1999 100 Series center diff and rear lock logic?

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Fireman

Fireman

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Iowa Park. TX
After wheeling with a few other 100 Series Cruisers of various years this past weekend in Big Bend, I've come to realize that my center diff and rear locker act differently than some of the others. My center diff lock doesn't come on when I put the truck in low but it does when I push the center diff lock switch in both hi and low. My rear diff light just blinks and doesn't activate ever. I hear no relays clicking or anything. What is the logic built into the system on the 99's when it comes to engaging the center and rear diff locks?
 
Alright I don't know if this is your situation, but I've seen others say it before especially in the 80 forum, and I've got it going on as well: the light never goes solid but the rear locker is for sure engaged. Test it by doing some figure 8's and watch/listen for that tire dragging. Rear locker only works in low range, btw.
 
Yes, in both hi and low. It performs just like it should. I had some wheel spin on a climb in hi, engaged center diff lock and went right up. Worked just like our 80.
 
I've tried that as well, Now just looking for the what the computers do as far as actuating the both and that way I can get a better understanding of what the truck is supposed to be doing so I can correctly diagnose the issue.
 
Sounds like CDL has pin 7 mod applied by previous owner perhaps? LX470 Cabin Air Filter Replacement DIY (auto link has weird title, but the post is pin 7 mod...)

And rear sounds like either truly not engaging because of stuck actuator or bad solenoid as suggested or is engaging but just not triggering the light to go solid...here's a link to a thread with similar problem where it was suggested to look through the 80 section for a possible wiring solution if you can verify wheels are actually locked...

Rear locker won't engage on new to me 98.
 
Rear diff not locking but my center diff doesn't lock up when placed in low unless you physically push the center diff switch unlike the other 98 and 99's on the run this past weekend. They both came on automatically when placed in low range.
 
I should be hearing a relay click but don't on the rear locker. I doubt if the 7 pin mod has been done since it was an elderly female doctor who owned it from new.
 
Fireman said:
Rear diff not locking but my center diff doesn't lock up when placed in low unless you physically push the center diff switch unlike the other 98 and 99's on the run this past weekend. They both came on automatically when placed in low range.
Click to expand...

As
Mentioned in post #7, it sure sounds like the CDL mod has been done. This renders the CDL to be manually operated only. It will no longer engage the CDL automatically when you shift the transfer case into LO Range.
 
I agree that it sounds like it has been done. That's how our 80 is with the mod done. The rear locker has got to have a relay somewhere that should be clicking. I've been under the rig with my wife engaging the rear locker switch with it in low with the center diff locked and hear nothing at the rear diff actuator motor nor up front inside where you normally hear a relay click.
 
I'd be thankful the center diff operates as you say it does, better that way IMO as it allows for more control/select-ability. As for the rear locker, yes you're right about that you should be hearing the click. I hear mine, then after I make some turn maneuvers I can feel it engage. If you're not hearing the click I'd guess it's not locking either. Unfortunately there's not too much rear locker info in this forum, but the good news is that there's plenty in the 80 forum. I'm sure you know that. From what I understand it's very similar.
 
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