Jr. Bacon

hi my name is kyle just joined and am proud to own my ford truck. I just bought my first truck a 1991 f150 lariat extended cab short bed with the 5.0L in it, 4x4 of course. however i have run into a problem. I usually fix everything myself, its just cheaper and im more confident in my work than others. However, i am not sure what this problem is and was wondering if anyone else could help. I was driving my truck to work yesterday and when i stood on it to pass someone it sounded like i was grinding to plastic gears against each other. Now when i was in low rpms (2000-2500) it would go through every gear fine but when i was in 3rd at low rpm and i stood on it, it down shifted to second and shot the rpms up and that when the grinding sound came back soon as i dropped the rpms back down to about 2000 the truck seemed to kind of grab and things when on as usual. It does this when downshifting from any gear. I think it may be the torque converter not sure, it has the E4OD tranny, and a borg warner 1356 manual shift, any help is appreciated and i still will always be true to the blue oval.

diamonbird

You will find out more if you change the Trans fluid, drop the pan and look in it for anything that's not supposed to be there.
I had a problem with my windstar (03) with 87,000 miles on it, When I first started it in the mornings and put it in Reverse(R) it just set there and made a starring noise to which I quickly put in Drive(D) and then in Neutral(N) and then back in Reverse(R) and it was fine..........It scared me that I might need a Trans. so I decided to change the Trans. oil and filter, I put Amsoil Trans. ATF fluid in it and have not had a problem since. 96885 miles later it still shifting fine.
I have bought Amsoil Trans. fluid for my f150(08) but the dealer just changed my fluid in the Trans. so I'm going to wait awhile before changing it out.