tims@shark.UUCP (Tim Stoehr) (09/16/83)
I've heard alot of good information on the net about motor oils, but I haven't heard anything about gear oils. If anyone has any interesting info about this, I'd like to read it, especially if it answers the following questions. 1.) What is the meaning of the API rating, i.e. GL4? 2.) Can GLx gear oil be used where GLy oil is required if x < y? If x > y? 3.) Is it useful to change manual transmission oil? Why? How often? What can happen if you don't?
vfm@ihu1f.UUCP (09/20/83)
API GL ratings: I searched my documentation for the definitions/specifications of "GL" to little avail. I did find the following: 1. GL1 - + FIAT: Having anti-wear additives without chlorine, sulfur or phosphorus. + MACK: Specification GO-A. 2. GL4 - A product exclusively rated as such should not be used in transaxles. 3. GL5 - Must meet many additional specs by EATON, MILITARY, GM, INTERNATIONAL and MACK. Most of these specs state that the lube must not contain zinc. 4. GL6 - Meets FORD ESW-M2C105-A-H.P specification. I could not find anything on GL2 & GL3. For petroleum/mineral lubes I don't know if the higher GL suffix number can replace the lesser one/s. AMS/OIL synthetic gear lube statement: "AMS/OIL 80W-90 Gear Lube exceeds in the lubrication and performance requirements for gear boxes where MIL-L-2105C and AUTO SPEC. GL2 through GL6 lubricants are specified for 80W-90 grades." When to changes: Some reasons to change the lube are the manufacturers recommendation to do so and possibly a high-performance lubrication (such as a synthetic) may improve performance. In general applications gear lube does not require frequent changes, but there are some "unpublished" reasons for changing it. One that I can think of is if a differential vent (most of them have a vent that runs into the frame someplace) becomes submerged in water. If such a situation could have taken place, check it ASAP and if water is present change it pronto and continue to do so for awhile thereafter! Eventually these lubes under normal conditions will get very black and possibly thicker. Now if you have some sort of limited-slip or "posi" differential you definitely should change it more often. These rear-ends can cause the lube to get very hot and the same thing that happens to oil (evaporate) can happen to it and definitely get thicker. Synthetics in this application have a service life several times that of a petroleum product. Vet owners from years past that used to rely on a now "not-legally-obtainable" whale oil additive appreciate the synthetic lube. In extreme cold the synthetics really show their stuff again. If you've ever tried shifting a granny-geared, stump-pulling truck in temps <-40 F (not a wind chill - as in North Dakota) your chances of bending a shifting fork before making the shift are much higher. Synthetic gear lube runs about $6/gt (AMS/OIL 80W-90) and it does its job superbly!