The 510 Realm

From a bit of reading, it sounds like the GM synchromesh is not GL-4 rated but it is yellow metal friendly so it can be used in our transmissions.

I'd respectfully disagree about the performance of MT-90 and Sunchromesh. I ran them back to back and can say without a doubt that the synchromesh shifts smoother at all times but particularly when cold. I don't drive my car in the winter either so "cold" is maybe 10C, not freezing temps.

I'd put the smell of Sunchromesh somewhere between the good smell of MT-90 and the skunky conventional oil.

Most people (myself included) are looking to fix an old transmission with tired synchros. The friction modified fluid does wonders compared to something like MT-90. Both my KA trannys had a crunchy 3rd gear before but the new fluid limits it to only immediately after a cold start. Even then, it isn't nearly as crunchy as it was with MT-90.

I had a Redline oil (forget exactly which) in my Mazda tranny for a whole year before switching to this GM stuff, and like Jordan says there was no comparison in my case too. To be honest I didn't find the Redline any better than the oil that was in the tranny when I bought the car-- crunches galore. I'm not saying Redline is junk for everybody, or all the time... but in my application it was quite a disappointment.

As for cold temps, my Mazda experiment has unfolded over the past month (Jan-Feb) in Edmonton, when the mercury has ranged from about -20 to +10 Celsius. Shifts are a little slower and stiffer at the lower end of that range, sure, but surprisingly similar to those at operating temperature. (Can you tell I'm impressed???)

Price-wise, I paid $13- something a bottle at a GM dealer here in Edmonton. Overpriced, obviously. I'll shop around a bit next time, namely when I pick up some for my 510 when it gets back on the road in a couple of months...

JordanTr wrote:From a bit of reading, it sounds like the GM synchromesh is not GL-4 rated but it is yellow metal friendly so it can be used in our transmissions.

I'd respectfully disagree about the performance of MT-90 and Sunchromesh. I ran them back to back and can say without a doubt that the synchromesh shifts smoother at all times but particularly when cold. I don't drive my car in the winter either so "cold" is maybe 10C, not freezing temps.

I'd put the smell of Sunchromesh somewhere between the good smell of MT-90 and the skunky conventional oil.

Most people (myself included) are looking to fix an old transmission with tired synchros. The friction modified fluid does wonders compared to something like MT-90. Both my KA trannys had a crunchy 3rd gear before but the new fluid limits it to only immediately after a cold start. Even then, it isn't nearly as crunchy as it was with MT-90.

That's cool to disagree as we do have our own experiences. I suppose the sycros smooth shifting would have a lot to do with the condition of the syncros in the first place when using any gear lube. All's I know is my trans shifts like butter even when semi cold 35-40degs. 510 gets put away at first salt anyway. The GM elixir price is compatible with the Redline stuff so. I once ran Royal Purple GL5 because it did say it was fine in GL-4 yellow metaled trannies. Ran it for a year and replaced it back with the Redline because my trans wasn't nearly as smooth as with the MT-90 even in the heat of summer.

If it feels good use it-

The skunky smell is the sulphur anti scuff additives that give oil it's EP rating. GL-5 has around 6% which protects steel gear teeth in differentials from scuffing by bonding to both metals and forming a film. Transmissions can't handle that much sulphur on their copper/bronze alloy synchro rings. The bonded layer simply flakes off in use exposing fresh copper beneath it which bonds and flakes off over and over, slowly eroding them. For transmissions, the sulphur additives are held around 4%. This isn't a 2% difference, actually the difference between 4 and 6 is more like 50%.

I don't know what they put in synthetic oils for transmissions and differentials or if anti scuff additives are even needed.

Regarding newer transmissions, is this GM (Shell/Mopar) oil something I should put in my SR trans, instead of the MT-90 Redline? I have a slight but annoying 1-2 shift syncro tick that I'd like to make go away.

S15DET wrote:Regarding newer transmissions, is this GM (Shell/Mopar) oil something I should put in my SR trans, instead of the MT-90 Redline? I have a slight but annoying 1-2 shift syncro tick that I'd like to make go away.

That was exactly my goal and I'd say that the Synchromesh fixed er all up!

Tried the AC Delco synchromesh oil. I have had a semi synthetic oil in my transmissions for years and did not expect much difference and there's not. But there is a definite subtle change that has taken a couple of weeks for me to solidify.

Down shifts were always quiet and grind free but effort increased with increased speed difference. First was a straight arm push. Second was a strong pull. Effort increased more when the transmission was cold. Up shifts were more effort when transmission is cold and second was balky unless you pulled it slightly towards the left against your knee. Third can't be shifted fast, it won't grind, it's just slow.

Now, second is just straight back warm or cold, third is slightly faster with the same effort I used to use. The transmission is just plain 'looser' to shift. I have to admit I like the change and probably woth the $17 a liter.



Tried the GM dealer. Showed him the part number, told him I wanted this oil with this number. Know what he said? "what vehicle?" I said it didn't matter. He said "it sure does matter..." (geezus) I said a '76 Datsun and he looked all pissed off like I had tricked him. Didn't have it in but this other stuff is just as good.. I went to Lordco.

Well I have about 3 thousand miles on my transmission oil and nothing bad to say about it. Mostly to Canby then Calgary and home. Shifts are faster and silky smooth. Gone is the dropping of RPMs below the next gear by the time you get the clutch out. What a thrill to down shift almost at will and to almost any gear. It's just plain more fun to drive and well worth the $40.

Juts an FYI. The GM fluid is a GL-S fluid. The " S " ( not a Five ) stands for " Specialty " oil in API standards. These are proprietary oils formulated for specific Manufactures. BMW, Honda, Toyota all have their own proprietary GL-S formulations. It just so happens that GM got their formulation better.

The GM oil was made specifically for their Gertrag transmissions ( Cobalt SS and a few others ) , which use Bronze synchros. It is definitely yellow metal compatible.

Note it is a semi synthetic and the additives don't last forever. I change mine in my Audi if I start to notice the shifting deteriorate. Right now that around 50,000 km