Another 4lo thread

[mudpie]

I've done a bunch of searching and came up with some questionable results that generally end with someone shifting into N to fix their problem.

I have an '02 that won't go into 4lo. It goes into 4h, and the 4wd clearly works, but when I hit the 4lo button, the button flashes maybe 10 times and then nothing happens. No low range, and no light on the dash (I assume there's a light on the dash that should come on). I've got it in neutral, foot on the brake. For what it's worth, it's a manual trans.

I pulled the transfer case actuator for no particular reason, just to check the wires and connections, and everything looked clean and solid. Beyond that, I'm kind of lost. So here's my questions....

Can I assume that the actuator is good if it goes into 4h? I would think if the actuator is bad, it wouldn't do anything.

I've seen posts about the 4wd control module. That's the module behind the glove box, right? I poked around with that about a year ago and tried to swap in one from an automatic. All the warning lights on the dash lit up and my speedo didn't work. Clearly they don't swap. Is there a way to test it? The module for the manual is no longer available. How often do these really go bad compared to other causes?

The manual says if the 4lo switch is flashing, that means the vehicle is waiting for driver input, like shifting into neutral. Previous owner told me he put a clutch in it. I'm thinking maybe the sensor that detects if it's in neutral may be damaged or something, but if that were the case wouldn't that affect starting somehow? The truck won't start in gear, so I assume that switch is working.

I'm lost. Any thoughts on what I should check would be appreciated.

 

[RangerX]

Try it with the clutch pushed in.

 

[mudpie]

Try it with the clutch pushed in.

I've tried it with clutch in and clutch out, with shifter in neutral and foot on the brake. Nothing.

 

[RangerX]

here’s a troubleshooting thread for first Gens, maybe there’s enough similarity to your year that it could help you.
How to: - 4x4 Troubleshooting guide

 

[mudpie]

I appreciate the link, and I'll go through it, but I'm looking up the control module on RockAuto and they list it as a 2002 part only. I don't know how similar the systems are going to be from first to third gen. And I really don't want to buy a $160 part just to see if that's the problem. I'm not a fan of the "throw money at it" approach.

The way I figure it, there's only 5 possibilities. First, the transfer case shift motor could be bad. I eliminated that as a possibility because the truck shifts into 4hi, no problem, and I figured if it was bad I wouldn't get that. However, I read somewhere online that the transfer case doesn't actually shift anything to go into 4hi, it simply engages the front through some kind of magnetic actuator engaging what is already basically a full time 4wd system. Any input on that process would be appreciated. I'm not really a "Ford guy", just a guy who happens to own a Ford.

Second, I'm thinking maybe an issue with the transfer case itself. I'm going to pull the shift motor off today and see if I can manually turn it to 4lo, and see what kind of resistance I get on the shaft.

Third, the TCM. I don't know how to determine if that's bad without just replacing it and seeing what happens. Last resort kinda thing.

Fourth, the brake sensor. I assume the TCM wants to see a signal from the brake sensor, telling it that I've got the brake on. If that's bad, I'd get no 4lo, but I presume I'd also have no brake lights. I've got brake lights, so I assume that switch is good.

Fifth, I assume there's a neutral sensor of some sort that signals the TCM, and also tells the ECM not to start the truck if it's in gear. Presumably there's a clutch pedal bypass of some sort so I could start the truck in gear with the clutch depressed. The truck starts and / or doesn't start properly in terms of in gear vs. not in gear, so I assume all those switches are working as they should.

Obviously I'm going to check all those switches, but if anybody has any idea on something I've overlooked, any input is appreciated.

 

[mudpie]

I generally like posting as much detail as possible, like I did above, for the sake of anybody searching in the future. I hate when I find a thread discussing the same problem I'm having, and it just ends with no comment on what they did, and whether or not it fixed the problem. Anyway, with that in mind, I wanted to post up this video I found. This looks promising. I find it entirely likely that a 20+ year old plastic bushing could be my problem (skip to 11:15).

I'm going to pull the shift motor and see what's inside.

 

[J_C]

I appreciate the link, and I'll go through it, but I'm looking up the control module on RockAuto and they list it as a 2002 part only. I don't know how similar the systems are going to be from first to third gen. And I really don't want to buy a $160 part just to see if that's the problem. I'm not a fan of the "throw money at it" approach.

The way I figure it, there's only 5 possibilities. First, the transfer case shift motor could be bad. I eliminated that as a possibility because the truck shifts into 4hi, no problem, and I figured if it was bad I wouldn't get that. However, I read somewhere online that the transfer case doesn't actually shift anything to go into 4hi, it simply engages the front through some kind of magnetic actuator engaging what is already basically a full time 4wd system. Any input on that process would be appreciated.

