Models: 710, Years: ALL

by Jim “Ack” Cambron

INTRODUCTION:
The following document is an abridged version of a blog that I published on the Internet.  It describes in words and photographs how I rebuilt parts of the drivetrain on my 1973 Pinzgauer 710M. Much of the information in this document can also be applied to other versions of the Pinzgauer. Specific items dealt with include the replacement of the old front drive shaft with a better-balanced unit, the replacement of the damaged bushing on the output of the 4x4 locker unit, a rebuild of the 4x4 locker unit, disassembly of the rear differential, installation of the “EXEC II” kit and finally, a rebuild of the rear differential locker unit.

Due to the length this article is on multiple pages.......

I did this rebuild at a trash compactor fabrication business located inside an underground storage facility.  Assisting – no make that mentoring – me was my friend Jack Braton.  Jack, along with a combination of heavy equipment and temperature controlled climate made the task a lot easier to do, epecially during the winter months.  It is not necessary to have such an environment available to do this task.  The most difficult task of the process was figuring out how to support the truck’s body in such a way to work on the drivetrain unobstructed.  Remember, no matter how you solve this problem, do so with safety first and foremost in mind.

Part 1:  Drivetrain Teardown

It is assumed that you have a copy of the Pinzgauer Shop Manual to refer to when reading entries and looking at photographs in this blog. The purpose here is not to re-invent the shop manual but to further illuminate the processes described in it.

Most of the dealers have the shop manual for sale in paper or CD form.

It is imperative to properly support the truck while working under it.

Serious injury or death can occur if you use techniques or materials that cannot safely support the truck while working on it. For example, it was suggested that stacking 2x4 lumber under the truck in a log-house fashion would be an inexpensive way to support the truck.  Dennis Williams of LinDen Engineering does NOT recommend this method.  Always use jack stands designed for the job or build a steel stand using acceptable design and fabrication practices. Don't take shortcuts with your life!

The Truck is supported on beefy jack stands at the rear pipe bumpers.  The front tires are blocked on both sides to prevent the truck from accidentally rolling off the jack stands. Below is a close-up of the jack stands.

As disassembly progressed we used freezer bags to store and organize the parts as they came off the truck. The neat thing about freezer bags is that there is a white square on them where you can write down what is in the bag with a felt-tipped pen.

Suspension Dissassembly
Suspension disassembly was straightforward:

Drain both the rear differential and the transfer case before disassembly. Not doing so makes the rest of the job very messy at certain key points in the process.

Apply industrial-strength (we used something called Zap) penetrating lubricant to all bolts to be removed.

Remove wheel and thread two lug nuts back on to prevent the drums from falling off (yeah, right... the shop manual said to do it so we did).

Using a 19mm socket, remove the lower shock mounting bolt.

Support the end of the axle with a jack just enough to remove the tension from the rebound strap...  Here we ran into a bit of trouble.   As we jacked up under the axle, the bumper would lift off the jack stand on the side we were working before the slack would come out of the rebound strap.  About the only solution was to compress the springs manually, or pile some heavy stuff in the back of the truck. We managed to load down the truck a bit in order to get the springs to compress so that there would be slack in the rebound strap.

Using a 22mm socket, remove the spring support bolts from inside the lower spring cup. Just before we did this, Jack related a horror story about the time he compressed a spring on a Pontiac in order to work on the lower A-arm. Suddenly, the spring whizzed past his left ear and crashed against the wall behind him.  Being very careful, Jack backed the support bolt out. Nothing untowards happened.  Once the bolt was removed, I tugged at the bottom of the spring. It gently fell onto the ground!  Here is a picture of the support bolt in place and a spring cup sitting next to it on the axle.  Note the indentation in the center where the top of the bolt rests in the cup.

Disconnect the cardan shaft from the Auxillary gearbox (Transfer Case).

Before doing this, make sure that the transmission is in neutral so you can easily rotate the shaft while removing the bolts.

There is something interesting about the six bolts and nuts holding the cardan shaft flange to the input flange.  The bolt heads are 13mm and the nuts are 14mm.  This means that you can use the separate 13mm and 14mm wrenches from the toolkit to do this job.

You know that length of wire that you got in the tool kit with your truck? I now know why it is there!  I used it to hang the cardan shaft up so it wouldn't separate. I also used it to hang a lot of other dangling pieces.

