will it hurt to run this heavier gear oil 85-140 in the truck? I wasnt paying attention when I grabbed it just seen the GL-5. So can I run this in my tranny or rear ends? Or do I need to take it back and exchange it for the lighter stuff? I plan on adding a quart of lucas oil to everything. I got about 2 quarts or 80 90 so if the heavier stuff is okay in the diffs and transfer case then I will use it there and use more lucas if it needs it in my tranny.

 

Ford's specified manual transmission lubricant is 50W engine oil in normal temps and 30W in extremely low winter temps. 85-140 is WAY too thick. Take it back and get 80W-90 for the axles. 20W-50 engine oil works well in the transmissions, especially if you live in a cold climate.

 

I hope my '79 Ford Truck Shop Manual - Maintenance & Lubrication doesn't have a misprint.

For a 3 speed manual, a 4 speed manual, or a 4 speed Overdrive manual transmission it specifies (Ford spec ESP-M2C83-C) "Standard Transmission Lube", which IIRC, is a GL-4 rated lube. (Not the (Ford spec ESW-M2C105-A) "Hypoid Gear Lubricant" specified for the differentials, and not (Ford spec ESE-M2C144-A) engine oil).

Ford does spec the SAE 30 and SAE 50 (ESE-M2C144-A) engine oil in the main and auxilliary transmissions in their Heavy Duty (600 through 9000 Series) Trucks.

 

I've ran 80w-90 and up to 140w in Ford diffs, transmissions and transfer cases for many years without problems, down to -25* F. If you have hard shifting when cold, you might switch to 50w trans oil.

Jason

 

Ford spec ESP-M2C83-C "Standard Transmission Lube" is what they went to in the late '70s instead of engine oil IIRC. I mistakenly put 80-90 in my NP-435 when I first got it (changed all the fluids in the truck) and the synchronizers wouldn't work worth a hoot when it was cold, even in spring and fall, and the truck only had 30,000 miles on it. As soon as I replaced it with 20W-50 all was fine.

 

so use 80 90 in the diffs and transfer case and 20-50 motor oil? in the tranny? I live in north central washington so its 0 in the winter and 100 in the summer

 

I run 85/140 in the Dana 60 rear of my Supercab. I tow and carry heavy stuff so I like the thicker stuff. Probably giving up a little mileage but it's a 460. I'd never know the difference.