Having some trouble with my trans in my 94 k2500 6.5. It shifts alright driving normally but if I accelerate hard it will shift to second and stay in second. Like it's in a safety mode or something, also does this climbing hills, it'll be in 4th and shift down hard to second. Reverse slips in 2 wheel but with gear reduction in 4 low it works decent, slips but it actually backs up. I bought a low reverse servo as another forum told me it was a problem area and should fix it, also installing new check *****. If this doesn't fix it do I need a trans or what? Can I save this old thing?