4405 stuck in 4wd

[dynamite196]

Here's the scenario, 97 explorer sport with control trac. Already had the TC replaced with a jasper unit by the previous owner approx 3 years ago. What i'm currently facing is a rather odd problem with the 4wd system. The truck is constantly in 4hi and as a result there is lots of driveshaft binding and clunking when I turn. I've been unable to solve the problem and decided to pull the front drive shaft out. The interesting thing about the problem is that it will shift into 4lo if i flip the switch right after the car is started. It will shift between hi and low just fine until i go above 35mph which is when i get the 4hi/low lights blinking. I've done lots of research but I haven't been able to come up with much. I tried testing the relays under the steering wheel but they all checked out okay. I also cleaned the speed sensors to no avail. I'm completely lost on this one. I dont even know if it's a mechanical or electrical issue. Any help would be greatly appreciated. Things would probably be a lot easier if I had the proper scan tool but I havent been able to find which one or where to get one either. Like I said, I'm completely lost on this one so any help would be great.

 

[gijoecam]

Before pulling the driveshaft, do this simple test: Unplug the electrical connector to the transfer case and take it for a drive. If the binding disappears, we have an electrical gremlin to chase down. If the binding persists with the electronics disconnected, then you have a mechanical problem with your t-case.

Start there and let us know what you find.

-Joe

 

[dynamite196]

Here is the latest: when I unplug the connector everything works fine, no binding. What I discovered was the binding happens only between when i first start the car and before i hit 35 mph. Interestingly, the 4wd hi and low also works when I first start the car. Once I hit 35 mph the 4wd disengages and I can't get it to switch between hi and low modes and after a couple minutes the 4hi and 4low lights start flashing (6 flashes every 2 min). So to summarize, the 4wd works but binds when I first start the car and after I hit 35 mph I get flashing lights and no more 4wd.

 

[IZwack]

You're not supposed to switch between 4HI and 4LO if your vehicle is moving -- it should be at a dead stop. I'm not sure if the computer would even let you but if it did try to switch from 4HI to 4LO while the vehicle is in motion, the transfer case would probably shatter as the casiing is a lot weaker than its gears.

 

[gijoecam]

You do not need a new transfer case. You have an electrical problem. The system is (incorrectly) actuating the 4 wheel drive when it shouldn't be. The blinking lights are an indication that the system has detected a problem. Odds are it's a bad speed sensor on the t-case, but without an NGS tester to scan the GEM codes, it's a guessing game at best. My suggestion would be to find an independent shop with an NGS tester and pay them to scan the GEM DTCs and PIDs to see what's causing the system to fail. That could save you from throwing money at it blindly.

Good luck!

 

[dynamite196]

Sorry if I was unclear about shifting between hi and low, I know the vehicle must be stopped and in neutral in order to shift between the two. I think you're right that it won't even let you shift between the two if it is moving. Is there any other way of testing the sensors, i.e resistance?

 

[dynamite196]

Took it to a shop today to get the codes scanned and the mechanic came up with a P1837 (bad rear output speed sensor), replaced the sensor and everything is fine. Thanks for the help guys.

 

[gijoecam]

Much better outcome than a replacement t-case, huh?

I rarely trust mechanics anymore... Unless they can explain to me what failed and WHY they think that failed, it doesn't get fixed. The first shop that told you that you needed a new case should have explained what led them to that diagnosis. They clearly didn't.

Glad she's back up and running!

 

[dynamite196]

I dont trust mechanics either thats why i do all my own work. Nobody actually said i needed a new tcase, i was stating that the previous owner had replaced the tcase not too long ago. In this case i only took it to a shop because i needed the codes pulled and didnt wanna spend 700+ on the tester. Im fairly confident that they cant screw anything up pulling codes although i might be surprised one day lol. She's running like a champ again