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Discussion Starter #1 (Edited by Moderator)
Amsoil Synchromesh is highly recommended for our manual transmissions. You can order some from XtremeRevolution in this thread: http://www.cruzetalk.com/forum/10-engine-technical-discussion/29009-amsoil-your-cruze-engine-transmission-fluids.html

Here is a basic overview of how to change the manual transmission fluid in the M32 6-speed gearbox/transmission in the manual transmission Cruzes.

Tools list:
Ramps (or jack and jackstands)
8mm hex key/socket
10mm hex key/socket
10mm box-end wrench
Lots of extensions
10mm ratchet
Drain pan
8mm socket
Interior trim removal tools or flat-bladed screwdriver
2.32 quarts of synchromesh-type MT fluid (2.5 quarts is fine as well)
Long-necked funnel
Latex or nitrile gloves
Beverage of choice

Time: 1 to 1.5 hours.

Skill level: Moderate. If you can barely do an oil change, this one isn't for you. If you're fairly comfortable changing oil in the Cruze AND have the tools listed, it's up to you whether or not you want to attempt this. Experienced DIY'ers should have no difficulty with this.

Fluid selection: The M32 needs a GL-4 gear oil with about a 70w-80 weight. I used Amsoil Synchromesh (MTF). Cost should be about $40-50 for 3 quarts. The Amsoil Synchromesh I used appeared to be about the same viscosity as the fluid that drained out.

My apologies about not having pictures for everything. Both cameras died on me after the MT fluid drained out.

I am posting this how-to as a service to the members. Neither I or CruzeTalk have any responsibility or liability if something bad happens. FOLLOW THIS AT YOUR OWN RISK.

0. Break free the fill plug. If you cannot open the fill plug, STOP! Get a buddy or some more tools. If you can't open the fill plug, then re-filling the transmission will get much more difficult. Not impossible, just much more difficult. The transmission can be re-filled through the level plug if you're so inclined using a fluid transfer pump like a pump-type hand soap dispenser uses. I'd recommend against this, however.

The fill plug is the quarter-sized round thing with the hex head on it.



Use the 8mm" hex bit on the long extensions to break the fill plug free. It's on there pretty well, so it will need a bit of a heave-ho to get free.



1. Get the car up in the air. I used my Rhino Ramps and drove up them.



2. Detach the under-engine panel with the 8mm socket and the flat-bladed screwdriver. There are 6 8mm screws, 6 plastic pop-out connectors, and 2 other plastic pop connectors holding the panel on. 4 screws are located at the front of the panel, while the other two are located at the back, one on each side of the oil pan cutout. There are 3 pop-out connectors on each side. One holds on the little airdam in front of the front tires. The other two attach the under-engine panel to the fenderwell skirts. Remove these and set them with the screws.



Note the two raised screw holes at the back of the panel.



If your Cruze has had the shield recall done, your shield will not look like this. Per feedback from other folks, removing the remaining shield is not needed.

3. Locate the level port. It's on the side pan of the transmission. (NOTE: This was deleted on the later 2012 and 2013+ Cruzes. Ignore this step if you have a later Cruze.)



Use the 10mm hex socket on a short extension to take it out.



4. Locate the drain port. It's underneath the differential housing, next to the subframe.



Another view:



Here's the tool I cobbled together to undo the drain plug. It's the 10mm hex socket with the box end of the 10mm wrench slid over the socket. A ratchet does not have enough room to clear the subframe.



5. Make sure your drain pan is a foot to the right of the drain plug, as the fluid will shoot out in a glorious jet almost to the tire.

6. Give the drain plug a good heave-ho, as it's on there pretty well.

7. Adjust the drain pan as needed to catch the fluid.



8. Let the fluid drain.

I have no pictures after this point. All this is now is re-filling the transmission and re-assembling the underbody panel.

9. Replace the drain plug. Make this fairly snug.
10. Remove the fill plug you loosened in step 0.
11. Put your long-necked funnel into the fill port.
12. Put in 2.32-2.5 quarts of MT fluid.
13. Check to see if any fluid came out the level port. Wipe up any spilled fluid.
14. Replace the fill plug. Snug down until it stops, and do not tighten further.
15. Replace the level plug.
16. Replace the underbody panel, ensuring that all the screws and the 6 pop-out connectors go back.
17. Drive the car down the ramps.
18. Enjoy a smoother-shifting transmission!

Edited Note: GM factory fills 1.6-1.9 quarts of the transmission, but reports have been coming in that dealers re-fill 2.25 quarts. Most Cruze owners are now filling 2.5 quarts to help prevent a known failure of a 6th gear shaft bearing. Refer to the following thread for more information:

http://www.cruzetalk.com/forum/10-powertrain/36617-cruze-manual-transmission-m32-issues.html

Enjoy!
 

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Good write up!! How did the transmission feel after the oil change?
 
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Discussion Starter #3
Good write up!! How did the transmission feel after the oil change?
Thanks!

It's smoother going into gear. Also, quick gear changes are much smoother. I did a 6-4 downshift today at 45 mph, and it went smooth as butter. I was surprised, as it usually fights a little bit to go into gear. Overall, I'm glad I changed the gear oil.
 

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Awesome How-To! Plan on switching over to the Red line 70w-80 and was wondering if this change voids the warranty?
 

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Discussion Starter #5
This could present warranty issues if the transmission fails and they determine it's the fluid's fault. I'm going on faith that the fluid I used that meets GL-4 compatibility and 70w-80 viscosity range won't cause any issues. Seeing how the transmission is operating more smoothly and consistently, I do not foresee any issues that would need warranty coverage.

