Hummer Differential Field Repair

One of the most over looked areas of off roading is field repairs. What happens if you are 30 miles away from civilization as we were yesterday at our off road facility in the California desert and the front differential detonated? Obviously you always want to travel with a buddy vehicle for safety and support. Even with a buddy vehicle it is extremely important to be able to perform a field repair if necessary.

We were traversing a remote location of our off road training grounds when a spotter noticed the front diff leaking oil. Fortunately we noticed it right when it happened and the impact on the environment was non existent as all lost fluid was recovered.

In this situation a spider gear snapped off two teeth inside the diff and was lodged between the ring gear and the diff cover resulting in a punctured diff cover.

This required a visual inspection as we weren’t sure what was going on inside. We began by removing the Under Carriage Protection, and then loosening the brake caliper to gain access to all the bolts on the diff cover. We were short a few tools including the drain plug Allen so we had to crack the cover open slightly to contain the spill into a water jug that was cut open. After removal of the cover, we found the cause and determined that we were very fortunate that the teeth were on opposite spider gears! This meant that they would not skip causing complete failure.

The next step was to clean up the diff and repair the hole. A quick repair was made with JB Weld.

Getting the oil in was a little tricky because of the lack of a funnel and even worse, access to the fill hole because we did not have an Allan wrench big enough. We improvised using several Plastic Zip-Lock bags from out lunches filled with the recovered oil. After filling the bags, we sealed them and carefully placed inside the diff. This allowed us to reinstall the cover without oil loss. Once we began moving, the gears would tear apart the bags releasing the gear oil into the diff.

After getting the diff cover back on, we reinstalled the caliper and were off to civilization.

All in all, we were very lucky we didn’t have to leave the Hummer. The total repair took about 4 hours working with minimal tools and improvising with the tools on hand.

The lesson learned is to rereview your tools and supplies. Bounce your list of tools off a few Hummer friends and see if they have any additional items or fluids you have overlooked.

You can never be too prepared!