow Ratings
Engines
| RPO | Engine | Power(hp) | Torque(ft-lb) | Notes |
|---|---|---|---|---|
| LB4 | 4.3L (262ci) V6 | 160 @ 4000 | 235 @ 2400 | Below 8600 GVWR |
| LB4 | 4.3L (262ci) V6 | 160 @ 4000 | 235 @ 2400 | 8600+ GVWR |
| L03 | 5.0L (305ci) V8 | 175 @ 4000 | 270 @ 2400 | |
| L05 | 5.7L (350ci) V8 | 210 @ 4000 | 300 @ 2800 | Below 8600 GVWR |
| L05 | 5.7L (350ci) V8 | 190 @ 4000 | 300 @ 2800 | 8600+ GVWR |
| L19 | 7.4L (454ci) V8 | 230 @ 3600 | 385 @ 1600 | |
| LH6 | 6.2L (379ci) V8 Diesel | 135 @ 3600 | 240 @ 2000 | Below 8600 GVWR Manual Transmission |
| LH6 | 6.2L (379ci) V8 Diesel | 140 @ 3600 | 250 @ 2000 | Below 8600 GVWR Auto Transmission |
| LL4 | 6.2L (379ci) V8 Diesel | 150 @ 3600 | 265 @ 2000 | 8600+ GVWR |
Manual Transmissions
| Model | 4-SPEED SM465 | 5-SPEED W/OVERDRIVE |
|---|---|---|
| RPO | MM4 | MM5 |
| Synchronized Speeds | 2/3/4 | 1/2/3/4/5 |
| First | 6.55 | 4.02 |
| Second | 3.58 | 2.32 |
| Third | 1.70 | 1.40 |
| Fourth | 1.00 | 1.00 |
| Fifth | – | 0.73 |
| Reverse | 6.09 | 3.74 |
Automatic Transmissions
| Model | 3-SPEED TH400 | 4-SPEED w/OVERDRIVE 700R4 |
|---|---|---|
| RPO | MX1 | MX0 |
| First | 2.48 | 3.06 |
| Second | 1.48 | 1.63 |
| Third | 1.00 | 1.00 |
| Fourth | – | 0.70 |
| Reverse | 2.08 | 2.29 |
