c0rbin9

iTrader: (2)

Another manual transmission fluid thread... there hasn't been one in a while.

My Redline MT90 is very notchy and does not like cold weather, which matches the forum consensus. My question is what to replace it with. A lot of people seem to like the super whizz-bang synthetic fluids with ultra heat stability, but these are not always the best for street driven cars.

NEO seems to be the most commonly recommended, but I'm also curious about Idemitsu and OEM Mazda. I'm tempted to just go to the Mazda dealership and use whatever fluid they have on hand... anyone have any experience with OEM fluid? Is it synthetic? I'm more concerned about decreasing transmission wear and cold shifting performance than I am about track performance. Shifting the Redline when cold actually feels destructive.

SwappedNA

iTrader: (1)

I've used the XT-M5-QS in both my Series I RX-8 when I owned it (the Aisin AZ6 that's known for being made of glass) it fixed my 2nd gear grind on high RPM shifts with that transmission. I also put it in my FD transmission a few months ago. I've had amazing results with it both times.

However, not that this applies to you, but I figured I'd mention it anyway: The two newer Mazda transmissions (well, transaxles, but you get my point) I've tried it in have not liked it. I've used it in my 2nd gen Mazdaspeed 3, and it caused cold shifting issues until it warmed up when the car previously had no issues whatsoever. I've also noticed issues when I put it in a 2015 Skyactiv 6MT Mazda 3 sGT hatchback. Same thing, cold shifting became an issue when there wasn't one before. I swapped to Redline MTL (75W-80) and the issues in the 3 went away.

But back to the original topic, I'd recommend the ford fluid. Miata guys swear by it, and I've had great results in both transmissions I've used it in. My FD is my daily driver, and I have no issues with cold shifts, it actually improved cold shifting compared to whatever was in there before. High RPM shifting isn't an issue, either. Neither is noise. The car is my daily driver like I mentioned, and I don't have any issues with that fluid. Just my two cents.

Retserof

iTrader: (1)

I switched from from factory lube to Redline MT90 in 1999 and then to Amsoil MTG 75W90 in 2014. I noticed each lube was better than the previous one -- easier to shift when cold and easier shifting in general. Also quieter.

c0rbin9

iTrader: (2)

Interesting quote from another thread about the Ford magic fluid:

AMSOil MTG also has a reasonably low 40C viscosity at 84.5.

aceeca

I've been considering trying Mitsubishi MTF 75W-85 but i haven't seen one thing about using Mitsubishi Transmission Fluid in an RX7. I'm currently using the same Redline fluid and have the same notchy issue.
The Mitsubishi Trans Fluid looks to meet the minimum standards of whats needed and its convenient for me because I keep some around for my other car.

Manny_Apex

iTrader: (1)

I had the same issue a couple years ago, then switched to Royal Purple. I’ve been very happy every since.

Jatt

iTrader: (2)

I'm going to do a full fluid overhaul soon after my build is done, even though it was done when i bought my car back in ~March(?). I'm personally considering either RP or Red Line. Saw some people say Red Line is good for older Syncros.

Have no experience either, so curious what everyone says.

Sgtblue

iTrader: (16)

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Pretty sure it’s already been said in the dozen or more previous threads on this.

j9fd3s

iTrader: (3)

the Mazda number is 0000-77-5W90-QT, they actually don't have a listing for the Rx7 anymore

TeamRX8

iTrader: (2)

a couple of people on RX8Club have been swearing by the newer Redline MT-LV trans fluid as being the most notch-shift free, but haven’t tried it yet myself. I was having my best luck with the Ford fluid previously mentioned. I never was a fan for MT90.

https://www.redlineoil.com/mt-lv-70w75w
.

nmoffatt

iTrader: (15)

I’ve been using eneos in both my 7 and 8 based on the recommendation from Charles at BHR racing. Been very happy with the results.

used to use redline for years and don’t plan on going back.

c0rbin9

iTrader: (2)

The more I read about the Ford fluid (the XT-M5-QS), the more it seems like the only thing that should go in these transmissions, at least for cars that aren't going to see extreme heat on track.

It is the only fluid I have seen that is specifically recommended for older transmissions, and it has the lowest 40C viscosity I have seen, and it is an OEM fluid. That plus the plethora of positive testimonials, even some directly mentioning Redline, Neo, etc., it seems like it will be a winner.

I'm going to try it out and will report back with the results. This will be a 14k mile transmission with a fresh fill of Redline MT90, so will be interesting to see the comparison.

SwappedNA

iTrader: (1)

As I've said before, I swear by it. Many people do. It's rather costly, but its worked in every transmission I've used it in, minus the newer Mazdaspeed3/Mazda3 transmissions.

Jatt

iTrader: (2)

Nice find, going to try it as well most likely.

cewrx7r1

iTrader: (2)

I have used a few trans fluids with MT90 being my favorite for many years. Then after helping an acquaintance, he gave me some
trans fluid from Pettit Racing. What really impressed me was it's winter shifting.
Have been using it for about 8 years now. I was told that it is a blend of regular oil with synthetic oil.

https://pettitracing.com/collections...ube-80-90-3-qt

nmoffatt

iTrader: (15)

When changing the fluid does everyone change the washers each time? Last time around I picked up a set for the trans and diff from a forum member to be safe. Was thinking of just reusing them for the next change.

cloud9

iTrader: (4)

For what it's worth, I use NEO in mine. No complaints, feels great all the time.

Sgtblue

iTrader: (16)

I’ve looked them over for splitting and mushrooming and reused them before with no problems. But I decided not to push my luck… like you I got some replacements the last time fluid was changed a year or so ago.

DaleClark

iTrader: (55)

I've re-used the crush washers more than once, never had a problem.

BTW the fill plugs on the trans has Teflon tape wrapped around it. Clean the old tape off and put on new tape when re-installing.

Dale

j9fd3s

iTrader: (3)

the part number is 9956-41-800, it breaks down like this:
9956 = crush washer
4 = Aluminum, 2 is Copper
18 = 18mm ID.

Mazda has the two in all the sizes, so if you need a washer they have it.

Manny_Apex

iTrader: (1)

Do you use it in the transmission and diff, or just transmission? I'm looking to change my diff and trans fluid on this RX-8 I just bought and being that it's cheaper than what I'm currently using and sold by Petit, it seems like a good option for me!

cloud9

iTrader: (4)

Do you have a 'key' documenting the breakdown of all the various codes? Would love to have a copy of that

Pete_89T2

iTrader: (4)

9956 = crush washer
4 = Aluminum, 2 is Copper
18 = 18mm ID.

^That's the key, here's some practical hypothetical examples:

9956-41-200 = Aluminum crush washer, 12mm ID
9956-21-200 = Copper crush washer, 12mm ID
9956-21-400 = Copper crush washer, 14mm ID
9956-41-000 = Aluminum crush washer, 10mm ID

nmoffatt

iTrader: (15)

Good to know. I may have missed the teflon tape last time around. Thanks Dale!

nmoffatt

iTrader: (15)

I purchased the washer from Max_Spd 4 years ago. He still has some left in case anyone is interested.