Originally Posted by
eagleclaw
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