i bought my 99 f250 not too long ago and it pretty much makes it through except the 4x4 doesnt work and every time i get stuck i start to look and check it out and end up giving up but now i got stuck again in a stupid spot for an hour which wouldnt have happend if it just worked anyway heres my problem.....

no 4x4
*with the truck running in park the front drive shaft spins by hand freely
*i turn on the 4x4 switch (i have no locking hubs) the way the owners manual says and put it into park
*with e the 4x4 switch on the axel now doesnt spin, so the 4x4 switch is telling the motor to engage the driveshaft and the drive shaft is locking in 4x4 but i have no 4x4

my guess is that when it spun freely in park with the 4x4 off the transfer cash didnt lock it obviously (which it shouldnt) but when i spun the front drive shaft by hand in park the front tires should have tried to spin right?

so to me it seems i have a problem in my front axel, maybe a stripped gear? but i think a stripped gear would make nasty sounds while trying to drive?? or is there a way the front axel locks in besides at the transfer case? i just need other possable ideas because so far i dont have a solution

 

Does the light come on the dash? it could be the 4x4 switch itself or the module behind the glove box. Not sure tho if your transfer case is locking in then it will be your hubs. you can get new ones with manual locking hubs and that will fix it if its just the hubs not locking. If you want to keep automatic locking hubs there are vacuum lines that run to them that lock them in which are probably messed up in someway.

 

if its an automatic..you have to put it in reverse to put it in 4wd..

 

yeah the light came on, and low light comes on when i put it in low gear. im thinking its the vac lines. i had an old jeep that had a vac line problem.... the front driveshaft locks in so its something in the front axel but i dont have locking hubs its on the fly only, my friend has a 250 superduty and its on the fly but he has locking hubs...i finally bought a chiltons repair book and there is a actuator vac fed motor on the front axel so im going to look there tomorrow and see if its all woking

 

yep its an auto. another weird thing when i switch it to 4x4 and put it into reverse and then drive the truck revs high and doesnt really shift acting as if its in 4 low and then when i stop turn the 4x4 off and go again it drives normal, so im guessing everything is working like its susposed to but everything points to something on the front axel...but at least i know something else to look at tomorrow when i start messing with it again.

 

ya..for some reason you have to put it in reverse..(not moving)..put your switch to 4x4 high/low..whichever you prefer..then put her back in drive..then take off..it will seem like its reving high cause of gearing..it does seem like you have something going on, but it still should at least shift into 4x4..also the front end i had problems with it locking..i just locked the hubs instead of leaving it on automatic..then it will always lock..and sure enough it does now..

 

No you do not need to put it in reverse. There are no locking or unlocking hubs. You need to check the vacuum lines from the solenoids on the firewall all the way down to the acuator mounted on the differential. If you have any vacuum leaks 4wd will not engage. With the right front axle not locked 4x4 will not work.. The vacuum line leading down to the acuator are blue and red...

 

i messed around today and took off the cover for the front driveshaft and the actuator, i have a blue and red vac line that goes to 2 sylonoids on the firewall on the passenger side. the actuator on the axel doesnt move when someone in the cab switches it in to 4h/L. the vac lines seem fine, im going to check if the sylonoids have power and if theres a vac leak.... i found the vent tube from the axel just ended near the sylonoids which was kinda weird, and one of the vac lines was broken at what looked like a check valve or filter but i fixed that and still nothing....hopefully its something stupidly dumb thats wrond and once i figure it out it will work and not cost an arm/leg.

 

If you dont have a vacuum leak you possibly might have bad solenoids. Check them with a 9v battery and see if they click.. Its very likely you have a bad acuator. Remove the acuator and see if you can move the shift fork. The shift forkes are known to brake....

 

so i had a broken vac line i fixed it and the lever on the front axel now moves back and forth when i turn 4x4 on/off but nothing engages so now its down to something ni the front axel???