By the way, you REALLY don't want the cardan shaft to separate.  If it does separate, you need to find the alignment marks on each piece of the shaft and use them to correctly reassemble the shaft. I learned the hard way about this with the rear drive shaft of my '88 Suzuki Samurai -- the differential end yoke disintegrated from the strain of mis-assembly.

Remove the cover on the "all wheel drive indicator" switch on the driver's side of the truck just forward of the transfer case. There is a plate and spacers there designed to direct heat away from the muffler next to it.  Note that my truck has a non-OEM muffler...

Remove the two wires connected to the switch mechanism and then remove the switch itself from inside the unit. Doing this will prevent the drivetrain assembly from hanging up on this switch and possibly destroying it as you pull the drivetrain away from the tube frame.  The brown wire is the grounding wire and the other wires connect to the “4x4 engaged” lamp in the cab.

Remove the hydraulic acutator assembly to the 4x4 drive and differential lock.

This is a picture of the 4x4 drive actuator unit.  This unit contains the piston that moves the mechanical "guts" that causes 4 wheel drive (or differential locking in the case of the differential output acutator unit) to occur.  Notice there is a pin in the center of the unit.  This pin easily slides out of place and has a small o-ring on it.  The one on the 4x4 drive unit should be removed before the drivetrain is separated from the rest of the truck. 

Above is a picture of the rear locker switch and its cover hung on the right with wire.  This unit had a lot of corrosion on it and the ground wire was broken off. How it actually worked is hard to believe.

This is a picture of the rear differential locker acutator unit. Note that, like the all wheel drive output cylinder, it was removed as a unit instead of simply unbolting the hydraulic line on the end of the unit.  If you unbolt the hydraulic line instead of removing the unit, you'll need to bleed that part of the hydraulic system – something to avoid. So take the time to remove the entire unit with the line connected.

Disconnect the parking brake cable and pull it back to the muffler area though the guide mounted on the crosspiece that connects the truck's body to the drivetrain assembly.

See the horizontal bar next to the exhaust mount with the wire running through it? That's the "angle lever" or brake link arm.  The cable from the parking brake handle in the cab connects to it.  The cable is connected to a u-shaped piece of steel, or yoke, by two nuts that act as a tension adjuster.  The yoke piece is held to the angle lever with a pin and a locking spring that slides into a groove in the pin. Remove the locking spring and push out the pin to disconnect.  Then, use some wire to pull the lever forward off the brake light switch.

In order to completely disconnect the parking brake cable from the drivetrain assembly, you need to knock the nylon guide (pictured above) out of its mount, remove it from the cable (it is split down one side -- simply spread the gap and pull the cable out) and pull the cable forwards from in front of the muffler.

While Jack and I tried to remove the rear body mount and discovered that the whole drivetrain from the transfer case back had to somehow be lowered in order to slide the rear body mount clear of projections on the body itself.  Before doing this, we removed the parking brake switch assembly (two 9mm bolts on the body side of the switch) and the parking brake arm (slide out the snap clip and remove the pivot pin).

We decided to support the entire structure on a heavy-duty truck transmission jack and then remove the four bolt rods that ran from the rear of the differential to the front of the transfer case.

This was a bad idea.

It soon became apparent that those four bolt rods would provide a lot of support and stability to the drivetrain assembly if left where they were.

Using a 3/4" air-powered impact wrench and a 15/16" socket, we gently backed out the side body mounts while carefully lowering the drivetrain assembly with the transmission jack until the rear body mount section cleared the bottom of the body.  This amounted to about 1/2" of space between the body mount and the pads on either side. The parking brake assembly came out next which exposed the drive shaft and the rear locker "witches' cap".

Now we had plenty of room to work with in moving the rest of the drivetrain away from the from the frame tube.

We raised the assembly back up to relieve any strain on the connection between thee frame tube and the transfer case. Then we removed the bolts on the transfer case-to-frame tube joint.  Remember, at this point there was nothing external connected to the drivetrain. All electrical lines were disconnected.  All hydraulic lines were untied from the clamps on the driver's side of the spacer section and differential.  The brake line was detached from the t-block. We had to unscrew the T-block hold-down bolt in order to get a brake line wrench to fit around the nut.  The shifter cable had been removed from the transfer case by removing the capture spring and prying off the ball joint.

