Ways to get power both front and rear


BW 1339 The original "QuadraTrac"

When I first bought the Wagoneer back in 1990, it had the QT without the low-range unit. I used it for a year with 33" tires and the 3.07 R&P before it proved it's limitations in the terrain. It did this at the same time it destroyed my torque converter and left me stranded in the mud.

Quick Spec.

MileMarker Part-Time Kit
2.56:1 Low Range
Custom Air-Shifted 4wd
later converted into
Manual-Shifted 4wd

Something had to be done so I began the search for a low-range unit for my QT. I found this at a wrecker in Sweden and as soon as we agreed on the price I had a low-range unit. I also bought a MileMarker part-time kit before the rebuild.

At this time I did not have a garage that was big enough for the Wag, so seeking help from a friend we used a class room at the school were he was employed. Of course we had to be finished during a weekend so a 48 hour wrenching marathon was set. Because the last event without low-range burned and destroyed my converter I had to rebuild the TH400 at the same time and this made the weekend a very short one:-)

Inside the Case


Installing the MileMarker part-time kit can be done without removing the front half of the QT, but as I was going to overhaul the TH400 at the same time I removed both the tranny and the transfer as one unit. This is a very easy operation except for the weight of the combo. Using a engine hoist through the floor together with a big shop lift underneath we managed to get the package out of the Wag without damage or injury. With the TH400 and the QT on the workbench we could begin the install.

Installing the part-time kit with the aid of MileMarker's very good instruction manual was straightforward. A couple of things I've learned the hard way is that without modifying the QT and the coupler inside the new hub that MileMarker supplies there's very little spline engagement in 4wd. In stock form the 4wd control light will go on at the very beginning of spline engagement, so if there is something wrong with the vacuum actuator (a very common fault) the coupler splines can be engaged as little as 1/8". This maybe fine until 4wd are needed, then the splines WILL be ruined. Luckily enough, the coupler are softer than the shaft so it's the cheap part that will be in need of replacement.

MileMarker Coupler


The splines on the coupler are chamfered so I first took the coupler and welded extension to the splines. I then reformed the outer ends of the splines but with very little chamfer. This will make the QT a little more difficult to get into 4wd but the added strength are worth the hassle. The shifter fork was modified for more engagement by removing a little of the front extension and putting a spacer between the rear of the fork and the lock-ring. Together with this modification I grinded a little of the front of the QT were the shifter fork meets the case. These two modifications will let the shifter fork move further so the splines will engage more. When doing this modifications to the shifterfork it is very important not no grind to much. Grinding too much will result in the shifter fork not being able to move far enough to the rear to dis-engage 4wd. I also modified the 4wd control light switch so that the light will stay off until the fork is moved all the way forward.

Different Ways of Shifting


I never liked the vacuum actuator on the QT so I sat down thinking on other (and better) ways of solving the shift setup. Because I had an on board air supply I though this could be the solution. First I had to customize the actuator to work with an air-piston. I cut the rod from the vacuum clock and then welded a bent piece of metal on to it so that I could stick the piston rod through it and fasten it with a nut. Then I made a bracket for the air-piston using the bolts on the inspection cover on top of the shifter assembly to hold the air-piston to the QT. This way, when air was applied on one end of the piston it would move the shifter rod forward and select 4wd, applying air on the other end would select 2wd (or full-time if the case is not converted into part-time).

Then I had to make some selectors for the air into the piston. First I split the air supply after the pressure switch and inserted a regulator taking the pressure down to 3 psi. Then this air goes through two manual air-switches which routes the air either to the rear of the piston or to the front. This setup proved to be very much better than the original vacuum setup because it gives a very positive shift and really holds the t-case in whatever mode I select. Gone where the mushiness of the selector due to low vacuum.

low range shifter

I have later converted the shifter into a full manual shifter using a morse cable. This was not done because the air-shifter setup wasn't good enough, but I plan to use the QT in the J20 I intend to build as my daily driver instead. This truck does not have any air-supply so I needed another way to shift the QT and I did not want to go back to the stupid vacuum design.. However, the QT still sits in my Wag and as long I haven't decided what transfer case to use in the Wag it will probably stay in the Wag another year.


If you click on the picture on the left you can see some pictures of the various modifications I did to my transfer case shifter mechanism

Questions ?

Here are some rough drawings off the various shifter setup, they may be helpfull

Download drawings for the airshifter HIT ME TO DOWNLOAD
Download drawings for the Mechanical shifter HIT ME TO DOWNLOAD


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