Transfer Case Linkage Upgrade - Write-Up - JeepForum.com
 
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post #1 of 6 Old 06-23-2009, 04:57 PM Thread Starter
lupinsea
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Transfer Case Linkage Upgrade - Write-Up

This is mostly just upgrading the stock shift linkage in in my t-case linkage system since the top link was bent and not working propertly. For all who complain they don't like the spongy feel of the stock shifter, this is a reasonably easy / cheap way of getting a more robust linkage setup and would work as a great compliment to either the Advanced Adapters or Skyjacker t-case shift linkage relocation bracket.



Transfer Case Linkage Upgrade and Write-Up




CONTENTS

1) Vehicle Setup
2) Performance Review
3) Installation Write-Up
4) Additional Resources




1) VEHICLE SETUP

- 2001 Jeep Tj 4.0L Automatic
- 1" Body Lift and 1" Motor Mount Lift
- Low Profile Skid Plate
- Skyjacker T-case Linkage Relocation Bracket

While this Jeep has extensive changes to the stock drive train / frame / body relationship, the concept of the write up is still valid provided measurements are taken off your own rig.




2) PERFORMANCE REVIEW

Difficulty With Transfer Case Shifter:
For many years the the Rube-Goldberg-esque shift linkage for the transfer case shift system has been very problematic on this Jeep and many others. Even before the installation of the Skyjacker relocation bracket the stock upper shift rod was bent for some reason. For years when ever the shift linkage was removed the rod would be re-straightened and reinstalled only to have it re-bend again in short order. Then, with all the removal and reinstalls of the linkage the plastic bushing in the 4WD shift lever finally wore out to the point that the linkage would pop out on it's own quite easily. This, coupled with a fussy adjustment block, yielded spongy, vague shifting, difficulty getting into 4WD, misaligned stop gates in the shifter, and difficulty accurately adjusting everything.

Solution:
The solution to this was to finally fix the upper shift linkage. A new shift linkage was built using quality spherical rod ends and a threaded rod. This required modification to the shift linkage system to accept the new rod ends which involved some welding and steel fabrication and re-using the factory 4WD shift lever.

Performance:
The new linkage has breathed new life into 4WD shift linkage system. By eliminating the old, bent rod and half the plastic bushings in the linkage system the shift feel is vastly improved. No more misaligned stops in the shift gate, no more spongy, vague shift feel. Now a simple pull on the lever results in a crisp, satisfyingly notchy, mechanical feel as the shift lever snaps with authority into each mode with the transfer case's range selector. And with proper jamb nuts and rod ends the linkage stays adjusted to it's proper length.

Cost:
Total cost for all the parts was approximately $25. This included rod-ends, all-thread rod, some regular nuts, some nyloc nuts, a few washers and a couple bolts.

Bottom Line:
If your shift linkage is working just fine then leave it be. But if you're having difficulty shifting, keeping the linkage in adjustment, or have bent or damaged linkage components then consider this modification as it greatly improves shift feel and accuracy with higher quality components that are stronger than stock.




3) INSTALLATION WRITE-UP

Gaining access to the linkage is not terribly difficult, nor time consuming, but there are several layers of the Jeep that need to be peeled back to access everything. More difficult is the welding that needs to be done for those without the skills or access to equipment. And careful measurement and calculation of the linkage length is needed.

Remove Shift Linkage System:
Shift the transmission into neutral and shift the 4WD lever into 4-Lo. Support the transmission and driveline. Remove the skid plate. The linkage system was originally snapped into place with barbed metal end tips so everything can be popped out for service. Using a screw driver or other implement, pry the adjusting block on the upper linkage out of the plastic bushings in the end of the 4WD shift lever. To preserve the life of any other plastic bushings, remove the whole linkage system by next unbolting the range shift lever from the side of the transfer case. Finally, remove the cross shaft. In stock applications this mounts to the transfer case one side and the body tub on the other.

