Transfer Case Interlock

Won't run? Engine, cooling system, fuel pump, carb, clutch, tranny, brakes, etc. The old messages from the NPCA 'Engine & Mechanical' category are here.

Postby Esteban » Sun Mar 15, 2015 9:29 pm

The Patrol transfer case, as many others with 2 levers for low/high and 4WD, have an interlock mechanism that prevents shifting into low gear without first engaging the 4WD.

Years ago I decided with my brother, to get rid of this mechanism, and allow low gearing in dry surface conditions. After reading the posting about the PeerlessPatrol- FourWheeler Magazine Dec 1992 where the owner removed the interlocking mechanism, I thought that I had posted before. It was probably at the other forum, since the pictures are still in the Photobucket hosting site.

Please refer to the following picture from the parts manual, at the front of the transfer case, showing the levers among other things. There are four steel balls that act as detents for the levers' position. Also refer to the cross section that follows. Under plug marked with #78, there is a spring and a ball #73 (in red) There are two plugs #78, one for L/H and the other for the 4WD. They are the same red balls in the cross section below. Also present are two additional balls #73 that are located in a horizontal hole with the plug #74 in the parts diagram. These are the green balls in the cross section. The blue circles correspond to the rods that move the forks of L/H or 2WD/4WD.

Unless the 2WD/4WD lever is engaged into the 4WD position, the green balls will prevent moving the lever for L/H. The simple process of removing the interlock mechanism is to dismantle the front of the transfer case and get rid of the green balls. Like you forget to put them back :twisted: :twisted:
The rod for the 2WD/4WD will have to come out at least, to allow removing of the green balls.

Transfer Case Interlock.jpg
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Postby LKR » Tue Oct 23, 2018 7:32 pm

Great info thanks for posting!
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Postby plateaucal » Mon Jul 27, 2020 8:20 pm

It seems that maybe a simpler solution is in order. Perhaps a set of locking/unlocking hubs would solve this problem. Works for me.
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Postby Esteban » Mon Jul 27, 2020 9:33 pm

plateaucal wrote:It seems that maybe a simpler solution is in order. Perhaps a set of locking/unlocking hubs would solve this problem. Works for me.


It depends. For one, there’s the challenge of modifying a design that doesn’t make any sense. Why do you have to engage the 4wd first in order to shift into low gear the transfer case? I guess that everyone was doing that, so everyone followed the trend. Some will say, to protect the rear axles due to the added torque (I say, leave the driver the decision)

The other reason for me, was my driving style way back when I was still in Ecuador and my Patrol was my daily driver. Twisty roads and hilly conditions that when wet were very slippery. Suddenly you are beginning to loose control, but engaging the 4wd “on the fly” gets you out of trouble easily. Not feasible with locking hubs disengaged! :twisted: I’m talking paved roads, not dirt ones.

Also, when towing a trailer at close to 10,000 feet of altitude you loose lots of power. 3rd gear and low range becomes an intermediate ratio between 1st and 2nd in high gear. If that’s the ratio you need, my modification works like a charm. Again, not feasible with locking hubs.

And I will add, in every old time 4wd you’re able to shift on the fly no matter what speed you’re going provided you have the locking hubs engaged, though.
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Postby plateaucal » Mon Jul 27, 2020 10:45 pm

Good point Esteban...true words from a true hardcore. I just remember running in 2wd-low at the Lake City parade so that I did not have to use the clutch so much. But let me tell you...it was intense with all of those kids rushing up to the car.
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Postby G60michael » Tue Jul 28, 2020 5:04 am

Awesome Post Esteban, I regularly speak to customers at the workshop how there clutch always stinks when there backing around trailers etc. and they don't know why, My best advice to them is that anywhere that you may need to haul a heavy trailer and get moving on an unsealed surface, rather then riding the clutch and prematurly wearing out bits, slip it into Low range and let the car do the work easily.

Also I Have never had them balls out, I've had the vertical detents out in the past but no the horizonal interlock balls.

I see it working the same, but just thought its worthy of noting incase you didn't know that from around 1975 in Australia (not sure of other countries) the 2wd/4wd Detent was changed away from a Ball that would lock and locate into the shift rod to hold into that position, to a Detent similar to that if you were to pull apart a Taper Roller Bearing apart and keep the roller (A rectangle Cylindrical shape) with no locking groves in the shift rod, the locking mechanism was located at the base of the gearstick's.

I have some photos of these minor changes in the detents, as said they would still work the same as the earlier type would but I have some photos i can dig up and post if you'd like.

cheers Mike
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