Hopefully I've come to the right place for this question.

I have a 1991 F-150 I bought in the middle of last summer. Everything ran great(other than the brakes, which were crap and promptly replaced) on it until this winter.

We got a lot of snow this February and I do work orders for a company that does sidewalk snow removal for several condo communities. This means I end up driving on the roads in the middle of the night after a snow storm, and usually before much plowing has taken place. So, of course, the truck spent a decent amount of time in 4wd to get through some of the deeper snow.

Since that time my transfer case has been acting funny. When I start driving the car after it's been parked for a day or so (and not always will this happen, mind you) it will act like the transfer case is trying to engage the 4wd. I can hear the gears start to touch each other and grind. As soon as this happens I stop the truck and it will made a loud thunk once the truck reaches nearly a dead stop. As if the transfer case finally succeeded in mated the gears. If I shift the truck into 4wd and then back to 2wd the problem stops until the next time the truck sits for a little bit.

That being said it makes me wonder if the shifter linkage is sloppy. I poked around under the truck and found the linkage but cannot see any way to adjust it. Does this seem like the likely candidate or is it more than likely something else?

I have not had a chance to check the fluids in the transfer case yet. If it were low on fluid could that also be the culprit?

Any help would be great.

On a side note, the truck has also recently started acting like it will stall within the first ten minutes of driving it at the moment I lift my foot off the brake. That makes me think there might be a vacuum leak somewhere that is causing this. Does that sound about right? It's really not a big issue, I just need to be careful about getting on the gas after I brake for the first few minutes and then it goes away. Any thoughts on this as well?

If it helps any, here are the specs on the truck:
1991 F-150 Extended Cab XLT Lariat
Automatic Transmission
5.8L EFI Engine
3.55 rear gear (not locking)

Thanks again!

Mark

 

I would suggest that you drain the t-case and see if there is any metal in the fluid. It is possible that the shift fork in the t-case is worn enough to allow it to work into 4wd. As for the engine wanting to stall, a vacuum leak is a very good possiblity. You may also want to do a tune up.

 

I had planned to drain everything out this weekend, so I'll look for the metal shavings. If they are there, what is the next step?

Good to hear someone else suspect the brake issue is a vacuum problem. I'll see if I can trace everything down this weekend when I'm draining the fluids.

I shouldn't need a tune-up this soon though. The truck got new plugs, wires, fuel filter, air filter, distributer cap and rotor last summer(less than 7,000 miles since). I also changed the front and rear brakes at the same time and flushed all the old brake fluid out of the lines. The oil and filter were changed just last week.
MGH

 

If there is metal in the fluid then you will probably need to get a new or used one.