Center Diff Mod on 100

[Jukelemon]

I know that many have done the mod on the late 80's, but what about the 100? I do not have my FSM yet (I will get that info to you soon Cdan) and was wondering if the circuit is the same for the center diff sending and receiving units. And location of course. I did search but found nothing for my year(99 LC).

Thanks.

Juke

 

[uzj100]

According to the manual it does not have to be done on the 1999 100 series. Another 100 series owner informed me of this and I have still not looked in the owners manual. The CD will lock when low range is selected however you can unlock it with the button. I did the mod (just like the 80) before reading my owners manual so I have to select center diff lock if I select low range. I need to get under there and undo that mod.

Regards,

Andrew

 

[ELLTEE]

Andrew -
My 99 TLC automatically locks the diff when I shift into low range. The CDL button does not come into play.
What did you disconnect to change that? Under the truck, or did you do the "pin 7" mod?

LT

:-\

 

[uzj100]

LT,

Once shifted into low range, you can push the center diff lock button and unlock in low range? Supposedly that is how the 100 works.

I will go check the owners manual.

My mod is under the truck, not the 7 pin mod.

Andrew
Raleigh, NC

 

[uzj100]

LT,

The owners manual did not say much about it. Can you go out and test it in your cruiser? I am interested to know if I need to undo my mod.

Thanks,

Andrew
Raleigh, NC

 

[Jukelemon]

I have tested it before. In Low range, the center diff locks and cannot be unlocked. The center diff button ONLY allows for a switch while in High range. Low range ONLY has the option of Rear Lock. You cannot rear lock in High Range.

I would love to make a mod of allowing for all options i.e. High with center and rear, and Low with center and rear. Anyone?

 

[uzj100]

This mod took me less than 5 minutes. It is about the same as an 80 series mod. The connection is on top of the transfer case. I pulled into ditch, climbed under the truck, unplugged the connector, wrapped both connections in electrical tape and that was that.

Rear diff mod, I think that would have something to do with the connection at the rear diff lock ecu and plugging the connection for the low range connection, so the computer always thinks you are in low range.

Andrew

 

[Jukelemon]

Andrew:

Just so I am with you, you are talking about the mod that aloows you switch the center diff on/off in Low Range right?

 

[ELLTEE]

Andrew -
Juke and I have the same experience.
In low range, the CDL is locked and the dashboard button has no effect. In high range, the button locks and unlocks the CDL (although I often have to reverse about the length of the truck to get it to unlock).


LT

 

[uzj100]

Yes, I am talking about the center diff mod. There is a pigtail on top of the transfer case (near the center of the vehicle) that needs to be disconnected and taped up.

I think there is a write up on the slee site about this mod for the 80 series and it is very similiar for the 100 series.

It is a great mod and cheap too.

Andrew

 

[drewloch]

According to the owners manual of my 2000 LX470, the CDL is fully controlled by the button on the dash:

(b) Shifting procedure
To shift between unlock and lock modes in ”H”, push
the center differential lock button.
To shift between unlock and lock modes in ”L”, push
the center differential lock button.
To shift between ”H” and ”L”, stop the vehicle, put the
transmission into ”N” and move the four–wheel drive
control lever.

”H” (high speed position, center differential unlocked):
Lever at ”H”, center differential lock button left out
Use this for normal driving on all types of roads, from dry
hard–surfaced roads to wet, icy or snow–covered roads.
This position gives greater economy, quietest ride, least
wear and better vehicle control.

”H” (high speed position, center differential locked):
Lever at ”H”, center differential lock button pushed in
Use this for greater traction when you experience a loss
of power, such as wheel slipping, in the center
differential unlock mode.

”L” (low speed position, center differential unlocked):
Lever at ”L”, center differential lock button left out.
Use this for maximum power and traction. Use this for
climbing or descending steep hills, off–road driving, and
hard pulling in sand or mud.
In this mode, the braking feeling that occurs when the
wheels are negotiating a sharp corner is further reduced
than in the “L” (low position, center differential locked)
mode.

“L” (low speed position, center differential locked):
Lever at “L”, center differential lock button pushed in
Use this for maximum power and traction. Use this for
hard pulling in situations the vehicle cannot negotiate
even in the “L” (low speed position, center differential
unlocked) mode. Also, using this mode when driving
down steep off–road inclines will help contribute to
increased vehicle stability.

 

[Jukelemon]

Then either the LX's are different period or the 2000 LC and LX had that option. I wonder if the 2000's had that option due to the fact they lost the rear lock option. But I just checked my manual and it is very different than you manual. I cannot unlock the CD in Low.

 

[Augie]

On 100 series center diff ECU are located on the left side of ECM behind the glove compartment. The wire are the same as 80 series. Its pin #7 black wire with blue stripe. You just need to remove the wire from the connector and tape it.

 

[ELLTEE]

Never having torn into the dash of my 99 TLC, can you point me to a simple step-by-step like the very clear examples on Slee's web site?
I can follow directions, but I have no experience with auto wiring.

LT

 

[Augie]

LT,

Open you glove compartmet. You would see 2 plastic pin that need to be removed to allow you to get access to the ECU. Once you could see the ECU look to the box on the right side of it. The box would say Transmission control unit. Grab behind the connector to get to the locking mechanism. You need to press the lock in before you could remove the connector. Then use a micro scredriver and insert it behind the connector on the black wires with blue stripe. The scrediver would unlock the pin that held the wire in place. Use slightly bigger screwdriver to push the pin out from the front of the connector. Tape the wire and you are done.

 

[ELLTEE]

Augie -
I found my way into the dash behind the glove box.
I assume that very large silver box is the ECU. I can see the Transmission Control box to the right, but it looks like it will take smaller fingers than mine to get in there and unplug the connector. I can't see the top of the TransCont box, so I assume that I'll unplug the connector that's in the bottom of the box?

Thanks for the help! I'm a one mechanic just starting to do some of my own work.

LT
8)