I'm replacing the rear rotor and brake pads on my 87 k100rs. I figured I'd change the rear wheel gear oil also. I looked in my manual and it says the rear wheel gear oil is 80 or 90 weight I believe. When I drained the oil it was clearly not gear oil. It was clean, but red like transmission fluid. I've only owned the bike for a few months, so I don't know the history of it. Is there a reason anyone knows of for there to be a different fluid other than traditional gear oil inside? Should I put gear oil in after there's been a different fluid in there? Also, is there a specific type of brake fluid I should use or anything I should be aware of with the rear brakes and rotor, it seems pretty straight forward. Thanks for any info.

Use the recommended gear oil that ATF is not suitable for helical cut gears. As for brake fluid any good brand DOT 4 fluid is suitable.

Don't trust PO, check gearbox oil as well.

moriarti wrote:Don't trust PO, check gearbox oil as well.

It's the reason I change all the fluids and do a complete service when I get a "new" bikes. There are people out there who have no business wrenching on a motorcycle.

Point-Seven-five wrote:

moriarti wrote:Don't trust PO, check gearbox oil as well.

It's the reason I change all the fluids and do a complete service when I get a "new" bikes.  There are people out there who have no business wrenching on a motorcycle.

EXACTLY

Point-Seven-five wrote:
It's the reason I change all the fluids and do a complete service when I get a "new" bikes.  There are people out there who have no business wrenching on a motorcycle.

Got a point there


A year ago had a Yamaha XV535 here, making strange noises.
Owner did a full service himself, been 500km since.
Saw it has enough "oil", altough it didn't look like oil.
Drained it, found coolant.
Enigine non-savable

Thanks for all the replies. I'm going to go ahead and change all the fluids.

Redline in the US make appropriate gear oil in hypoid GL5. No prizes for guessing what colour it is.

Point-Seven-five wrote:It's the reason I change all the fluids and do a complete service when I get a "new" bikes.  There are people out there who have no business wrenching on a motorcycle.

100% agreed

If it were my bike I'd put in a good 90W gear oil,ride it 20 or so miles and drop it in a clean white container to have a look at it. Then,I would put in fresh 90w gear oil . Oil is cheap gears are not and it's better to be safe than sorry.

It's probably just Redline Gear oil.... it's red
I wouldn't worry too much about it. Just replace all your fluids so you have a baseline for all future servicing.
75w90 is recommended in the riders manual
DOT 4 brake fluid.