Yes, the shift motor just shifts the drivetrain axle to engine RPM ratio and has no effect on the front wheels getting power. They get power from an electromagnetic clutch, which when it is in Auto, senses the transfer case shaft speeds to determine if there is wheel slippage, and gives incrementally longer pulses to the clutch to energize the front wheels as needed till slippage is gone.

In 4WD mode, instead of pulses, it full time engages the clutch by continuously applying power to it.

Second, I'm thinking maybe an issue with the transfer case itself. I'm going to pull the shift motor off today and see if I can manually turn it to 4lo, and see what kind of resistance I get on the shaft.

You can pull the shift motor and apply 12V to it, then reverse the polarity to shift it the other direction. I don't know how many amps it needs but probably a fair amount of current to get the job done. You can get an equivalently sized screwdriver and stick it into the transfer case, to manually put it into high or low gear. Remember if you do either of these things, to return both to the same position before trying to bolt the shift motor back on.

Third, the TCM. I don't know how to determine if that's bad without just replacing it and seeing what happens. Last resort kinda thing.

When you switch it to low, or out of low into high, you should be measuring 12V on the respective wiring connector wires to the shift motor. If you have power to it, then it's the motor or transfer case. If you don't, it's something electrical upstream of those.

Fourth, the brake sensor. I assume the TCM wants to see a signal from the brake sensor, telling it that I've got the brake on. If that's bad, I'd get no 4lo, but I presume I'd also have no brake lights. I've got brake lights, so I assume that switch is good.

Fifth, I assume there's a neutral sensor of some sort that signals the TCM, and also tells the ECM not to start the truck if it's in gear. Presumably there's a clutch pedal bypass of some sort so I could start the truck in gear with the clutch depressed. The truck starts and / or doesn't start properly in terms of in gear vs. not in gear, so I assume all those switches are working as they should.

Obviously I'm going to check all those switches, but if anybody has any idea on something I've overlooked, any input is appreciated.

I agree that the clutch or brake switch could be issues. I'd first see if 12V is getting to the shift motor when selecting high vs low, to see if it's electrical before, or electrical or mechanical after that point.

 

[mudpie]

I pulled the shift motor and took it apart. It's different than the shift motor in the video I posted above. I seem to recall reading in another thread (or maybe a video description) that the shift motor was redesigned in later years. My truck was built in early 02 (Jan? Feb?) so I assume the shift motor fix in the video probably doesn't apply to any of the 02's.

I put 12v to the motor and it works in both directions.
I crawled under the truck and turned the little stub coming out of the transfer case so as to point it to where "Lo" is cast into the case. I drove around the yard and low works.
I turned the stub back to "N" which aligned with where the slot on the shift motor was pointing, and reinstalled the shift motor. I assumed this system would detect where the transfer case is set and move the motor accordingly. Apparently it won't. I tried to drive, and the transfer case is in neutral. No gears engaged. I pushed the "4Hi" button and no gears engaged. I pushed "4Auto" and no gears engaged. I pushed "4Lo" and I got 4Lo, and drove back and forth in the driveway.

I assume the shift motor has to go in pointing in a specific direction, yes? I further assume it should be set to "4Hi" when I put it together, right?

Any thoughts appreciated. I'm currently stuck in 4Lo, so I guess I'm spending my Friday night reading all those threads....

 

[mudpie]

Problem solved.
Warning....stupidity alert!!

I haven't really done much with the truck because I don't really need 4lo. But I'm planning on selling it, and I'd like for everything to work, so it continues to roll around in my brain. I was going on the assumption that it must be the X-fer case control module, because what else could it be? I've pulled the shift actuator and it works. I've manually engaged 4lo and know it works. The truck won't start unless I've got the clutch in, so obviously that switch is working and presumably sending a signal to the control module, and my brake lights are working so that module is undoubtedly sending a signal to the module as well.

And then I discovered the brake switch is actually not sending a signal. I was driving down the road with the cruise control on a couple days ago and when I hit the brake it didn't disengage the cruise. That seemed odd, so I checked the switch. Turns out it's not working, so I replaced it and all of a sudden I've got 4lo working just fine. There's a couple clicks I never had before from some relays, and then the "4LO" light pops on in the cluster, and everything works. Saved $200 on a module that wouldn't have solved the problem.

Here's the fun part....
Turns out, with a bad brake light switch, I also had no brake lights. Seeing as how the 4lo didn't work when I got the truck, and now a new brake light switch fixed the 4lo, it is entirely possible I've had this truck for a year and a half with no brake lights. That includes the time when I drove it 2500 miles from Washington to SoCal and back. I was just going on the assumption that my brake lights must be working or I'd have a warning light on the dash, which I didn't. Moral of the story, check your lights. Don't assume.