Understanding syncros

Bill Douglas · 10-13-2002, 06:14 PM

I have a '92 Toyota Corolla with a gearbox that graunches badly when cold. It's particuarly bad for the first few minutes then it's fine after 10 minutes of driving. I changed the gearbox oil to Castrol VMX and it still does it. I added "gear-up" additive to the oil and it still does it.

At first I thought it was a clutch problem, but a clutch place said it was fine and that the syncros were a bit worn and it needs THINER oil. The reason for this is the gearbox works fine when it has warmed up and the oil thined. I thought when syncros were worn you used a thicker, less slippery oil to make them grip and work quicker - I don't know.

If I do need a thinner slippery oil would Redline synthetic lightweight gear oil be a good bet? Or do you have some other ideas?

Thanks, Bill.

Wayne 962 · Wayne 962's Garage

It's worth a try. There are several different designs for transmissions - the slip-synchro one used in the Porsches may be different than the one in your Toyota. The transmission depends upon friction to spin up the gears. If the oil is really, really thick, it could be acting like too much of a bearing surface, kindof like the way it does in the engine along the mainshaft bearings...

-Wayne

Bill Douglas · 10-14-2002, 02:11 PM

Thanks Wayne. A chap at work said try Autotmatic transmission fluid. He said it is very thin and will get the metal to metal, that the Jap syncos need, to work better. It may ultimately knacker the gearbox but if I can get a few years out of it, it's worth a go.

Wayne 962 · Wayne 962's Garage

Uhh, I would get a 2nd opinion on that. AutoTranny fluid is designed to work both as a lubricant, a coolant, and a hyrdraulic agent. I wouldn't use it in a manual transmission if I were you...

-Wayne

Dave at Pelican Parts · Dave at Pelican Parts's Garage

Second that. I'd use lighter-weight MTL, possibly something like the Redline synthetic. Second pref to that, a motor oil. ATF would be about my last choice...

--DD

SuperWheel · 10-14-2002, 08:52 PM

I'll third that. I'd use old cooking oil before ATF - sounds like a hack.

Seriously, the Swepco stuff is what I swear by - I think that they have different weights - let me check...

Yes, check here:

http://www.drivewerks.com/catalog/car_care/Swepco.htm

Jared at Pelican Parts · 10-15-2002, 01:12 PM

DO NOT, I repeat DO NOT run ATF in a manual gearbox. this is a bad thing. You will almost instantly burn it all up, and then you will have a nice big glop of sulphides floating around your gearbox, causing all sorts of corrosion, not to mention higher temperatures, as well as the general inability of ATF to provide any sort of lubrication for manual transmission gears.

Bill Douglas · 10-15-2002, 02:52 PM

Ok, four people whose opinions I respect say NO. No it is.

I'll source out some Redline Lightwieght oil.

Thanks Guys.

Wayne 962 · Wayne 962's Garage

I would try the Swepco first...

-Wayne

deltajetfixer · deltajetfixer's Garage

Quote:

Originally posted by Jared at Pelican Parts
DO NOT, I repeat DO NOT run ATF in a manual gearbox. this is a bad thing. You will almost instantly burn it all up, and then you will have a nice big glop of sulphides floating around your gearbox, causing all sorts of corrosion, not to mention higher temperatures, as well as the general inability of ATF to provide any sort of lubrication for manual transmission gears.

Person who advised to try ATF might've had a Mustang like I did. The 93 V-8's ran Mercon in the 5-speed Getrag...

Jared at Pelican Parts · 10-17-2002, 08:33 AM

Sounds like typical Ford engineering.

deltajetfixer · deltajetfixer's Garage

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