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I just bought some Castorol Hypoy C 80-90 gear lube for my newly rebuilt M38 trans,transfercase, and overdrive.It has a GL-5 and MT-1rating.Any reason why I shouldn't use it?
Chuck

Hypoid gear oil is not necessary in your tranny/transfer. GL5's have high sulpher and are known to be corrosive to non-ferrous tranny parts like brass synchro rings.

The hypoid oils were designed for hypoid gear sets found in differentials and that is where they should be used.

The tranny and transfer will shift better and last longer with NON hypoid gear oils. I run 50 weight engine oil in mine and they shift a lot better and have less whine.

i used GL-1 90 w oil from napa. it was a 90 weight mineral oil i believe the part number was 65-201.

chuck, what i can tell from all the conversation's from the mv's forum's. this is the oil most people use. IS this true wesk?? i used it in transfer/trans, diff's.

Yes, The GL-1 works fine. Most folks will use it or a similar Royal Purple product. I still like the more modern GL4/5's Hypoid lubes in my diffs. The farm tractor dealers will usually carry several good tranny gear oil choices.

Just a note: the SAE weights we use in this conversation are not the same between Gear oils and engine oils. A 90 wt gear oil is close to a 50 wt engine oil in viscosity.

OK, so tomorrow I will go to Tractor Supply and get some GL-1 for the trans/transfer/od, and use the Casterol for my diffs.

Whats the best way to get it in the tranny/transfer - 1q bottle and tube its definately not it!

matt, oreilly's sells a funnel that looks kinda like a sheet rock plaster hopper. it has and on and off knob, the container has oz's, pint's and qt marks with a 3ft hose. it came in handy for me, whats cool about it is the fluid will not start to flow untill you turn the knob. around 6-7 dollars.

I have been using Sta Lube GL4 85W90 available at NAPA. The bottle rated this ok for manual Trans with yellow parts.
It specifically is labeled: "not corrosive to copper, bronze or other non-ferrous bearings and bushings"
and
"Perfect for auto bus truck standard transmissions"

5-gal pail of GL1 Chevron RPM that I have is very thick stuff. I have not used it.
Some references:


API ratingsGear oils are classified by the American Petroleum Institute using GL ratings. For example, most modern gearboxes require a GL-4 oil, and separate differentials (where fitted) require a GL-5 oil. It is important that purchasers check the oil against the vehicle manufacturer's specification to ensure it does not contain any aggressive chemicals that may attack yellow metal gear components, such as phosphor bronze.

API viscosity ratings for gear oils are not directly comparable with those for motor oil, and they are thinner than the figures suggest. For example, many modern gearboxes use a 75W90 gear oil, which is actually of equivalent viscosity to a 10W40 motor oil. Multigrade gear oils are becoming more common; while gear oil does not reach the temperatures of motor oil, it does warm up appreciably as the car is driven, due mostly to shear friction (with a small amount of heat conduction through the bellhousing from the engine block).

Fully synthetic gear oils are also used in many vehicles, and have a greater resistance to shear breakdown than mineral oils.

API classification subdivides all transmission oils into 6 classes:

API GL-1. Oils for light conditions. They consist of base oils without additives. Sometimes they contain small amounts of antioxidizing additives, corrosion inhibitors, depressants and antifoam additives. API GL-1 oils are designed for spiral-bevel, worm gears and manual transmissions without synchronizers in trucks and farming machines.
API GL-2. Oils for moderate conditions. They contain anti-wear additives and are designed for worm gears. Recommended for proper lubrication of tractor and farming machine transmissions.
API GL-3. Oils for moderate conditions. Contain up to 2.7% anti-wear additives. Designed for lubricating bevel and other gears of truck transmissions. Not recommended for hypoid gears.
API GL-4. Oils for various conditions - light to heavy. They contain up to 4.0% effective anti-scuffing additives. Designed for bevel and hypoid gears which have small displacement of axes, the gearboxes of trucks, and axle units. These oils are standard for synchronized gearboxes, especially in Europe, and may also be recommended for non-synchronized gearboxes of US trucks, tractors and buses and for main and other gears of all vehicles. GL-4 oils may also be used in many limited-slip differentials.
API GL-5. Oils for severe conditions. They contain up to 6.5% effective anti-scuffing additives. The general application of oils in this class are for hypoid gears having significant displacement of axes, generally non limited-slip differentials. They are recommended as universal oils to all other units of mechanical transmission (except synchronized gearboxes specifying GL-4). Some GL-5 oils in this class, which have special approval of vehicle manufacturers, can be used in synchronized manual gearboxes. API GL-5 oils can be used in limited slip differentials only if they correspond to the requirements of specification MIL-L-2105D or ZF TE-ML-05. In this case the designation of class will be another, for example API GL-5+ or API GL-5 LS.
API GL-6 is not applied any more as it is considered that class API GL-5 well enough meets the most severe requirements. When API GL-6 was still in use, it denoted oils for very heavy conditions (high speeds of sliding and significant shock loadings). They contained up to 10% high performance anti-scuffing additives. They were designed for hypoid gears with significant displacement of axes. However, in 2011 at least one company offers new polyol ester based API GL-6 oil, mostly for racing applications.[1] The application is limited to certain types of manual transmissions, but improvements in BSFC of about 5% in standard weather and driving conditions and up to 15-20% in cold extremes (arctic weather conditions) can be expected.[2]

wilfreeman wrote:Whats the best way to get it in the tranny/transfer - 1q bottle and tube its definately not it!

I use a plastic tube with and funnel. You can do it better with the floor pans off.

But if the floor pans are on. Then I do it this way. When doing the T/C, tape the tube to the wind screen frame with funnel on it. then run the tube under the tub but over the frame and into the T/C. Take care that you don't have a droop (a low spot) in the tube when it goes under the tub over frame and into the T/C. It is slow going but will work. Do the same for the Transmission, but feed the tube with the hood raised and down by the steering column that way.

I use a suction gun that I bought from Harbor Freight.

Yeah, I was under the jeep with a quart bottle(with a screw on spur top) with a tube pused on it and running to the tranny/trans. It was very slow going and the tube popped off of the oil jug a couple of times - covering me in oil! I knew there had to be better ways. I thought of the gallon jug with the pump on it, but didn't want to got back to town, after changing cloths, to buy one. I like the floor pan idea, but that's a lot of work just to change the oil. The hanging it from the windshield idea is good, but you need some kind of shut off at the tranny end don't you? Really need a combination of Ken and circleburner's ideas. What type of suction gun Chuck? Do they have it on their website?

It basically looks like a grease gun.
Oil suction gun #95468 $9.99

Get a 5 gallon pail of lube, and buy the pump that goes on top of it. Quick,easy,and enough for a couple of changes.

I use a garden pump sprayer - took the wand off the end of the hose, fitted a small gate valve to the end of the hose to control flow. Pour the oil in, pump it up, stick the hose end in, open the valve and lay there and contemplate the underside of the jeep while waiting for it to top off. Its slow but no mess.

I like the suction gun idea - cheap, and definately easier.