Symptoms
Oil sprayed on the inside of a tire, oil dripping off the lower ball joint, or a CTIS pair that loses pressure overnight. Pull the hub's breather line and put it under water: bubbles mean CTIS air is leaking past the spindle seal into the hub.
The fix, step by step
- Jack under the lower A-arm and chock the truck.
- Disconnect the CTIS line on the opposite wheel so it doesn't deflate.
- Drain the hub with a 5/16-in hex.
- Remove the CTIS line and the four 3/4-in steering-arm cover bolts, then the snap ring, and tap out the small spindle seal.
- Remove the clamp-nut lock screw and the clamp nut, and lay out the nut, keyed washer and bearing in order.
- Pull the spindle, drive out the output seal, clean the bore and the spindle's sealing surface, and drive the new seal flat.
- Reassemble following the AM General manual's clamp-nut sequence with red Loctite 272 inside its 10-minute window (lock screw 90 lb-in).
- Clear the hub vent line, then refill with GL-5 80W-90 or 75W-90 to just under the fill plug, about half a quart.
Tools & part numbers
- 5/16-in hex
- 5/8 and 13/16-in wrenches
- 3/4-in socket
- 5/32-in hex socket
- clamp-nut socket (Flash Off-Road made one from a NAPA 2467 Dana 44 spindle socket)
- snap-ring pliers
- inch-lb and ft-lb torque wrenches
- Loctite 272 and 518
- output seal 5579060, spindle seal 6005193 (Flash Off-Road)
Where to buy the parts
Wheel seal, 1998 H1 6.5 TD (catalog)RockAuto ↗
Gear oil, 1998 H1 (catalog)RockAuto ↗
H1 Geared Hub Heat Sink (billet access covers, set of 4)Predator Inc ↗Amazon ↗
Heavy-duty billet aluminum geared hub kit, 1992–2006 H1Pacific Performance Engineering ↗Amazon ↗
Hunting a used or discontinued part? Search eBay Motors for AM General Hummer H1 parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.