I've changed my transmission oil over to MT 90 and I have fresh gear oil in the front and rear diff's. What are you guys running in your transfer cases? The FSM calls for a GL-4 or GL-5 75W90. Would Redline do the trick or should I go with a thicker GL-5?

I just checked and Redline has a 75W90 GL-5 for differentials would that be better for my t-case?

 

Yes.

I run heavy shockproof in mine to quiet them down a little.

 

You can use MT90 in your transfer case. Differentials need GL-5 because they use hypoid gears. Your transfer case doesn't. GL-5 contains additives that can actually damage some transmissions.

 

Cool, thanks i know I can't use GL-5 in the transmission but I've heard some people recommend it for transfer cases in the past I think.

 

You can use GL5 in Toyota transmissions - the synchros will not be eaten by it - but it's often too slippery for good shifting

 

Ive been running MT90 ever since I did my clutch 8 months ago. Shifts so nice in any weather condition, t case and tranny.

 

I've gone through 2 T Cases on this thing and its a pain to find non destroyed refurbished unit

 

I've gone through 2 T Cases on this thing and its a pain to find non destroyed refurbished unit

 

I've gone through 2 T Cases on this thing and its a pain to find non destroyed refurbished unit

 

I've gone through 2 T Cases on this thing and its a pain to find non destroyed refurbished unit

 

Holy quadruple post Batman!

I have a side question about MT90 in the transmission and transfer case.

I've heard MT90 makes it shift better. Currently I don't have any problems shifting with GL-5, except for downshifting. When I downshift, the shifter seems to snag or catch on something and I get resistance, which is why I rarely downshift unless the RPMs are appropriate (usually 2000 to 2500). Will MT90 assist with downshifting? I don't mean to hijack the thread, but this could be relevant.

 

Hey Dave, i can only speak for myself, as i just switched to MT90 today in both my tranny and transfercase. I dont know what fluid i had in there before, it was not synthetic thats for sure. But once i got a few miles on the oil change, i could down shift from 5th-4th-3rd much easier than before. I assume 2nd would as well but i think my 2nd gear syncro is on its last legs.

 

Nice. I may switch over to MT90 after I get this new clutch in.

 

If you read any past threads on MT90, you'll see folks have had slight shifting issues with GL-4/GL/5 rated lub's. MT90 improved every one, as I recall. It did on mine. I won't use anything else, personally. New shifter seat bushing helped a lot, too.

 

I just didn't know if the resistance when downshifting was normal for every standard transmission, or if it was just my truck. My last vehicle did the same thing. Only manual transmissions that I've driven that don't do it have all been sports cars.

 

Tranny design, maybe? Don't know. Try reading some of those old threads, though. I had sticky issues downshifting into 2nd from 3rd. All gone.

 

Downshifting (without rev matching/double clutching) relies on the synchomesh rings spinning things up to the right speed to shift smoothly. With a slippery GL-5 oil, the synchro rings slip instead of grip and take longer to spin their gear up to speed. A GL-4 oil has more grip and lets the synchros spin up to speed faster, making for faster downshifts.

T-case in not synchromesh, so does not care what kind of oil is in it.

 

^^^^^ There ya go!