Gear Lube

50 merc

50 merc

Member
I was wondering if 80-w-90 GL5 gear lube is ok to use in the transmission of my 3 speed overdrive manual transmission? I am certain it is ok for the rear end. But I just thought I would check here first

Thanks
 
Thats what I use in My o.d. been using it for years no problems, some will say no.
 
Why do some say no ? I have been trying to source a manual for this car, The automotive flea market is comming up perhaps I will find one there.
 
Some Say No for a reason but it is outdated. My 49 through 51 Mercury Overhaul Manual has a statement about not using gear lube with high pressure additives. They used a form of sulphur as an additive in those days that was reactive with yellow metal (bronze/brass with any amount of tin). Modern GL5 grade lubricants used less reactive additives and have for a good many years. There should be no problem using the late type lubricants other than possibly more seal leakage due to less viscosity. You can still purchase straight grade SAE GL1 type lubricants but they are increasingly harder to locate. If you have a nearby lubricant sales outfit that is a dealer for Lubriplate products, you can get them to order GL1 grade lubes in several viscosity levels.

Kerby
 
Not to hijack the thread, but when a manual calls for gear lube in "Lbs" is a pint a pound? I know water is a pound a pint, but isn't gear oil heavier than water?
 
Gear oils with a GL5 rating are reputed to be detrimental to the synchros. A GL4 rating is minus the sulphur additives and is the one recommended for our early transmissions. I just checked the local parts store and after some searching did find one GL4 rated oil. I then checked with a local Model A parts supplier, and he has good stocks of Penrite GL4.
 
Mike51Merc said:
Not to hijack the thread, but when a manual calls for gear lube in "Lbs" is a pint a pound? I know water is a pound a pint, but isn't gear oil heavier than water?
Click to expand...

Gear oil is approx. 7.5 # per gallon. Some of the hand pumps for dispensing are rated at say 1 oz. per pump, so to get a pound you count the pumps. If you go to a lube supplier the approx. 5 gal size container is referred to as a 35# bucket or pail, and the approx. 15 gallon (aka 1/4 barrel though that's not really accurate) is referred to as 120 #.

BTW there is such a thing as a dry pint (measurement of produce), which is typically 12oz. in say blueberries.
 
Last edited:
Brits used to say a pint is a pound the world around but I always wondered if it was a pound sterling and the pint was beer. A US pint is probably nearer 12 fluid ounces than 16.
 
I run 80-95 synthetic in mine and it works great. I ran 80-95 Castoroil, gear oil, in my Merc OD for years with no problem.
 
You must log in or register to reply here.
Back
Top