H2 DIFFERENTIAL & TRANSFER CASE FLUIDS
by HXC Club Member "Rich"

I've noticed not everybody gets under their rig and gets greasy. Some don't think the trouble is worth the money saved and some just lack the confidence or basic knowledge to try it themselves.

These procedures are individually no more time consuming than an oil change, and certainly no more difficult. However, unlike a simple oil change - doing this yourself will likely save you hundreds of dollars.

It is worth cleaning the area you have been working on with a good degreaser after completing the fluid change. This not only keeps your vehicle clean, but makes it easy to spot any potential leaks.

Always remove the fill plug first, if you remove the drain plug first and for some reason cannot remove the fill plug you are stuck.

It is best to drive the vehicle for a mile or so before changing any fluids, as this suspends any contaminants in the fluids and ensures they will drain out with the fluids, and not sit in the bottom of the case. The fluids should not be hot, so don't drive too far.

Rear Diff
Both the drain and fill plugs on the rear diff simply accept the drive of a 3/8" square drive. No socket needed - just plug a 3/8" ratchet directly into the plug. You may find this a little easier with a short extension.

You will find the plug on the forward side of the diff near the bottom.

Put a drain pan under the diff and remove the fill plug first, then the drain plug. Let it completely drain.

You may notice the end of the drain plug (and the fill plug) has a magnet. This magnets purpose is to collect small metal shavings. A silver looking paste on the end of the bolt is normal. Any bigger shavings could indicate a problem.

After your diff is completely drained, replace the drain plug and tighten to 24 lb-ft.

Fill the diff until fluid is level with the fill hole. Be sure it's not pour back from the bottle and the diff is really full - this can be achieved by using a rag to wipe inside the hole - if after removing the rag, fluid continues to drain out of the fill hole you are full. Insert the plug and tighten to 24 lb-ft.

The manual calls for synthetic fluid only - 75W90. The manual states it requires 4 pints of fluid, but fill it until it is full.

Front Diff
Remove the front skid plate.

Use a 15mm socket to remove the fill plug half way up the driver side of the diff, and a 13mm socket to remove the drain plug which can be found on the lower driver side of the diff. Let the fluid drain and replace plug. There are no magnets on the plugs, so try and get a look at the fluid to watch for metal shavings.

After your diff is completely drained, replace the drain plug and tighten to 24 lb-ft.

Although not absolutely necessary - You may find it helpful to get a 12" section of small clear tubing to fill the front. Place the tubing on the end of diff fluid tip and insert other end into the fill hole. Turn bottle upside down above the diff and squeeze the bottle.

Fill the diff until fluid is level with the fill hole. Be sure it's not pour back from the bottle and the diff is really full - this can be achieved by using a rag to wipe inside the hole - if after removing the rag, fluid continues to drain out of the fill hole you are full. Insert the plug and tighten to 24 lb-ft.

The manual calls for synthetic fluid only - 75W90. The manual states it requires 2.6 pints of fluid, but fill it until it is full.

Transfer Case
Remove the small skid plate under the transfer case.

Both the drain and fill plugs on the rear diff simply accept the drive of a 3/8" square drive. No socket needed - just plug a 3/8" ratchet directly into the plug. You may find this a little easier with a short extension.

If your drivetrain is cool you should get little or no fluid out of this plug. If you do get a lot of fluid it may indicate that you have lost the seal between the transfer case and the transmission. Since they use the same fluid, this is one of the few indicators to let you know you could have trouble. ATF explands when warm and a small amount will exit if the vehicle is warm.

Now pull the lower plug and drain your fluid. Inspect the fluid for signs of thermal break down, dark brown or black color, burnt smell. If the fluid is breaking down from heat, then reduce your service interval accordingly.

After your fluid is completely drained, apply pipe sealant to the drain plug threads and tighten to 18 lb-ft.

Since ATF comes in a container like motor oil, you will find it necessary to use one of the fill tips from the diff fluid bottle and it will thread right onto the container, obviously make sure it is clean before using it. Alternatively, you can purchase a small fluid hand pump from auto or marine stores that fits directly on to the container.

Fill the transfer case until fluid is level with the fill hole. Be sure it's not pour back from the bottle and the case is really full - this can be achieved by using a rag to wipe inside the hole - if after removing the rag, fluid continues to drain out of the fill hole you are full. Apply pipe sealant to the fill plug threads and tighten to 18 lb-ft.

The manual calls for Dexron III ATF, but synthetic Dexron III will have better resistance to heat and is recommended. The manual states it requires 3 pints of fluid, but fill it until it is full.


Rear Diff Drain

Rear Diff Fill

Front Diff

Transfer Case


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Note: The information on this page is offered for guidance purposes only and is not a recommendation that anyone perform any task described. Consult a qualified technician before performing any work on your vehicle. Any task performed based upon this information is at your own risk. The Hummer X Club, it's members and affiliates, this web site, the creators, owners, contributors to this web site, advertisers or sponsors of events, and any other individual or organization involved with the information provided do not take any responsibility whatsoever for any damage, either directly or indirectly, that may occur based on the information provided. You perform any task described on this web site at your own risk and assume responsibility for your own actions.


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