Here's a thinker (MTF)

[gavinl]

Many Merkur XR4Ti owners said that Redline's MTL is the best suited manual transmission lube for our T-9 transmission.

This is the response from AMSOIL when I gave them the Ford spec for cross referencing

"In response to your inquiry, specification ESD M2C-175-A refers to Merkur Manual Transmission Fluid part Number ESRY-19C-547A. The requirement is synthetic MERCON fluid. Our AMSOIL ATF meets and exceeds this specification"

Ain't the chemistry of Syn ATF different from a light weight MTL?

 

[MolaKule]

ATF Transmission fluid is approx 0W20 to 5W20 or ISO 32/46 fluids, with low levels of ash-type anti-wear additives and large amounts of friction plate (wet clutch) friction modifiers.

Most MT fluids are 5W30 to SAE 45 weight and contain higher levels of Phosphorus and other ash-type Anti-Wear Additives, and contain about 10 times the calcium and other acid fighting additives than do the ATF fluids.

Viscosities of MT fluids average 13.5 cSt while those of ATF's average 7.5 cSt.

I recommend you go with the Redline MTL/MT90 Fluid.

 

[gavinl]

Thanks Molakule, the Merk's T-9 gearbox (same as the Pinto) is really a sensitive piece.

MT-90 is considered too heavy that's why many owners went with MTL or a MTL/MT-90 mix. Some used regular 75/80W-90 and commented cold shifts are stiffer but it ran fine....I'm not taking chances though

Also, it specs a GL-4 MTF, besides the sulphur content, what other detrimental effects could a GL-5 have on such a gearbox?

 

[MolaKule]

First of all, I think the GL5 corrosion/Yellow metals problem has been blown out of proportion and pose less of a threat today since new chemistries have emerged for metal deactivators and anti-corrosion agents.

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=21;t=000029


From what I have seen to-date, the synthetic chemistries of GL5 rated 75W90's pose less of a problem with corrosion today than did the petro chemistries of GL5 rated 75W90's a decade ago. I would still be cautious about buying bulk GL5 gear oils from Farm and Home and Ranch types outlets for use in manual transmissions unless your manual transmission specifically requires GL5's. For example, most 3 to 10 ton farm and ranch trucks with manual transmissions might be able to use these fluids on a daily basis, but the econobox daily driver manual transmission might suffer.

I think that when manufacturers specify the GL4, they are attempting to guard the operator from the old harsh GL5 chemistries of yesteryear.

So what is the bottom line for MT's that require GL4 and non-ATF fluids? I see two choices:
1. Run a full synthetic 75W90 with Used Gear Oil analysis (such as Amsoil's TGR
http://www.amsoil.com/products/tgr.html or
Schaeffer's #741
http://www.schaefferoil.com/data/740-741.htm or
Mobil's
http://store.avlube.com/mob1syngearo1.html ), focusing on copper-alloy corrosion, TAN, viscosity change, and shifting quality at temperature extremes.
2. Run a Redline type Gear Lube chemistry rated for GL4 (such as MT-90, MTL) with confidence that corrosion will be minimized.

 

[gavinl]

Thanks again Molakule! That's really informative!

 

[cvl]

Royal Purple Sychromax might be worth looking at as well. It's lighter than MT-90.

 

[gavinl]

Is the RP Synchromax's weight similar to Redline's MTL?

 

[1 FMF]

no. the mtl is around 10 cSt, the royal purple synchromax is around 7cSt which is typical ATF. I am running the royal purple in my 6-speed 2002 SS (tremec t56). I have had it grind 3 times over the past few weeks going into 2nd at slow speeds. But 95% of the time it shifts fine, and it's excellent when it has been very cold out and having to shift when just starting out. Just those few times where the synchro would grind going from 1 to 2, but I know I have some problem with 2nd gear to begin with so don't take my post to mean the RP synchromax is no good. However, it has never grinded before like it has with the RP, so the fluid is having some effect.

[ December 16, 2003, 04:52 PM: Message edited by: 1 FMF ]

 

[1 FMF]

a quick follow-up if anyone is still reading,
I've driven the car about a dozen more times since my last post. Haven't had any grinding when shifting since. It's been shifting excellent all around, especially when it has been 20-30F and the car has been parked. And it seems like the shifting is getting better the more I drive it so I will keep my fingers crossed.

 

[cryptokid]

i have 12K miles on a gl5 syn oil which is in a manual gearbox that says gl4 only.
no prblems so far, and it shifts just as good as it did with the gl4. the synchros work just fine, even when doing clutchless shifting.

the gl5 issue is blown out of perportion imho.

 

[userfriendly]

I don't think the GL-5 issue is blown out of perportion. It is a CYA the manufactures placed in the lube requirement/spec so OLD STYLE GL-5+6 lubes are not used.
Interestingly enough two examples of this new lube tech are Exxon's SGO 75W90 and 80W140.
Both meet API's GL-5 AND pass a 1a copper strip test.
My favorite MTLs are like Exxon's SGO 50, a GL-3 I believe. The buffered sulphur additive in these lubricants, say barium sulphonate, a metal de-activator, plays a duel roll in lubes of this class.
1. The additive provides moderate but sufficient EP protection for manual transmissions.
2. Coats the internal transmission parts and gears to reduce gear traction which makes shifting easier.
Other GL-3s include mono and synthetic multi-grade Cat TO-4s.
Most THFs are GL-4 rated, are copper safe, and cost about $1.50/qt.

[ December 23, 2003, 07:18 PM: Message edited by: userfriendly ]