[Jeff]

Switched over to Redline MT-90 manual transmission fluid this past weekend, and it seems to have smoothed out shifting a bit.

I have been thinking about using it form months, but I was in Advance Auto Parts this weekend and saw that all Redline oils were on sale for $6/quart, and they just happened to have 4 quarts of MT-90 on the shelf.

Although it's barely been in for a few days, the shifting feels more smooth, and overall the syncros spin up faster making the shifts a little quicker. It helps the most with downshifting, especially going from 3 to 2 and 2 to 1. No miracles, but I think it is worth the extra money.

 

[SmellyTofu]

Is there such a thing as too slippery gearbox oil for our gearboxes? I haven't been able to find an oil that's not fully synthetic for the gearbox that any of the Australian oil company recommends.

 

[Jeff]

Yes there is, and it's not just our gearboxes. I've heard that Royal Purple, Mobil 1, and some of the other Red Line oils are too slippery for the synchros in many gearboxes.

Prior to using the MT90 I was using Red Line 75W90NS and that was pretty much the same as conventional 75W90 gear oil in terms of performance. My gearbox was still notchy so I figured it may have been a little too slippery.

However I spoke to a few people who've used Red Line MT90 in their various Toyota vehicles and the overall opinion was that it works fairly well. So I gave it a try, and although it is not really a "night and day" difference, the switch was worth it.

You can either stick with conventional 75W90 gear oil, or try some of the synthetics until you find one that works right. It's really a trial-and-error process, because you don't know for sure how well a gear oil will work until you put it in and try it out.

For non-synthetic gear oil, I've heard that General Motors (Penzoil) Synchromesh works pretty well.

 

[SmellyTofu]

But in choosing an oil, there doesn't seem to be much in terms of what is OK and what is not apart from GL5 and 75W90 whilst the transfer case and rear diff is just GL5. There are full synth in 75W90 easily available but some of my non RAV4 owners say not to put in anything other than what is specified.... I guess the gearbox itself is fine. As for the transfer case and rear diff. I have NOOO clue.

 

[noodlerooney]

Have had Mobil 1 75w-90 synthetic in the transfer and rear diff for 10000 miles now, was not expecting anything major but noticed a big difference for the better. Changed it in both at 2K then 10K miles. The change at 2K was well worth it, lots of metal/discoloration from break-in wear. The change at 10K miles had nowhere near the metal/discoloration that I saw at 2K miles.

 

[Jeff]

Well it's been a year and almost 30K miles since I switched to Red Line MT-90, and now I can say it's the only manual transmission oil that will ever be used in my Rav4 for the rest of the time I own it.