Synchromesh GM Part Number

[Johnny Mullet]

Here are the types of Syncromesh I know of that work great in these transmissions. The Part # is on the one bottle...................

[SirKeats]

thanks gents!

my search continues for either the Penzoil or the Amsoil. I use Amsoil in my big toy-hauler and like it a lot. good news is that i can at least buy the amsoil online if i have to.

btw... is it pronounced A-M-S-OIL, AMS-OIL, or AM-SOIL?? just curious. lol

[IndyIan]

I have had the GM magic synchromess fluid in my tracker(2nd gear grind is a common problem, it didn't help).
Now I have the stuff from Canadian tire for 1/4 as much and I can't tell the difference. There might be some efficiency gains to be had but at operating temp I don't think the viscosity is much different.
Buying the good stuff can't hurt though, just don't pay way way more for it.
Ian

[SirKeats]

i called every auto parts supplier in town. not a single one has the penzoil or amsoil synchromesh fluid. i'm SOL for local supply. looks like i'll be ordering online. i can get the amsoil for 8 bucks a quart so i'll just do that. will cost me about 30 bucks w/ shipping for the 3 quarts. not too bad.

pretty surprised that i can't find it from anyone in town.

[SirKeats]

found some!!

royal purple is making some now. replacement for the GM synchromesh.

http://www.royalpurple.com/manual-tr...ion-fluid.html

and

http://www.royalpurple.com/transmission-chart.html (click on GM for the part number cross reference)

picked up at the local schucks for 9 bucks a quart.

[JohnnyGrey]

With rare exception, specific gears grinding is a symptom of poor driving technique. ie: downshifting into said gear without double clutching for the last 50K miles. Synchros will take only so much abuse and no fluid is going to fix that.

[IndyIan]

Originally Posted by JohnnyGrey

With rare exception, specific gears grinding is a symptom of poor driving technique. ie: downshifting into said gear without double clutching for the last 50K miles. Synchros will take only so much abuse and no fluid is going to fix that.

Well, I guess the tracker/vitara is the rare exception, the problem is that the ratio change from first to second is big, 4000rpm in first equals about 2200 in second, and they didn't double synchro 2nd gear. It hasn't really changed since new and I guess I could've been an ass about it and got a new tranny(which would probably be the same) out of GM but I didn't. I do rev match my downshifts but never double clutch, that's what synchros are for. I'll try double clutching once in a while but I need to practice. Most of my driving is highway so normally I use 2nd gear maybe 10 times a commute and I don't take the tracker most of the time. If its the biggest problem I have with the gearbox I'll be happy with that!
I didn't have my scangauge when I had the GM fluid in there so unfortunately I can't post any before and after data. I suspect with my car unless I changed all the fluids to synth and back it would be undetectable. The loses at the rear dif and transfercase are much bigger I would think than the gear box, especially in 5th gear.

Ian

[Bror Jace]

SirKeats, RP Synchromax is not really a direct replacement for GM or Chrysler synchromesh fluids. It is too thin: 7.7cSt versus the 9.0-9.5 cSt you should be looking for (both @ 100 degrees).

OK, this is a site for hypermilers, people willing to go to extremes. A thin oil would offer less hydrodynamic drag, right? And that can save a few percent in fuel economy? True, but you can damage the tranny too, depending on the conditions, driving styles, climate, etc ...

So, is that extra 2-3% more mileage worth the chance of a transmission replacement in a year or two? Each has to make his/her mind up on that one.

[SirKeats]

my intent wasn't to goto any extreme. RP though specifically states that this is suitable for trannys calling for the GM Synchromesh (PN1234359) which is the exact same part number called for in the geo tranny's.

RP even posts this exact part number for the synchromesh fluid in their compatibility chart.

i've emailed them regarding this as you've got me worried now... but just to clarify, are you suggesting they're being less than forthcoming with respect to compatibility?

[Bror Jace]

SirKeats, pretty much.

The manufacturers each have their own comfort level as to how far out of factory spec they are willing to go. Red Line, Amsoil, RP and others do this as a way of expanding the potential customer base. I look at their recommendations and try to double-check

I am going to try Amsoil MTF for my '06 Civic's 5-speed manual tranny. Amsoil claims it is a direct replacement for Honda MTF (I & II) ... but I thought Honda MTF was 10-11.5 cST ... and the Amsoil is 9.6 cSt. I just can't confirm the Honda spec ANYWHERE. If the Amsoil doesn't seem right, I'll dump it in a year and go back to genuine Honda MTF.

While I've seen some people have good results with RP products, in my opinion they are short on engineering/innovation and long on bling-bling. If your tranny called for ATF, I'd say go ahead and buy the Synchromax as it is the only true synchromesh gear oil in that super-light weight now that Specialty Formulations has closed its doors.

However, if yours asks for GM-brand synchromesh, I'd try one of the several fluids available in the correct thickness. This is a popular weight and you have plenty of appropriate choices.

Remember, I'm using actual weight numbers ... not vague, brand-specific puffery.