Hi guys,

Tried switching on the 4H setting on my '99 F150 4wd **** the other day. The "4x4" light came on but not accompanied by the usual under vehicle engagement noices. Silence from uner the hood on that. Drove around a bit but no 4wd engaged. Turned the **** back to 2H but the "4x4" light would not extinguish.
I found the electric 4wd engagement motor (housing rusty) and tried tapping on it with a hammer to see if that would free things up. It did! Switching between 2H and 4H produced the undercarriage engagement and disengagement noises quite audibly. But only for about 5 mins. As soon as I put it on and went to drive away, it stopped working (even before putting it in drive). Is it the motor? If yes, what's the removal and replacement process if anyone could help. Thanks a lot.


Lou

 

Hey guys,

Can anyone offer any assistance with this? Thanks again.


Lou

 

I've never looked at mine but I'll give you word for word what it say's in my manual. I'm not sure which transfer case you have but here it is;
1. If equiped with air suspension turn it off. ( I would disconnect the neg. terminal on the battery too )
2. Raise the vehicle and support on jackstands. ( I doubt you need to. Mine is high enough to work on )
3. Unplug the shift motor electrical connector.
4. Remove the wire spacer to the electrical connector for the shift motor.
5. Remove the coil wire and pin from the electrical connector.
6. Remove the 4 bolts holding the shift motor.
7. Remove the shift motor.
Installation is the reverse.
I have a 99 F250 LD 4x4 which is somewhat the same as your truck. I guess it depends on which transmission and transfer case you have. I
doubt that it is very complicated , depending on your skills. Good Luck.
P.S. I'm sure there are some threads in here that will give you another
choice.

 

Thanks a lot for the info. But now it's working again (after I sprayed the inside of the connector of the wiring harness with silicone spray)! There is one problem, though, in that it takes a while for the 4WD to disengage when going from 4H to 2L. It requires a full stop most times to disconnect the 4WD.
Does anyone have any idea as to why it's doing that and what the solution would be. Thanks for any thoughts.

Lou

 

Probably a vacuum problem. I would check the actuator motor on the front differential. Remove the plastic cover and get someone to switch the truck in and out of 4wd and see if that motor is sluggish. Could just need lubing . Might be a vacuum problem, check the lines and solenoids.
Could also be the actuator going bad.

 

to get into or out of 4 x 4 ii normally shift the trans into neutral and let the truck roll a foot. THey do have a tendance to "stay" in or out. Sometimes need some hlep.

 

Won't have a chance to check for a day or two, but would the '99 have one on the front diff and vacuum too? The only assembly I remember seeing is the actuator motor on the transfer case (this is the part I've been working with) and it seems all electric. Will look for this part you're mentioning (should it have vacuum lines into and out of it or is it just vacuum actuated internallt like with a diaphragm?). Thanks.

Lou

 

there is a small vacuum cylinder on the side of the pumpkin with two vacuum hoses to it... IN and OUT. coonnected to the two solenoids on the firewall.

 

steve(ill) is correct. On the front diff. is a vacuum actuated motor that locks and unlocks the front axles. There's also a vent tube. On your transfer case is an electric shift motor .

 

Well finally got to thoroughly test this situation. Looked at the front diff vacuum module and as my son turned the slector **** from 2H to 4H back and forth, I could see the plunger moving in and out of the vacuum housing which in turn moved the lever which locked and unlocked the front wheels.
Tried to take for a road test and then the fun began again. Moved the selector **** to 4H, heard the very loud clunk of engagement (sometimes it goes in quietly. Guess it depends how it catches inside the mechanism) and so was in 4wd. Turned the **** back to 2H and this is what I found (happens this way each time it goes on the fritz)

1) the "4x4" instr cluster light stays on

2) the front diff vacuum piston is in the full vacuum position (so the front wheels are engaged)

3) the front diff to transfer case half-shaft cannot be spun by hand (again confirming the front diff is engaged)

4) moving the selector **** back and forth from 2H to 4H repeatedly does not shut off the "4x4" light nor does it allow the front vacuum assembly to release the front wheels and so the assembly stays in full vacuum mode.

I can only guess the transfer case motor is not engaging the case to allow the entire drive system to experience the 4wd, but I don't know enough about the system so I'm wondering why the front wheels are staying engaged. Does the electric transfer case motor activate the front vacuum assembly somehow even if the motor part of it is not allowing the transfer case to engage?

Bottom line is...what do I need to do (or replace) next. Thanks for all your help so far guys.

Lou

 

Forgot that I needed to add this as well in case I didn't make clear:

5) the 4wd is not engaged at this point and is in 2wd even thought the dash says "4x4" and the front vac and shaft are engaged as if in 4wd.

 

i dont think i follow you 100%. but there are two systems. The electric motor on the transfer case selects two speeds, hi and low and engages the drive shaft on that end. If the electric motor or plug is not working, you can not changed from 4H to 4L or 2H. The vacuum cylinder works seperate from the transfer case. You are triggering two solenoids on the firewall to send vacuum to one or the other vacuum hose at the cylinder on the pumpkin. take off both hoses and switch from 2H to 4H... vacuum will be noted on one hose, then the other. if that is o.k., then you need to spray penetrant on the vacuum cylinder rod and stroke it in and out untill free.

 

hehe...............JK


anyway, from what im getting, it sounds like the switch is bad.

 

How can I test the switch? Can it be tested while in the vehicle? If not, how can I take it out or access it to test if you or anyone can tell me the procedure. Thanks.

Lou

 

Steve (ill), yeah I thought it might get confusing. The thing is that when it's in non function mode, the vacuum plunger is in all the way, the 4x4 lt is on, but the front wheels are not receiving power. Also the electric motor is not going on no matter which setting I put the selector **** to. When the system is working, when I turn the selector **** from 2H to 4H, you can here clicking behind the instrument cluster then you hear actuation noises from the electric motor at the transfer case. When the system is not working, there are no noises at all when I turn the **** to 2H or 4H and the 4x4 indicator light is always on. Could that mean that it is either the electric motor or the switch vs the vacuum part of the system?

Lou