news for those that use GM Synchromesh MTF
10-20-2005, 01:18 PM
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news for those that use GM Synchromesh MTF
http://www.mr2oc.com/showthread.php?t=4124
you need an account to login and read it tho, but anyway here's the cut and paste:
A while back we had a discussion about the "miracle" gear oil, GM Synchromesh. It's been a miracle cure for bad synchros in our old Toyota trannies. It seems that it's even better then Redline MT-90 in this regard.
So, GM needed a new oil a while back. They put out the spec (9985648) and a bunch of companies responded with a product that was what GM needed. One of them OEM's it as GM Synchromesh (GMS) in one-liter bottles as part number 12345349.
How many of you knew that Pennzoil makes a comparable product? (Thanks Craig) As a matter of fact, it says on the back of the Pennzoil Synchromesh bottle, ".... specifically formulated for synchromesh transmissions used by General Motors requiring General Motors Part No. 12345349 (Specification No. 9985648) Synchromesh Transmission Fluid.... In other words, pretty much the same as GMS.
You can buy Pennzoil Synchromesh at some (or maybe most) Autozone stores. Unfortunately, most of the employees have no clue that they have it on the shelf. It sells for $4.99/quart, making it quite a bit cheaper than GMS, despite the fact that you get a little less per bottle in the Pennzoil quart.
I bought five bottles a few days ago (more than one car at home). I drained out the MT-90 in my '91 N/A tranny and replaced it with Pennzoil Synchromesh. (My third gear synchro has often been grinding when shifting ever since the autocross a few months ago.) One drive down the road and it was obvious that the problem is pretty much gone. And as most of you that are already familiar with GMS know, "healing" the synchros doesn't typically happen instantly, it takes some driving to clean up the issues.
OK, now for the "bad news". From the spec sheet (http://www.pzlqs.com/Tech/Pdsheet/Domestic...romeshFluid.PDF) on Pennzoil Synchromesh, "Pennzoil Synchromesh Fluid is NOT intended for all GLS Applications....).
So, what's this mean? According to the Pennzoil tech rep namded Randy that I talked to at the other end of their 800 number, a transmission with "yellow metal" synchronizers should have gear oil with a certain sulfur content. GMS and PS do not have sulfur content, as they are full-synthetics.
According to Randy, "the absence of sulfur in the gear oil will lead to long-term corrosion of the yellow metal parts of the synchros, pretty much destroying the tranny." And pretty much undermining the whole reason for putting synchromesh in there in the first place, to fix synchro issues. Note that Redline MT-90 is a GL-4 rated gear oil, hence according to Randy, it has some sulfur content.
More bad news. Let's say that you just bought a nice new '93+ MR2 LSD tranny and you want to preserve it's life, so you fill it full of GMS or Pennzoil Synchromesh. BAD IDEA, since it's operational life will be shortened.
So, some GOOD NEWS. If you have an S-54 tranny ('91-'92 N/A) that was designed to run Dexron II ATF fluid, it will be very happy with GMS or PS.
If you have a '91-'92 Turbo, I'm not really sure what the correct oil to use would be, but I suspect that it's better to use synchromesh than to grind up your synchros.
Possible solutions:
1. Put MT-90 in there instead. (Or maybe Royal Purple, or Amsoil, or whatever else has at least a GL-4 or GL-5 rating.)
2. Blend it with MT-90, perhaps 2:1 (one part MT-90).
There's more to be learned on this topic, and I welcome corrections and clarifications from all of you.
------------
Good thing I have always used Honda MTF. The GM fluid will eventually eat the soft, yellow metals in the S2k's transmission.
you need an account to login and read it tho, but anyway here's the cut and paste:
A while back we had a discussion about the "miracle" gear oil, GM Synchromesh. It's been a miracle cure for bad synchros in our old Toyota trannies. It seems that it's even better then Redline MT-90 in this regard.
So, GM needed a new oil a while back. They put out the spec (9985648) and a bunch of companies responded with a product that was what GM needed. One of them OEM's it as GM Synchromesh (GMS) in one-liter bottles as part number 12345349.
How many of you knew that Pennzoil makes a comparable product? (Thanks Craig) As a matter of fact, it says on the back of the Pennzoil Synchromesh bottle, ".... specifically formulated for synchromesh transmissions used by General Motors requiring General Motors Part No. 12345349 (Specification No. 9985648) Synchromesh Transmission Fluid.... In other words, pretty much the same as GMS.
You can buy Pennzoil Synchromesh at some (or maybe most) Autozone stores. Unfortunately, most of the employees have no clue that they have it on the shelf. It sells for $4.99/quart, making it quite a bit cheaper than GMS, despite the fact that you get a little less per bottle in the Pennzoil quart.
I bought five bottles a few days ago (more than one car at home). I drained out the MT-90 in my '91 N/A tranny and replaced it with Pennzoil Synchromesh. (My third gear synchro has often been grinding when shifting ever since the autocross a few months ago.) One drive down the road and it was obvious that the problem is pretty much gone. And as most of you that are already familiar with GMS know, "healing" the synchros doesn't typically happen instantly, it takes some driving to clean up the issues.
OK, now for the "bad news". From the spec sheet (http://www.pzlqs.com/Tech/Pdsheet/Domestic...romeshFluid.PDF) on Pennzoil Synchromesh, "Pennzoil Synchromesh Fluid is NOT intended for all GLS Applications....).
