I have a 1999 f15 off road. The 4x4 system disengages randomly. I here a double click when I engage the panel switch. And I here engageing at the trannny. It seems like the front wheels are not locking out.

Now in summer time, I here a random clicking that seems to becoming from under the drive shaft area. Almost sounds like a chain clanking on a trailor.

When the 4x4 is engaged, it works fine. Vehicle has 208,000 miles. I had no troubles in warm weather.

Any Ideas?

 

I had the same issue. I just finished fixing the problem. It is the engagement fork in the front diff. It took about 3.5 hours to complete the job. There are nylon shoes on the end of the fork that mesh into a gear collor and is moved via the vacume actuator. What happens is the nylon shoes wear or break off and the fork no longer catches the collor. The kit was just over $200.00 and includes a new fork, collor, o-ring, pin and e-clip. You need to remove the passenger side wheel, unhook the sway bar and remove the drive axle from the tube and swing it out of the way. then you must remove the axle tube and then you will be able to get to the fork. You will need to remove the bolts that attach the diff and the axle tube to the frame so you can get the clearance you need. Not a hard job but requires patience and basic tools.

 

Thanks for your input. I'll take a hard look at that. Doesn't sound like that fork would cause the clanking sound, must be a separate issue. But I think you gave me a solid lead to the main problem.

 

Could you tell me how you determined this was the problem. How was your vehicle acting?

My vehicle seems to pop out of 4x4 when I'm turning, but not always. Sometimes I will be on a straight road and it pops out. Once I was backing out of a parking spot, and heard a thud from the front diff, and it seamed to pop out of 4x4 at that time.

I'm draining (of possible water) the vaccum lines again to see if this helps. How did you diagnose that the fork was your problem?

Appreciate your input.
Dave.

 

My truck started out randomly popping out of 4x4 but as time went on my main issue became that it would not engage into 4x4. When I switched it over on the dash I would hear the clicking sounds and the light would always come on but no 4x4. I noticed that if I made sharp left hand turns it would then engage. I looked into how the system works and came to the conclusion that it was the shift fork. These trucks no not have hubs that lock in and out. The axles are turning all the time. When the 4x4 is engaged this actuates the fork which slides a geared collar over on the end of the axle which marries the axle and the diff shaft. When the nylon ends break off the fork this allows the collar to slide freely back and forth engaging and disengaging the 4x4. I took pics but can't figure out how to post on this forum.

 

Thanks, Maybe you email the pics to my email address @ airmorales@hotmail.com.

Thanks for responding so quickly. I think my truck is getting to the point where it won't engage at all.

Would I be able to see the fork, if I took off the diff. cover?

Thanks again.

 

Got the problem fixed!! Turned out to be the fork as some (mac) suspected.

After checking with a local dealer, and a random mechanic (both requiring a $80 and $60 diagnosing fee), I took my vehicle to Colwell Ford in Hudson Ia. I was treated better than I"ve ever been by any dealer. They put my truck on the rack, and in five minutes told me it needs a new lock out fork. They fixed it the same day for $348.00. Now it works great.

I told them about a transmission leak that developed this week. Turn out I broke the transmission filler tube bracket while trying to drain the vaccuum line for the lockout (forks) prior to taking it in. They could easyly taken me to the cleaners here. They didn't. They simply showed the what I did and how to fix it.

The only other problem I notice is that I have to slow to 10mph before 4x4engages (previous problem), However, I can live with that.

This site is a great help!!