Ridgeline VTM-4 Explanation from Gary Flint

[ChrisM]

Originally Posted by Pug

How does reducing the drive train to FWD help in deceleration?
It would seem to me, that using all four drive-wheels' resistance would be more effective at slowing a vehicle. Are the rear wheels then turning freely?
Or am I completely misunderstanding the following excerpt...

This statement doesn't make sense to me either. The only thing that I can possibly speculate is that decelerating in 2wd eliminates any drivetrain resistance that may hinder braking. Since the RL is an automatic, the drivetrain cannot be used to slow the vehicle like when you downshift in a manual transmission vehicle.

Maybe I'm wrong. Someone else may have a more accurate answer.

[HH4]

In a 4WD vehicle where side axles and / or front and rear drive axles are linked or even locked in some conditions, braking at one wheel will also have an effect at the other wheels. Perhaps decelerating in FWD mode enables maximum individual control at each wheel from the ABS and VSA.

[2Hondas]

Hopefully, the people who are thinking or have already put a fluid in the VTM besides the Honda fluid will give it a second thought. The VTM system is similar to an automatic transmission in its inner clutch and ring materials, and without all of the proper stick/slip additives and anti wear additives it won't work as designed. I will be changing the fluid every 15,000 miles using the Honda VTM-4 fluid ONLY! I also plan on doing a transmission drain and fill every 15,000 miles. This cost is very small compared to the truck cost and potential repair costs. Mobil 1 in the engine according to the MM however.
The article did answer one of my questions, Saturday we took a trailer full of rocks and tree branches to the farm to unload. I back down a pretty steep slope to unload and when I pulled up with a full trailer (probably 2,500 pounds) the truck felt as if it was bogging down. I was in 2nd with the VTM locked, so now I know in this set-up the truck starts off in 2nd gear, not first. Something to remember next time.

[shovelhd]

Next time try it in D without the VTM-4 locked. You'd be surprised how well the truck pulls up an incline without any intervention. VTM-4 lock is designed to get you unstuck. Trying to out-think this truck leads to more problems than it solves.

[Pug]

Originally Posted by ChrisM

This statement doesn't make sense to me either. The only thing that I can possibly speculate is that decelerating in 2wd eliminates any drivetrain resistance that may hinder braking. Since the RL is an automatic, the drivetrain cannot be used to slow the vehicle like when you downshift in a manual transmission vehicle.

Maybe I'm wrong. Someone else may have a more accurate answer.

Originally Posted by HH4

In a 4WD vehicle where side axles and / or front and rear drive axles are linked or even locked in some conditions, braking at one wheel will also have an effect at the other wheels. Perhaps decelerating in FWD mode enables maximum individual control at each wheel from the ABS and VSA.

These explanations/speculations make sense to me, but I'm no auto mechanic, and these new systems sometimes boggle my mind.

If we then accept the above as accurate (for discussion sake), wouldn't the lack of drag (for lack of a better word) at the rear wheels, increase the wear of the rear brakes disproportionately to the front ones?
If this is true, then all RL's would be replacing their rear brakes before their front ones.

The drive-by-wire "grade" system that seems to grab hold of my truck when decending a hill feels/sounds like the engine "braking", not the actual brakes grabbing the discs, so I'm not so sure about what's going on here.

[MBB]

You're missing the point in regards to the quote about "decelerating in front wheel drive mode to maximize fuel efficiency". We're talking fuel efficiency here, and if a vehicle's rolling resistance is reduced, fuel efficiency will be increased. There is less rolling resistance in front-wheel-drive mode than in all-wheel-drive mode.

[MikeT]

Originally Posted by Pug

...How does reducing the drive train to FWD help in deceleration?

Just my understanding here (I could be wrong ): I beleive the reason for using front wheel drive under decelleration is to prevent the rear wheels from losing traction (Like ice or rain or both while decending a steep hill). I took a high performance drivers course where we were shown films of cars losing the rear end under heavy deceleration (Not braking) by down shifting into lower gears. The cause was explained by the instructor as the torque from the engine that makes the car go when under throttle will be used as breaking power when the throttle is closed. Back then we were driving Plymouth with a 440ci and a four speed manual. I will never forget going into the first turn trying to break into the turn, engage the clutch, and match the revs at the same time...what made the experience unforgetable was the resulting spin when I did not properly match the RPMs to the lower gear (2nd) and the rear end lost traction.

