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Klune V Extreme Underdrive !

By Bill Cooke

For anyone that hasn't yet heard of the Klune V Extreme Underdrive, where have you been? It's only the best thing to happen to 4x4's since the locker was invented. The unit bolts in-between your transmission and transfer case and offers either a 2.72:1 or 4:1 gear reduction. The "Goliath" unit is the 2.72:1 ratio and is for people that either don't need the ultimate reduction or already have some kind of additional gears. If you have an Atlas II or 4:1 kit in your transfer case then this is the unit for you. Too much gear can be a bad thing, anything over 200:1 is starting to get ridiculous for most of us. For those that want a little more, Klune V offers the "David" underdrive. It has a 4:1 low gear and is for people with stock geared transfer cases. It also probably shouldn't be used behind a big block in a full size that will see a ton of full throttle abuse. The experts over at Klune V can help you decide which unit is best for you and are a wealth of knowledge on the install and use of the crawl box. We talked to them plenty of times before deciding on the "David" box for our '79 Dodge Ramcharger.

I know what you're thinking, "Someone finally makes cool parts for a Dodge?" It's even better than that, it's a relatively easy install too! Seems that Dodge T-cases have the common 6 bolt "Jeep" style bolt pattern and the same 23 spline shaft. That means the box will bolt right in if you are running a NP 208, married NP 205 or a NP 241. That's what we have in our truck so for us it's a no brainer, sort of. If you are driving something other than a Jeep or Dodge, Klune V has the adaptors you will need to install it in just about anything with 4wd. The crawler itself is 6 1/2" and then a 3/4" spacer for the Dodge and 1/4" mount for a total of 7 1/2" added to the drivetrain. This means custom mounts, crossmember and new driveshafts. That's the only trick to overcome with the whole job. Transfer case shift linkage and an extended speedo cable are also on the list of things to do but that's not as hard as it sounds. Is it all worth it, YES!!!!!!!!!!!! Here's how we installed the Klune V Extreme Underdrive and what you should know before you install yours.


This is what all the fuss is about. The Klune V Extreme Underdrive is basically a planetary gear reduction unit in a custom made housing. The gears share a basic design of the NP 231 type unit but everything is custom made for the Klune V. It's stronger and better than anything else out there. For normal driving the unit is shifted to high gear and is 1:1 at that point. When you feel the need to hit the hard stuff just give the shifter a pull and you then have the low range of the unit. It can be used in 2 hi, 4 hi and 4 low, giving you  plenty of options off-road. What this will do for your 4x4 is amazing. The control and power it gives you is out of this world. It really must be seen to be believed.

We were doing a little more than just installing the Extreme Underdrive in our Ramcharger. The truck was also getting a new tranny. It's a custom built 518/618 O/D unit and added a few extra wrinkles to our install. It's a few inches longer and has a completely different mount. That means we are going to be doing some fab work to install ours. If you are working with a stock transmission then it's much easier to just pop the unit in. We are also running a NP 241 in our truck and that actually makes it a little easier. If you have a NP 203 installed you should swap it out before you install the crawler. Besides the fact that it has a funny mount the thing weighs a ton. That's too much force to put on the Klune. The other question is why? Why do you still want that old piece of junk anyways? Swap in a NP 241 from a 91-93 Dodge and be far better off.

Since we are working with a 106" wheelbase and we are adding almost 1 1/2' to the drivetrain we decided not to use the 3/4" spacer supplied with the box. This meant we were going to be doing some serious work to make it all fit. If we had to do it over we would just use the spacer and cut the rear driveshaft another 3/4".

Here's why you need the spacer on some Dodges. Most of the transfer cases have a long input shaft and need the extra clearance of the 3/4" spacer to make it fit. Since we like bashing our brains in and doing the most work possible at all times, we decided to cut the  t-case's shaft and Klune's output shaft for the clearance. DO NOT DO THIS!!!! It's just not worth it and not necessary. Turns out the rear driveshaft is just fine. Use the spacer and spend the extra time and money you saved on more important things.

Here's why we thought we needed to keep the whole thing as short as possible. With almost 8' of drivetrain we got a little nervous about the rear driveshaft. While it's not the longest shaft in the world (that would be our front shaft) it's just fine and doesn't vibrate at all. We did put a CV on it but that's not that uncommon on a 4x4 with a 6" lift anyways. With the whole shebang in the truck it was time to start working on the mounts. This is going to be the hardest part of the whole job. It will require some welding, cutting and maybe even some bending. If this is out of your league, find a shop that can do it for you.

This is also the time you'll have to modify the transfer case linkage. The easiest way to deal with this is to find the flattest part of the stock linkage and simply cut and weld in 7 1/2" of rod to make up for the added length of the Extreme Underdrive box. For the Klune V unit there are two options. They offer a direct linkage shifter and a cable shifter (see photo). I know that someone, somewhere is going to need to direct linkage but I do like the ease of install of the cable shifter. Just drill a hole in your floor board, find a location for the shifter and bolt it down. We didn't use the stops that come with the shifter because the underdrive will tell you when it's in gear or not. There's very little guess work here but if you have any trouble just pick up the phone and call Klune V for assistance. The support they offer is amazing and is worth almost as much as the underdrive itself. I can't say enough about the help they offered us.

Since this truck will see a ton of abuse at the hands of it's driver we thought a little extra protection would be a good idea. This is slightly overkill but it never hurts to be prepared. The arrow shows the extra foot for the Klune V box. With the kind of force this unit will put on the truck you want to make sure it's bolted in very well. A skid plate was installed after it was all finished to help keep the bottom as slick as possible. You can also see the massive front driveshaft. The thing is so long it made designing the crossmember a nightmare. The leg that crosses under it had to be dropped down to allow full travel. So far so good! It hasn't gotten caught on anything but we'll keep an eye on it just the same. Exhaust was also a bit tricky as there isn't much room under there. Here's where a first rate fabrication shop will come in handy. The guys at R2K Concepts had a solution for everything and it came out great. This isn't something they do for just anyone so we were lucky to get their help.

Here's what it's all about, climbing stuff! We took a quick little trip out to the desert to shake down the truck and play a little. While the soft sand of Ocotillo Wells isn't exactly the perfect location to test the Extreme Underdrive it did show us a few things about the truck. The thing SPANKED Project Powerwagon on this climb. The pick-up was really struggling to get up while the Ramcharger just motored right up with ease. This picture doesn't do it justice. You can't even walk up this hill! Both forwards and back the truck made it look silly. Compression braking is something that most automatic guys don't know much about. With a 122:1 crawl ratio you can't go over 3 MPH if you wanted to. 

Contact Info:

7323 Coldwater Canyon Avenue
N. Hollywood, California 91605


We have a 2.45 first gear in the trans, 4:1 Klune V, 2.72:1 in the T-case and 4.56 axle gears. Multiply that all together and you get a 122:1 crawl ratio. The auto tranny multiplies that number again so you can see that very little is going to stop this truck.  That's the kind of gearing that allows you to tackle the hardest trails in the easiest manner, under control. Whether you drive a GM, Ford, Dodge, Jeep or anything else, Klune V probably makes an adaptor to install their Extreme Underdrive in your 4wd. For you Dodge guys you are already ahead of the game and have few excuses for not installing one of these. Start saving your pennies and give Klune V a call. Just don't tell your buddies about it until you start smokin 'em on the trails. They won't know what hit them!

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