GM Synchromesh Fluid....25K report

As my 2004 TDI approached 200,000 miles last summer, second gear on the five-speed manual transmission began graunching/grinding on both the 1/2 and 3/2 shifts unless I carefully double clutched. The problem was progressive. I had always used VW fluids on the schedule in the owners manual, previously replacing the tranaxle fluid at the 100K mile service and this seemed to be the perfect excuse to finally buy a new two liter TDI.
However, at the 200K mile service, I changed the transaxle fluid to GM Synchromesh Fluid (actually supplied to GM by Pennzoil and available under the later label...has the GM part number on the bottle).
The improvement was immediate and the transmission has shifted "as new" since then. I am now approaching 225K miles and performance of the transmission continues to be perfect in all gears with absolutely no trace of the 2nd gear problem regardless of temperature. Operating conditions have ranged from August heat to the current, persistent sub-freezing temperatures. The car is driven quite a bit, regardless of conditions.
I plan to keep it and do nothing more until I replace it with a fresh two quart dose of the same stuff at the 300K mile service. I will, of course, continue to change the oil and filter every 10-15K miles, whether it needs it or not.

2004 Jetta TDI-PD, 5-speed manual transmission
Bellaire, Ohio

Thanks for the long-term report... lots of tranny-fluid "a friend told me" stories out there... so great to hear first hand.

Is there an official GM part number on the oil you used?

Vince,
The GM parts counter guys all know about it if you ask for GM Synchromesh Transmission Fluid. It is the factory fluid for the 6-speed manual transmission used in the Corvette and is actually rebadged Pennzoil Synchromesh Manual Transmission Fluid. The Pennzoil bottle lists the GM part number on the back:

"Pennzoil Synchromesh is specifically formulated for manual transmissions used by General Motors requiring GM part number 12345349 (specification 9985646) or GM part number 12345577 and Chrysler part number4874464 (specification MS9224)

Cool test.I may try the same in my B4. I have some of that GM fluid on hand, I think.

I second the Synchromesh smoothness. My 01 has been using it for 70K now

It is kinda thin though and that worries me when it comes to diff carrier bearings. In my case the 01 does not see as much use or abuse as the 04. I used Motul 300 gear oil for 100K on that one and it was pretty good, slight notchy at very cold weather but warmed up pretty fast

I used synchromesh in my 92 ECOdiesel with "so far so good" results, though it only has 15k on the change and I didn't check for metal flakes before I sold the car. I used the Amsoil fully synthetic synchromesh fluid, which was labeled as a 5w30 oil.

-J

Hmm. Sounds like I may want to try it on my VW Cabrio. It has 105k miles and has a problem going into 1st gear. Maybe time to change the 2 quarts of fluid anyway.

There are 2 different Amsoil MT fluids. A 5w30 based one and a GL4 gear oil based one.

My experience is with a Chevy S-10. The 4 cyl model uses a New Venture NV1500 trans that has an unusual sycromesh material ( nylon ? ) and requires a special GM spec fluid which the Amsoil 5w30 meets. When I changed out the incorrect Gear Oil that was in it the change in shift quality was dramatic, instant, and lasting. The right stuff. However it is not GL4 spec for diff. gears and is not for extreme pressure gears like in a diff. I am pretty sure our VWs share the Manual Transmission fluid with the differential.

It sounds like your specific case is a high mileage car with a shifting problem that makes this a " try this or park it" situation.
In this circumstance I agree with what you have done and would do the same BUT keep in mind you are likely under-protecting your diff. gears. Drive easy, don't carry heavy loads ( include passengers as load ) be careful about long trips. As an experiment I think this will work out well for you. As an experiment I have hopes that the quality of the oil is good enough to cover for some error of application.
Good Luck
/
Manual Synchromesh Transmission Fluid 5W-30 Product Code: MTF
Designed for manual transmissions and transaxles with synchromesh systems that require light viscosity, non-extreme-pressure fortified oil. Additive technology provides proper friction characteristics for smooth shifting. The ultimate in gear and bearing protection & outperforms motor oils in manual transmissions.
///
Manual Transmission & Transaxle Gear Lube 75W-90 Product Code: MTG
Formulated specifically for maximum protection in the most demanding manual transmission and transaxle applications where an extreme pressure GL-4 gear lube is specified, including those where high horsepower/high torque engines and towing or heavy loads increase transmission stress.

Do NOT use a syncromesh fluid in a VW transaxle if it does not carry the API/GL-4 rating. Most syncromesh fluids (including Amsoil), are essentially SAE 5w-30, synthetic engine oils with a beefed up additive chemistry. They are typically equivalent to API/GL-1 Spec fluids and do not contain the necessary Sulfur/Phosphorus, EP additives needed to properly lubricate the differential gears inside the transaxle. A manual transmission has to be properly designed to use one of these very low viscosity fluids.

A better choice for cold weather if you're concerned about durability (keep in mind I'm a experienced Amsoil dealer), would be the excellent Redline MTL oil. This is an SAE 70w-80, GL-4 rated Gear Lube...

