I took a look at the link. Nowhere on the bottle does it state if it is a GL-4 or GL-5 fluid. I tried RedLine MTL-90 and found that it made the tranny (an O2J) notchy as all heck. Drained it. Refilled with the G060 VW tranny oil and all seems good again. I like the idea of synthetic oils as many on here do. I'd give the GM Synchromesh a try but want to somehow confirm GL-4 or GL-5 rating on it first.
(this started off short, but ended up rather long.)
Just because something is or isn't GL-4/5/6 rated doesn't mean all is well/perfect. It means the fluid company has paid the testing entity to test their fluid and the fluid passed. Shear, viscosity, moisture retention, etc. It certainly doesn’t mean the fluid is going to make your transmission ‘happy’ if the trans is in less than brand-new OEM condition. I felt exactly the same way and that’s why I spent good money on top-of-the-line (so to speak) Amsoil fluid for my 6sp quattro trans.
This is GL-4 rated and approved for VW use based on that claim/designation.
https://www.amsoil.com/lit/databulletins/g2077.pdf
I tried it twice. Once on an 02J in my ALH TDI and once on an 01E from my '02 S6 swapped to a manual (uses an '01 A6 manual trans.) Results... notchy, hard to shift. Swap to the FM Synchromesh and it shifts better. Both trans could have worn synchronisers and the FM is covering it up, but it’s literally the result I was after. Trans is still in the car and I’ve put about 10k miles on it (the 01E.)
Both Redline MTL and Redline MT-90 are GL-4 rated.
https://www.amazon.com/Red-Line-50304-Transmission-Transaxle/dp/B000CPCBEQ
https://www.amazon.com/Red-Line-Transmission-Transaxle-Lubricant/dp/B000CPCBEG
People have notoriously said the same about Redline's fluids; trans is hard to shift. (I have no personal experience with Redline's fluids.) Some people like them, some really don’t. (I’ve yet to read anyone who tried FM Synchromesh, didn’t like it, and went to a different fluid which they did like. I have
at least five instances where I ran something initially, swapped to FM Synchromesh, and liked the improvement.)
I've literally used brand-new OEM VW fluid (circa 2012) as that was my first go-to on a particular '00 ALH 5-sp, but the trans with new OEM fluid was no different than
whatever I took out. Swap to FM Synchromesh and its night/day difference. I was prepared to pull that trans out and put in new synchros. Also, I dropped the fluid in the ALH TDI after a few thousand miles as I was worried about wear on the synchros, etc and put it right back in the trans. Fluid looked like new, shifted perfectly, and didn’t have any copper/gold looking filings I was worried about.
Lastly, maybe the OEM fluid, Redline, Amsoil, etc all work extremely well when the trans is new, but once the trans wears a bit, specifically the synchros, it’s harder to shift and those particular fluids didn’t cut it anymore. Fact is, on MULTIPLE different occasions and two different platforms, the 02J FWD and 01E Quattro trans specifically, the FM Synchromesh saved me from pulling two transmissions apart for synchros. It literally made that much difference.
Lastly x2... I'm an engineer. Engineers often don't put the absolute best product in their designs for lots of reasons. Be it fluids, plastic parts which may fail in the future because machined billet is expensive, maybe a popular supplier knows the project manager and you "need" to use this because he sponsors the company retreat, etc. Pick one, it happens ALL the time. Sometimes it's a design/calc error, sometimes I have to use something off the shelf that does-the-job with less than perfect results (perhaps GL-4 is the 'standard' VW/Audi
had to use at the time, sometimes a bean-counter tells me I'm too expensive. Fact is, once you get to the aftermarket, you SHOULD use what WORKS if the factory stuff doesn't work as well. Friction Modified Synchromesh works, has given me literally zero adverse side effects, and it's not an isolated case. IndigoBlueWagon posted the same about a year ago and he's a vender who sells fluid. I doubt he sells FM Synchromesh.
