What is GM 12346190 Lube?

[Todd H 26112]

All I have is 'Synthetic Manual Transmission Fluid' ~$20/qt. I don't have an ACDelco cross reference # nor a Daimler-Chrysler part #. I've made inquiries of GM but have learned little so far. I've found nothing to indicate this is or has anything to do w/ their 'SynchroMesh' fluids.

Could this be the GM branded version of Castrol Syntorq LT mentioned by John H earlier?

[Joe L.]

Re: What is GM 12346190 Lube?

Todd-----

I did a little more research on this one since responding to your e-mail. GM #12346190 is, indeed, the GM-branded Castrol Syntorq. It is a GL-4-rated and SAE 80 wt gear lube. It's possible that it's been uprated to GL-5 specs by now, too. I don't know that, for sure.

The GM #12346190 is specified for use by GM on a wide range of later model vehicles with manual transmissions. 1988-91 Pontiac LeMans, Geo Prism, Geo Metro and trucks with MT8 manual transmission are some of the GM-specified applications. In any event, I'm sure that the fluid is also compatible with any of the applications which Castrol recommends for it.

[Todd H 26112]

Re: What is GM 12346190 Lube?

Thanks for verifying my guess. In addition to Syntorq LT (Low Temp) I believe there is also another Castrol product called 'Syntorq GL5'.

It is worth mentioning that GL-5 is not a standard that supercedes GL-4. They are independent and separate standards which co-exist and one simply happens to have a higher number than the other.
What adds to the confusion is that most other lubricant standars do in fact supercede previous ones based on cardinality. Making the matter worse are some gear oil makers that try to imply this very thing as well. In fact there is even one lubricant maker offering a GL-6 for manual transmissions under the mistaken guise of suggesting to consumers it is better than GL-4 or GL-5 for manual transmissions.

[Joe L.]

Re: What is GM 12346190 Lube?

Todd-----

I did not intend to imply that GL-5 was an upgrade from GL-4 in the sense that GL-5 REPLACES GL-4 or is superior to GL-4. Many manufacturers have created lubricants which have DUAL ratings. In this sense, a lubricant originally rated only as GL-4 might be "upgraded" to have a DUAL RATING of BOTH GL-4 and GL-5.

As I recall, the GL-4 rating was issued well before the GL-5 rating was issued. Lubricants which met the GL-4 rating might also have met the specifications for GL-5 but that rating may not have existed at the time. Later, when the GL-5 specs were issued, that rating could have been added to the published information for a particular product. Or, the product could have been reformulated so that it would meet BOTH GL-4 and GL-5 specs.

[Duke W.]

Re: What is GM 12346190 Lube?

The GL-specs are not necessarily chronological. The basic issue to understand is that GL-5 is a requirment for hypoid gear sets. GL-4 is not suitable for hypoid gear sets, but is suitable for typical manual tranmissions or transverse type transaxles that use a large helical gear set as the final drive rather than a hypoid gearset as is typical of RWD vehicles.

GL-4 and GL-5 are blended for different applications. Technically a GL-5 will easily meet GL-4 specs, but may not be suitable for a GL-4 application, such as manual transmissions, because the additional EP additive of a GL-5 may result in degraded synchronizer operation. If the manufacturer's recommendation is a GL-4 a GL-5 should NOT be used because it is "better".

The GL-6 spec was developed for high offset hypoid gear sets, but it is now considered obsolete and GL-5 should be used.

GL-3 is also considered obsolete, and GL-4 should be used.

Duke

[Todd H 26112]

Re: What is GM 12346190 Lube?

"Technically a GL-5 will easily meet GL-4 specs, but may not be suitable for a GL-4 application"

The GL-4 spec is a composition of various tests. Part of the GL-4 spec is a specific test for measuring corrosiveness to yellow metals (e.g. traditional synchro composition). Traditionally, most GL-5s will at least fail that specific test due to their traditional EP additives. Some newer GL-5s incorporate newer generation EP additives that are more yellow metal friendly supposedly and 'may' indeed pass this aspect of GL-4 performance however in most cases the manufacturers rarely bother to seek an additional GL-4 certification. However some may suggest it in their advertising or labeling or even put in writing that their GL-5 product is yellow metal safe. That being said, many many times GL-5s have been used in transmissions and people report acceptable performance. Some may argue it is not 'optimal' but it can typically be considered 'acceptable' at a minimum. It's a surprisingly subjective issue with respect to smooth synchro function. I personally believe the corrosion aspect is mostly a long term issue. But I can also say that fewer friction modifiers (GL-5 additives) can benefit smooth synchro function in most cases.

The reverse is of course not true. As you indicated A GL-4 CANNOT be used in GL-5 applications.

THere are a few specific GL-4/GL-5 'combo' lubricants around. One of the best application I can find for them is convenience where a single product can be used across a variety of vehicles or applications requiring both. Essentially what you are getting with such a combo fluid is a GL-5 that guarantees it is safe for yellow metals. It still may not offer the most 'optimal' shifting in some synchro transmission applications however.

thanks,

[Joe L.]

Re: What is GM 12346190 Lube?

Todd-----

In fact, that's exactly why I think thatit's possible that the GM #12346190 lube MAY have been dual-rated since it's original introduction (at which time it was definitely rated GL-4 only). GM likes to have SERVICE items which will SERVICE as wide a range of applications as possible. I noted in my research that the 12346190 has progressively replaced several earlier GM products and, currently, has a much wider application than it was currently issued for. However, as far as I can tell, all the applications are for transmissions, albeit transaxles. So, it also may well be that it is still GL-4 only rated.

GM ahs long had a policy of SERVICE part consolidation, especially as vehicles age and owners (except the relatively "small uniuverse" of Corvette owners) are just glad to obtain a SERVICE part and don't care if it's exacly like the original. In fact, I think that GMSPO is working toward the goal of a single part SERVICING every application for every vehicle. They're not likely to reach that goal, though.

Incidentally, there is ONE part (not a maintenence product, either) which SERVICES EVERY SINGLE GM car or truck on the road. It also SERVICES every other brand car or truck on the road. Does anyone know what it is?

[Kevin #38315]

Re: What is GM 12346190 Lube?

Valve stem cap? ( I have no idea what part number that might be!)

Kevin

[Joe L.]

Re: What is GM 12346190 Lube?

Kevin-----

Your close and you may have identified another item that's common across all cars and trucks. Although the valve stem caps are made in all sorts of configurations, as far as I know they are all functionally interchangeable.

The part that I was referring to is the valve stem CORE. There were a few slightly different designs for this piece, but, as far as I know, they are interchangeable for every modern vehicle, car or truck.

Actually, though, I "fudged" a little bit. The valve stem core was never available from GM as a seperate part so it has no part number. I don't think that these were ever used in PRODUCTION as a seperate part, either. So, there is likely no GM PRODUCTION or SERVICE part number for it.