Engine tach going to 2-3k when applying brakes.

I've got a 96 Explorer (4.0 V6) with around 227,000 miles on it. I have a problem that I only see when I drive it 37 miles to go fishing. I don't see the problem driving around town. When I get to the lake and apply my brakes to slow down I notice my tach will rev up to 2k-3k which makes it tough to stop. If I put it in neutral the tach really shoots up. It seems that if I pump the gas a few times it settles down. I had this problem a year or two ago and for the life of me I can't remember if I took it to the shop or if it just went away. Any help appreciated.