96 4wd troubleshooting, Step 4 completed

[myf16]

Symptom: 4WD light illuminates, 4WD Low light does not. Flashing $WD and 4WD Low lights either 6 times or 4 time (it varies) on ignition turn-on.

I did the procedure described in the sticky: http://www.explorerforum.com/forums/showpost.php?p=1817539&postcount=1

Step 1) Jack up the front end OK
Step 2) Verify that the front driveshaft turns by hand. OK
Step 3) Start the vehicle and let it idle. Place your foot firmly on the brakes, place the transmission in NEUTRAL, engage 4low, then place the vehicle back in park. DO NOT ENGAGE ANY GEAR!! The lurch as the transmission engages could cause the vehicle to lurch and potentially fall off the jack stands.
**If the front driveshaft does not turn, the transfer case is locking properly and we need to continue searching. OK, except I had to engage Auto since 4low does not engage.
Step 4) With the front wheels in the air, engine idling in PARK, spin one front wheel.
If the front wheels do not spin in opposite directions, there is a problem with the front axle. This could be due to a mechanical problem with the diff, or a failure of the center axle disconnect to engage the passenger side axle shaft.
THIS APPEARS TO BE MY SITUATION, except that I couldn't get the 4WD Low light to turn on, so maybe the controller isn't commanding the front axle to lock.

What are my next steps?

The car is a 96 4WD with 105k miles and running pretty well in other respects. The previous owner reports never using the 4WD during the last several years. I am not positive that Auto is working correctly, but the above Step 3 indicates that it is.

Also, my local Ford dealer will diagnose this for $100. Is this case of sufficient difficulty to warrant that?

 

[PopRichie77]

When 4WD low does not in gage it is usually a problem with the shift motor.

 

[myf16]

4high (Auto for the 96 Explorer) engages OK, or at least the front driveshaft locks up in park. So I think the transfer case is switching from 2high to 4high OK. It's reasonable to assume it is capable to switch to 4low as well.

Is there a picture somewhere for the vacuum motor on the center axle disconnect? I'm trying to see if the vacuum lines are present and properly connected, and for some reason I can't feel any vacuum lines or vacuum ports on that actuator. Just an electrical connector, which I know should go to the solenoids rather than to the vacuum motor. It's weird.

Edited to add: Is it possible that I have an electrical motor rather than a vacuum motor actuating the center axle disconnect? If so, is it aftermarket or a Ford part? Again, this is 1996 Explorer.

 

[myf16]

The solenoids are near the right headlight, as described in post 15 of this thread:

http://www.explorerforum.com/forums/showthread.php?t=169186

A functional diagram of the CAD is at:

http://www.2carpros.com/questions/ford-f-150-1997-ford-f150-transfer-case

Tracing the vacuum lines from the solenoid revealed that 2 of them look a lot like wires and lead to the vacuum motor. The other 2 join together and in my case that junction was just hanging. It had fallen off the vacuum reservoir, a softball-sized chamber consisting of two hemispheres bolted together.

The front axle now locks, and step 4 was completed successfully. I now have 4auto mode working correctly.

4low mode still gives an error message. One clue is that the battery voltage drops as the truck attempts to engage 4 low. Maybe the transfer case motor is too weak. However the transfer case motor does NOT overheat as a shorted starter motor would. Maybe the transfer case selector is jammed going to 4 low but not jammed between 4auto and 2high?

In summary, I am halfway there now. What are my next steps?

 

[KPT]

So I think the transfer case is switching from 2high to 4high OK. It's reasonable to assume it is capable to switch to 4low as well.

No, you are assuming incorrectly. Four wheel drive and hi/low are completely unrelated in this t-case.

Maybe the transfer case selector is jammed going to 4 low but not jammed between 4auto and 2high?

Again, there is NO "selector" for four wheel drive. The shift motor has nothing to do with four wheel drive. If you take it off, you will see the case is marked H N L.

I would guess you have one of two possible problems. Either the contacts that tell the GEM what position the shift motor is in are dirty. There is a thread somewhere on here about cleaning them. Other possibility is your shift rail bores are f****d and the motor can't change ranges. You could pull the shift motor off and see if you can manually change ranges.

 

[PopRichie77]

I will second that. For 4x4 auto and 4x4 Hi, the computer sends power to the magnetic clutch in the transfer case. The shift motor comes in to play for 4x4 Low only.

 

[myf16]

I will second that. For 4x4 auto and 4x4 Hi, the computer sends power to the magnetic clutch in the transfer case. The shift motor comes in to play for 4x4 Low only.

Thanks for the clarification, guys. I'll focus on the shift motor.

I'm not yet understanding the H N L states of the transfer case. I thought that on this car (96 Explorer) the 2high mode requires the transfer case to be in Neutral, whereas 4auto requires the transfer case to be in High and 4low requires the transfer case to be in Low. (Only the 95-96 trucks have a 2high mode.) Is this correct?

If yes, then the shift motor is switching between H and N but not to L. However, now that I mention it, I never verified that the front driveshaft spins freely with the front off the ground in 2high. I'm going to do that now.

 

[KPT]

No, that's not correct.

2 high requires the t-case to be in high. 4 high requires the transfer case to be in high.

If the t-case is in neutral you get no power to the back or front wheels.

