Okay I have read numerous post and checked all the issues, but I seem to be ina fix here and I can not tell what might be going on.

2002 FX4 Lariet with swicth for 4 wheel on the dash.

4 wheel Drive stopped working a frew months ago but I have other issues so I didnt need it and left it be.

Last night I dug into in it and I am baffled. For one, The low range light never comes on. Just the 4wd light.

Volt meter showed 12V at both selinoids by battery. Vacum lines appear sound and no leak or crak detection.

I did not pull the plastic cpver off the bottom to verify the actuator pump yet, mostly because It's odd the I get a 4wd light in high or low but I can't get low range to light up period.

When I turn the switch no cluck or crazy noise a simple click like it use to do but now 4wd.

Im now Im starting to think fuse? or possible tcase problmes.

I do not have an woners manula that Identifies fuse number for the 4wd, can some one tell me what number that is?

Also any ideas, should I pull the actuator? or the vacum lines it and makie sure I am getting Vacum Pressure in and out?

Any help or leads would be appreciated.

Thanks

Dave

 

When you tried to use 4low, did you put the truck in neutral and press on the brake?

 

First off sorry about my typing earlier I posted this at my office and the heater was off this morning so I was trying to type in 30 degree temps

No I didnt try to use 4 low, or shift it in to nuetral and apply break.

I checked the voltage with the truck in park and the keys turned to the on postion, and then the truck in park running.

I have shifted into 4 low with the truck in park in the past so I didnt think that should be a problem, although I was in tha cab and my foot may or may not have been on the break.

Dummy light for 4 low does come on during crank up so I know bulb or light for the 4 low is not burnt out.

I would think if it was a fuse, there would not be voltage on the selinoids. But I could br wrong. Un fortunatley My real experience is building Jeeps, and rarely work on something like this so it has me confused.

Some posts I have read mentioned A shift fork on the Tcase. I see no evidence of a shift form on my Tcase, It appears to be 100% vacuum controlled. Or maybe thats my problem, there should be a shift form some where on the T case from the actuator and its fallen off but I could not see anything that would control the fork. Again this is what I could see and feel with the plastic shield still over the actuator.

 

Well my 4low light never lit up on either my 97 or my 06 on startup. I read the 4low instructions in my manual when I bought my 06, always thought the 4low was broken, even sold it as broken, but came to find out it worked the entire time.

 

I know for a fact my 4 low light would come on when I put it in Low range as I had used it numerous times in the past pulling our old boat out of one particuarly nasty wanna be boat ramp.

 

Since posting this, have you tried shifting to 4Lo with the truck in neutral?
Seriously. I've seen a few people assume something's wrong, but the truck was actually in Park.

 

Sounds like there is no vacuum. I would check that first.
I believe it is fuse 23?

I would try this section of the forum where these things are particularly discussed. You will have a better chance of finding the right answer there. Good luck
https://www.f150online.com/forums/other-powertrain-15/

And yea, you must be in neutral with foot on the brake for 4low to engage. Is 4h working?

The shift fork is inside the differential

Posted by Jbrew

"Quote:
Originally Posted by Jesso View Post
i believe i have read about vacuum lines being a culprit for 4x4 problems.


Right!

Yea, they become frail/dry out and break between the battery box and firewall. The Pink & Blue 1/8 lines, that run from solenoids (2wd/4wd) at the firewall to the actuator on the front axle.

Keep in mind, if your lines look good, then chances are, your actuator is hanging. You need a cheap Vacuum tool you can get from just about any 3rd party parts supply to preform this. WD40 the actuator rod on the axle. Disconnect the blue line at the actuator/ connect Vac tool/ supply vac (about 12 hgs), watch pin or rod for movement/reconnect Blue, disconnect Pink/ do the same.

Once the pin or rod moves, it's in working order, just lube it up a bit.

With the vac tool, you can also test the lines. Nothing special has to be done to preform. Leave the key off. However, you really need to remove the battery to check the supply lines thoroughly.

If you happen to get mixed up with what line goes where at the actuator, DO NOT follow Fords diagram from Service/Workshop manual. They have it back wards. It's best to mark these lines down on paper for yourself. This may only be with certain years.

Good Luck.

BTW- Problems elsewhere within the system could exist. These are two common ones.

 

Since then I have tried putting it in Nuetral but still no Low range light.

Odd that the Low Range light is not coming on when it use to even though the 4wd would not engage.

I agree seems like its a Vacuum mal****ion, I think, and I dont now since I don;t have a FSB or a Haynes that the 4wd Articulater is just a vacuum port. Manifold Vacuum goes in switch opens articulator and it goes to the selinoids. Locking hubs.

