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GM Synchromesh

MellowVR4

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Jul 25, 2009
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Milwaukee, Wi
Who is currently using this in their gvr4/or DSM transmission's, Do you like it? Any input would be great.

Thanks in advance

Alberto
 

MellowVR4

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What about if your planning on running a little more then 400+hp?
 

presterone

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Jan 23, 2012
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brunswick maine
I dunno man you might want to look into it more. Im pretty sure syncromesh isn't GL-5 rated and its corrosive to the metal that makes up our gearsets and differentials. I looked into this years ago because I wanted to run it in my scirocco and if its not gl-5 rated don't run it for long.
 

G

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zompton
Not me! Don't trust it.
 

MellowVR4

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Milwaukee, Wi
Because I just had a DEEP conversation with a guy here in town about GM synchromesh, and he swears by it. He said he has been dealing with dsm's ever since the conquest came out in the 80's. Seems to know what he's talking about /ubbthreads/images/graemlins/dunno.gif But idk, so many different brands of fluid out there that i guess you wont know how it does in our transmissions until you try it for your self. /ubbthreads/images/graemlins/dunno.gif What about mixing fluids?
 

transparentdsm

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Cherry Hill, NJ
Quoting presterone:
I dunno man you might want to look into it more. Im pretty sure syncromesh isn't GL-5 rated and its corrosive to the metal that makes up our gearsets and differentials. I looked into this years ago because I wanted to run it in my scirocco and if its not gl-5 rated don't run it for long.



if your running gl-5 in your trans and transfrer case your wrong and your going to wear out the syncros. you need gl-4, gl-5 will destroy the brass syncros in our transmissions and it eats something in the transfer case, you can use it in the rear end, but thats it.

Mellow VR4 - i would go with 2 bottles of redline MT-90 and 1 bottle of redline light-weight shockproof for the transmission and transfer case, use 1/4 of the shock in the transfer case and the rest in the trans then dump the other two bottles in. for the rear end redline 75w-90 gear oil. i'll swear by this stuff. i have had transmissions that were grinding, drained the fluid ran some cheap gl-5 for 20 miles, drained that to get the rest of the stuff out(the fluid changed colors and pulled some sludge), put the fluid in(same way i mention above) and the trans felt 35% better. no more grind unless i was in the high rpms(6500-redline).

edit: im sure when phil(dynastylsd) gets on he will chime in and help sort this out much better then i can.
 
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thecman02

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Nov 3, 2007
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917
Location
Kalamazoo,MI
Here is good reference material on the subject.

Oil Reccomendations by a Mechanical Engineer/DSM Trans Specialist

If your beating on your car hard and making lots of torque your doing yourself a disservice not using mt-90. I've been to Jon Ripples shop multiple times. One of the easiest things to identify in a transmission failure analysis would be from inadequate lubrication. When I built my trans 5 years ago he stressed that I used mt-90. I've put 40-50k miles on my car with lots of hard miles. I looked at my gears a year ago when I had the trans out of my car, and their was basically no wear on the gear teeth.

If your transmission grinds with mt-90 you have a clutch disengagement problem or worn syncros. I wouldn't even put syncromesh in a grinding tranny to fix the syncro problem because your asking for gear problems. A tranny rebuild with new syncros can be had for less than 500. Replacing gears gets expensive real fast.
 
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Mitsuman3KGT

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Jan 9, 2013
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Location
Dayton & Toledo, Ohio
Quoting presterone:
I dunno man you might want to look into it more. Im pretty sure syncromesh isn't GL-5 rated and its corrosive to the metal that makes up our gearsets and differentials. I looked into this years ago because I wanted to run it in my scirocco and if its not gl-5 rated don't run it for long.



Where have you seen that it's corrosive? I've never had any problems with it. Granted its thinner than redline but I've had some nasty synchros last a few more months on synchromesh.

And yes definitely run some sort of shockproof in the transfer case.
 

DynastyLCD

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May 12, 2006
Messages
761
Location
Harwinton, CT
wait, wait, wait.... i've got a question here. if GL-5 destroys synchros, why are people using Diaqueen? isn't that GL-5?

personally, my transmission comes out and goes back in so many damn times that i just run cheap sh*t... typically whatever 80w90 gear oil i can get at the cheapest cost. i've got the Kia version of Diaqueen i was planning on trying, maybe i'll hold off considering the GL-5 thing.

i used to use Shockproof Lightweight, and after tearing apart enough of my own transmissions, i found that what others said about it was true - it can clog the smaller oil passages. my recipe is: tcase and rear diff get heavyweight shockproof, transmission gets 80w90 or MT90.

i've never liked Synchromesh. i feel as if it's too light and too thin. makes for some excellent shifting, but i could see how it wouldn't protect the way MT90 or another quality gear oil would. there's even some schmuck around here who tells people to put 5w30 in their DSM transmissions... WTF!? i've been told in the past by a VERY knowledgable DSMer to either pick Synchromesh and beat up the transmission or use gear oil and deal with the slower shifting. pick your poison, i suppose.

if/when i ever actually construct a real built transmission with Evo gears or dog cuts, i'll go MT90 only in the transmission. i agree whole-heartedly with that idea, just never had a transmission worth it. the Synchromesh i never liked. regular gear oil has treated me well but i don't typically put anything more than 5k on my car without the transmission coming out for something or other, so it's difficult to base longevity from that.
 