You can do a brown wire mod and get 4 low and 2 low with this t-case. I actually use 2 low most of time of trails.

Once again, the shift motor has nothing to do with four wheel drive. It only selects between high and low.

You say the voltage drops when you try to shift to 4 low. I'm leaning towards the worn shift rail bores. The motor doesn't have the power to turn the selector.

 

[myf16]

KPT, thanks for the clarification. Now I understand.

What would be the repair for worn shift rail bores?

Is it possible for the shift rail bores to be worn on a truck that only has 105k miles and that was used only in 2high for the last 5 years?

 

[KPT]

You have to rebuild the t-case if it is indeed the shift rail bores. Look through Glacier's 4405 rebuild diary up in the stickies.

I would still find the thread on cleaning the shift motor contacts and try that first.

Typically you get a grinding noise when coasting if your shift rail bores are very bad. Yours might just not be that bad yet.

I think the first thing I would do is take the motor off and see how hard it is to manually change the range.

 

[myf16]

You have to rebuild the t-case if it is indeed the shift rail bores. Look through Glacier's 4405 rebuild diary up in the stickies.

I would still find the thread on cleaning the shift motor contacts and try that first.

Typically you get a grinding noise when coasting if your shift rail bores are very bad. Yours might just not be that bad yet.

I think the first thing I would do is take the motor off and see how hard it is to manually change the range.

Thank you, KPT. In the interests of saving time and improving reliability, I went ahead and ordered a motor (Dorman 600-803) for $80. Once I have the old motor off I'll know whether the t-case works OK. If yes, I'll install the new motor and hope for the best. Spending $80 beats rebuilding the old motor and then worrying about when it will fail.

 

[KPT]

Not the route I would have taken but ok.

I have 172K miles on my original transfer case shift motor... Never done anything to it.

T-case itself is a different story though.

 

[myf16]

I have 172K miles on my original transfer case shift motor... Never done anything to it.

T-case itself is a different story though.

You had trouble with your T-case? Please tell us the war stories!

BTW, my dealer's service guy told me that the shift motors tend to fail if they are not used for long periods of time. The previous owner told me that he never used 4wd for 5 to 6 years, so that fits. Is it just dirt and corrosion inside the motor? Probably. But I'm saving an hour or two by not taking the motor apart.

 

[KPT]

If you read through glacier's thread you will see what happened to my t-case and will happen to all 4405's.

But we can tell you didn't or you wouldn't have had the questions you did in this thread.

Bet you a beer that shift motor does nothing for your problem.

 

[PopRichie77]

I will second that. For 4x4 auto and 4x4 Hi, the computer sends power to the magnetic clutch in the transfer case. The shift motor comes in to play for 4x4 Low only.

Yes as KPT said, what i said above is not worded correctly. The transfer case stays in high all the time, the transfer case motor only turns when 4x4 low is selected and of course back again to high when auto or 4x4 high is selected. You should have checked the motor before buying one, by removing it and with the electric plugged back in, turn the selector to see if the motor rotates, this would also test the Gem also you could have manually checked the transfer case for proper operation.
Do read glacier's Rebuild of the 4405, if you can't find here is the link.
http://www.explorerforum.com/forums/showthread.php?t=182071

It is also possible that you are not selecting 4x4 low correctly.

 

[myf16]

If you read through glacier's thread you will see what happened to my t-case and will happen to all 4405's.

Yes, I saw that but I figured mine was too young to die that way. Also, the dealer said that 80% of the time lack of 4 low is due to the motor. I take it that the experience here is very different from that assessment. I should know by Sunday either way, and I wanted to have the new motor in hand to complete the job if possible. If it's the T-case I may return the motor for partial refund and settle for having AWD (4high) plus 2high as the only working modes.

 

[PopRichie77]

AWD, 4High and 4x4 auto are all different things depending on year and model. AWD only comes in the Explorer V8 models and it is not a 4405 case. I believe your selector says 4x4 high and you can not drive in this position on dry roads, binding will occur on turns and something can break.

 

[myf16]

AWD, 4High and 4x4 auto are all different things depending on year and model. AWD only comes in the Explorer V8 models and it is not a 4405 case. I believe your selector says 4x4 high and you can not drive in this position on dry roads, binding will occur on turns and something can break.

Yes, sorry about that. 4high is similar to AWD but not suitable for dry roads unless you just want to test it driving straight and never turning.

I like the ability to select pure RWD (2high), an ability that disappeared after 1996. I wonder why Ford decided to drop it.

 

[PopRichie77]

The front axle disconnects were problematic , also people didn't like having to lock and unlock manual hubs also they didn't fully understand the function of auto hubs. AWD or just one selector for the TC was easier for people to use, nothing much to learn, just flip the switch or push a button. Most manufactures went to the same thing.

 

[myf16]

I unbolted the old motor today. I put a small visegrip on the triangular shaft. I could turn it about 60% of the way from high to low against increasing resistance, as if I were fighting a spring. It needed about 15 pounds of force (say 10 foot-pounds of torque) to turn that far, then I ran out of room with the visegrip handle.

Is this normal T-case behavior? The force seems large, but then the designers would want the case to fail safely into the high gear.

Please tell me this is normal so I can replace the motor tomorrow.