Will Royal Purple Synchromax In Differential Do Any Harm?
 

This is for my 82 240d.

So this weekend my buddy and I took on the task of changing the engine oil, manual transmission oil, and differential oil.

I got 75-90 synthetic gear oil for the differential.

I got Royal Purple Synchromax for the manual transmission.

Completed the manual transmission change, filled with the Royal Purple. Came in the same looking bottle that the 75-90 gear oil came in. I added about 95% of the gear oil in, and some dripped on my face. So I had to get up and wash it off. While I was in the house, my buddy was adding what was left of the royal purple into the differential. Thought it was the gear oil.

So basically, there is about 95% 75-90 synthetic gear oil in the differential, with a very small, about 5%, of the royal purple. I do not know what weight the royal purple Synchromax fluid is.

Will this do any harm?

Thanks.

I doubt it would do harm in very small quantity and would only notice a difference if you ran it that way for a very long time(several years). Again, it mostly depends on how much you think the original weight rating was diluted. Royal Purple is an excellent product and a call to their 800# might ease your mind on what to do.

I thought the diff got the same fluid as the manual gearbox did. no?
John

From what I understand, the diff gets 75-90, while the manual transmission takes standard grade motor oil or even ATF fluid (from what others have posted). Royal purple syncromax claims it replaces manual gearbox fluid that takes ATF, multi-grade, and single grade engine oil.

The Haynes manual shows "Type A atf". With tighter tolerances in manual trannys, many manufacturers went to atf back in the 70's.

Well, I called Royal Purple and they said that it should be fine.

A little off topic, but does anyone know the interval to change the manual transmission? Isnt it something like 30,000 miles?

Another a little bit off topic question (but dont want to flood the forum with new threads) - When reinstalling the drain plug for the manual transmission, it was very hard to screw in. Went in fine about halfway with my hands, and had to wrench the rest. Even took it out and tried again to make sure I had the threads locking correctly. Is this going to be a problem? Either with possibly some metal shavings or draining in the future?

the drain plug is a pipe fitting, so the threads are progressive. this means that the plug should be tighter as you get the plug in.
John

If the fluid is GL4 or GL5 rated, it should be fine in the diff.