For 1991, the new low-cost W/T trim was release. The W/T was a stripped down fleet side, long bed, regular cab work truck…the 4.3L V6 and manual transmission were standard. A/C and radio were not! The 454 SS was also updated with an more powerful 255hp/405ft-lb 454 V8, 4.10 gears, and a 4 speed 4L80E automatic. Still no SUV’s, but they will be coming soon!
Here you will find specifications and information for 1991 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 | 155 @ 4000 | 230 @ 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 | 8600+ GVWR |
| L19 | 7.4L (454ci) V8 | 255 @ 4000 | 405 @ 2400 | 454SS (RPO B4U) |
| LH6 | 6.2L (379ci) V8 Diesel | 140 @ 3600 | 255 @ 1900 | Below 8600 GVWR Auto Transmission |
| LL4 | 6.2L (379ci) V8 Diesel | 150 @ 3600 | 280 @ 2000 | 8600+ GVWR |
Manual Transmissions
| Model | 4-SPEED SM465 | 5-SPEED | HD 5-SPEED NV4500 |
|---|---|---|---|
| RPO | MM4 | MM5 | MM5 |
| Synchronized Speeds | 2/3/4 | 1/2/3/4/5 | 1/2/3/4/5 |
| First | 6.55 | 4.02 | 6.34 |
| Second | 3.58 | 2.32 | 3.44 |
| Third | 1.70 | 1.40 | 1.71 |
| Fourth | 1.00 | 1.00 | 1.00 |
| Fifth | – | 0.73 | 0.73 |
| Reverse | 6.09 | 3.74 | 6.34 |
Automatic Transmissions
| Model | 4-SPEED w/OVERDRIVE 4L60 | HD 4-SPEED w/OVERDRIVE 4L80 |
|---|---|---|
| RPO | MX0 | MT1 |
| First | 3.06 | 2.48 |
| Second | 1.63 | 1.48 |
| Third | 1.00 | 1.00 |
| Fourth | 0.75 | 0.70 |
| Reverse | 2.08 | 2.29 |
