Torco RTF, Manual Trans. Fluid???

[Joseph Fihn]

I have an '03 Dodge/Cummins with the NV-5600, 6-sp. gearbox. This is a large, slow shifting trans. The major complaint about it is the "notchy" shifting characteristic. The explanation is the massive geartrain is slow to align for smooth gear changes. The brass synchro's just can't slow things down fast enough.

I've tried the recommended Mopar fluid, Pennzoil's recommended Synchromesh fluid, Specialty Formulation's MTL-P (which is the only product that showed any improvement in the shifting quality but, only a slight improvement).

One of the "Wizard's" at the Turbo Diesel Register.com recently tried Torco's RTF & reported a "significant improvement" over the other fluids he'd tried. The previous fluid was RedLine MTL, which, provided a slight shifting improvement.

The factory recommended gear oil is supposed to be a GL-4. I called Torco Oil International & they told me that their RTF is a GL-6 & that it would be compatible where a GL-4 is called for.

I would like to try this product out but, am concerned about the GL-6 rating.

I know nothing about these rating systems other than the GL-4 is recommended because it is "healthier" for the "yellow metal" synchro's. I guess it is not as slippery as the GL-5's & the extra friction allows the synchro's to do their job more efficiently.

Do any of you have any experience with this product & should I be concerned about the GL-6 rating?

Thank you.

Joe Fihn

 

[unDummy]

I would think that the MTF would be a better choice. Why do you want to go thicker???

 

[Rubiconjeeper]

Have you tried Amsoil MTF?, it worked wonders for my NV 3550, wich uses the same Mopar fluid.

 

[youngbuck]

Interesting... I haven't heard of a GL-6, and what is even more interesting is that they say it is compatible where a GL-4 is recommended. I know that if your transmission shifts notchy, and either GL-4 or GL-5 is recommended, the GL-4 is suppose to help the notchiness more. Has to do with what you said about there being more friction and allowing the synchros to do their job better.

So, anyone else know about GL-6?

 

[goodvibes]

I've tried the RTF but only for about 600 mi. so I can't say a thing about longevity. The dealer drained it for some uneeded work. It shifted better than 3 others I tried. It's a thin 75w90 but probably a bit thick for yout ap.

 

[Joseph Fihn]

unDummy,

The only reason I was interested in the RTF was because of the TDR member that experienced "Significant Improvement" in his shifting quality after using it.

I agree. It seems like the GL-4 MTF would be more appropriate. I would think that the GL-6 RTF would be so slippery that the synchro's would not have enough friction to slow down the gear train. You would think the shifting quality would deterioriate, not improve. But, that does not seem to be the case.

Member "goodvibes" tried the RTF & found it to "shift better" than 3 others he had tried.

I'd love to have better shifting quality but, not at the expense of damaging my synchro's.

Thanks.

Joe Fihn

 

[unDummy]

It all depends on what additives Torco uses.
Don't confuse slippery from friction modifiers to the gear protection provided by the AW/EP additives. I'm assuming that Torco is using an additive that isn't damaging to synchros.
http://www.torcousa.com/assets/files/rtf_racing_trans_fluid_tech.pdf

Transmissions need trial and error. I've had several identical transmission models respond differently to fluids. One persons success could be another persons failure. I personally think that it is too thick to move freely around when cold. But, its a truck and your weather is different then the blizzard that I'm in right now.

Give the fluid a try and post back with results.

 

[youngbuck]

What is the difference between a GL-5 and a GL-6?

 

[MolaKule]

GL6 is an obsolete specification.

GL4 and GL5 refer to increasing levels of EP protection and logically to increasing levels of EP additive.

Redline MTL (a GL4) has about the same viscosity as MTL-P so I can't see why there would be any advantage of using MTL over MTL-P.

What's the viscosity specs of the Torco?

I think the reason we suggested MTL-P was that while the SynchroGlide was specified in terms of the required factory viscosity characteristsics, the transmission was having to deal with a lot of horsepower and torque through it, and the GL5 rating would offer more EP protection than other fluids. This transmission has long shift throws for a reason; they don't want you doing any quick power shifting.

We can make you a GL5 SynchroGlide if you want to try a slightly thinner fluid with the same protection as the MTL-P.