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4wd high slips?

i have a 1991 5 speed F-150 that i only use to plow my private rd… and have been using it like that for about 8 years. we have had quite a snowy season in NH, and it has been running good, until yesterday. while pushing snow, it idled really high… like the clutch went (had a new clutch put in 4 years, 400 miles ago.) i checked the clutch fluid. nasty brown, but no leak. it sat over night and i tried again today. same thing… except I realized it only seems to be doing it in 4 high and 2wd. in 4wd low, it seems to work fine. hoped to find some solution on the site, but there was nothing. any ideas? help! we’re getting another 4-6 tonight…

I can’t think of anything that would link the clutch to idle speed. Those may be separate problems. Among other things, high idle speed can be caused by vacuum leaks or the PCV system on the fritz.

Does the truck have a manual or electronic shift transfer case?


hey George the high idle just me describing the clutch quitting… foot on the gas, but no go. sorry. bad writing skills. tester… its a manual shift transfer case…

Pushing a snow plow can probably put a lot of wear on the clutch, maybe it is just kaput and you need a new one. I have a Ford 4wd truck, sometimes when under load 4wd-lo the transfer case will slip into 4wd-neutral. It has a U-shape for the transfer case pattern. I just shove it back into 4wd-lo when that happens. Mine is 40 years old, so the technology isn’t the same for you probably. But could it be your transfer case is just slipping into neutral?

I wish it were slipping into neutral … but its not. It reminds me of teaching someone to drive stick. riding the clutch. when i release the clutch and step on the gas (in 4wd high and 2wd high) it sounds like, and feels like i’ve only let up 1/4 way on the clutch. I’m confused… and know nothing about vehicles. (obvious?)