I have a '95 e-150, 351, e4od, 165K mi. trans slips in low and/or reverse before warming up. especially if going up grade. I'm sure it should be rebuilt, but trying to prolong it. Can I try a different trans fluid besides the slippery dexronIII mercon? or use a suitable additive? I read once that these trans's need to be run a quart over full, could that be it? I run it just full, not over. When warmed up, all works perfect, except last year trying to climb Mt. Washington, NH, pretty steep road, in low gear, after 2 mi., turned around, too much slippage. works good on flatland. It does have cooler in front of radiator. Thanks for any advice. Would Mercon V be compatible, or help any? Might be more slippery than Dexron III Mercon? Thanks, Huey