Great post. Very informative. Here is a problem that I am having...

I have a 1997 Ford F-150 and the following problem occurs with the 4x4 engagement. When the vehicle is cold, the 4x4 shifts from 2 wheel into 4 wheel drive without a problem. If I drive the truck say 20 miles or so at around 50 mph and the operating temp. is normal, the truck will not engage into 4 wheel drive. (4x4 dash light does not come on) I had a mechanic check the whole system. He replaced the shifting linkage, 2 vacuum relays on the firewall, checked fluid in transfer case and checked the actuation of the front differential. Everything seems to be operable. When the truck sits for several hours, the 4x4 works fine again. To me it seems to be a heat issue. My mechanic seems to be baffled by this. Could it be a relay issue? Any help would be greatly appreciated. RC

 

I hate to ask how much your mechanic charged you for all of this work, but I'm guessing it wasn't cheap. And this is a perfect example as to why one should never just throw parts at a problem (hoping that at least one of them will solve the issue) without at least doing some pre-diagnostics first. This is why you should always get a good repair manual for your vehicle and learn as much about your truck as is possible---before giving up and writing big checks to mechanics and the parts suppliers.

You said that he replaced the 2 vacuum relays, but now you're asking us if that/those could be the problem? Hmmm, did your mechanic ever run tests on the old ones? And did he verify that the new ones are good (out of the box?) And you've made no mention of the vac hoses themselves----did he test those for leaks and replace if needed? If not then it's possible that when they're warm that a small crack opens up---something you may not notice when they're cold. I'd take a look and see for myself. And what about the linkage---did that really need replacing? Or just adjusted,cleaned and lubed? Hmmmm.........

Regardless, I think you're gonna find that after you threw a bunch of money on this, that the problem will be something small and stupid and easily repairable. This happens more times than you would think. Come back and let us know what it finally turns out to be,.....I for one am very curious.

Good luck,

RB

 

Hey Ricky. Thanks for the additional info. I will definitely check for hairline cracks in the vacuum lines. I am also going to check the Transmission Range Sensor Switch part # 4L3Z 7E440 AB located on the left front of the transfer case. I saw that JackPiner57 had a similar problem but the opposite of mine. His truck stayed in 4x4 drive when hot and would shift back to 2x after the truck sat and cooled down.
I normally work on my own truck but this time I was told by several people that I need to find a mechanic who could rebuild the transfer case. The mechanic I used came highly recommended. I would tackle just about any job but this called for a lift that I did not have.
He looked at the transfer case and shift linkage and informed me that he did not feel that the transfer case was the problem. He stated that the linkage was sloppy and was not engaging the shift fork all the way. I did have some binding problems with the linkage from time to time. I hit it several times in the past with white lithium grease. While he was working on the linkage, I had him change the automatic tranny fluid, filter and gasket. I also had him replace the rear transfer case yoke seal. (starting to leak slightly). After he changed the linkage, he took it for a ride and everything seemed to work smoothly. I asked him to drive the truck for while and then he noticed that the truck would not shift back into 4x4 when hot. That's when he swapped out the 2 vacuum switches on the firewall. I don't know if he checked for vacuum leaks on the lines. I will ask him and then check them myself. I am really hoping that it is the Transmission Range Sensor Switch part # 4L3Z 7E440 AB . After this, I am going to tackle the Blend Door. (This door stopped working several years ago. I just got the improved door from Dorman). Thanks again for your help. I will keep you posted on my findings.
RC

 

 

PLEASE helpful info on how to fix backup sensor for an F250 2003 truck. was @ the dealer explaining my c oncerns and safety issues but @ $90.00 diagnostic fee to have a look before telling me whats wrong, what parts i need, and how much $$ i need. i thought i'd look around and see if i could do something to save some $$.

 

Hey,

Sorry, this is a 4x4 thread and although I know a lot about my truck, it has no back-up sensor....

Best luck would be do what I did in gathering this post..;search, search and search the internet. However, sensors and electrical, if you feel you really need that backup sensor to work, are better looked at by someone who has the tools to do the diagnostics.

 

i have a little problem. the vacume lines that go to the front diff. have been burnt in half by my headers. i know there was a little plastic peice that the lines went through but it lost. can sombody post pics so i can see how it goes? thanks

 

Wanna help me out?

I got a 97 Expedition 4x4 with the electronic shift crap, (the switch on the dash), i was out at the local orv park and lost my 4x4 hi and low, no dash lights, no engagement, but my Auto 4x4 still worked, now ive lost everything.......i have no clue wahtg could be wrong with it....any ideas?

 

I have a 2000 4.2. When i engage 4 wheel drive the light comes up on the dash "4x4" and "low range". My problem is when engaged it always says "low range" whether I am in high or low. Everything works great it's just one of those annoying things....Any ideas?

 

good info thanx! i will run thru the list as soon as i can and let yall know!

 

@Eagleclaw
from my experience heat applied + things not working = wiring issue. when i had my 84 1/2 5.0 right after i got it, once the engine heated up and i shut her down she wouldnt start up again till she cooled. turned out to be a wire was too close to the massive amounts of heat under the hood, and when the shielding got hot would short out.
my recommend is to check for shorts or opens in the wiring.

 

I am beyond frustrated! Ever since I rolled 75,000 on my 2003 Ford F150 that Service Engine light keeps coming on. I have changed out all O2 sensors, got a tune-up, replaced the alternator and battery, replaced the lower intake valve gasket, changed the fuel filter - 3 time, changed the air filter, and may other things but it is still on!

The last diagnostic I got was that it is running lean on the left bank. What could be causing this? I am at my wits end and will more than likely never buy a Ford again unless they make drastic changes to the engines!

 

Ford makes great engines, as does Dodge, Chevy, Mack, International, Toyota, Perkins, Mercury et al----so check your vacuum hoses, especially to the PCV (if so equipped). That was what threw my code for a Lean Bank on my '97 F350. Took me all of 12 minutes and $2.87 to fix...........

 

I concur with rick on the vaccuum hose. And on the fact that ford still makes wonderful engines, and we should do everything in our power to keep as much as possible of what we purchase from american soil. Before you check the vaccuum hose, unplug the battery and let it sit for 10 to 30 minutes. This will allow for the computer system to reset and it will reset all of the error codes. If the check engine light comes on after this then check the vaccuum hose, and run a diagnostic check again.

 

Everyone who has posted here has been awesome - I like to think this is what it's all about.