Remove Center Console:
With transmission shifted to neutral and 4WD lever in the 4-Lo position, pull off the automatic's shifter handle. Just pull straight up to pop it off the detents. Do not twist, pull straight up. Pop out the shift lever bezel on the top of the console after feeling which side is easier to pry up. Disconnect the light bulb from the bottom of this bezel. Then feel under the forward edge of the bezel opening for the release tabs for the air bag on/off switch panel. Pop out the on/off switch panel an disconnect the wiring harness plug. Pull out the rubber cup holder trim, it should lift right out for full-console setups. For mini or half consoles you might need to take out the bottom rubber disk. Locate and remove the two 10mm screws holding the console in place (Fig 1) and remove console.



Fig 1. Removing the center console takes about 5 minutes


Remove 4WD Shift Lever:
Pry up the wiring harness from the side of the shifter bracket. Locate and remove the five 8mm screws holding the shift lever in place (Fig 2). Remove (Fig 3).



Fig 2. Removing the actual 4WD shift lever



Fig 3. Bent linkage and bushing failure



Modifying 4WD Shift Lever:
With a hack saw or other blade cut off the protruding tapered side of the plastic bushing on the end of the 4WD shift lever. The rest of the bushing should pop out revealing a depressed lip around the mounting hole. Grind down to bare metal and weld on a pair of washers on either side of the hole to tighten up the tolerance for your rod-end fasteners. Grind down welds flush with the surface of the washers (Fig 4).



Fig 4. Modifying the stock 4WD shift lever with some washers and a welder


Modifying Cross Shaft:
For this particular set up I used two different rod ends, one was a eye-type rod end that would accept a bolt and tucked tighter to a flat surface and the other had a built-in threaded stud off one side of the spherical bearing with a greater offset. Both rod-ends used a carbon fiber bearing race liner. This arrangement worked well with the factory off-sets, though I could have used two studded rod ends, too.

A new lever arm was fabricated out of 1/4" x 1" steel flat stock by first drilling a hole sized to the rod-end fastener. Then careful measurements were made to determine how far off the cross shaft the stock hole was located. This distance was marked on the steel flat stock, about an extra 1/8" was added and the steel cut to length. With a grinder a radius was ground into the end of the new lever arm to match the curvature of the cross shaft. A few test fits and the proper distance was established. The new lever was rotated approximately 1/4" - 1/2" "backward" on the cross shaft. This gives better leverage for shifting in to 4Lo and gave the bulky rod-end more clearance so it wouldn't hit the cross shaft at it's maximum extent (fully shifted forward into 4-Lo). Rotating the lever backwards is fine but the length of the hole-to-cross shaft needs to be the same as the stock arm to maintain any shift ratios (Fig 5). The lever was also located along the length of the cross shaft such that it provided as close to stock (or straight) connection to the 4WD shifter lever after taking into account any fastener offsets. With the location and position noted, the new lever was tack welded into place. The old lever was then cut off and the shoulder ground down and cleaned up for better rod-end clearance. (Fig 6).



Fig 5. Welding new lever arm onto cross shaft, position
optimized for better rod-end clearance



Fig 6. Modified cross shaft with new lever arm
welded on and old arm ground off.


Reinstall and Measure:
Re-install the 4WD shift lever and the console in the reverse order they were removed. Likewise, reinstall the shift linkage and hook it back up on the transfer case (minus the top linkage, of course). Make sure the transfer case range lever is in the 4-Lo position and make sure the 4WD shift lever is in the 4-Lo position, too. These are the Factory Service Manual's recommended adjustment positions.

To measure the linkage length needed, loop a piece of string through the hole in the new lever on the cross-shaft and the hole in the end of the 4WD shift lever, pull taut. Using a fine felt tip pen or pencil, mark the near-edge of the holes on the string. Remove the string and measure the distance between the two marks. Add the diameter of one of the holes to this distance to get the center eye-to-eye measurement for your total linkage length. For example: my measured distance on the string was 7 1/4". To this I added 3/8" for my hole diameter to arrive at a 7 5/8" total center-to-center length. All applications are different so do your own measurements.

