1993 Volkswagen LT 4x4 - Project Volksmogen 4x4

Part one - this page - why Unimog Axles ?
Part two - hasn't this been done before? - the Noriker
Part three - steering setup
Part four - converting from coil springs to leaf springs
Part five - installation of drive shafts
Part six - installation of an air compressor for differential locks and water fording
Part seven - brake setup
Part eight - conclusion

Why Unimog Axles

In the spring of 2008 my front ring and pinion started to make some noise on my LT 4x4 and I discovered how expensive it will be to repair, I decided to go big or go home.  Considering how much money I have into my LT at this moment with the initial purchase, transportation from Germany, new injector pump, rebuilt transfer case, etc etc etc, it's gonna have to be a keeper for now.

LT ring and pinion is about 1200 EUR which is about 1800 CAD and by the time I get that installed the bill will be in the $3500 range.  Unimog 406 axles, a pair of them, with some careful searching cost about the same amount.  The benefits of using Unimog axles are many.  Parts are available in North America, larger brakes if you go with the disc brake version and most of all 14cm / 5.5" more ground clearance due to portal gearing in the ends of the axles with the ability to keep my existing wheels.

After a lot of research I decided not to go with the common 404 Unimog axles.  Few reasons for this:

  • They are narrower than the LT axles
  • Drum brakes on all four corners
  • Long pinion housing
  • 7.56:1 final drive

The less common and more expensive 406 / 416 axles are a lot better

  • Same width as the LT axles
  • Disc brakes on all four corners with two calipers per disc up front
  • Relatively short pinion housing
  • 6.52:1 final drive

The LT 4x4 has a 5.38:1 final drive and my 285/65R20 tires give me a 3250 100 km/h rpm which is about perfect for the output of the engine and noise level of the cab.  Unimog axles will bring the final drive to 6.52:1 which is quite tall - good thing that Ted from Granville's Coffee in Quesnel gave me a set of 12.5R20 (335/85R20) tires from his Unimog 406 which he upgraded to 14.5R20.  These 104.1cm / 41" tall tires will give me 3310 rpm which is pretty much spot on!  With the 14cm of additional ground clearance the port hole gearing gives me I will be able to run 14.5R20s if I wanted to.... hmmm....

One of the big issues with Unimog axles is that they don't use a conventional drive shaft like just about every other vehicle out there.  Instead they use a torque tube.

Torque Tube
Torque tube on a Unimog 1300L

Essentially the Unimog drive shaft is encased in a hollow tube that acts as part of the suspension with the front having a constant velocity joint as opposed to a universal joint.  To make these axles work on a conventional 4WD system like the LT 4x4 the torque tube needs to be cut down and the internal drive shaft must be shorted and have a flange attached to it.  At the end of the cut down torque tube a bearing and oil seal is installed. 

Pinion Conversion
Unimog axle with a pinion conversion

The search for Unimog axles had a turn for the worse...
Rusty 406 ring and pinion

I got a "good deal" on some 406 axles from Vermont - problem was they were sitting for seven years and both axles were full water... lots of water... thousands of dollars and a few months later I found another set in Germany... they wern't the best, but the worked, seals leaked gear oil but the truck is drivable with the exception of some vibrations in the rear drive shaft.  As of January 2009 I am redesigning the rear drive shaft to use Porsche 930 CVs instead of Spicer Universals.  Seals will be repaired after this.

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