Some of the newer VW Spec fluids like G60 and G70 are also going to be excellent for cold weather shifting issues. I'd check and see if VW recommends these for your particular transaxle and if they do that would be another way to go.

TS

While writing the earlier post I remembered long ago I did the reverse. I had a FIAT that required 30w motor oil in its transmission and I listened to an old school mechanic and used GL5 gear oil ( the FIAT also shared MT fluid with the diff. like our VWs and the mechanic didn't trust motor oil to be good enough).
Very wrong stuff. It shifted terrible. Stiff, slow action, and a tendency to grind if you pushed it. I have since learned that GL5 fluid often has an additive that attacks the metal in MT sychromesh ( GL4 is ok ). So double wrong stuff.
The extreme pressure additives that are good for hypoid gears probably interfere with the action of the MT sycromesh which is why your shifting improves when you don't use GL spec.

TooSlick said:

A better choice for cold weather if you're concerned about durability (keep in mind I'm a experienced Amsoil dealer), would be the excellent Redline MTL oil. This is an SAE 70w-80, GL-4 rated Gear Lube...

Some of the newer VW Spec fluids like G60 and G70 are also going to be excellent for cold weather shifting issues. I'd check and see if VW recommends these for your particular transaxle and if they do that would be another way to go.

TS

Click to expand...

I forgot about the newer VW fluids, that is a good idea since they would have taken hypoid gears into account.

I was trying to stress that what this guy is doing is working for him in his very specific case and is not a good idea for everyone and why. If I were in his shoes I think I would look into the newer VW fluids you suggested and try that first. That is a much better idea than resorting to using a fluid that is very good for one half of his trans and very bad for the other half.

When the FIAT was built they had to choose one or the other, MT or DIff, high tech synthetic trans fluids were not available and the car wasn't designed to last all that long anyway.

You can't say what he's doing is working without the oil analysis test data that shows he's getting the proper protection of the differential and transaxle gears. The unit could be shifting perfectly fine for an extended period and you could still be getting excessive gear wear. The reason why it's shifting better is solely due to the very low viscosity of the syncromesh fluid and nothing else. Good shifting does not imply superior wear protection in this case....

If I was racing a VW and had lots of $$$, I might be tempted to use one of these very low viscosity fluids just to reduce the frictional losses and get more power out of the drivetrain. But I'd plan on rebuilding the transaxle on a regular basis....

TS

The key to me is his VW has over 200,000 miles on it and his shifting problem was becoming severe. He could either 1. park it ( shame ), 2. repair it ( expensive ), or 3. fudge along with it. His solution avoids 1. and maybe puts off 2. until it is a moot point.

I do think he should try one of the newest VW fluids first, cheap and easy compared to opening it up or risking more damage than he needs to. Only if that doesn't work would I go back to the 5w30 and all it's caveats.

Tooslick is right and I feel the same about the synchromesh. You have to use a fluid thick enough to protect the diff but also allow for Ok shifting in winter.

FWIW the Amsoil product I used claimed to be a GL4 fluid as well.

-J

Not sure if it's the same thing you used, but Honda/Acura folks swear by GM Synchromesh "Friction Modified" gearbox oil in their gearboxes.

I had an '05 Acura TL stick which was always very difficult on the 2-3 upshift--after putting in the above oil the problem was solved!

Years ago I had a Mitsubishi 3000GT VR-4 a 300 BHP beast with 4wd and 4 wheel steering. This thing was a rocket sled and handling that was nothing short of incredible. Its one weakness was its infamous transaxle to the point of taking the joy out of thrashing it on the mountain roads as you could not enjoy shifting even with proper double clutching on downshifts coming into corners.

Mitsubishi sent out a technical bulletin suggesting the use of GM Synchromesh to cure its poorly designed Getrag unit with 2 ounces of friction modifier. This did wonders for every ones tranny. If I recall correctly this unit had a front diff in the transaxle as well as the center diff and a rear lsd. I never heard of one of these units failing after long term use of Synchromesh. These cars were built from 1991-1999 and many are still running strong today.

From that experience I used it with success on my TDI when I changed out the factory fill at 100k and it works great in my Mini Cooper S with the JCW package today as well. I think this is a safe bet for use in a TDI

I got my Synchromesh at Autozone. Worked excellent in my NB for over 170k. It cured a not wanting to come out of 5th gear problem. I will be using it in my golf soon, already picked up 2 quarts.

The difference is that Honda/Acura engines specify the use of a Syncromesh fluid and not a GL-4, gear lube. I think even the latest VW transaxle oils are technically gear lubes (but more like 70w-80, instead of 75w-90) and not Syncromesh fluids.

TS

I just put Castrol synthetic in my '97 gearbox; it shifts so much smoother now. I noticed on the bottle that it was rated and approved by Mack for use in their tractor trailer rigs, so I bought it.

CFM said:

I just put Castrol synthetic in my '97 gearbox; it shifts so much smoother now. I noticed on the bottle that it was rated and approved by Mack for use in their tractor trailer rigs, so I bought it.

