Final Drive service

[cjames431]

I drained and serviced my final drive with Royal Purple 75w140. I have it in my notes that that is what I used previously. Now I'm second guessing myself. I know the book says 80 and the pumpkin case says 80. My concern is synthetic vs hypoid.
I checked the gear teeth while the fill cap was off and all looks good with a consistent wear pattern.

 

[dwalby]

overthinking things.

My 1100 is 27 years old and I've changed the final drive oil twice in 120-something thousand miles. The owner of Maxima oils told me changing it once with a good synthetic would be enough, but just to be on the safe side I changed it again about 10 years later. I think I've gone about 15 years since that change.

there are people here who change it every other oil change, or maybe even every oil change. Pick whatever makes you comfortable, but in the end it really doesn't matter.

 

[Andrew Shadow]

My concern is synthetic vs hypoid.

Synthetic oil vs hypoid oil is not a comparison. Synthetic hypoid gear oil vs mineral hypoid gear oil is.
As long as both are hypoid gear oil rated you are good.

I would be more concerned with straying so far from the recommended viscosity of gear oil than whether it is synthetic or not.

 

[W0QNX]

Reading the RP site claims you should be good. Says hypoid in the second brag area:

Max Gear 75W-140 is recommended for use in truck and automotive front or rear differentials, manual transmissions and lower gear units of marine engines that specify the use of an API GL-5 or GL-4 fluid. It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.) and synchronizer safe. Specially designed to extend gear and bearing life, Max Gear provides superior corrosion protection over competing conventional and synthetic gear oils. We engineered this ultra-tough, high performance automotive hypoid gear oil to provide maximum protection to heavily loaded gears while maximizing power throughout the drive train. Above all, Max Gear outperforms ordinary gear oils by combining the highest quality synthetic oils with Royal Purple’s proprietary Synerlec® additive technology. As a result, Max Gear makes gears run smoother, quieter, cooler and longer without overhauls. A direct reduction of drag in the drive train has a huge advantage for trucks and other 4-wheel drive vehicles, therefore, better gas mileage. Formulated with a friction modifier additive, therefore no additional additives are necessary. Max Gear is available in the following viscosities: 75W-90, 75W-140, 80W-90, 85W-140 and SAE 90

Recommended Use​

Max-Gear is recommended for use in truck, motor home / RV, and automotive front or rear differentials, manual transmissions, and lower gear units of marine engines that specify the use of an API GL-5 or GL-4 fluid. Formulated with hypoid friction modifiers necessary for use in clutch or cone type differentials. Therefore no additional additives are necessary when using Max Gear 75W-140.

Max Gear 75W-140 High Synthetic Gear Oil

Max Gear 75W-140 is an ultra-tough, non-corrosive, high performance automotive hypoid gear oil to provide maximum protection to heavily loaded gears.

royalpurpledirect.com

And you're not really overthinking caring good for your bike but that thick gear oil will provide you service for a long time. I use the good walmart stuff and my change interval is way up there maybe even at 75,000 plus miles.

 

[ST1100Y]

API GL5 is important...

rest is secondary...

 

[W0QNX]

API GL5 is important...

rest is secondary...

My cheap stuff even has it:

Super Tech Synthetic Blend High Performance SAE 75W-90 gear oil is multi-purpose extreme pressure (EP) gear lubricant. This superior quality, synthetic blend gear oil is recommended for manual shift transmissions, conventional differentials, rear axles and steering gear boxes as found in passenger cars, trucks, tractors and farm implements. Can be used for top off of Limited Slip/Positive Traction rear axles. Protects against rust, foam, high temperature and corrosion of copper or bronze bushings. Recommended where API GL-5, API MT-1, SAE J2360, MACK GO-J, MIL-PRF-2105E (PG-2) are specified. Check equipment manufacturer's recommendations for proper SAE grade and API classification for your particular application.

 

[Al st1100]

If you poured 75/90 and 75/140 in to separate cup mix em up and pour them out you would not see any difference. 75/140 is not thicker to the eye. At room temperature they are the same. Bought my RT used, po had all sevice receipts. Fliud changes in trans and final drive were done with 75/140 by BMW dealer. 75/140 is not recomended in tempetures below 5 degees fahrenheit.