Linkage Length Calculation:
At this point there is some math calculations to work backward from the total needed rod length to determine how long you need to cut the all-thread rod. Refer to Fig 7 as I use my measurement for an example here.

Measure the center of your rod end (the eye or stud) to the end of the rod end body (1 9/16"). Do this for each rod end and write this down (I diagram everything so it's easier for me to follow).

Next thread on a jamb nut and fit the all-thread into a rod end until it bottoms out in the rod-end body. Snug the jamb nut to the rod end body and then remove the all-thread. This will show you how deep you can screw in the all-thread, measure this distance and note it (7/8").

Typically, you need to leave at least as much threaded rod in the rod body as the diameter of the rod (3/8" dia. all-thread). So subtract the diameter of the all-thread from the depth of the threads in the rod end body you just measured. This is your adjustment range for each rod end (7/8" - 3/8" = 1/2" adjustment range).

For adjustment sake, we want to be in the middle of this range. So, take half this remaining distance (1/2" divided by 2 = 1/4") and add it to the diameter of the all-thread you're working with (3/8"). This is how far in the all-thread should be from end of the rod-end body (1/4" + 3/8" = 5/8"). This is your initial engagement distance for each rod end.

Subtract the length of both rod ends (center of eye to end of body) from your total linkage length (7 5/8" linkage - (2 x 1 9/16") = 4 1/2"), then add both engagement distances to this number (4 1/2" + (2 x 5/8") = 5 3/4"). This should be the length of all-thread you need to cut. Whew.



Fig 7. Calculations for new length of top shift rod.


Assembly, Installation, and Fine Tuning:
Thread on the jamb nuts to the proper depth, then thread the rod-ends onto the all-thread for your new linkage (Fig 8). Leave it a bit loose and install the linkage between the cross-shaft and 4WD shift lever. If it's a tad short or long make the necessary adjustments and tighten down the jamb nuts. Then bolt the linkage into place (Fig 9) using nyloc nuts and test out the 4WD shift lever making sure everything works properly. Use any washers for fine tuning the spacing between a rod-end and the lever arms they connect to to allow the rod-end body free movement.

Reinstall the skid plate and do one final test shift and you're good to go.



Fig 8. New shift linkage (top) vs. old bent linkage (bottom)



Fig 9. New linkage installed on Jeep





4) ADDITIONAL RESOURCES

Rod ends can be sourced from:
McMaster-Carr
Grainger
or local specialty fastener suppliers

Make sure you get matching all-thread and nuts/jamb nuts.






.


- Jay
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post #2 of 6 Old 06-23-2009, 05:03 PM
vtjeepguy97
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seeing that my TC bar bent just recently, this thread is perfectly timed.
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post #3 of 6 Old 06-23-2009, 05:06 PM
ecdriver
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Nice write up & pics, something else to add to the "to do" list!
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post #4 of 6 Old 06-23-2009, 05:24 PM
Humboldt
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Neat. For 125$ novak did all the prep work for me. Easily less than a half day of my time tinkering. YMMV. Good job.
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post #5 of 6 Old 06-23-2009, 06:21 PM Thread Starter
lupinsea
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Quote:
Originally Posted by Humboldt View Post
Neat. For 125$ novak did all the prep work for me. Easily less than a half day of my time tinkering. YMMV. Good job.
About the same time I've spent on this but it only cost me $25 instead of $125.

- Jay
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post #6 of 6 Old 06-23-2009, 06:23 PM
Jeepguy1977
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I went the Novak route and it still didn't solve my kickout issue so, I think I need to start looking around inside.

1998 TJ, 4.0L Auto and various junk
Rolled Red Jeep Club Member #7
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