# AMSOIL 75W-90 GL-4 Manual Transmission Fluid



## XtremeRevolution (Jan 19, 2012)

We've had enough reports of this fluid for me to confidently make this a recommendation for the Cruze. For most driving conditions, the AMSOIL Synchromesh fluid performs well as a strong synthetic that is close to the viscosity requirements of the OE fluid. However, more demanding applications benefit from the higher viscosity of the 75W-90 fluid, product code MTG. 

The AMSOIL 75W-90 manual transmission fluid is a GL-4 fluid. Unlike the Synchromesh, the 75W-90 has extreme pressure additives. I recommend the 75W-90 for the following conditions:
- Hard, "drive it like you stole it" driving and shifting
- Racing
- Power levels that exceed stock + tune, such as methanol injection, e85, etc. 

So far, this fluid has completely eliminated the 1-2 shift grind that some people have noted. However, the transmission can feel a bit clunky when very cold, while the Synchromesh will shift a bit smoother in those same conditions. As with the Synchromesh, I recommend filling 2.5 quarts. You can purchase the 75W-90 fluid directly from the AMSOIL site through this link:

AMSOIL 75W-90 Manual Transmission Fluid

Disclaimer: This product isn't officially recommended by AMSOIL's technical team due to variations in specification (and the constantly changing OE specification). Use at your own discretion, as I cannot be held liable for any side effects or problems. This thread was created to raise awareness of the success others have had with this product.


----------



## Mackwrench (Mar 13, 2014)

Thanks, I just ordered 3 quarts from your link.....mines got 26k on the factory transmission fill, I look forward to smooth(er) shifting!


----------



## Gnfanatic (Oct 2, 2013)

why only 3 quarts?


----------



## Mackwrench (Mar 13, 2014)

Gnfanatic said:


> why only 3 quarts?


Because I couldn't buy 2.5 quarts?....not sure of your question, the owners manual calls for 2 quarts of the GM transmission oil, Xtreme above has determined that 2.5 quarts works better....


----------



## Gnfanatic (Oct 2, 2013)

I thought you were going to do a flush. I am planning to do one at 10k. I dont like the idea of adding high quality fluids and then they get contaminated with dirty/crappy fluids.


----------



## Diesel Dan (May 18, 2013)

XtremeRevolution said:


> Unlike the Synchromesh, the 75W-90 has extreme pressure additives.


Recommended for NV4500 and GV overdrive units because it has about 1/2 the EP additives of a GL-5 lube.
Also does not attack brass synchronizers or "yellow metal" parts.

The amsoil runs $10+/quart cheaper than the fluid from the Ram dealer.


----------



## XtremeRevolution (Jan 19, 2012)

Diesel Dan said:


> Recommended for NV4500 and GV overdrive units because it has about 1/2 the EP additives of a GL-5 lube.
> Also does not attack brass synchronizers or "yellow metal" parts.
> 
> The amsoil runs $10+/quart cheaper than the fluid from the Ram dealer.


Correct, a GL-5 fluid will be a bit more abrasive. The "attacking" of yellow metals was only an issue with initial variations of GL-5 lubricants and is no longer an issue. The concept here is that the extreme pressure additives function by creating a chemical reaction when under pressure and heat. That chemical reaction creates a sacrificial film. In the case of ZDDP, this is a phosphate glass that protects the two moving parts. It is a sacrificial film because it peels away after use. The problem is that this "peeling away" takes a little bit of the surface of the synchro with it, which will be a softer yellow metal alloy. The more extreme pressure additive you have, the thicker that protective film will be and the more it will erode the synchros. On the flipside, having too little can cause wear in other areas such as gears and bearings. It is important to note the conditions under which this chemical reaction occurs. Most normal driving will never see these conditions which is why the Synchromesh has worked excellently for many of us including myself. However, higher power levels demand better protection. 

Oil testing analysis will reveal just how much of an issue this is depending on which wear metals are more significant. 

Sent from AutoGuide.com App


----------



## XtremeRevolution (Jan 19, 2012)

Gnfanatic said:


> I thought you were going to do a flush. I am planning to do one at 10k. I dont like the idea of adding high quality fluids and then they get contaminated with dirty/crappy fluids.


A warm drain will evacuate all but an inconsequential amount of the old fluid. I wouldn't worry about flushing a manual transmission. 

Sent from AutoGuide.com App


----------



## Mackwrench (Mar 13, 2014)

Got the trans oil changed today, took about an hour, and that's with 30 min of warm oil drain time...easy enough when done on a lift.....I put 2.5 quarts in....Then measured what had drained out, 52 oz....factory calls for 62 oz (2 quarts)....
...So mine was 12 oz low...no visible leaks, so I'm left to believe it's been that low since new.....

Transmission seems to shifter smoother and quieter.....Thanks Xtreme!


----------