We carefully wiggled the assembly until the Transfer case broke away from the tube frame.  Then we carefully backed the assembly away from the tube frame.  During this process, we had to raise the front of the assembly about an inch so that the hydraulic acutator socket for the 4x4 selector would clear the lip of the tube frame. This was easily done because the transmission jack’s support pad was adjustable front-to-back and side-to-side so we could tilt and yaw the transmission with a turn of two adjusting screws on the jack.

As the assembly moved apart, the brake line cleanly separated from the T-block mentioned in the past paragraph.

The front drive shaft hung in position as it separated from the 4x4 locker output shaft.

Once the assembly was clear of the frame tube, we gently lowered it with the transmission jack and moved it sideways out from under the truck.

Remember my warning about draining the differential and transfer case? I forgot to do this and things got real messy at this point.

Pictures of what we found:

The front drive shaft

(note: I wrote "front" with a marking pen on the drive shaft just in case...)

I was expecting a long thin rod as pictured on a website covering the subject of shaft balancing that I viewed recently.

Dennis Williams (LinDen Engineering) pointed out in a post on the Yahoo Pinzgauer group that the shaft I saw is actually inside the tube (one sees the shaft sticking out of the center of each end of the shaft assembly.  The shaft-inside-a-tube design acts to reduce torsion strain on the driveline when a front wheel, or wheels, lose contact with the ground while the drivetrain is under a load. I do not quite understand the concept yet, but I'll accept that it works.

Here is a picture of the splines on the output of the 4x4 locker Witches' hat. These fit into the end of the front drive shaft.

At first I thought that the pictured splines were seriously damaged. This is not the case.  Comparing the pictured splines with a replacement unit, I discovered that the splines are purposely machined down as part of the design. The splines are machined this way to make it easier to assemble the drive shaft connection while installing the transfer case on the end of the chassis tube.

Next to it is all that is left of the bushing that was inside the locker mechanism.

Here is a picture of the face of the locker throwout unit. The bushing is seated inside the depression indicated by the arrow.  The teeth on the coupler look okay.

Here is a picture of the Transfer Case output shaft. The end of the shaft slips over the bushing. The coupler teeth here also look good.

Oddly enough, both the ball bearing at the point of the witches' hat that supports the splined output shaft appears to turn smoothly and firmly. The front output shaft on the transfer case also displays no radial motion.  I took no chances on the reliability of the bearing and replaced them along with the seal anyway.

Next, we broke down the Differential/spacer body/Transfer case assembly into their individual units in search of more wear and damage.

We took care to be sure that, when removing the transfer case, the whole assembly would not overbalance and fall off the truck transmission jack.

We kept the assembly from falling off the jack by moving the assembly forward on the transmission jack.

The only thing holding the transfer case onto the spacer was a long stud in the upper right corner (as viewed from the front output) and an acorn nut on  a shorter stud located on the lower left of the rear face of the transfer case (again, facing the front output of the transfer case). Using the 19mm box wrench from the handy-dandy Pinz toolkit, we broke loose the nut.  Then with a few well-placed and gentle whacks of my deadblow hammer, the transfer case slightly came away from the spacer. I was suprised how light the transfer case was as it smoothly separated from the rest of the assembly.

Then we separated the spacer assembly from the body mount plate/rear differential unit by removing two hex bolts on the left side of the spacer (facing from the front).  A well-applied smack from the deadblow hammer also separated the spacer assembly.

Inside was a short shaft that connected the Transfer case to the differential.

Aside from a bit of blueing at either end of the shaft (which may be there as part of the manufacturing process), it looked fine.  There was no tooth damage on the front of the shaft.

There was no damage on the corresponding output splines of the transfer case.

There was no damage evident on the differential end of the shaft or on the input splines of the differential.

There was no play in the bearings on the transfer case output or the differential case input.  Both the differential shaft and the transfer case shafts turned smoothly.

About the only oddity spotted was about a cup of water sitting in the bottom of the hollow section of the spacer assembly.

We believe that the soapy water got inside the spacer when we power-washed the assembly right after removal. The water entered the spacer block through the bolt hole for the brake line tee block. As dirty as everything looks, learned from this to clean each assembly separately.

Continued, Part 2, Part 3