1990 B2 4wd low problematic

[switt]

My B2 easily goes into 4wd high but not so much with 4wd low. The low light just flashes and doesn't engage 4wd low. Strangely though, if I shut off the engine and turn the ignition on, it engages the 4wd low. However, I then need to turn the motor off to disengage 4wd low. Anyone have any idea what's causing this? Thinking it may be a faulty sensor, but aren't the same sensors needed for 4wd high?

 

[ford4wd08]

My B2 easily goes into 4wd high but not so much with 4wd low. The low light just flashes and doesn't engage 4wd low. Strangely though, if I shut off the engine and turn the ignition on, it engages the 4wd low. However, I then need to turn the motor off to disengage 4wd low. Anyone have any idea what's causing this? Thinking it may be a faulty sensor, but aren't the same sensors needed for 4wd high?

Are you trying to make the shift to 4 Lo while the transmission is in neutral?

 

[alwaysFlOoReD]

^^^
Yes. Foot on brake and trans in neutral .

 

[switt]

Yes, like always said, foot on brake, neutral, and clutch in for good measure. Took it for a short drive and it worked in neutral, and in 1st, R, or any gear. Then it quit working, but still worked with ignition on and engine off. It must have something to do with sensing neutral. Not sure how neutral is being sensed, but it seems to be a problem.

 

[RonD]

Neutral in a Manual trans is clutch pedal down
Some years did have a neutral switch on the transmission, but I don't think the BIIs ever had that

There is a Speed sensor, with speedometer cable on the transfer case, make sure its plugged in
It was only used for cruise and shifting to 4low with manual trans
Speed sensor has to show 0MPH to shift into 4low, for 4high or 2WD its not used

Just thinking out loud that at Start up and shut down 0 MPH is assumed, lol, so it shifts

 

[switt]

I think you may have nailed it down. My cruise control has been substantially nonfunctioning lately. I'll be checking that speed sensor or plug out tomorrow. Who knows, may even fix my cruise control.

 

[switt]

Checked the ele connection to the speed sensor at the transfer case, looks good. Going to clean connection and if that doesn't work, buy Doorman 917-614 vehicle speed sensor for less than 12 on amazon. Also doing same with ABS wheel speed sensor on rear differential since my ABS light occasionally comes on, Dorman 970-012 for less than 10. Thanks all, I'll keep you posted.

 

[switt]

Cleaned, with crc ele cleaer, the ele connection to the speed sensor at the transfer case and the ABS wheel speed sensor on rear differential. Things appear to gotten worse. Can no longer count on switching into, or out of, 4 low with ignition only. Was worried would have to drive home in 4 low, errrr. Anyway, also have the ABS light coming on. Ordered the Doorman 917-614 and 970-012 sensors. Any other suggestions while I await arrival of the sensors?

 

[RonD]

Can't make it worse if it wasn't working, lol

Since cruise AND 4low were giving you issues the new VSS on transfer case is not a bad gamble
Can't speak to the rear axle ABS sensor, although it is a common issue

Once you have the time pull off the shift motor and plug it back in, run thru the "gears" see if its shifting OK when it doesn't have the torque needed to turn the shift rod
Then you turn the shift rod manually too see if hard to turn past 4H

The shift motors can lose torque power, so they can shift between 2wd and 4h but can't muster enough strength to go to 4l or back, not a common failure mode but not unheard of either