So, what's this mean? According to the Pennzoil tech rep namded Randy that I talked to at the other end of their 800 number, a transmission with "yellow metal" synchronizers should have gear oil with a certain sulfur content. GMS and PS do not have sulfur content, as they are full-synthetics.
According to Randy, "the absence of sulfur in the gear oil will lead to long-term corrosion of the yellow metal parts of the synchros, pretty much destroying the tranny." And pretty much undermining the whole reason for putting synchromesh in there in the first place, to fix synchro issues. Note that Redline MT-90 is a GL-4 rated gear oil, hence according to Randy, it has some sulfur content.
More bad news. Let's say that you just bought a nice new '93+ MR2 LSD tranny and you want to preserve it's life, so you fill it full of GMS or Pennzoil Synchromesh. BAD IDEA, since it's operational life will be shortened.
So, some GOOD NEWS. If you have an S-54 tranny ('91-'92 N/A) that was designed to run Dexron II ATF fluid, it will be very happy with GMS or PS.
If you have a '91-'92 Turbo, I'm not really sure what the correct oil to use would be, but I suspect that it's better to use synchromesh than to grind up your synchros.
Possible solutions:
1. Put MT-90 in there instead. (Or maybe Royal Purple, or Amsoil, or whatever else has at least a GL-4 or GL-5 rating.)
2. Blend it with MT-90, perhaps 2:1 (one part MT-90).
There's more to be learned on this topic, and I welcome corrections and clarifications from all of you.
------------
Good thing I have always used Honda MTF. The GM fluid will eventually eat the soft, yellow metals in the S2k's transmission.
10-20-2005, 01:35 PM
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You don't specify in your post, is this the "friction modified" version? My understanding is that there is a GM Synchromesh tranny fluid and a GM Synchromesh Friction Modified version. Everything I've read on "this" forum was pretty insistent that we should be using the friction modified version of this oil.
I don't know if anyone in this group has been using the GMSFM tranny fluid long enough to know if it's had a negative impact on the transmission itself. It would certainly be nice to know if there's any truth to the last sentence in your post!
Drive Safe,
Steve R.
I don't know if anyone in this group has been using the GMSFM tranny fluid long enough to know if it's had a negative impact on the transmission itself. It would certainly be nice to know if there's any truth to the last sentence in your post!
Drive Safe,
Steve R.
10-20-2005, 03:10 PM
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Can we please throw this thread in the garbage it is completely 100% inaccurate.
Whoever is the source of the information is a complete idiot.
Let's look at the dumbass logic here.....
Pennzoil makes a product that is considered a replacement for GM Synchromesh.
That Pennzoil product is NOT a GL-4 oil and is NOT yellow metal safe
Since the Pennzoil product is considered a 'replacement' for GMS then it MUST therefor absolutely and 100% always in every case be exactly the same formula as GM Synchromesh.
I'm sorry just because the manufacturer say's it's a replacement doesn't mean it's the same formula. Also you're referring to GMS not GM Synchromesh Friction Modified again a different formula.
Remember our local tribologist has commented on the advantages of GMSFM. Do you really think he would miss something so obvious as a non-yellow metal safe fluid??? Give me a break.
This is the classic case of some random idiot posting something that if you don't look to closely at it appears to make sense. But if you look at it in depth you realize that the guy's an idiot. Let's not let internet rumor be viewed as fact here. If Pennzoil isn't GL-4 then great it would be stupid to use it. However the fact that Pennzoil isn't GL-4 doesn't mean that GM Synchromesh isn't GL-4 just because Pennzoil can be used in some applications where you would use GSM.
Can we lock this now and throw it in the dumpster before more people are suckered in?
Whoever is the source of the information is a complete idiot.
Let's look at the dumbass logic here.....
Pennzoil makes a product that is considered a replacement for GM Synchromesh.
That Pennzoil product is NOT a GL-4 oil and is NOT yellow metal safe
Since the Pennzoil product is considered a 'replacement' for GMS then it MUST therefor absolutely and 100% always in every case be exactly the same formula as GM Synchromesh.
I'm sorry just because the manufacturer say's it's a replacement doesn't mean it's the same formula. Also you're referring to GMS not GM Synchromesh Friction Modified again a different formula.
Remember our local tribologist has commented on the advantages of GMSFM. Do you really think he would miss something so obvious as a non-yellow metal safe fluid??? Give me a break.
This is the classic case of some random idiot posting something that if you don't look to closely at it appears to make sense. But if you look at it in depth you realize that the guy's an idiot. Let's not let internet rumor be viewed as fact here. If Pennzoil isn't GL-4 then great it would be stupid to use it. However the fact that Pennzoil isn't GL-4 doesn't mean that GM Synchromesh isn't GL-4 just because Pennzoil can be used in some applications where you would use GSM.
Can we lock this now and throw it in the dumpster before more people are suckered in?
10-20-2005, 03:19 PM
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The 'tech' isn't even correct about pennzoil syncromesh...look at the product description....
http://www.pennzoil.com/products/gea...cro_fluid.html
It provides excellent oxidation stability, low temperature performance, excellent synchronizer performance and compatibility with yellow metals, such as bronze, brass and copper components found in manual transaxles and transmissions.
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