# Manual transmission fluid change.



## XtremeRevolution (Jan 19, 2012)

AMSOIL Synchromesh is the best stock replacement fluid. For a high performance fluid, AMSOIL 75W-90 transmission fluid and gear lube. That specific description. The Synchromesh is ~75W-80 in weight, and the 75W-90 has extreme pressure additives if you are planning to put more power through it. 

How-to:

http://www.cruzetalk.com/forum/57-how-library/6627-how-change-manual-transmission-fluid.html


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## Hazlitt777 (Nov 2, 2013)

Thanks for the reply. Very helpful. Another question: What is the current (original) oil's viscosity? 75W-80? 

I thought I read that the synchromesh AMSOIL which was recommended was 5W-30. Are you saying that is not correct, but rather a 75W-80 or 75W-90 is the actual weight of this replacement oil?

And would both 75W-80 and 75W-90 last the same amount of time under normal use conditions?

Also, in one of your links I see that two quarts are needed to do the manual transmission change. Yet elsewhere I've read it is a good idea to overfill to 2.5 quarts to reduce the wear and tear of the 5th and 6th gears. Any clarification on this would be greatly appreciated...before I actually do this.


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## XtremeRevolution (Jan 19, 2012)

Hazlitt777 said:


> Thanks for the reply. Very helpful. Another question: What is the current (original) oil's viscosity? I thought I read that the synchromesh AMSOIL which was recommended was 5W-30. Are you saying that is not correct, but rather a 75W-80 or 75W-90 is the actual weight of this replacement oil?
> 
> And would both 75W-80 and 75W-90 last the same amount of time under normal use conditions?
> 
> Thanks.


The OE fluid is a petroleum based 75W-80. At least...that's what the transmission spec requires. 

The 5W-30 synchromesh is labeled as such because some transmissions require an engine oil. Engine oil SAE weight grading is different from gear oil grading. A 5W-30 has about the same viscosity as a 75W-80 gear weight. 

The 75W-90 AMSOIL gear lube has extreme pressure additives for people who push their cars way beyond factory limits. It is compatible with transmissions requiring an 80-weight oil as it is on the low end of the 90-weight range.

Both would last about the same amount of time, and both would last at least 4x as long as the OE fluid from what we have seen.

Sent from mobile.


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## Hazlitt777 (Nov 2, 2013)

And do you recommend 2.5 quarts rather than 2 quarts?


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## giantsnation (Oct 11, 2012)

I think 2.5 is now the recommended amount but I used 2 and its running fine.


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## XtremeRevolution (Jan 19, 2012)

giantsnation said:


> I think 2.5 is now the recommended amount but I used 2 and its running fine.


Correct. The guys overseas noticed they were losing 6th gear shaft bearings due to a lack of lubrication or oil starvation and learned that filling an extra half a quart fixed it. 

Then I found a tech service document for this transmission that listed the capacity at 2.5 quarts. 

Sent from mobile.


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## Hazlitt777 (Nov 2, 2013)

Thanks for all the help guys. Xtreme, I would like to purchase 3 quarts (or 2.5 quarts) from you if that is still possible. I will see if I can figure out how to do that by viewing previous posts...or if you wish to pm me that is fine to.

all the best,
Joe


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## obermd (Mar 3, 2012)

Andrei,

Can you post the TSB number showing 2.5 quarts? My service adviser is looking for this information for me but has had no luck finding it.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> Andrei,
> 
> Can you post the TSB number showing 2.5 quarts? My service adviser is looking for this information for me but has had no luck finding it.


It isn't a TSB. It is a recommendation based on experiences people in the UK had with this transmission blowing 6th head shaft bearings. It has happened to a few people on this forum as well but GM quietly removes those transmissions and replaces them instead of replacing the failed bearing.

https://www.diagnostics.org.uk/2010/01/m32-6-speed-manual-transmission-1-9-cdti-vxr/

Sent from mobile.


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## sx sonic (Nov 25, 2013)

+1 for Xtreme.

The bearing failure was a big problem overseas. It's been a few months since I visited the Vauxhall forums but last I'd heard the suspects for the bearing failure were lack of lubrication on the 5-6 shaft bearing, overheating and oil breakdown, inadequate oil (they used a different weight oil than us), or any combination of the former. At some unspecified time GM modified the internals of the trans case to promote better lubrication of the 5-6 gear shaft, so that's telling.

Their fix was to run a better fluid and overfill with a 1/2qt which woul effectively eliminate or substantially reduce the root cause(s) of the failure. It sounded like it worked for them.

At the time, and I'm sure nothing has changed, GM was just replacing the trans and had neither produced a repair or inspection procedure, nor had they released the tools or Part Numbers to perform ANY trans repair. It was impossible to rebuild the M32. One of the Vauxhall guys took it upon himself to start R&R the trans and sourced out the parts; one of the cool things about bearings is if you get the dimensions or a PN you can get them direct from the bearing manufacturer


Note: the bearing failure has been extremely uncommonly here but overfilling a half qt is still a good preventative measure.


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## XtremeRevolution (Jan 19, 2012)

It is worth noting that in the last 6 months, I've seen at least two threads surface about drivetrain whining issues with the M32 that were resolved with a complete transmission replacement. The noises described sound exactly like a bearing failure as described here:

https://www.diagnostics.org.uk/2010/01/m32-6-speed-manual-transmission-1-9-cdti-vxr/

I agree that it is an uncommon occurrence. It is also worth noting that GM under-filled some of these transmissions.


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## RPHenry250 (Dec 8, 2011)

My M32 was one of those that had a whining noise. It was replaced. I never heard anything as to a failure analysis of it, but I place my bet on failed 5-6 shaft bearing. My transmission was also underfilled, but not much (~1.75Q), from the factory.

I'm planning on swapping in 2.5Q of AMSOIL Synchromesh soon.


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