Oh well, fingers are tired now. That's my thought on it....

[brandont]

Originally Posted by MikeT

I beleive the reason for using front wheel drive under decelleration is to prevent the rear wheels from losing traction (Like ice or rain or both while decending a steep hill). I took a high performance drivers course where we were shown films of cars losing the rear end under heavy deceleration (Not braking) by down shifting into lower gears. The cause was explained by the instructor as the torque from the engine that makes the car go when under throttle will be used as breaking power when the throttle is closed.

Not exactly. You can spin a FWD car the same way. Enter a corner very near the limit, get on the gas until the front starts to push, then close the throttle. If the car is anywhere near balanced & good handling, the back end will come around. Get back on the gas to stop the back end coming around. You can do basically the same thing in a RWD car, but it is a bit easier because the back end does add 'braking' when you get off the gas.

However, the MAIN reason the back end comes around in either car is weight transfer. As much as 20% of the vehicles weight transfers forward under braking (less under lift throttle). This removes traction from the rear wheels.

Enter the same corner at the same speed and apply light braking (all 4 wheels) and the car will quickly stabilize, as you only need to scrub a TINY bit of speed in order to regain control. So from this, I would say no - cutting the rear wheels out does NOT help with stability under braking. In fact, the less cutting in / out of power & braking you have - the more predictable the car. That's why racers don't clutch going into a corner.

[MikeT]

Originally Posted by brandont

Not exactly. You can spin a FWD car the same way. Enter a corner very near the limit, get on the gas until the front starts to push, then close the throttle. If the car is anywhere near balanced & good handling, the back end will come around. Get back on the gas to stop the back end coming around. You can do basically the same thing in a RWD car, but it is a bit easier because the back end does add 'braking' when you get off the gas.

However, the MAIN reason the back end comes around in either car is weight transfer. As much as 20% of the vehicles weight transfers forward under braking (less under lift throttle). This removes traction from the rear wheels.

Enter the same corner at the same speed and apply light braking (all 4 wheels) and the car will quickly stabilize, as you only need to scrub a TINY bit of speed in order to regain control. So from this, I would say no - cutting the rear wheels out does NOT help with stability under braking. In fact, the less cutting in / out of power & braking you have - the more predictable the car. That's why racers don't clutch going into a corner.

The films I refered to were cars losing the rear end while traveling in a straight line on a reduced traction, closed course. You are correct about not clutching while entering a corner as I mentioned above. I did certainly did learn that lesson The point of my little diatribe was for people who drive pickups and the Ridgeline in particular when it comes to our AWD drivetrain working in FWD only during deceleration and breaking. I believe the reason for this is to remove the torque from the rear wheel during deceleration and breaking to help prevent the rear wheels losing traction (Due to weight transfer and reduced traction). The main reason a lot of other rear drive trucks and cars end up in ditches (Especially pickups) is that the drivers lifts the throttle when on ice or near hydroplaning and rear end loses traction (From a combination of engine break torque and reduced traction) and the driver doesn't correct for this by either shifting into neutral or maintaining a steady throttle.

Next time you drive on ice, find a safe place to experiement. Try my simple suggestion that whe the rear end breaks lose on the ice, just shift into neutral. It has worked on my 98 Dodge Dakota (318ci) 2wd p/u, my brother inlaws Dodge Ram 4wd, and my sister inlaws Jeep Commander 4wd.

[Pug]

Originally Posted by MBB

You're missing the point in regards to the quote about "decelerating in front wheel drive mode to maximize fuel efficiency". We're talking fuel efficiency here, and if a vehicle's rolling resistance is reduced, fuel efficiency will be increased. There is less rolling resistance in front-wheel-drive mode than in all-wheel-drive mode.

It was not so much "missing the point", as looking past it, after it was well-taken.
I have no contention about whether dropping drive to the two rear wheels increases fuel efficiency while cruising. At the risk of getting this out of context... My confusion lies within the statement that when braking, the Ridgeline operates in front-wheel-drive only.
Regardless of the resultant boost in fuel efficiency, I'd think that the first and foremost concern would involve whether or not braking efficiency is effected (at the expense of greater mpg).
That is what spawned my question: "How does reducing the drive train to FWD help in deceleration?"

I dunno... sometimes my brain gets disjointed as I tend to "dig a little deeper", so although I did "get it", my thoughts and resultant question may have seemed irrelevant... but I don't think so.