The question for me is use the poor-shifting OEM fluid and use the warranty, or use a better-shifting aftermarket fluid and avoid any issues?
 

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How many miles did you have on your transmission when you changed this fluid? I ask because I'm at 5900 now and shifting is quite smooth. Of course, there's always the possibility that it will degrade over time if my fluid becomes as unsuitable as yours was, but I'm just trying to get an idea.
 

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Discussion Starter #7
My car had just over 19k miles on it when the fluid was changed out. The MTF might last longer in a city environment since there's less pumping of it going around. I'm doing lots of hilly highway driving, so the transmission fluid gets pumped around a lot, and is subjected to decent torque loads in the higher gears.
 

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One note I'll mention is that with the T56 transmissions, the amount of fluid recommended in the US is different than in Europe/Australia. Less here than there. Many people filled it to the level of the Aussies because it helped with transmission noise and worked smoother. So maybe check that the same isn't the case here.
 

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My car had just over 19k miles on it when the fluid was changed out. The MTF might last longer in a city environment since there's less pumping of it going around. I'm doing lots of hilly highway driving, so the transmission fluid gets pumped around a lot, and is subjected to decent torque loads in the higher gears.
Good to know. I'll probably end up doing this toward the end of summer. It has been shifting beautifully for now.
 

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Mine from day one has not shifted smoothly and im at 12k now. Occasionally I will shift and it will be completely smooth and i wish every shift could be like that.
 

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Discussion Starter #11
Mine from day one has not shifted smoothly and im at 12k now. Occasionally I will shift and it will be completely smooth and i wish every shift could be like that.
The biggest difference I've noted is that the transmission is consistent now. It's a bit smoother, and much more predictable. After it warms up a touch, it shifts the same every shift the rest of the drive. It doesn't matter if I'm shifting slowly or quickly.
 

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good write up :)

did all this last fall with the clutch swap, I personally only use the level plug since its the tattle tail indicator to let you know EXACTLY when your under or over full. I couldn't find a reason to use the top plug since filling through the level was just as easy to me. /shrug :)

Like Sciphi said, this isn't much harder than changing your oil. Just MAKE SURE you use a GL-4 MT fluid. Which you won't find on most auto parts house shelves, so don't expect to run down and get some after youve already drained it... it won't happen. Your most likely gonna have to order it and have it on hand.

The only other thing I seen in doing mine is that the drain plug does not have a stop when your putting it back in, so don't put it in any farther than it was when you took it out. DIRECTLY On the other side of the threads is the differential and you don't want the back of your plug up against the gear because you put it in to far. Just be very mindful of this, shine a light in the drain hole so you get an idea what i'm talking about. No room for a mistake here.
 

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Discussion Starter #14
I'm really liking the Amsoil Synchromesh (MTF) in my transmission. Give this stuff a few shifts, and it's smooth sailing the rest of the time. Search Amsoil's Web site for it. It's about $15-16/quart shipped.
 

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Mine has 22K and has shifted beautifully since new, but I think I'll switch to synthetic the next time I change the motor oil.
 

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Mine has 22K and has shifted beautifully since new, but I think I'll switch to synthetic the next time I change the motor oil.
Folks have noticed these transmissions being all over the place with shift quality. Some shift really nicely, others shift poorly. Others, like mine, shift somewhere in the middle.

I'm still glad I got the OEM fluid out. Whether it had break-in debris in it or was just not a good batch, shifting improved with the new fluid.
 

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Nice write up Sciphi. The Castrol BOT 402 fluid is a full synthetic fluid, 75W-85.
 

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GM makes an excellent manual transmission lube specified for the Corvette and it's GL4 but I don't know the other specs to be able to say it's suitable for the Cruze. The Tremec manual trans in the 2005 Corvette was factory filled with Dexron III but later they changed the specs and developed a new lubricant. It really worked well in my old Corvette, especially the cold weather shifting. Here's a link to the place I got it from.

21018899 - GM Manual Transmission Lubricant - 32 oz.
 

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I was trying to think of the different ones I wanted to try... /thinking.. (i've slept since then)

Joe Gibbs Driven - Qualifying Gear Oil this is the one i REALLY want to try out. I'm not recommending anything, i just really liked the data on the oil in comparison to the OEM stuff. The biggest difference with this oil is that it doesn't have all the extra chemicals that street fluids have for longevity. This stuff has extremely low parasitic drag but has a short life as well. Of course in our cars it would still be lots and lots of miles.. but no where nearly as many as the street oils.

Red Line Synthetic Oil - Gear Oil for Manual Transmissions - MT-85 75W85 GL-4 Gear Oil I think this is the closest version to the OEM fluids numbers of the redline oils.. you'd have to double check.. once again, i've slept since then.


AMSOIL - Synthetic Manual Transmission and Transaxle Gear Lube 75W-90 (MTG) the reason i went with this over AMSOIL - Synthetic Manual Synchromesh Transmission Fluid (MTF) was.. ummm.. i can't be for sure. I think it was because I plan on putting a LSD in the car which MTF isn't recommended and I think the kinematic viscosity or the viscosity index... or both were closer to the OEM stuff. Don't quote me on that, do your own research plz.

The Castrol BOT 402 fluid is a full synthetic fluid, 75W-85.
and there be the OEM.. thanks for pulling up the name OnlyTaurus, i had forgotten what it was and would have had to dig it up again. haha
 
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