It's in the rear diff. It's not a true locker. In more circumstances you don't even need to press the button, the VTM will still do some magic back there so it is not useless. I drive a lot in snow and slippery conditions, I've never used the button. If you google 'how does VTM work?' you will probably get some pretty good explinations of the entire system.

That being said, it is not meant to be a rock crawling off-road monster.

 

This graphic and the attached PDFs may help you understand how and when the VTM-4 system functions as well as the VTM-4 Lock option.

 

I used it when I pulled into an unplowed pullout. I got stuck with one side of the vehicle on ice and the other side buried in frozen slush. I pulled out my trusty shovel and dug out the frozen slush to dirt. I activated the VTM4, rocked the vehicle back and forth, and punched it until I made it back onto pavement.

 

how does VTM work

 

The two attachments in @McChizzle's post should answer your question. They were written by Gary Flint, the chief engineer and large project leader for the Ridgeline.

 

Thanks to who ever provided the 2-part explanation to how the system works!
For anyone who understands 4WD systems, this is a bunch of hocus-pocus.....
This truck primarily exists in Front Wheel drive mode (it seems) and allocates power to the rear 'as needed'
That 'locker' system where ever, or what ever it is, drops off after 6mph and is gone at 18 mph ...low speed assist
It either controls the distribution of power straight off the transmission heading to the rear wheels (a front/rear 'locker' or whatever)
However, once that is done they have a clever idea of using a signal from the wheel sensor to see if the 'open - diff' side is spinning
Apply a brake to it and you have a diff locker !! (kind of)

Sounds like if you want to drive on the beach or some other low brow 4WD, best bet is to turn OFF the VSA and Turn ON The VT-4 lock
(It also has a sensor that tells you if you are over heating it if you drive 20 miles down the beach)

 

Thanks McChizzle....that explains alot.....its basically a rear diff locker that only works from 6 to 18 mph in low gear
You guys are awesome, thanks !
Ever Wonder if Gen 1 Ridgelines are a modern classic ???

 

Ever Wonder if Gen 1 Ridgelines are a modern classic ???

I wouldn't go that far, but I can accurately state that even the older VTM-4 system used in the 2006-2014 Ridgeline is still superior to nearly all AWD systems in use today even nearly 23 years after it was introduced. The newer iVTM-4 system used in the current Ridgeline is even more capable in that it adds torque vectoring capability.

 

It seems to me a simple cooler could be made. Mounted on top. The issue would be circulating the fluid. I'll look at it closer when I replace the rear spring towers.

 

Considering how rare it is for the rear differential to overheat when the vehicle is used as intended and expected, Honda likely didn't think it was worth designing an external cooling system.

External cooling would be easier on the iVTM-4 system used in the second generation Ridgeline since it includes an electric pump that runs whenver the engine is running.

 

Sounds to me like it was a major screw-up on their part. Very, Very odd that you can only use it for short bursts
It also seems odd that you have to wait to get stuck before you can use it
Anyone who has any experience with off roading knows that by that point you have only a 50 / 50 chance
Seems like the smarter thing would be to never get stuck in the first place

 

You can use VTM-4 Lock to, for example, drive through the sandy beach of Baja, but if you were to do so for many hours with no letup, it will overheat. This video is a great example of how the VTM-4 system helps when a driver got stuck, the VTM-4 Lock got him out of it when he needed it (go to 2:29 in the video): https://commons.wikimedia.org/wiki/File:2012_Honda_Ridgeline_Mexican_RTL-offroading_in_Baja.ogv

 

I had a Blazer with a limited slip rear differential and a Colorado with an automatic locking rear differential. It seems like a bad joke to have a locking rear differential that needs to be babied after driving with the real deal. That said I did buy the Ridgeline because it had a locking rear differential so I guess I'll live with it.

 

The first Gen Ridgeline rear differentials are no where near a real locker of any kind.

 

Several hours or less would be OK, But everything I read seems to indicate it will overheat after just minutes of use....use it sparingly.

 

The time it takes for the rear differential to overheat is primarily a function of clutch pressure and slip.

The rear drive unit (VTM-4 aka "differential") uses friction clutches instead of a mechanical lock. If the torque capacity of a mechanical lock is exceeded, the locking mechanism will experience a fatal failure. If the torque capacity of a friction clutch is exceeded, it simply slips and generates heat due to friction.

The clamping force applied to the clutches (mechanically in the 2006-2014 Ridgeline and hydraulically in the 2017-current Ridgeline) and what the speed difference is between the two halves of the clutch determines the amount of heat that is generated by the clutches and transferred to the fluid. If the heat in the fluid cannot be transferred to the case and then to the surrounding air faster than it is rising, then the unit will eventually overheat.

The rear drive unit has a small amount of overdrive built in for handling and driving feel, so there is always clutch slip occurring even when driving in a straight line. One reason the system reduces clutch pressure as vehicle speed increases is so that that rear drive unit doesn't overheat and wear out prematurely in normal driving. Another reason is efficiency.

Normally, the VTM-4 system engages the clutches in proportion to the rate of acceleration and how much (if any) front wheel slip is occurring. The idea is to get the vehicle moving with as little front wheel slip as possible using just enough rear wheel torque, but not too much.

VTM-4 LOCK overrides this proportional clutch engagement and applies maximum clamping force to the clutches which increases heat and wear and decreases efficiency when slip occurs. This is why it should be used only in situations where the vehicle has or is likely to become stuck.

The Ridgeline was not designed or intended to be used in hard-core off-roading conditions where 4WD vehicles with mechanically-locking rear, front, and center differentials have an advantage. Is it designed to keep the vehicle moving in more common conditions like snow, mud, sand, gravel, and wet vegetation with a bit more capability than a typical AWD system with open front and rear differentials and a single clutch sending power to the rear.