A few years ago MileMarker made a viscous coupler that bolted onto the front of the transfer case, and the driveshaft bolted to this coupler. It allowed the front axle to remain engaged on snow/ice patched roads without fear of damaging the drivetrain while on the sections of clear road, going around turns, etc.

I'm really interested in finding one of these units. I contacted MileMarker and they no longer make them. I searched the web for another manufacturer and found nothing.

Has anyone every tried one of these?

Does anyone know of one for sale?

 

Did you cahck EBay?

How about this web page: http://www.craiglook.com/

 

I remember those. They had an extremely, astronomically high viscosity fluid in them, with odd shaped castings for the fluid to flow through. It was this fluid, coupled with the odd shaped channels, that allowed some slippage. You would not have 100% FWD with it installed, and to go back to normal, you would need a new driveshaft, because this coupler installed in the driveshaft itself. I remember reading articles about it, but it never took off, from what I've gathered. I would imagine that the temperature of the fluid would control the amount of resistance, and I would imagine that it would lose its effectiveness over time, reducing the amount of torque to the front wheels.

 

I would bet a Cummins would explode it like a balloon........

 

Remember the AMC Eagle? They used a transfer case built on the same coupling.

 

If you are intent on having all-wheel-drive, you could replace your transfer case with a NP203, which has all wheel drive and lockup.

 

Is the swap to a NP203 pretty straightforward? What vehicle is the NP203 used in?

 

70's Ford pickups and broncos is what you are after. They are pretty rare though, most are 205's.

 

Looking on the information on the drivetrain.com site, it looks like Dodge and GM both used the full-time version of the NP203, and Ford used a part-time version. Rebuilt units from them are kind of expensive, like around $1200 just for the tranfer case. I'm looking for something way less costly, and I don't want to have to do a lot of fabrication to get it to fit. I guess I'll keep looking for something to do the job.
I'd love to have a heavy duty version of the NP231 that was on my Jeep Cherokee. It was the Select-Trac unit, that had full-time and part-time operation, as well as a neutral and low-range.

 

$1200 is cheap, considering what you are wanting. Full time four wheel drive in a heavy duty truck with diesel torque. That is a tall order that spells money. I would imagine that the viscous coupler put out by milemarker didn't have the strength to handle a diesel.

 

203's are full time, 205's are part time, all three manufacturers used them. The Ford's are the only ones that are driver drop though, so if you are after full time, a Ford NP203 is what you need.

 

The ss silverado, awd gm vans, denalis, escalades, yukons, etc that are awd all use them. They are unbeliveably strong. I ve never heard of a failure even, and many guys are run blown 427's with nitrous in 6500 lb suvs. They do not wear out either.

 

Well, this is just turning out to be more expensive than I was hoping for. The information I had on the Milemarker unit is many years old, and the price at that time was still kind of expensive, but reasonable enough for me for what I thought I was getting, and I was just making the assumption that it worked as advertised (yea, I know, a sucker's born every minute) and would survive being used in the application that it was intended for. I guess I'll just have to wait for something else to come along or do without.

Thanks for the information guys, I appreciate it.