Why This Isn't a Confident Chart
Every other guide on this site has said "torque to spec" without giving a number, on purpose, because for several of the most-asked-about fasteners on this platform, there isn't one clean number. Wheel lug nut torque genuinely changed across the production run. Differential cover bolt torque has real, documented disagreement even among experienced GMT400 owners. Presenting a single confident figure for either would be exactly the kind of "one truck's experience treated as universal fact" mistake this site exists to correct, not repeat.
Where a number below has strong, independent corroboration, it's marked. Where it's reported once and worth double-checking against your own truck, that's marked too. Always verify against your own vehicle's tag, VIN-specific manual, or physical inspection before trusting a number here for anything safety-critical.
Genuinely Changed by Year — Confirm Before You Torque
| Years | Torque | Confidence |
|---|---|---|
| 1988–1990 | 90 ft-lbs | Reported once |
| 1991–1995 | 120 ft-lbs | Reported once |
| 1996–1998 | 140 ft-lbs | Corroborated |
| 3500HD (5/8" studs) | 175 ft-lbs | Corroborated |
Front End & Driveline
| Fastener | Torque | Confidence |
|---|---|---|
| Front axle nut (outer) | 165 ft-lbs | Corroborated |
| Front shock mount bolts | 66 ft-lbs | Corroborated |
| Outer tie rod end nut | 46 ft-lbs | Corroborated |
| Upper control arm cam bolts | 140 ft-lbs | Reported once |
| Lower control arm bolts | 121 ft-lbs | Reported once |
| Brake caliper retaining bolts | 15 ft-lbs | Reported once |
| Pitman arm nut to steering box | 175 ft-lbs | Reported once |
| Rear differential cover bolts | 18–30 ft-lbs | Genuinely disputed — see note |
Approximate — Fill to Level, Not to a Number
Capacities vary meaningfully by engine and configuration across this platform, and the guides elsewhere on this site already give the specific, verified fluid type for each system, front differential, transfer case, and so on. Rather than guess at precise capacity figures here and risk the same false-precision problem as the torque specs above, the honest approach is simpler: fill to the dipstick or fill-plug level specified for your specific system, not to a generic number that may not match your engine or trim.
Where the real numbers already live: front differential fluid type is covered in 3.2, transfer case fluid type and the Dexron III vs Auto-Trak II distinction is also in 3.2, rear axle fluid for the TrueTrac conversion is in 3.3. This page won't repeat those, follow the links for anything system-specific.
Deliberately Not Reproduced Here
Fuse box layout and circuit numbering changed multiple times across the 1988–99 production run, closely tied to the same electrical architecture changes covered in Section 2, RWAL versus 4-wheel ABS, the different transfer case electronics, and more. A single diagram claiming to cover the whole platform would almost certainly be wrong for a meaningful share of readers.
The genuinely reliable source is the one already on your own truck: the underside of the fuse box cover on virtually every GMT400 has the circuit diagram printed directly on it. That's specific to your actual truck's build, not a generalisation, and it's always going to be more trustworthy than a chart on a website.
This Guide Applies To
Applies platform-wide as a reference starting point, but the whole point of this page is that "platform-wide" doesn't mean "one number fits all." Check the confidence marker and your own truck before trusting anything safety-critical here.