Hooked on Redline MT90

[Jerry Bransford]

Thanks for the clarification jerry, so what would you recommend? I saw a older thread where you said you didn’t like royal purple. Felt like it was a overpriced gimmick. I have never used royal purple so I don’t really have an option about them other than a lot of people seem to really follow the stuff. Should I try to find a GL5 so I’m replacing my fluid with what it needs according to the book? Or go with the redline that meets the requirements? I just want to used the one that will prolong the life of the tranny. And definitely not one that could damage it. Same question goes for the transfer case, but I’m guessing what I use for the tranny is what I should use for that as well right?

GL-5 lubes are meant for differentials and most of them are too harsh for use inside transmissions. The sulphur-based compounds most commonly used to make them a GL-5 attack the brass synchronizers inside a transmission The ONLY GL-5 lubes that are safe for transmissions use an unusual formulation described on the back label as "safe for yellow metals" which means they won't attack the brass (yellow metal) synchronizers. Not many GL-5 gear lubes are safe for yellow metals but they're out there but that means reading a lot of back labels to make sure it won't attack the gear synchronizers.

Assuming your Rubirob name means you own a Rubicon, that means the 5-speed or 6-speed manual transmission would require the slightly lower viscosity of Redline MTL which is a GL4 lube. That's what I would run if my Rubicon had a manual transmission.

For your Rubicon's chain-driven transfer case, it requires ATF. The transfer case literally doesn't care what type of ATF It runs on. ATF+4 is a full synthetic of very good quality so that'd be a good choice.

 

[Rubirob]

GL-5 lubes are meant for differentials and most of them are too harsh for use inside transmissions. The sulphur-based compounds most commonly used to make them a GL-5 attack the brass synchronizers inside a transmission The ONLY GL-5 lubes that are safe for transmissions use an unusual formulation described on the back label as "safe for yellow metals" which means they won't attack the brass (yellow metal) synchronizers. Not many GL-5 gear lubes are safe for yellow metals but they're out there but that means reading a lot of back labels to make sure it won't attack the gear synchronizers.

Assuming your Rubirob name means you own a Rubicon, that means the 5-speed or 6-speed manual transmission would require the slightly lower viscosity of Redline MTL which is a GL4 lube. That's what I would run if my Rubicon had a manual transmission.

For your Rubicon's chain-driven transfer case, it requires ATF. The transfer case literally doesn't care what type of ATF It runs on. ATF+4 is a full synthetic of very good quality so that'd be a good choice.

Thanks for the advice jerry, I do own a 04 rubicon. So when the time comes I will give the redline MLT a shot for the transmission and a good quality ATF+4 for my t case. I was under the impression that because my transmission was slightly newer it didn’t have brass inside. But if it likes the GL-4 just the same then it would be a safe bet to stick with that. I know I have seen guys running syncroMAX in there’s but I don’t know if that is considered a GL-5 or a GL-4


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[basic]

I wish I had a manual in my LJ, but a friend with an XJ with the AX15 echoed this sentiment this past weekend. I can also attest to MT-90 being good in the manual transmission used in S-chassis Nissan cars.

 

[bobthetj03]

I ran MTL in my NV3550 and noticed a marked improvement in shifting when cold. I now am running RP Synchromesh and can tell no difference between the 2. They both seem to improve cold shifting. I say get which ever one is cheaper for you.

 

[ac_]

I went with Jerry's recommendation when I changed my fluid in my NV3550. I bought the oil from Summit Racing @ $16.95/quart.
Fonz

That is about the same price as the Redline. It is like pouring actual gold in your transmission. But without the resale value.

 

[SteveBarrus]

Here is a very informative write up on gear oils. https://www.powerperformancenews.com/tech/the-great-lube-hunt/

 

[Coach U]

Redline MT-90 for the older AX-15 and AX-5 transmissions but Redline MTL for your newer NV3550 as well as the later NSG370. MTL is a GL4 gear lube just like MT-90 is, it just has a slightly lower viscosity that meets the requirement of NV3550 and NSG370.

Jerry question I am a new member and new to Jeep TJ. When I checked with Redline they did not recommend the MT-90 for the AX-15. I am going with the Forums and your recommendation of using MT-90, but any idea why Redline says no?

 

[Mr. Bills]

For manual transmissions specifying GL-4 and 75w90 viscosity the following products are widely recommended on the forums for "other" manual transmission vehicles experiencing "notchy" shifts:

Motorcraft Full Synthetic Manual Transmission Fluid (P/N XT-M5-QS) - very expensive and somewhat difficult to find 75w90 GL-4 oil that is often referred to as "Unicorn Tears,"

Redline MT90 (75w90) and to a lesser extent MTL (which is 75w80)

Valvoline Synchromesh Manual Transmission Fluid 75w90 GL-4 - conventional rather than synthetic, cheap, and reported to be among the best for dealing with notchy shifts when cold - even better than the two Redline products.

Synthetic lubricants aren't always the "be all/end all" in every situation as some think. Sometimes the synthetic manual transmission fluids are too slippery for the synchros and conventional lubricants actually work better and for less money as well. The AX-15 may be one of those situations. If it were me, I'd try Valvoline and only go with the more expensive stuff if the Valvoline manual transmission fluid doesn't resolve any shifting issues.