HUMMER H1
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in the humvee and humme rh1 world there is terminology called the vampire,AFAIK the cooling loop has nothing to do with using ATF, every chain drive aluminum case I have seen uses ATF, not saying gear oil would be bad.
This ATF crap started with the transmission in the Chevette as a fuel saving measure during the oil crisis, man we got tons of complaints about noisy transmissions.
when cooling loop brakes inside theT case, it floods with extra ATF that supposed to go through the cooler loop, it makes the oil go up all the way to filer housing through air tubes, the transfer case starts to leak everywhere draining the ATF that belongs to the transmission and contaminating by aluminum shavings, eventually killing the transmission
by bypassing the cooling loop the T case becomes full isolated unit.
that cooler loop is only 242 HD units not on jeeps 242,
If I was living in colder climates I would think ATF is better
and maybe even fuel saving by 5c per tank ? Less friction?
but oil makes it run a lot quieter and I am sure gears love it.
yea you see the Tacoma , tundra , 4 runner all have chain but with gear oil from the factory
honestly I think it’s just a preference and both are ok depending on climate and usage