98-99 Rear Diff lock in High Range (1 Viewer)

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Nov 5, 2005
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Napa, California
Having a rear locking diff that only worked in low range bothered me. I figured that the 7 pin modification could work on the CDL, so why can't we bypass the rear? So a little time in the service manual, and this is what I came up with. Fiddling around for about 1-1/2 hours, locating a nice hidden route for the wire, and cutting the plate for the switch, and one trip to the hardware store for about $7 gave me this setup.
The rear locker is controlled by the "4WD control unit" which is located on the firewall behind the blower motor.
diffwire003lr7bj.jpg

Unclip it frm the bracket & pull it down with the harness.
diffwire004lr3mz.jpg

Locate the black with blue tracer wire in the #7 location (figure that one) and install a Scotch-lock or splice connector.
diffwire005lr5md.jpg

diffwire007lr6nw.jpg

By putting 12v to this, your giving a false signal that it's in low range, and the rear will lock with the switch. Being locked in high could be useful in the snow and mud without having TRACS, and a little less torque than low range.
Next I purchased a simple rocker switch and ran a 16 gauge wire from the splice to the dash switch area.
diffwire006lr4mu.jpg

I then ran wire from the fuse area to the rocker switch from a 12v source. By leaving the switch off the rear locker remains stock. Turn the switch on to use in high range. The ABS lamp will come on signaling that the ABS is off in low range. I was lucky enough to find a decent size rocker that fit ok with a little cutting.
diffwire08lr2ab.jpg

I just thought some of you might want to utilize that E-locker a little more. And with the 7-pin CDL mod, the rear will work independently on it's own.
 

spressomon

glutton
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I did have some that asked why I would want to use the rear locker in Hi...if you are traveling on a muddy road it really helps to keep speed up and rear locked. A/B'd it 10-days ago in this exact situation and locked in H definitely provided better traction and overall control on a long, flat muddy stretch of trail compared to non-locked or locked in L.
 
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Napa, California
:doh:
Guess I should search more before losing myself in the service manual.:D
Oh well, it works, and now I can....:beer:
 
Joined
Nov 16, 2003
Messages
534
That mod works realy well on slippery stuff. Its like poor man traction control. Well the principle of traction control is by reducing power to the wheel anyway.

Samol also found a way to disable the ABS in low range without engaging rear diff lock after doing 7th pin mod also.
 
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Raleigh, NC
I am asking more old questions. The basic concept on the rear diff in high range is running a jumper from the black with blue wire to a blue with black wire. I am not concerned with turning the mod on and off.

Is this correct?

Thanks,

uzj100
 
Joined
Nov 5, 2005
Messages
662
Location
Napa, California
uzj100 said:
I am asking more old questions. The basic concept on the rear diff in high range is running a jumper from the black with blue wire to a blue with black wire. I am not concerned with turning the mod on and off.

Is this correct?

Thanks,

uzj100

No! You should be running 12 volts to the black with blue tracer through a switch. You need to switch it or the ECU sees the "low range" signal and then locks out overdrive through the transmission control unit. This modification is simply sending a false 12V signal instead of the low range switch on the transfer case. The last picture shows the rocker switch I installed to supply voltage. I found a 12V source off the fuse block.
 

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