H2 Oil leak aboe front differential.
 

I think stuff on a Hummer lasts longer than my fellow owners think. My 2003 H2 has 198,000 miles and I never changed the front differential oil. I bought it new in 2003. There is some kind of oil leak in that area so to rule out the differential having a leak I measured the oil that came out of the drain... it was two quarts. The oil looked and smelled totally new. There were no particles on the bolt.. I put in just under 2 quarts of new oil. But I think that differential would have been just fine with the factory oil for another 200,000 miles.

Now I need to find where the oil drips are coming from. My master brake cylinder leaks a little with clear oil. The oil drips I see on the garage floor are very black and thick, not power steering fluid or brake fluid. My engine oil gets low after a few months. Is there a gasket on the engine over the front differential that has a history of leaking? The engine viewed from above shows no oily places, the spark plug wires are clean.

check the oil cooler plate that mounts above the filter. they tend to leak. if thats the source of the leak do not over torque the bolts because they mount onto the oil housing thats made of aluminium. they can strip quite easily. a slightly longer screw might save you if they strip.

oil cooler plate
 

Thanks, I see oil all around the filter area, I just tightened the filter. I will check that oil cooler plate.

My suggestion to everyone with any leaks is to remove the front skid plate. Take the H2 to the nearest high pressure hand held car wash and spend lots of time cleaning underneath the entire engine, frame, transmission, suspension, etc......after everything dries, it will be very easy to see where any leaks are coming from. This should be done yearly at least.

Preventative maintenance is your best friend.

Just spray degreaser, clean off the oil residue and monitor the areas around the engine to see what’s leaking. As someone mentioned take the skid plate off to make it accesssible. Oil cooler lines, near the oil filter, valve cover gaskets, oil pan gasket leaks are common. Could also be the rear engine cover gasket. Btw that’s a lot of miles on the diff fluid. Should be changed about 30k miles, 50k tops.

Sneaky leaks...
 

I will do more spray cleaning to try to locate the leak. I had taken the ski plate off last year. I put the tubing grid panel back on last week to maybe prevent my cats from getting stolen. Wish there was a dealer or mechanic I could trust to do good work. Five years ago I went to the local oil change place and watched him set the oil filler cap on top of the radiator... which had a layer off sand on it. I watched until he picked it up with no hint of cleaning it off before moving it toward the filler tube. I screamed... and called him a stupid idiot. If I had not been watching, there would be 5-10 grains of beach sand inside my crankcase. That would ruin the engine. I do all my own oil changes now.

I didn't change the front differential fluid because I feel the risks of doing the job and getting dirt inside is greater than possible degradation of the oil. Or the risk that I bought a jug of oil made in China with a manufacturing defect. Or the risk I put in too much or too little. The 20 year old oil looked, smelled, and felt like new. There were no particles or scum on the drain plug. The gearboxes in wind turbines get the oil changed at two year intervals. That is about 12,000 hours of spinning. My Hummer over 20 years put about 4,000 hours on the front differential . It has a constant stream of ambient air blowing over it. I think it never needs the oil changed. The risk exceeds the reward.
The transfer case in my Hummer failed at about 150,000 miles. The plastic forks broke. The oil inside the transfer case did look well worn.with a blackish tint, not to mention several cups of ground up aluminum and plastic.