I am not sure if the selinoids are low and High range lor left and right? Also not sure if its - vacuum or + pressure that activates the selinoids. I would assume its Vacuum as the actuator appears to be little more than a diaphram housing but I havent seen a full blown pic of it yet and I havent pulled the shield to look at it.

I can always do the old fashion vacuum test by tying into the vacuum hose on the selinoids and running a line into the truck and sucking or blowing on those lines to activate the selinoid. I can not imagine they need more than 5psi of Vacuum to open or close.

Anyone have a link to a FSB online? or full tech data on the 4wd vacuum operated system for the 02 ford trucks with the 5.4? (switch operated).

Thanks

Dave

 

If the truck will shift into 4wh,and not 4wl than i would assume that the problem would be in shift motor or gem. i have a 97. Mine might be totally different from yours.

 

WHen I say shift, I mean lights come on that tell me it engaged, but it is not engaged now 4wd.

I will put my vacuum tester on the lines, I will aslo check fuse 23 and I read fuse 104 under the hood.

Also I will check the GEM and the shifter fork this weekend.

 

This might sound strange, but the had lines are routed from firewall to front axle by way of the inner fender. it so happens that they are right under the battery. corrosion from the battery can eat a hole the plastic line. I have seen 3 trucks with this exact problem. mine included.

 

The vacuum switchs on firewall will have 12 v on the when key on. the gem will ground which switch it needs to operate. good luck

 

Well no chance of corrision, even with 128K miles on my truck the engine bay looks like it came of the showroom floor. Building Jeeps and Rat rods for fun kinda makes me keep all of my cars in perfect and clean condition.

I dont know if I can rull out the selionods yet as they do register 12V with key in, but that does not mean they are ****ioning, not sure if there is a way to tell except buy keying on the truck removing the vacuum lines and holdind my figer under connection port or attaching vacuum read to selinoid and the turning the 4wd switch at that point the selinoid should send out - or + pressure again not sure how the selinods work.

I wish I could hear a clunk or other shifting noise from the truck but I can't so unable to tell if its the fork untill I remove the platic sheet and inspect fork mark position turn swicth and see if anything has happened. If I had a second person turning the switch would make it easier

I'm going to try to find out before this weekend.

Thanks

Dave

 

Okay,

Im really confused now, on this and I think I may have a tcase failure of some kind.

AS before I have checked above questions.

Hover yesterday I was determined to find out why Low range wouldnt come on. AGain I STarted the car, put it in Nuet and with break pressed turned to 4 lo. Nadda no light just the dummy light for 4wd.

So turned it back to 4wd, backed the car ouot of driveway slowly and came to a stop. Put it in Nuetral and applied break then switched to 4 low. And boom like magic the 4 low light is on, but Boom like magic when I hit 4 low I heard a horrid CLUNK from under the truck. I put the truck in gear and attemped forward movement Nothing appylng gas in drive or reverse the truck would not move as if the Lost the drive shaft completely.

I Had to Put it in park and cycle the 4wd Swicth a couple of times and 4wd came of no noice besides the normal click. and Im driving like normal again.

I am not familar with the Tcase for the Fords. But I am famaliar with many different T cases (Dana 20, Danan 300, NP231, NP 231OR, Atlas 1 and 2.) all of the above cases are gear or chain driven.

The ford Tcase, Gear? Chain? driven unknown, but the simple matter is that the shifter fork like all single stick (not twin stick for those that are more familar with twin sticking a Tcase for Rock Crawling) SHould engage the gera for the front axle drive only. What I understand is the truck is constantly in a regressed 4wd mode as in the front axles spin hubs are always locked but the front axle is free spinning on momentum the fork engages the gear inside the tcase to apply actuallual momentum to the front axles. With this in mind How in the world can the shifting of the 4wd fork effect rear output?

But duh, this happened in low range where the gear set is shifted in 2 postions. So based on the information, I woud say I have a semi exploded Tcase? shifter fork that slides the gears into 4wd partially engaging or fully engaging but maybe case is chain driven and I have a broken chain? then 4wd low shift I loose front and rear out put beause of broken gear set or chain? or the fork?

Anyone have any exploded diagrams of the tcase for the F150? 02 5.4 Fx4 model?

Thanks

 

It could also be that the case shift motor is going bad. i was told that motor has plates in it that make different contacts so the gem knows its In the correct gear. Check for a bad connection at the shift motor. the loud cluncking you hear is the motor shifting the tcase. i hope this helps