I was reading an article over at The Truth about Cars on the best manual transmissions and happened to notice in the user comments a few people exclaiming the benefits of GM Synchromesh trans. fluid. Here's a couple of them.

“I’ve personally seen GM’s “Synchromesh” fluid work wonders on GM, Ford, BMW and Nissan gearboxes, turning hard-to-shift cogs into child’s play. I wouldn’t be surprised if Synchromesh would’ve fixed that Hyundai’s worn out synchros, too. And at $15-ish a quart, you won’t break the bank saving an old tranny.”

I had to register just for this… The Synchromesh tranny oil is actually “Synchromesh FM”. FM stands for friction modified and it’s semi synthetic. That’s the stuff thats $15/qt. GM spec’d it originally for manual light truck transmissions."
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"The 6MT transmissions in the 2004-2007 Acura TL’s are famous for a stiff 2nd to 3rd shift. I have no idea why, and there’s no shortage of people *****ing about it online and at the dealerships - me too! There’s something about that 3rd gear…

After replacing the factory manual transmission fluid with GM Synchromesh in my 2005 TL, shifting improved immensely. Engagement into all the gears - especially 3rd is much better."

http://www.thetruthaboutcars.com/pis...6/#more-315019


My 6-speed has a notchy 2nd to 3rd shift like most other 6-speed Maximas have. I switched to Redline MT-90 when I bought my car a few years back because of the good feedback it got from members here. The only problem is, I never noticed any real improvements in the way the car shifts. The 2nd to 3rd problem is most noticeable when the car is cold. The trans. shifts great after I've driven the car for at least 20 minutes, but then I'm usually at my destination!

Has anyone here tried this GM Synchromesh fluid in their 6-speed? I ran a search for this and was surprised to come up with nothing.

EDIT: Here's some more info on this over at an S2000 forum. Apparently this is safe to use around yellow metals (bronze/brass). This was my biggest concern as I know we need to use GL-4 oils in our trannys.

http://www.s2ki.com/forums/index.php...ic=230001&st=0

More info on the oil itself:

The information presented here is gathered from the documents listed in the References section below.

Pennzoil-Quaker State Synchromesh is a unique transmission and transaxle fluid that is not API "GL" rated. It has an approximate gear oil grade of about SAE 80W and can be used when temperatures range from -40ºF (-40ºC) to 300ºF (150ºC). According to Pennzoil's product description it is "formulated with high quality paraffinic base stocks, a fluidity modifier, multifunctional performance additives, corrosion inhibitors, a foam suppressor and a shear stable viscosity index improver additive. 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." This description makes Synchromesh suitable for use in some transaxles or transmissions where GL-4 gear oils are specified.

A post on the message board at http://forums.maxima.org/5th-generat...ilanalysis.com found Synchromesh to consist of a 5W30 non-detergent oil with a friction modifer and an EP (extreme pressure) additive. It is made under contract for General Motors by Pennzoil (APC 3378) or by Texaco (Code 1874 MTX Fluid).

According to Don Johnson, Synchromesh fluid was developed for use in the New Venture manual transmission used by Chrysler and General Motors. Specifically, Synchromesh is formulated for transmissions that require GM Part No. 12345349 (Specification No. 9985648), GM Part No. 12345577, or Chrysler Part No. 4874464 (Specification MS-9224). Owners of Diamond Star Motors (DSM) Eclipse, Talon, and Laser cars with MMC (Mitsubishi Motor Corporation) transaxles have reported positive experiences using Synchromesh. The same can be said for owners of the Mitsubishi 3000GT and Dodge Stealth cars with the Getrag-manufactured AWD transaxles. The main benefit to DSM and 3/S owners seems to be excellent synchronizer performance, with reduced grinding and easier shifting compared to using some other gear oils.

Pennzoil Synchromesh Fluid can be purchased as that brand or as the equivalent products: Quaker State Synchromesh (Quaker State is part of Pennzoil), Texaco Synchromesh, GM Synchromesh, or AC Delco Synchromesh (part number 89021808). GM Synchromesh retails for about $10 per quart bottle at GM dealerships. Pennzoil Synchromesh is sold at many Auto Zone auto parts stores for about $5 per quart and should be available from Pennzoil distributors. Texaco Express Lube stores use Synchromesh but the stores I contacted would not sell the product by itself to customers. Pennzoil Synchromesh can be purchased in 5-gallon containers from oil-store.com.

References
Lubrication Basics by Don Johnson
Noria Message Board - Synchromesh what is it?
Pennzoil Synchromesh Fluid Product Description
Pennzoil Technical Information P-21-C; Automotive Gear Oils
Texaco Synchromesh Transmission Fluid
Viscosity and Engine and Gear Oil Grades

http://www.subaruforester.org/vbulle...mt-fluid-2694/

 

The description on your 6MT reads exactly as if I'd written it myself. I feel your frustrations, man. I really do.

I just swapped the fluid for MT-90 two weeks ago. It's slightly different overall, but the 2nd/3rd gear crunch is still there.

I'd love to swap the tranny for a '06 HLSD... but that's a huge expense.

So anyway, I don't have anything to offer, except to commiserate and subscribe to this tread to see what others say. G'luck.

 

I've heard good things about the GM Syncromesh. I'm replacing the clutch in my VW soon, and when I do i plan to switch to the GM syncromesh.

 

talkinghorse makes some interesting points about syncromesh here:

http://forums.maxima.org/fluids-lubr...esh-fluid.html

There are several threads that mention using syncromesh (including in the 6MT), so maybe you just have to refine your search keywords? :totme:

 

I personally have never used Syncromesh. About 3-4 years ago EVERYONE in the 3000GT/Stealth community swore by it, saying that it 'solved' a lot of syncro issues that some people were having. Now years later those same people are draining their syncromesh and discovering that it has basically liquefied some of the metal parts in the trans. There are pics of it in the drain pan where it clearly has metal suspended in the oil.

As such the Syncromesh has fallen out of favor with pretty much everyone in the 3/S community. Most of the trans experts reccomend running MT-90 or a 50/50 mix of MTL/MT-90.

EDIT: Found some of threads http://www.3si.org/forum/f35/pics-my...id-wtf-254510/

http://www.3si.org/forum/f116/gm-syn...tranny-233862/

 

Hmm, I don't think I want a liquid metal tranny. <Insert inevitable joke here> I think I'll try running the MT-90 (what's in there now) with MTL. This 3rd gear "catch" is pissing me off.

 

I switched my Mobil 1 syn to Amsoil and the 3rd gear crunch is still there. I don't think fluids can solve my problem.