I'm finding a lot of different types of Redline MT-90 and I know it should be gl-4.

Red Line 58205 Heavy ShockProof Gear Oil shock proof stuff

vs.

Red Line 50205 MTL 75W80 GL-4 Gear Oil regular stuff

I don't know which one to buy, they're about the same cost but I don't want to mess anything up.
also, I think I read it takes 3.1quarts, true?
what size crush washers should I buy?
please and thank you.

also, apologies, I don't see how to make the text smaller... links for clarification.

 

Neither one of those are MT-90. MT-90 will say "MT-90" on the bottle.


The shockproof oil you listed is meant for differentials, not transmissions with synchronizers. The MTL is a different blend but serves a similar purpose to the MT-90.

 

New washers are not really required. Can't remember ever having one leak after re-use.

 

The Redline MT-90 is a 75W90 spec. You can also do a blend with some Lightweight Shockproof oil -- lots of feedback from folks with Toyota/Aisin manual transmissions saying that's a good combo. I run MT-90 in both my Aisin transmissions but will try that blend for fun sometime soon.

 

I wouldn't use shockproof in a transmission. The stuff is super slick. Spur and helical gears (like in a transmission) roll over each other so they don't need the super slickness. Synchronizers require a bit of drag to make the two shafts come up to speed with each other. So the Shockproof will actually degrade shifting performance. Same reason GL-5 gear oil isn't recommended for our transmissions.

The super slickness of the Shockproof line of oils is good in a differential because hypoid gears actually slide over each other to some extent. There's an exception to every rule though of course, Torsen differentials like the Eaton Truetrac work on the principle of the worm gears binding up under load. So for those specific differentials, you wouldn't want to use the shockproof gear oil.

 

And THAT is why I'm glad I posted before I purchased.... THANK YOU.
I glossed over the weight entirely and focused on the "MTL" which I presume is an acronym for manual transmission lube and almost bought it.


thank you everyone else too.

 

Transmission : MT90 or MTL (75w90 GL4 or 75W80 GL4) I run MT90 because 75W90 is Toyota spec IIRC

Per Marlin crawler you could run their 75W90 GL5 or the heavy shockproof in the T-case and diffs.
Chemicals | Marlin Crawler, Inc.

Arlindsay - I run HD shockproof in my diffs and have a truetrack in the front. Seems to be functioning as intended, but you have me thinking about it more so I may have to do some testing (when the truck is back together) and make sure the front is locking up as it should. Good food for thought.

 

I'm sure the difference in a Truetrac with standard gear oil and the shockproof stuff is minimal. Even the cheap gear oil is slippery.

I wouldn't be afraid of using the shockproof gear oil in the transfer case. My transfer case has no synchronizers so it's just a bunch of gears. But I think some transfer cases actually do have a synchronizer in them. Certain configurations of the V6 trucks, I believe.

 

I agree with you on all points.
I think the important part here is to never put GL-5 oil in something that specs out for GL-4. Chemical in GL-5 (sulfur?) chews up the brass syncros.

 

Update:
Completed front/rear differentials, transfer case and transmission.
Note: fluid was about a quart low in the rear diff and transmission while the transmission had some gold metallic sheen to it.

Driving used to sing around 45mph when I kept it steady but now it's quiet.
One further question I have is should I be concerned it was low and check it to ensure it stays full or is it being low sort of normal for something that's been neglected?

 

I would check that the drain plugs and fill plugs, along with the breathers, don't leak. Make sure the breathers are free and clear, so that as the items they're on warm up while driving. If the differential breathers are clogged, you'll get leaks in the axle seals, especially the rear one.
Axle seal leaks will also soak the rear brake shoes, ruining their usefulness.
If the drain or fill plugs washers have never been replaced, they may well leak. If that's the case, and it was as neglected as you say, the diffs or transmission may well be low on oil. They may not leak until you drive it for a bit, and get them nice and warm.

Leaks like all those should be pretty obvious to a visual inspection. Clean the area around them, making sure there isn't any oil on the area of the fill or drain plugs. Then take it and drive it for a few miles, and when you get done, look for indications of oil where you just cleaned it off.

Just a thought. I get so few any more...
Pat☺