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Discussion Starter · #1 ·
I bought 3qts of RP MaxGear 75w90, made for GL-4 and GL-5 replacement, and am changing out my fluid in my trans today.

I, however, came across several forums that claim RP is horrible for yellow metals(brass, bronze, copper, etc.), and became concerned.

So, I went onto RP's website, found the gear oil, and their description is as followed. Looks like we may have another fluid option for our transmissions.

I will try it out and post later on with thoughts.

Max Gear – High Performance Gear Oil

Max Gear is recommended for use in truck and automotive front or rear differentials, manual transmissions and lower gear units of marine engines that specify use of an API GL-5 or GL-4 fluid. It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.) and synchronizer safe.

Max Gear is an ultra-tough, high performance automotive gear oil designed to provide maximum protection to heavily loaded gears while maximizing power throughout the drive train. Max Gear outperforms ordinary gear oils by combining the highest quality synthetic oils with Royal Purple’s proprietary Synerlec additive technology. Max Gear makes gears run smoother, quieter, cooler and longer without overhauls. Max Gear is formulated with a friction modifier additive – no additional additives are necessary.

Max Gear is available in the following viscosities: 75W-90, 75W-140, 80W-90, 85W-140 and SAE 90
 

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Give it a shot and see. My quibbles would be the GL-5 specification. Synchros don't need all those extra EP additives, and the transmission in general isn't subjected to the extreme forces a hypoid-gear differential is subjected to.
 
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Discussion Starter · #3 ·
Well, I already noticed a huge improvement... transmission noise has extremely subsided. Of course, it doesn't help when all that drained out from the factory was just over a quart.. Nonetheless, the trans is much quieter now.

Shifting seems easier too, a little. It being a high performance gear oil, I wouldn't assume it would smooth out shifts by much, but it did help.

I'm going to continue to use it and see how it performs when the clutch is good to go, but all in all I'm satisfied with this fluid at the moment.
 

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I did that with my T56, ran great for about a month then the synchros disintegrated. Came to find out the T56 can't use synthetic fluid and had to have non syn Dexron III. The culprit was the paper blocker rings the T56 uses, the syn fluid ate them up and the synchros went adios. Don't know if the same applies here but be wary when it comes to transmissions.
 

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Keep us updated. I'd still be leery of running a 75w-90 that is meant more for gears, but can be used in transmissions.
 

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I thought you can go from a GL4 to a GL5 but not the otherway around, meaning that gl4 is gl5 compatible but gl5 is not gl4 because of the brass. And as far as the paper blocker rings... I just did a search on Google cause i did not know what those were....(Im a Noooob) Anyway it seems like every link was talking about the t56 with those, and no other trans... and a bunch of people with issues... My guess is they would have strayed away from that, and i feel like I would have come across that issue when i was researching this trans on the vauxhaul forums. They have had the M32 trans since 06 at least... btw M32 supposedly stands for Max320 Nm (just a little fun bit of info)
 

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Like I said, I'm not familiar with the internals on the Cruze manual trans, just saying to be cautious
 

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Discussion Starter · #8 ·
I'll keep an eye on it and keep this thread updated after some miles are driven.

But like I said before, it feels great at the moment.

I wanted to originally use Amsoil, but could not find it anywhere local. I didn't want to have to order it, so I went with the RP Advance Auto has on sale currently.
 

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I thought you can go from a GL4 to a GL5 but not the otherway around, meaning that gl4 is gl5 compatible but gl5 is not gl4 because of the brass. And as far as the paper blocker rings... I just did a search on Google cause i did not know what those were....(Im a Noooob) Anyway it seems like every link was talking about the t56 with those, and no other trans... and a bunch of people with issues... My guess is they would have strayed away from that, and i feel like I would have come across that issue when i was researching this trans on the vauxhaul forums. They have had the M32 trans since 06 at least... btw M32 supposedly stands for Max320 Nm (just a little fun bit of info)
From what I understood, GL4 and GL5 have to do with the type and amount of extreme-pressure additives in the gear oil. In the old days, the extreme-pressure additives that lasted were made using sulfur-containing compounds, which ate up the brass/bronze synchros. These days, with better additive technology, oils with the necessary EP additives for GL5 specification can be formulated to not attack yellow metals.

I found this thread on Bobistheoilguy.com concering GL4 vs. GL5 gear oils, and why something designed for gears might not be optimal in a transmission: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1137260#Post1137260

In short, a dual-rated GL4/GL5 gear oil will work, and there are likely better options out there if one isn't happy with how it shifts.
 

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Any updates on your tranny?
Mine with the Amsoil Synchromesh in there for 35k miles now has been fine. It shifts fine, no grinding (unless I really get on it with my tune and rush the 1-2 shift), and no odd noises. It works when I need it to work. That's about the best compliment I can give something.
 

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Discussion Starter · #12 ·
Mine's okay on the RP. Feels great when in the high gears, but second is problematic for me. It's not Royal Purple related, but rather the factory on put a quart of trans fluid in my case, because I drained about 90% of it. Didn't even get a quart out of the trans...
 

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How are y'all judging how much fluid to put back in because it tells me to let drain for 10 minutes then measure how much vame out thwn put back the exact same amount.

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Discussion Starter · #16 ·
I'm not convinced on the 'put back what came out' bull. My trans was starving. It's been noisy since day one, but figured it would subside at some point.

If you drain your fluid, keep it. It's your insurance.

We've found that transmissions are failing because of heat. Dissipation of heat is very critical of our trans. I actually put a little bit extra fluid in my case.
 
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but how many quarts did you put in.
 

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Discussion Starter · #18 ·
I let mine drain out excessively(30-40 minutes), since there wasn't much in it. Maybe there was a gigantic air bubble keeping the other quart of fluid in. Fail..

Service Info says 2.32 quarts. I put in an extra half quart.
 

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I let mine drain out excessively(30-40 minutes), since there wasn't much in it. Maybe there was a gigantic air bubble keeping the other quart of fluid in. Fail..

Service Info says 2.32 quarts. I put in an extra half quart.
Not possible. You either leaked it somehow, or it was under-filled from the factory.

I wonder how much fluid the case holds when you drain it completely, if at all. Either way, 2.5 quarts is a good bet. I don't think over-filling by half a quart will have a negative effect on it, and the extra fluid should provide some extra heat tolerance.
 

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Not possible. You either leaked it somehow, or it was under-filled from the factory.

I wonder how much fluid the case holds when you drain it completely, if at all. Either way, 2.5 quarts is a good bet. I don't think over-filling by half a quart will have a negative effect on it, and the extra fluid should provide some extra heat tolerance.
I have always wanted to stick a camera in a diffrental housing the drive.

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