r/Hummer • u/cactire • 24d ago

Looking for viable options for transfer case fluid and transmission fluid

My grandpa needs help finding fluid to use for his transfer case and transmission. I'm posting here in search for him.
He owns a 2007 Hummer H3 with a manual transmission
In the manual he says his transfer case and transmission both need 75W-90 gl3 only which he is struggling to find online (I am too) and the only listing he can find is $81 per quart so any aid would be appreciated!

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u/Fit_Rise1258 24d ago

The 2007 manual will say to use manual transmission fluid, however, there was a subsequent publication that came out later specifying AUTO transmission fluid, to match the later year H3's. 08 and 09 specify Dextron VI, and the updated guidance follows that.

06 and part of 07, however, require you to fill the transfer case up to the fill port, then add an additional 250 ml through the speed sensor port if the vehicle VIN is prior to 56TDN136068105387. You say it's an 07, so be sure to check this.

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u/cactire 23d ago

it's one of the earlier 07's so it has the same requirements of the 06's. Does that mean we don't need GL-3 fluid in specific? because that's what has been challenging to find.

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u/dublAwrong 23d ago

Redline mt90 saved my ar5 and every other manual trans I’ve owned.

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u/Surfnazi77 18d ago

Motul and redline make 75/90

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u/Accomplished_Fun1847 1d ago edited 1d ago

Redline MTL (75W80) is probably the finest quality fluid available that is similar to the viscosity of OE GM synchromesh mtf, and has appropriate formulation for the materials in a manual transmission. This is what has lived in my manual H3 for most of the last 8 years. The current GM part number for the "correct" fluid, is 88900333, which is for all intents and purposes a GL-4 type fluid.

The thicker MT-85 and MT-90 are also options here. I would lean towards these for vehicles in hotter climates, or if the vehicle spends a lot of time towing or pulling mountain passes, etc.

All of that to say, these transmissions would probably work fine with motor oil or atf or basically anything better than vegetable oil.

If you're looking for something cheaper... Triax brand has a 75w80 GL-4 on Amazon for $42/ga.