Been searching for gear oil for both 3 speed manual and 3.55 differential. According to the manual it requires SAE 90w or mineral oil. However, with all the new technology, it's difficult to determine what would be the best choice. I know that synthetic oils are not good for this purpose and the additives may or may not cause issues. The reference to GL-1 through GL-5 just increase the additives. PSC's American Petroleum Ins***ute (API) GL-1 SAE 90 Gear Oil category represents lubricants that contain no EP (Extreme Pressure) additives and have a viscosity grade of SAE 90. Most all the choices I have found are either GL-4 or GL-5. I did find at Tractor Supply, Traveller Ford Tractor SAE All Mineral 90 Transmission Fluid. API Service GL-1 For use in final drives, hydraulic systems and manual transmissions of Ford Tractors manufactured between 1939 and 1952 Guaranteed to meet performance requirements Mineral Gear Oils are straight mineral oils formulated with rust, oxidation and foam inhibitors. They are recommended for use in automotive and industrial applications that do not require extreme pressure (EP) additives. Mineral Gear Oils are sulfur-free and suitable for use in gear sets that contain copper, br*** and bronze bearings. GL-1 90W GL-1 formula Temperature rating: -22 to 435°F Recommended for mobile hypoid and industrial gear sets requiring: API GL-1 As far a I can see this meets Chevrolet's specs unless I am overlooking something. Is anyone using this product for their manual transmission and differential? Or have you found something better? Price is $24.99 a gallon.
I did a lot of research to find the correct gear lube for my 4 speed Muncie trans. Majority of folks on the internet recommended I try Sta-Lube SL24229 API/GL4 85W90. Been driving for four years no problems. I bought it on Amazon.
Sta-Lube 85/W90 is an API GL3/GL4 gear oil for differentials and transmissions. It is non corrosive to copper, bronze, or other non-ferrous alloy bearings or bushings
I used same lube for my '63 T-10. Br*** synchronizer gears have to have high sulfur content to prevent wear. GL5 doesn't provide that. Joe
I just dump the cheapest 85/90 I can get at walmart in them, and they work. It's surprising how long these old gear boxes lasted, with the same lousy oil in them for decades....getting new oil, of any kind, is a treat for them
Here is some technical information on various API Gear Oil Service Cl***ifications: https://www.machinerylubrication.com/Read/29213/gear-oils-cl***ifications Basically, there are 3 current specifications, GL-1, GL-4 & GL-5. Other grades that were in existence before have been obsoleted. GL-1 is pretty much straight mineral oil, with some rust and oxidation inhibitors and foam suppressants. These lubes are for automotive gear sets in transmissions and differentials prior to the development of hypoid differentials (lowered drive shaft that offsets the pinion gear relative to the ring gear). If the differential has a non-offset pinion this is spec is fine. It will also work in transmissions with bronze synchros. In the early days all cars had a drive shaft hump running down the floor from the transmission to the rear axle. Auto engineers developed the offset ring & pinion to lower the driveshaft and reduce or eliminate the hump. If you're not sure about your car you can always slide under and take a look at the differential. Non-hypoid diff will have the pinion entering the pumpkin in the center; hypoid diffs will have the pinion offset. Like this: GL-4 is for lightly loaded hypoid differentials. EP additives (sulfur/phosphorus) provide protection against sliding wear of the ring & pinion. Also OK to use in some transmissions with bronze synchros. Check viscosity requirements. It can make some transmissions hard to shift, especially when cold. GL-5 is for highly loaded & high speed differentials. Higher levels of EP additives provide additional protection against sliding wear in ring & pinion. All modern diffs can benefit from this. Not good for manual transmissions, EP additives can be aggressive on yellow metals. ETA: you can always use GL-5 in the earlier diffs, the EP additives won't hurt anything. But it's not wise to go the other directions, don't use GL-1 in a 9" Ford diff.
PSC. Petroleum Service Company in Wilkes Barre, Pa. Sells 90w Api Gl-4 in a 5 gallon bucket. 49.95 plus shipping. I use it in everything old. About as cheap as it gets if you brake it down per qt. $2.50, or $10 bucs a gallon. Just a heads up.
I use GL-1 from Napa only in early Ford trans ('48 down) and banjo rears. https://www.napaonline.com/en/p/FNJ65201
While it is quite popular to say that automotive engineers developed hypoid differentials to lower the driveshaft, and corresponding floor humps, that is only part of the story, if at all the case. It would seem that the primary reason for hypoid design is substantially increased tooth engagement between the ring and pinion gears. That offers at least two things of benefit. The increased tooth engagement distributes the gear load over greater surface contact area and increases the load capacity of a gear set for a given ring gear diameter. Or, conversely, you could reduce the diameter of the ring gear a bit and not lose strength for a given load. I think it is fair to say that the hypoid gear was a further refinement of gear design from straight cut bevel, to spiral bevel, to hypoid. Reduced floor height was a secondary benefit but not the driving force (pardon the pun) of hypoid design. Really, the difference in driveshaft tunnel height between center point and hypoid gear sets is not all that much. A front engine, rear drive vehicle floor design seems to be determined mostly by ch***is ride height. Ray
Thanks Blues4U. I missed that point about GL-1 not being good for Hypoid Transmissions. I'm going with Sta-Lube 85/W90 GL-4 along with Bcap55. Appreciate all the great feedback.
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