I recently purchased as used 2006 F-150 Lariat 4x4 with 77K miles. I am having an issue with the shift on the fly, I had a vacuum leak that was causing the auto hubs to make noise on occasion but it has never allowed me to shift from 2wd to 4H while moving. I have replaced the IWE solenoid and repaired the vacuum leak but it still will not engage while moving. The light for 4H comes on but the hubs will not engage. The dealer where I purchased the vehicle is not a ford dealership and whey have been trying to solve the problem but to no avail. Any suggestions?

 

Is the 4wd system in these trucks shift on the fly?

I may be wrong but as far as I know it has never been that way. I have never had an issue with my 4wd and it has never shifted on the fly I have had to stop and engage the 4wd then start up again.

 

Mine shifts on the fly. I can go from 2WD to 4H. In order to shift into 4L I must come to a full stop.

 

The 2006 Lariat is supposed to shift on the fly but mine does not. I am wondering if it is the shift motor or possibly a GEM problem. Anyone with the same issue?