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Mack tough heh ? I hope it wasn't the 85W-140 variety

I've been using GM Syncromesh full syn in all my gear boxes (5 and 6spds) with quaife/peloquin with no problems past 5 years. Extreme cold is also good too. My GM parts guys laugh when I buy vet parts and GM gear oil for vtroubleU's

Jeff

Do you use the standard fluid, or the one with the friction modifier in it?

-J

Old thread bump....

I know there is GM Synchromesh and GM Synchromesh Friction Modified.

Does anybody know if the normal Synchromesh is GL-4 and the GM Synchromesh FM is GL-5?

Getting exact information from manufacturers is difficult, but you may not necessarily want a friction modified gear lube in your transaxle. Why? The friction modifiers will make the lube more slippery. Synchronizers require a certain amount of friction in order to do their job. If the lube is too slippery, you will get grinding in your shifts. Notchiness or grinding may only indicate the current lube needs to be replaced rather than have a friction modified fluid used instead. I.e. just replace the current lube, or use regular Synchromesh as the Synchromesh Friction Modified may not be necessary.

One thing you could possibly try is to get Redline fricition modifier, add it 1 oz at a time to the transaxle, then stop when the problems disappear. This could be done if you replaced the current fluid but the shifting problem remains.

This is not a more-is-better type procedure, for best results you need to stop when the problem goes away.

I also checked the GM site, and the information for the products doesn't tell whether the Synchromesh fluids are equivalent to GL-4 or -5. However, I would bet that if regular Synchromesh is GL-4, then the Friction Modified variant is also GL-4, just with more modifier added.

GL-5 gear lubes are typically used in differentials where no shifting is going on. Therefore, there are no brass synchronizers to worry about. The levels of extreme pressure anti-wear additives are high. Since these additives are usually molybdenum disufide, they have that strong sulfur smell and are usually dark brown (Redline GL-5 is a notable exception to the color).

Cheers,

PH

mrrhtuner said:

Old thread bump....

I know there is GM Synchromesh and GM Synchromesh Friction Modified.

Does anybody know if the normal Synchromesh is GL-4 and the GM Synchromesh FM is GL-5?

Click to expand...

AC Delco part: 1 #89021808 labelled Synchromesh Transmission Fluid is what you want.

fossill said:

AC Delco part 1 #89021808 labelled Synchromesh Transmission Fluid is what you want.

Click to expand...

Thank you.

From what I've read in a past thread, seems like GM in Canada only has GM Synchromesh Friction modified only...but haven't been able to verify that yet.

mrrhtuner said:

Thank you.
From what I've read in a past thread, seems like GM in Canada only has GM Synchromesh Friction modified only...but haven't been able to verify that yet.

Click to expand...

Nope.... that part number is the non-friction modified version.
I'm in Canada and you can get whatever version you want.

Ted,
Sorry to bring up this old thread but I am having difficulties finding out if this oil is not GL-4 rated and whether it will eventually destroy our TDI's manual transmissions:

http://www.pennzoil.com/wp-content/uploads/2012/02/Synchromesh-Manual-Trans-Fluid.pdf

Any help would be appreciated.

TooSlick said:

Do NOT use a syncromesh fluid in a VW transaxle if it does not carry the API/GL-4 rating. Most syncromesh fluids (including Amsoil), are essentially SAE 5w-30, synthetic engine oils with a beefed up additive chemistry. They are typically equivalent to API/GL-1 Spec fluids and do not contain the necessary Sulfur/Phosphorus, EP additives needed to properly lubricate the differential gears inside the transaxle. A manual transmission has to be properly designed to use one of these very low viscosity fluids.
A better choice for cold weather if you're concerned about durability (keep in mind I'm a experienced Amsoil dealer), would be the excellent Redline MTL oil. This is an SAE 70w-80, GL-4 rated Gear Lube...
Some of the newer VW Spec fluids like G60 and G70 are also going to be excellent for cold weather shifting issues. I'd check and see if VW recommends these for your particular transaxle and if they do that would be another way to go.
TS

Click to expand...

tikal said:

Ted,
Sorry to bring up this old thread but I am having difficulties finding out if this oil is not GL-4 rated and whether it will eventually destroy our TDI's manual transmissions:

http://www.pennzoil.com/wp-content/uploads/2012/02/Synchromesh-Manual-Trans-Fluid.pdf

Any help would be appreciated.

Click to expand...

there is nothing special about "our.. transmissions" sychromesh is made for transaxles (we have transaxles) with brass synchros (we have brass synchros )
there is a thread iirc by "bob is the oil guy" that discusses synchromesh gl4 compatability ... i'm right at 60k miles on pennzoil synchromesh in my 05' golf with 358k + miles ... it had a pretty nasty second gear grind after changing out the oem stuff for new OEM G07, s'mesh completely cured the grind within a half mile ... imo OEM fluid is inferior and i won't use it in any gearbox with yellow synchros period ...