Added MT90 Fluid, Now 3rd Gear Grinds

It’s same as you, only when it’s first warming up and I also run redline mt90. I just make sure to shift slowly into third

 

It's not likely anything will fail to the point of not being driveable.

Had a company truck (Ford Ranger) that had 150K on it when I got it and ground when shifting from 2nd to 3rd. I drove it for 30K or so with no change. I would hesitate a half second between gears and it wouldn't grind that way. Last I heard that vehicle had 280K on it and was still running with same transmission.

 

This is the chart that you are looking for;


Now granted, that is PROBABLY part of one of those incredibly long AMSOIL advertisements, but I think it at least gives you a good picture that some gear oil is simply TOO THICK when it is cold.
I've never actually tried any of those oils listed as "FAIL", but I can clearly tell the difference even between two of them that are relatively close.
I *once* tried putting in mobile 1, and notch-notch-grind-grind. It was fine when I put it in while on vacation in a warm place. Drove back up to the January cold and it was absolutely terrible. I did the oil change while on vacation specifically so I wouldn't have to do it in the cold, unfortunately, it didn't work out that way. So I switched it out for AMSOIL, and no more notches or grinds.

And funny thing is that based on that chart, mobile is the second best. Well, I guess that second best just isn't good enough.

 

Update:

Tried the magical Ford fluid and I think it's worse than it was with the MT90. The best so far has been the 75/25 ratio of MT90 and MTL. I'm going to try using MT85. If that doesn't work I'll just go back to MT90 and accept my fate.

 

Thanks for the update at least. Much appreciated.

 

I have the exact same problem. I had the transmission oil in my 2007 changed at 195k and now when shifting into 3rd. I am putting in GL4 Now after the GL-5 was not working well. If this doesn’t work i will go back to the toyota factory stuff

 

I've never used Redline but have had good luck with Lucas and Royal Purple. I'm not a big believer in the snake oil claims of some of the boutique oils, but RP really did work well.
I've had my truck since it had just under 12,000 miles on it. I'm at 107,000 now and it sometimes grinds a little when shifting into 3rd. I think it's been about the same since I got it. Just don't force it.

 

Redline is definitely not snake oil, it's a POA group V top of the line synthetic used by tens thousands of owners both car and truck. That being said, Walmart Supertech synthetic is widely available, cheap and has great reviews even with their gear oil.

 

My snake oil comment was directed at Royal Purple. BUT it actually made my transmission smoother. You'll want to make sure you stay with a GL4 flavor for the transmission.

 

I wonder why people run full MT90
instead of half and half
or straight 100% MTL, which is thinner. Thinner usually means better shift and cold shift performance
while still being thick enough to withstand the stress
not like it's dropping down to being a 5w30 motor oil

 

I just put this stuff in my 2.7 5 speed before reading this thread. I have to say the shifts feel smoother, but the acceleration seems a tad bit slower after releasing the clutch. RPMs seem to drop lower between shifts. Not sure if that’s because it’s thicker and the fact that I was a 1/4” off level with the front end being higher than the rear, so it was ever so slightly overfilled I guess. Either way my shifts feel smoother. Gonna have to try and shift faster as I got accustomed to shifting slower with the factory oil. Wonder how this is gonna hold up in the 20 degree weather we get here in the winter.

 

So I hear nothing but positive traits about mt90, put it in my ‘09 6spd, then read this thread… lol

haven’t noticed any huge differences, shifts do seem a bit notchier which I like a lot, coming from an e39 m5 I’ll take any precision on this truck I can get lol

 

I just changed out my manual trans fluid on my 2008 with MT-90 and it made the shifts butter smooth! It used to be crunchy going into third...not anymore!
This is my second manual Tacoma I used MT-90 on with great success.

 

Hey op, did you ever get this sorted out?