MellowVR4

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All great info on this one.
 

transparentdsm

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Cherry Hill, NJ
Quoting DynastyLCD:
wait, wait, wait.... i've got a question here. if GL-5 destroys synchros, why are people using Diaqueen? isn't that GL-5?



no sir, diaqueen is a GL-4. 100% on that

For future reference GL5 has special additives like high sheer plus others for differential gear operation. These additive packages are not brass friendly.
Also not conducive for the best blocker ring operation.
GL4 is made/recommended for a reason.
 

Mitsuman3KGT

Active member
Joined
Jan 9, 2013
Messages
30
Location
Dayton & Toledo, Ohio
Quoting DynastyLCD:
wait, wait, wait.... i've got a question here. if GL-5 destroys synchros, why are people using Diaqueen? isn't that GL-5?

personally, my transmission comes out and goes back in so many damn times that i just run cheap sh*t... typically whatever 80w90 gear oil i can get at the cheapest cost. i've got the Kia version of Diaqueen i was planning on trying, maybe i'll hold off considering the GL-5 thing.

i used to use Shockproof Lightweight, and after tearing apart enough of my own transmissions, i found that what others said about it was true - it can clog the smaller oil passages. my recipe is: tcase and rear diff get heavyweight shockproof, transmission gets 80w90 or MT90.

i've never liked Synchromesh. i feel as if it's too light and too thin. makes for some excellent shifting, but i could see how it wouldn't protect the way MT90 or another quality gear oil would. there's even some schmuck around here who tells people to put 5w30 in their DSM transmissions... WTF!? i've been told in the past by a VERY knowledgable DSMer to either pick Synchromesh and beat up the transmission or use gear oil and deal with the slower shifting. pick your poison, i suppose.

if/when i ever actually construct a real built transmission with Evo gears or dog cuts, i'll go MT90 only in the transmission. i agree whole-heartedly with that idea, just never had a transmission worth it. the Synchromesh i never liked. regular gear oil has treated me well but i don't typically put anything more than 5k on my car without the transmission coming out for something or other, so it's difficult to base longevity from that.



Yes, PLEASE DON'T put engine oil in your trans. Working at Dana I've played around with plenty of trans and diff oils and I would never put 5W30 in my transaxle!

Yes synchromesh is thin but for DD (again Daily Driving) it's fine. I've tried MT90 and it's just too notchy for me (maybe my sychros are worse than I thought).

You are correct though, unless your racing, it's mostly preference as to what you want to run. Some oils have "friction modifiers" and what have you but it's all preference, you'll get 10 different people telling you that they all run different fluids.

You can get synchromesh that IS GL-5 and you can get synchromesh that is NOT GL-5... read below.

click
click
click


I'm not saying synchromesh is the best thing around because I'm sure it's not. Just throwing out some knowledge and experience I've had with it.

Zach.
 

presterone

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Jan 23, 2012
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brunswick maine
Yea I wasn't 100% sure about the gl-5 rating but its something to look into especially for a daily driver. With my old car I couldn't use synchromesh if I wanted the trans to last long.
 

iceman69510

Turn Right Racing
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Michigan
I have read and researched pretty much on the GL4 v. GL5 issue. GL5 is not recommended for many transmissions, specifically a lot of Japanese manufactures recommend GL4. GL5 is basically more designed for hypoid gears, like in a differential. Yes, GM uses synchromesh in the their manuals, and I did in my GM truck.

That said, there is some evidence that GL5 nowadays is "buffered" to not cause damage to brass parts. Will you be ok running it? Maybe, but maybe not for an extended mileage period as it breaks down. Bob is the oil guy site has many discussions on this subject, with strong opinions on both sides.

I personally have used MT90 and MTL mixed, but now Redline makes a 75W-85 which is exactly what is recommend by Mitsubishi. I will be ordering some of it soon to try for my next fill. I am willing to spend a bit more, but have to laugh at Phil's comment on using whatever cheap stuff he can get. I try not to take my trans out too often, but you know how it goes...
 

Wizardawd

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Aug 7, 2007
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Location
Franklin, NC
I regularly used 80w90 store bought gear oil and never really had issues. Recently, #17 was getting hard to shift. Not grinding, just long delays in getting into gear from lockout. Put in Pennzoil Synchromesh from Advance Auto Parts at a whopping $7 a quart and it shifts so much better. Granted, i'm not sure of the long term effects, but this tranny is getting swapped with a Jack's rebuild later this summer. But, this synchromesh has been really nice and cheap. Not to mention, available locally in my middle of no where town.

Wiz
 

transparentdsm

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Cherry Hill, NJ
well its one thing using what you can get to hold you over and using what you want if your swapping transmissions every 5-10k miles. i used what i suggested above in a 400+awhp 1gb laser and daily drove it for 13000 miles, when i decided to part the car out the fluid was almost as nice as the day i put it in. i use cheap crap for flushing out the trans or running the trans 100-500 miles to clean out the gunk, but then i like to use redline. i like my trans to last as long as it can and redline mt-90 and some shockproof is the combo.
 

turbowop

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Apr 29, 2001
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Yakima, WA
I use Neo RHD. It shifts well and provides excellent protection for the gears. Synchromesh is garbage and will turn your trans into a box of gravel if you make any kind of power. Sure it helps a trans with worn synchros to shift better, but it does nothing to protect the gears. If your trans doesn't shift well, either fix your clutch issues or replace your worn synchros.
 

Well i did used it in both of my rides i really liked it! Wouldn't use anything else for DD responsibility just the 02

 
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