Is synchromesh safe for my car?

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6,167
Location
Santa Barbara, CA
I’m currently using Redline MTL/MT-90 mix for gearbox oil. I am due for a change and not too impressed with the redline for fixing the notchiness, it improved but its still there. Been doing some research and I have read good things about GM/Pennzoil synchromesh. But what I have not read is anyone taking into account the oil weight. Mazda recommends GL-4 75w90 for my Mx6. Synchromesh is a modified 5w30 oil and I'm just wondering if it offers enough protection against wear at operating temperature. Take a look at the specs: Synchromesh (75w80?) / Pennzoil GL-4 75w90 Synthetic / MTL (70w80) / MT90 75w90 Flash Point oF: 385 445 450 465 Pour Point oF: -50 -44 -58 -49 Viscosity @ 40o C cSt: 41.6 108 56.2 90.0 @ 100o C cSt: 9.08 15.3 10.6 15.6 @ 100o F SUS: 209.4 554 @ 210o F SUS: 56.7 80.7 I've read that it improves shifting smoothness even over the Redline fluids, although will it harm anything if I use it? What temp do gearboxes run at anyways?
 

MolaKule

Staff member
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21,950
Location
Iowegia - USA
1. synchromesh type fluids are not just a modified motor oil. synchromesh fluids are a special 9.0 cSt fluid. If you need a synchromesh type fluid, try our SynchroGlide. For those requiring a 75W90 (GL4/GL5), then there is our MTL-R. Redline's MTL is an 11.3 cSt fluid and is similar to our MTL-P (GL4/GL5).
 
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68
Location
Pottstown, PA
Mmm.. I just put syncromesh in my 2000 Tiburon transmission. which is a one off of the elcipse gst/gsx transmission. Works good for them and work great for me. I am gonna to consider your fluid Molakule.
 
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843
Location
Grove City, OH
I've used Redline MTL in my Nissan sentra ser, I now have Specialty Formulations MTL-P in it. I prefer the SF fluid. I bought it in a gallon jug, which is like paying for three quarts and getting the forth one free.
 
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2,387
Location
Chicago area
Synchromesh is readily available, and really works well. It is dino, not synthetic, and should be changed more frequently. That said, get someting from Specialty Formulations instead.. Their products are superior, and they have a slightly higher viscosity available that would fit the mfrs. specs. for your car.
 

surfstar

Thread starter
Messages
6,167
Location
Santa Barbara, CA
I can get the pennzoil synchromesh for $5/qt locally. People at the MX6 and Ford Probe boards have had no ill effects reported and rate Synchromesh 2nd behind BG Synchroshift. I just wonder if there would be anything detrimental to the synchros or anything at warmer temps.
 

MolaKule

Staff member
Messages
21,950
Location
Iowegia - USA
quote:
molakule, whats a SF replacement for castrol syntorq (gl4) ?
Thanks for asking. That would be our MTL-P which has a GL4/5 rating. -------------------------------------- "Let's Geet 'er Done!"
 

surfstar

Thread starter
Messages
6,167
Location
Santa Barbara, CA
quote:
Originally posted by surfstar: I can get the pennzoil synchromesh for $5/qt locally. People at the MX6 and Ford Probe boards have had no ill effects reported and rate Synchromesh 2nd behind BG Synchroshift. I just wonder if there would be anything detrimental to the synchros or anything at warmer temps.
UPDATE: Synchromesh UOA I don't recommend it for cars spec'ing 75w90. I'm pretty easy on my car and drive mostly highway and the Synchromesh didn't seem to hold up well. The shifting was smooth and it eliminated any grinds I had, though. Despite the oxidative thickening it came out like water, although dark. Redline usually drained a lot cleaner previously. Next time I'll go for a SF fluid. Still not sure why my oil guard UOAs don't have Ca, Zn, P, etc tested.
 
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173
Location
IL
I thought "Synchromesh" was the trade name for a GM transmission oil. My partial bottle, bought some time back, says it's a straight 75W formulation. This stuff was the real deal for a used Ddoge Ram 50 (actually a bumper-to-bumper Mitsubishi Mighty Max) I bought about 10 years ago. When I got it, the 5-speed shifted fine until the temperature dropped below about 40F, then it was like trying to pull a stick through a bucket of molasses. I did a little consultation, decided against the additive Chrysler recommended, ended up deciding on the Synchromesh. Worked like a charm- and what changed out of that box was some kind of thick gruel, probably a 90W-140. The transmission was happy with the Synchromesh until I donated the truck (because it was rusting out) years later and after putting another 70K miles on it.
 
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