So I'm swapping out my Wavetrac front diff for an Mfactory (too cheap for Cusco) and got an inside look to the transfer case and how the fluid travels. I thought the tcase fluid circulated through the front diff and R&P but having shockproof in the Tcase made it pretty obvious that the trans passed fluid to the front diff.

So T-case fluid remains irrelevant of front diff but trans fluid does matter. Is OEM fluid alone the right way to go?

 

Your subject confused me, I assume you got pwn'd by auto correct lol. But ya thats interesting I too always thought since the front diff was "part" of the tcase so thats why shep and all them insisted on DQ in those areas. But every shop, clutch job, etc that i've seen uses all sorts of trans fluid.

 

I think the t-case fluid is all about keeping the R&P alive and it also bathes the center diff, ACD in my case. I had Redline Shockproof in the t-case and OEM in the trans so it was definitely clear when they came a part which oil went where.


I'm leaning towards just sticking with the OEM diaqueen for trans/front diff but not sure if some LSD additives would be needed.

 

LSD additives only serve to reduce the locking action of clutch packs. The would also reduce the ability of your transmission's synchronizer to....synchronize...and it will ruin them. So run whatever MTF you've been running.

 

Cool, that's what I was thinking. All the info I can see on what fluid to use don't take into account the need for synchro meshing.

 

We run mt-90 with no issues

 

Cool, thanks!


I feel like the front diff being oiled by the trans must be some deep dark secret cause in all my years of reading on Evo forums I've never seen in brought up.

 

I thought everyone thats ever done their own clutch job would know...lol.


That's what the 1/4" oil passage that the small o-ring between the trans and tcase seals. Inside the trans, that passage is next to the ring gear on the center diff, and it has a scoop on it, the ring gear throws fluid it at, which gets caught in the scoop and basically "pumps" the fluid over to the front diff.


Also, especially for those running shock proof, when you take the passeegr side axle off, trans fluid comes out, not shock proof.


The X does not share fluid though. And interestingly, the X trans holds about .3L less fluid, while the X tcase holds about .3L more fluid than the 8/9.

 

For the Transmission TRE recommends - MOTUL GEAR 300 75W90.

Per TRE- "This oil has incredible film strength while still allowing for quick shifts making it another wise choice of oil for your high power Mitsubishi transmission. Part# 100118. Note: We are talking about GEAR 300, not Gear 300LS which is a full GL-5 gear oil and has the friction modifiers that are required by limited slip differentials."

I use 3.5L in the trans and Jon from TRE said the faces on the gears show minimal scuffing, unlike the other fluids.

 

this^^

 

+1 to the Cusco. I had one of the old BerryMobile units in my car for a few years, took it out and sent it to Jacks for rebuild and they called me up and asked what I wanted them to do with my practically brand new diff and transfer case, no need for any rebuild. I was also using MT-90.

 

what were the specs of the t-case?

 

As far as I know it was just an OEM ACD t-case with the Cusco 1-way diff, but Marshall may know more... I just bought it from him and didn't ask any questions

 

i just use the same fluid in both. theres a balance pipe between them.

 

The front diff is inside the tcase, but is sealed off from sharing the gear oil with the tcase. It receives oil from the trans through a fluid transfer port. The front diff doesn't have fill/drain plugs because it's sealed off inside the tcase. It gets fluid delivered to it from the trans, so whatever goes in the trans goes into the front diff.

Do not put trans fluid into the tcase. You will wipe out the ring and pinions gears in very short order.