VTM-4 Fluid

[budrow79]

I changed the VTM-4 fluid today on my 2004 Pilot. There was 33,360 miles on the fluid I drained and it looked and smelled like brand new. I purchased the Pilot used and this is the first time I've changed that fluid.

Has anyone else noticed that Pilots are not very hard on VTM-4 fluid? Next time I'm going change it at 50K miles. I live in a very dry climate in Southern California.

I also changed the transmission fluid today a little before the 30K mile mark. It wasn't near as clean as the diff fluid. I'll certainly use the recommended OCI (30K) for the tranny fluid.

[samc]

Mine was pretty clean as well when I changed it and I probably used my VTM-4 in the winter only a few times.

Honestly I wouldn't risk any trouble over changing a $30 fluid over 30k miles, but it is your suv so do as you wish.

And yeah I plan to stick to the 30k miles for the tranny fluid as well.

[N_Jay]

The fluid never looks bad.

The VTM is VERY picky, so you need to change the fluid long before you notice any smell or color change.

[mclairmo]

My VTM fluid always looks good (after changing it 4 times now) but I have been told that old fluid causes all sorts of noises and problems with the rear diff.

[theirishscion]

As I understand it (and I'm a layman, I don't profess any official Honda Nolij on this topic, though I have done my research) ATF and it's close cousin VTM-4 fluid, are chock full of friction modifiers which make the base oil act just the right kind of slippery between the multi-plate clutches in our transmissions and VTM-4 "diffs" (same basic technology/principle used in both, by the way)

As the fluid does it's job (allowing just the right amount of friction between clutch disks for a given speed and pressure) it is slowly consumed (or degrades, if you prefer), thereby necessitating the periodic replacement Honda requires us to do. However, just using up the friction modifier won't change the colour of the fluid much. Tiny fragments of worn away clutch material suspended in it will change the colour of the fluid a bit, and any significant overheating will darken it a lot (and potentially make it smell burned or otherwise 'off')

Since the VTM-4 system in the Pilot activates not just when you're in a wheel slip condition, but just about every time you accelerate from a standstill as well, the fluid is really working all the time, even in summer months. Ergo, it's using up it's gently consuming friction modifier all the time as well. Hence, the seemingly rather frequent fluid service interval. If it's any consolation, we're not alone, I think the various Haldex-style systems in use by just about everyone else offering an AWD crossover require fairly frequent fluid changes as well, and mostly aren't nearly as zooty and clever as the VTM-4 in our Pilots. Audi, I'm looking at you, you unreliable gits.

P.S. If you want some deliciously geeky detail about VTM, I suggest you have a look here.

P.P.S. Also, you're not likely to ever see burned fluid coming out of the VTM system, the computer watches the temperature in the back diff carefully and if it gets too hot, it'll presumably just self-protectively stop activating the clutches (and flash the VTM light or give you a whingey message if you have a touring) to allow it to cool back down.

[pilot_rave]

Originally Posted by theirishscion

As I understand it (and I'm a layman, I don't profess any official Honda Nolij on this topic, though I have done my research) ATF and it's close cousin VTM-4 fluid, are chock full of friction modifiers which make the base oil act just the right kind of slippery between the multi-plate clutches in our transmissions and VTM-4 "diffs" (same basic technology/principle used in both, by the way)

As the fluid does it's job (allowing just the right amount of friction between clutch disks for a given speed and pressure) it is slowly consumed (or degrades, if you prefer), thereby necessitating the periodic replacement Honda requires us to do. However, just using up the friction modifier won't change the colour of the fluid much. Tiny fragments of worn away clutch material suspended in it will change the colour of the fluid a bit, and any significant overheating will darken it a lot (and potentially make it smell burned or otherwise 'off')

Since the VTM-4 system in the Pilot activates not just when you're in a wheel slip condition, but just about every time you accelerate from a standstill as well, the fluid is really working all the time, even in summer months. Ergo, it's using up it's gently consuming friction modifier all the time as well. Hence, the seemingly rather frequent fluid service interval. If it's any consolation, we're not alone, I think the various Haldex-style systems in use by just about everyone else offering an AWD crossover require fairly frequent fluid changes as well, and mostly aren't nearly as zooty and clever as the VTM-4 in our Pilots. Audi, I'm looking at you, you unreliable gits.

P.S. If you want some deliciously geeky detail about VTM-4, I suggest you have a look here.

Excellent post, very informative!