Longtime TTAC Commentator dolo54 asks:
You mentioned using GM syncromesh in your recent Piston Slap article. I have a 91300zx (NA) that has a very typical problem for the model. The syncro for the 5th to 4th gear change is worn (they were made out of too soft a metal until the 95 transmission). I use the recommended Red Line MT-90 transmission oil, which helped quite a bit. But I still get a bit of a grind unless I double clutch the downshift. I’m wondering if I could use this synchromesh safely. I’ve read that you can use a more slippery oil to cure the problem in the short term, but it increases wear and in a short time the syncro will be gone completely (great for a sleazy salesman I suppose). How does synchromesh work and would it speed damage to an already worn syncro?
Sajeev answers:
We have a saying here in Texas: pour some sawdust in the tranny and that shit’ll clear right up. Or not.
Now let’s get serious. Unlike the Red Line oil(CHECK) used in your transmission, Synchromesh is a mix of oil and additives. After a little Internet research, people are guessing that Synchromesh is made of 5w30 non-detergent oil with friction modifiers and an EP additive, which supposedly works well under “extreme pressures.” Sounds about right to me.
I’ve seen Synchromesh’s trio of unique properties fix an early 1990s Maxima gearbox that (formerly) needed granny shifting on the 1-2 upshift. Considering the chance that “EP” additives can cushion a fragile 4-5 synchro, your Z might follow the Maxima’s lead. So if you have $150 to spare, give it a shot: buy Synchromesh and save some cash for new Red Line if it fails. Or save your current Red Line in leftover Milk jugs if it is relatively new and clean.
[Send your technical queries to mehta@ttac.com]
8 Comments on “Piston Slap: Synchromech-ity...”
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I would be looking around for a 95+ tranny if that will fit.
bluecon +1. If the ‘95 trans is better, find a decent one in a junkyard and roll with it. Long term, that’s got to be the best solution.
Thanks! And yes, a new tranny is on my list, but they are in high demand and you won’t find one in a junk yard. They go for $1500 and up. So obviously I’m putting that off until it becomes a necessity.
“Unlike the Red Line oil(CHECK) used in your transmission, Synchromesh is a mix of oil and additives.”
All modern lubricants are a mix of base oils and additives, including Red Line MT90. I would ask the question here:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=postlist&Board=16&page=1
FWIW: The guys in the E-type Jaguar community who drive the early cars with the non-synchro Moss gearbox (Jeremy Clarkson compared using it to “stirring coal”) swear by Redline MT-90.
I love the cutaway Mini pic!
–chuck
What’s wrong with taking the transmission out and put a new synchromesh in 4th gear?
If necessary you can do the rest too.
You probably can take the revised synchro.
Stick to the MT90.
The RedLine MT90 and MTL are light GL4 gear oils specific to these types of application.
You specifically do NOT want anything rated GL5 or with EP additives in a manual synchronized gearbox. Think wet clutch, you do NOT want MORE slippery.
Dolo54,
Keep that white beauty running, its a classic, and enjoyed seeing one so well loved!