Hey guys, I am gonna order some Redline MT-90 for my '92 Pickup, 3VZE, 5spd. The owner's manual shows 3.2qts to fill the tranny, so it looks like I have to buy 4qts, so I was wondering if I can use this stuff in my rear diff also?

That way I can order a little bit more and fill up my diff with this stuff, rather than order 4qts just to have .8 of the last quart sitting around for years.

Unless I can get away with just putting 3qts in the tranny, then I will just order 3qts, but I don't really want to underfill the tranny.

Thanks.

 

Yes, it can be used in the rear diff. Diff and trans take the same weight oil. And do NOT underfill the trans. Fill it to the exact level it should be at. Having less oil in a trans is never ever a good thing.

 

Actually MT-90 is not a good idea in the rear diff. Why? MT-90 is a GL-4 rated oil and the rear diff wants GL-5. Why? If has hypoid gears and needs the extreme pressure (EP) additives in a GL-5 oil to work properly. A transmission works best with a GL-4 oil since it has gears without the high pressure sliding tooth contact that a ring/pinion gear has:
- http://www.4crawler.com/4x4/index.sh...ntheticGearOil

 

OK thanks. So it looks like I will be ordering 4qts and just wasting 80% of the 4th quart.

No big deal.

So I guess just any regular 75w-90 GL-5 gear oil is good for the diff?

How long can MT-90 stay in the tranny, like 50K miles? I'd but the gallon of it, but I'm not sure how I would pump it in, I only have a pump that fits quart bottles.

 

Always nice to have a little extra oil, sometimes you need a little extra to top off the tranny or if you get any leaks down the road you'll have some spare oil. You could also add a little to the diffs if you need a little extra to fill them.

I never routinely change my Redline tranny oil, but it does get changed any time I have to pull the tranny like to change a clutch or once when I had to send the dual transfer case out for repairs.

 

I thought MT90 was GL-5 rated as well?

I have run redline in my rear diff for years without any sort of issue.

 

Specs from:
http://www.redlineoil.com/products_g...7&categoryID=7

GL-4 oil can break down over time in a hypoid gear application (like ring and pinion gears) due to the shearing action of the sliding friction acting on the long chain oil molecules. Redline does make GL-5 oils as well.

I have run GL-4 oil in my diffs on occasion, one time when I was first breaking them in. I had a gallon of GL-4 and used it for a few hundred miles and it seemed to work OK.

 

You can use the MT90 in your tcase too.

 

Sure, as long as your case uses gear oil (not ATF like some of the automatic cases use). The t-case can basically use GL-4 or GL-5 since it is neither synchromesh nor hypoid gears:
- http://www.4crawler.com/4x4/index.sh...ntheticGearOil
- http://www.4crawler.com/4x4/4R_TechInfo.shtml#Fluids

Tranny likes GL-4 since it is synchromesh and the GL-4 oil has the right friction modifiers to make synchros spin up to mesh their gears faster. Diffs like GL-5 because they have that sliding friction of the pinion gear on the ring gear.

I usually throw whatever gear oil I have laying around in my t-case when I need to fill it.

 

Well, since he needs gear oil in the tranny, I assume he either has a gear drive tcase or the "normal" chain drive case, not the automatic.

But true, that's not always a fair assumption.

 

All good info.

Thanks guys.

 

x2

Clear and concise.

 

x3, more than an answer than what i was looking for and i think i am a better person because of it

 

Having a little extra is never a bad thing. For one, you'll have some around in case you get a small leak later on.

Another thing you can do is use it to "flush" your tranny. With the drain plug off, pour the new oil into the tranny until you see it come out the drain plug. At first, you'll see old oil coming out because the new oil is pushing it out. Of course, this is not a true flush, but it does help get more of the old oil out.

 

and don't tell anyone I said this, but in a pinch can also be used to top off the crankcase (but I'd add some ATF 1:1 to thin it out).