GM Dexron VI in manual Trans a No-No

[Mike_dup1]

I was looking up info and was referred to this info. I recall a discussion about this a while back so I wanted to share. Seems many dealers don't have a clue about not using Dexron VI in a manual trans.

FYI

This comes from prior issue (2006) of GM Techlink service news and it may applicable to current models.

Quote:
This information applies to 2007 and prior GM passenger cars and trucks.

Dexron III is being phased out as a product name. It is being renamed Manual Transmission Fluid and carries p/n 88861800 U.S. (88861801 Canada).

If fluid p/n 88861800 U.S. (88861801 Canada) is not yet available when servicing a manual transmission or transfer case, Dexron III can be used in its place.

DO NOT use Dexron VI in place of manual transmission fluid in any manual transmissions or transfer cases that specify Dexron III, as a failure may result.

 

[d00df00d]

Interesting. Do you know what the reason is?

 

[Mike_dup1]

The source never mentioned anything but it possible that additives in the new fluid may be incompatible with internal parts of the trans, i.e. corrosive to certain metals or other composites used in the trans and or gasket sealers etc.



Here is another bit of info although not related to Dexron VI but it gives insight into problems that can occur from using the wrong fluid.

Quote:
This information applies to repair of the manual transmission (fig. 6) on the Chevrolet Colorado, GMC Canyon, Saturn SKY, Pontiac Solstice, and Hummer H3. Manual transmission fluid requirements for the various units presently in service change from model to model.

Manual transmission fluid requirements for the various units presently in service change from model to model.

Using the incorrect type of transmission fluid in Aisin manual transmissions may affect the sealing ability of the seals. An incorrect type of sealer may not be compatible with the transmission fluid or may not have the correct characteristics for sealing the affected components.

TIP: Refer to SI documentation for correct sealers, adhesives, lubricants and fill quantity for each transmission you service.

Aisin manual transmissions require the use of p/n 89021806 - Fluid, m/trns 75W-90 GL-3, 1QT (89021807, 1L, in Canada). The use of the correct fluid is required to assure the desired shift characteristics and compatibility with adhesive sealers.

RTV is the only sealer that is compatible with this fluid. The use of anaerobic sealers on Aisin manual transmissions is not recommended.

 

[MolaKule]

Is this from two different bulletins for two different cases? I.E., Are you sure they are related?

In the first, they are discussing Manual transmissions which use Dexron III, while in the second Aisin trannys are discussed in terms of gasket compatibility.

There is huge difference in viscosities between a 75W90 MT (14.5 cSt) and a Dexron III fluid (7.5 cSt), not to mention the frictional property differences.

 

[Mike_dup1]

No they are not related, it just an example of what other considerations must be taken into account when using a fluid contrary to the recommended fluid.

How many times do you read of people making recommendations for fluid contrary to what it recommended? i.e. use Sychromesh in place of ATF or something like that. In the case with the GL3 lube mentioned above, how many do you think would consider it fine to use a GL5?

 

[brian12]

Its to thin. Ive heard guys complaining about it in other forums.

 

[MolaKule]

Quote:
How many times do you read of people making recommendations for fluid contrary to what it recommended? i.e. use Sychromesh in place of ATF or something like that. In the case with the GL3 lube mentioned above, how many do you think would consider it fine to use a GL5?


Point well taken. Just because someone sees a 75W90, it doesn't mean a 75W90 GL5 diferential fluid is appropriate. However, IMO MT synchromesh equivalent viscosity fluids should work in this application.

In the case of using an ATF in synchromeshes, IMO, I do think transmission engineers have sacrificed wear for cold weather shiftability.

 

[Whitewolf]

Originally Posted By: d00df00d
Interesting. Do you know what the reason is?


It's primarily to do with quite high revalidation costs for what is a relatively low volume product.

 

[PT1]

Originally Posted By: Whitewolf
Originally Posted By: d00df00d
Interesting. Do you know what the reason is?


It's primarily to do with quite high revalidation costs for what is a relatively low volume product.


Yes, I had a Borg Warner Tcase that speced DexIII. DexVI or Mobil1 ATF worked fine. On many of the AWD Tcases that spec DexIII there is just a chain & gearset (no clutches, no pump) so any ATF will probably work because they are splash lube. You don't want too thick of a viscosity because it has to splash lube the components when it's -10*F in the Winter.