Possible Transmission/Diff Damage - Wrong Fluid type

[itsonlygeorge]

I went to top off my fluids a few days ago and change my oil and I ended up flushing the diff since I think it had the wrong fluid in it when I last topped it off.

When I bought the car, the PO put the wrong fluids in the diff and trans. From what I understand the diff had Castrol Hypoy C 80W-90 Gear Oil and LS modifier added. The transmission, which is a green label w/ external 17mm plugs, had Royal Purple 75w140 Max Gear w/ Friction Modifier.

I initially topped of the diff with the RP 75w140 to address the diff whine. I know the diff has a small leak from the input shaft and thought it was low. The diff whine changed from a constant whine to a whine-warble. I realized that I may have put the wrong fluid in, check the bottles I had labeled when I bought the car, and sure enough the RP bottle was labeled "trans" and the Castrol bottle was labeled "diff".

I went and got Mobil1 75w90 LS diff fluid and drained and refilled the diff and I topped off the trans with the RP 75w140 that I had. I have had the car for about 6 months and have put about 6000 miles on it with those two fluids in the diff/trans and I am worried about what damage could have been caused.

I have the "Green Label" Getrag 260/5 and the diff is a 2.93 LSD. I am currently looking for Redline MT-90 since that is what most people run in this transmission. Apparently the BMW GLS is Mobil SHC630 which is very had to find and 26$ a quart.

My question is this:

1. Do I need to do more than drain and refill the trans with MT-90?
2. Do I need to take it to a shop and pay to have a trans flush? (VIP charges $179 for this service)
3. Is there any potential damage that has been done by running these fluids in the diff/trans for 6000 miles? Is there anything I need to watch out for down the line and should I start saving for a new trans/diff?
4. Is Redline MT-90 what I should be running and is it comparable to the Mobil SHC-630 or do I need to find/order the SHC-630 and bit the bullet on the cost?

[ForcedFirebird]

Redline MTL and MT90 are both GL-4 fluids meant for manual gearboxes with yellow metal synchros (brass, bronze etc) - MT90 is 75-90 and MTL is 75-85. Either works fine in either label transmission. By putting gear oil in the transmission, you reduced the life of the brass since it's a GL-5 fluid. Change it ASAP and keep your fingers crossed. It may or may not have done any damage.

Not sure why people say Redline is so expensive. It takes two $15 quarts of fluid and you only need to change it once a year maximum in a street car. We change it every third 14hour endurance race in our race cars, once a year in the sprint cars.

In the stock LSD's we use Redline 75-90. The diff is quite a bit more forgiving of oil choice, so long as it's meant for clutch type lockers, it will be fine.

[itsonlygeorge]

I ordered some Redline MT-90 off Amazon. It should be here in a few days. Can I just drain the fluid thats in the trans and pour the Redline in or do I need to do anything else. Will any residue from the RP thats in there now be a problem?

Also, it says on the back of the RP bottle that it is not corrosive to synchros.

Max Gear is recommended for use in truck and automotive front or rear differentials, manual transmissions and lower gear units of marine engines that specify 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.