Manual transmission difficult after drain and fill: CV joint grease to the rescue! What's the science behind it?

Superflan

Superflan

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Apr 28, 2015
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Hi,

sometimes, after draining and filling (with the correct oil) a filled for life manual transmission, shifting problems arise or get worse, right from just after the oil change, and will not get better even after hundred kilometers. In my groups of car enthusiasts and techs, we all put a dose of CV joint grease into the gearbox if this happens. after a few kilometers of driving, problems that appeared just after the oil change will disappear almost instantly and shifting would be really smooth.

I'm questionning exactly the science behind this. Usually the grease packs are labeled lithium/moly. Anyone has experiences or theories about this? Let's discuss ^^
 
What does it say on the Owner's Manual/Handbook. You might have used Hypoid gear oil instead of motor oil. On my Isuzu 4-speed MT, it requires Engine Oil. On my Ford Escape 5-speed MT, it requires Transmission gear oil or ATF
 
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Smoothing is probably from what is in the grease. But it is causing other effects too. How long have folks done this? A band aid may last a little or last forever.
 
I think everything is "filled for life" like some GM transmissions. Hoe long that life will be....will be short!
 
It may very well be short with Moly in there - the synchronizers may not work, they could slide instead of gripping and changing shaft speeds - and while it might feel smoother initially, I can see this causing gear wear and early failure.

Awfully risky.
 
If it shifts smoother, then the syncro rings are doing their job better. At least for now.

I wonder what would happen if you added friction modifier to the fluid instead of the grease. The stuff for limited slip rears.
 
Fabulous50s said:
If it shifts smoother, then the syncro rings are doing their job better. At least for now.

I wonder what would happen if you added friction modifier to the fluid instead of the grease. The stuff for limited slip rears.
Click to expand...
You might want to read this before placing your equipment in further jeopardy:

"A non-slip friction modifier additive for LS differentials has an entirely different chemistry than the FM's in MTF's.

Each fluid type and fluid application has a different additive package and contains different Friction Modifier Chemistry and AW chemistry for the specific materials used in Engines, transmissions, and differentials.

The friction modifiers in engine oils are NOT the same friction modifiers as found in ATF's. The friction modifiers in ATF's are NOT the same friction modifiers as found in LSD gear oil. The friction modifiers found in ATF's are NOT the same friction modifiers as found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluid. The friction modifiers found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluids are NOT the same friction modifiers found in ATF, etc. etc."
 
MolaKule said:
You might want to read this before placing your equipment in further jeopardy:

"A non-slip friction modifier additive for LS differentials has an entirely different chemistry than the FM's in MTF's.

Each fluid type and fluid application has a different additive package and contains different Friction Modifier Chemistry and AW chemistry for the specific materials used in Engines, transmissions, and differentials.

The friction modifiers in engine oils are NOT the same friction modifiers as found in ATF's. The friction modifiers in ATF's are NOT the same friction modifiers as found in LSD gear oil. The friction modifiers found in ATF's are NOT the same friction modifiers as found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluid. The friction modifiers found in Hy-Gard or UTTO fluid or a Trans-Hydraulic fluids are NOT the same friction modifiers found in ATF, etc. etc."
Click to expand...
I was just saying that due to the very "off the grid" nature of CV grease in whatever fluid is spec'd for a manual. Seems crazy anyone would even think of, or try that in the first place....
 
ammolab said:
Are there “filled for life” manual transmissions? Been driving manuals since 1966…changing my 2016 Chevy SS Sedans Tremec fluid Saturday
Click to expand...

Yes, quite a few are these days. You're only supposed to change the fluid after a cllutch change or other work on the transmission.
 
It's probably still quite a bit higher than 50% manuals in Europe if you count all cars on the road. last figure I saw a few years ago was 90%.

It's changing fast though, if the same question is asked of the new cars sold each year then it's more like 50% autos.

My C class is a manual but if I wanted a new C class now, it's no longer available as a manual.

The advent of DCT autos and hybrids is what's driving the trend to auto in small cars. Previously the torque converter autos were too expensive for small cars and sapped too much power. Even now a DCT will add as much as 10% to the price of a small car.
 
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