A Review of Bombardier's Visco Lok Differential

Visco Lok differential from Bombardier Quest

Having owned three Bombardier Outlanders, I feel I have had enough experience with the Visco Lok front differential to write a short review.

I suppose I can start with a quote from  Bombardier.

" Bombardier ATVs’ four-wheel drive system is the most intelligent in the industry. Visco-Lok constantly monitors front wheel speed and, if it detects one wheel spinning faster than its mate, it progressively sends more power to the wheel with the better traction. And it does it all without the rider even having to lift a finger."

That is exactly true.  Push the 4wd button and it works when needed and disengages when not needed. The big benefit to having this differential is with the 4wd button engaged, you have "3wd" or an "open" differential. This makes steering and handling very easy and also gives the extra traction of the 3rd wheel being driven. When things get a bit tougher going and you start to lose traction, the Visco Lok will sense the front wheel is spinning and lock in the other side. Now you have a locked front end, true 4wd to help claw your way out of that nasty mud hole.

This works very well in most situations, however, there are times when a "true locker" is superior to the Visco unit. For example: say you are climbing a steep technical rock trail. You start spinning enough to lock in the front dif. and things start going OK, but you have to let off the power. Now you are back to "3wd" and have to spin a front wheel again to lock it. This is a situation where you do not want any wheel spin and a true locker would be much better.

The Visco Lok only locks the front dif as long as you are on the gas. When you let up, it reverts back to "3wd" or open differential. This is because when the Visco Lok pumps up, the front end is locked in true 4x4 until you stop spinning, then the oil pressure bleeds off to unlock the front differential.  This is the only downside of the unit that I can see. Although it can be a big downside, if you are in that situation.

Here is a quote from the company, GKN Viscodrive:

"The new Visco Lok LSD features an uniquely designed self contained viscous shear pump that provides tremendous freedom in specifying the level of torque transfer that is provided at any particular speed difference. Small torque transfers can be provided at very low speed differences to improve handling while high torque transfer with immediate response reaction is available at higher slip speeds due to its new progressive characteristic.

The clutch pack is engaged by an unique patented viscous shear pump which is a self contained silicone fluid pump which generates a pressure against the piston based on a speed difference across the pump unit. The pump is 100% filled with silicone fluid and requires no servicing."

The Visco Lok is a huge improvement over the standard "open" differentials in other ATVs that claim to have a limited slip dif, but usually, really only have 3wd.

Pros:

The Visco Lok is a no-brainer. Just push the 4wd button and go. Steering and handling are very easy with it engaged and you don't have to stop to engage a locker. In most situations, the Visco unit works very well and for most riders is an excellent, true 4wd system.

Cons:

When in a situation where no traction of the front wheels can be found, the Visco Lok senses both wheels slipping, therefore it doesn't know which wheel to apply the lock to and it takes a few rotations of one of the wheels before it will then lock both wheels up and you will go . You have to stay on the gas or it will disengage back to 3wd.

More info on the Visco Lok technology:
http://www.a1.nl/phomepag/markerink/viscolok.htm

 Images and some information have been gathered from the web. The author makes no claims as to the accuracy of this article. It is provided as a review in the opinion of the author only.

Last edited on Tue Jan 31st, 2006 12:14 pm by kraked