jerry507

I was just doing some research on this subject. I changed all my gear oils a few months ago and had the same trouble finding GL-4 gear oil "locally". Eventually I found a straight 90 weight gear oil pretty cheap and put it in knowing I'd switch later on. It is very thick when it's below 60F Then I found this:

http://www.bobistheoilguy.com/forums...82#Post1231182

The long and short is that once upon a time GL-5 had chemicals in sufficient quantity to eat up the yellow metals in the transmission. GL-4 had a lot less, so you used that (though there are other reasons too). Now the chemicals have changed so you can use the GL4/Gl5 dual rated stuff and it won't HURT. But the rest of the oil properties are still very different and you'll get subpar performance from the transmission. The stuff like Redline are actual MT oils with the correct parameters to give you good shifting.

I'll be buying Redline Heavy Shockproof and refilling my transmission and transfer case before the end of the summer. Should work quite well! It should cost me about 75$ to do both. Not that bad at all.

Keith B.

Redline MT-90 certainly doesn't hurt the trans based on my experience.
I bought my truck with 142K miles on it. The POs may never have checked, let alone maintained, the trans oil.
The trans was about half full of grey oil when we first drained it.
MT-90 has kept it going all the way to 266K miles and beyond.
Once I had occasion to browse an owner's manual for a Nissan 4WD truck. The specs section stated clearly that only GL-4 was to be used in the Nissan manual transmissions.

jerry507

GL-4 was specified as a manual transmission oil grade. At the time of definition, the chemicals used were different. While today those chemicals are no longer used, the oil properties are still the optimal conditions for the transmission to operate. Nearly every manual transmission until recently will specify GL-4.

Now there are some that specify ATF, some that spec either, and a lot more that spec manufacturer specific oils. The latter is by far the most popular now.

SPARKS89

iTrader: (1)

That's one of the big reasons I don't like a lot of the new cars and trucks out there. I HATE that you would have to buy a specific BRAND of oil to put in it. I think it's all about marketing and forcing people to buy 'our product' so companies can make more money. It seems to me they're more concerned with making money than providing an affordable, quality product to the customer.

Ok, I'm done now.

Bingle

I love the redline products. Been running them in my truck for ~8years. Engine oil, mt90 in the trans and transfer case, and heavy duty shockproof in the axles. All work great and last extremely well. Expensive products, but I figured that I'd thrown enough $ at parts that good oil was cheap (ish) insurance.

Read an article in some car or 4x4 mag quite a few years ago where they tested most of the synth motor oils and the redline was the only one that showed hp gains over conventional. Very minor gains, but I can use anything I can get outa my 22R.

jerry507

I definitely see where you're coming from, but let me just throw this out there. If you're an engineer and you're designing a manual transmission for a new car, you're going to want to use something like GL-4 spec oil. Now remember back to how friggin hard it was for you, the customer, to find GL-4 spec oil

I'm not sure exactly WHY it's so hard, but it definitely is. Products from companies like Redline are most attractive not necessarily because of the oil itself, but because they actually TELL you something about the product. They give you equivalent motor oil ratings so you know the viscosity, they explicitly tell you it doesn't contain the sulfurs that harm yellow metals, and naturally they spec GL-4.

Obviously a car company doesn't want to put itself into a position of endorsing a particular brand for a number of reasons, so they'll instead create their own formulation and offer it through the dealers. It just ends up being a lot less work and less money for them then trying to manage another external company to supply a high demand consumable.

I worked at a heavy equipment manufacturer, and they supplied hydraulic fluid to their dealers under their own brand. Over the years it went from something special, to a standard, and then back again depending on the designs produced and pricing. But it was just trucked in, put into smaller barrels and shipped right out. It was just easier to control the oil than it was to have dealers penny pinch and create problems.

daved5150

iTrader: (1)

Damn, Jerry you hit the nail on the head with that last post.....

The 88 had MT90 in the tranny and TC. It shifted alot better after the Redline...but the Marlin seats helped out also.

Still have to buy three more quarts of Redline MT90 to put in with the other three I have left over from the 88 into the 94...

Summitracing.com sells Redline...that's where I buy it.

Use Redline MT90. You won't be sorry....

SPARKS89

iTrader: (1)

I understand what you're saying and it is a valid point. Where I'm coming from is my experience with newer vehicles such as a 2003 Ford Explorer I owned. It was specified to use Mobil 1 oil. Of course you can use other brand of your choice in your own car. I am probably the farthest thing from an engineer and will never claim to be one. Is it possible to design an engine to work best with a specific oil brand or are they testing many different oils in their engines before making them available to consumers our is it really just a marketing 'arrangement' between 2 companies?

I spouse now would be the time to ask...is there a corporate relationship between Ford and Mobil 1?

daved5150

iTrader: (1)

When you say "specified", what do you mean exactly? Does it say "mobil 1" in the owner's manual? I really can't see them specifying a certain brand of oil for a non-performance vehicle like an Explorer, but I could be wrong. Who knows? But it is possible that Ford would "recommend" Mobil 1 if they gave Ford a nice chunk of money. Let us know where your information came from.

annoyingrob

I love MT90. Made a noticable improvement in my Supra, so I just had to put it into the truck too.

But this:

Just take the shifter out and pour it in the hole.

RAD4Runner

Really??? Specify ATF for manual transmission?

woodyth

iTrader: (1)

Should I use the mt-90 in both differentials and transfercase and transmission? and if so how much goes in each?

BMcEL

Put as much as you can in everything. Transmission, diffs, engine, radiator, tires, turn signals, etc. etc.. Ignore the FSM.

woodyth

iTrader: (1)

I'll make sure I look in the fsm thanks

woodyth

iTrader: (1)

I'll make sure I look in the fsm thanks

daved5150

iTrader: (1)

Now that's funny.....I don't care who ya are...

I've always used Redline 75w90 gear oil in my diffs with no problems though the factory calls for this (From my 94 owner's manual):

Front w/ ADD 75w90 GL5; Front w/out ADD 90w GL5 (above 0 degrees F)
Front w/out ADD 80w or 80w90 GL5 (below 0 degrees F)

Rear calls for 90w above 0 degrees F and 80w or 80w90 for below 0 degrees F.

For the amounts in each, it's in the FSM that you can find free on the links here on the site. But you pour it in until it starts to run out of your fill hole. Then get the plug screwed in and you are set.

Hope this helps.