A little history:

Back in 2007, I picked up a used 2003 Evo with only 35k+ miles.

I got a deal on the car because the tranny would 'grind' shifting into 2nd on a cold start. I knew this was a Mitsu problem, so I didn't think much of it. The same day I bought the car, I bought Penzoil Synchromesh (same as GM Synchromesh for those who don't know - GM Part# 12345349) and the problem vanished, however..

GM Synchromesh alone does not protect the gears very well at all. Even after a long day of autocross, when the tranny is hot, the gears just seem to hate life; the gears shift slow, have a hesitant feel to them, and so forth. Also, straight up synchromesh only lasts about 6-8k miles max; after this duration, the tranny shifts very slowly, and synchros start to grind again.

So, I called shep transmission, who kindly rebuilt my transfercase (stage 2) and who recommends Redline Heavy Duty Shockproof, a GL-5 based lubricant, for the transfercase (NOT for the transmission). I asked him what he thought the best fluid to use in an OEM 5-speed transmission was.

His response: Redline MT-90. Period.

Unfortunately, my 2nd gear grumbling may return with straight up MT-90, he said, and that I might try mixing in Redline MTL in the transmission, which he hasn't tried.

So, after searching about mixing transmission fluids, I found some pretty outdated information and even someone recommending Redline HD-SP for the transmission!! Hence the creation of this thread.

For those of you with an unhappy 2nd gear synchro (or maybe another gear), synchromesh will help. I tried the following after clearing up my idea with ShepTransmission, who said mixing would be fine.

1Qt MT-90
1Qt Redline MTL
1Qt GM Synchromesh #12345349, courtesy of a Pontiac dealership. (PepBoys irregularly stocks it, and its only $2-$3 cheaper @ PepBoys, so you're not getting too hosed buying synchromesh at a GM dealership. Also, the idiot at the counter in the dealership told me had no "synchromesh" fluid, but when I gave him the part number, suddenly he had cases of the stuff in stock).

I've had 3 COLD mornings to test out the mix. So far, no 2nd gear grinds. Plus, I beat the **** out of the gearbox going through hard shifts, etc. and it shifts MUCH better than it did on straight synchromesh.

Therefore, if you are having grinding issues, or, if you want your synchros to be buttery smooth, try the cocktail I listed above. So far, I've had good luck with it.

So, per John Shepard, the best fluids to use for your 5-speed Evo:

Redline MT-90 for the transmission
Redline Heavy Duty Shock-Proof for the transfer case


If you have notchy/grinding synchros, in the transmission, try the mix. Next, I will try 2Qts MT-90 and 1Qt Synchromesh, or 2Qts MT-90 and 1Qt Redline MTL.


:discuss:

 

Bump for an old thread. Interested to see if others have done this or if Jeff has an update...

 

Redline Cocktail FTW! 2x MT90 1x MTL

I've run it for years now with awesome results.

 

nice write up

 

I've done Redline MT90x2 and Lightweight shockproof x 1 and it has worked great for me as well.