How hard of a shift is TOO hard (auto trans)

[DozerDan]

I just picked up an 01 F350 recently. 7.3L auto, dually. It came with a programmer, which I am currently running at +60hp. The trans shifts VERY hard imo. If you get on the go pedal the 1-2 shift seems like it is going to break the ujoints on the ds. The 2-3rd shift is not normally as bad, but it can be at times.


I redid the programmer to have a stock shift, thinking that it was the way running at +60 that was doing it, and while it is not as harsh it still hits hard.

Now I realize that a 'hard' shift is 'good' for the trans, but how hard is too hard when it comes to it.

[KS Toy]

What programmer are you using? Some programmers will make the tranny shift harder then others. I had an Edge unit that did the same thing (on my 02 F-250) and I got rid of it. I switched to the Superchips programmer and it is fine.

[Mechanos]

My built auto will snap your neck if it weren't for the anti-whiplash pads on the seats. The trans is running higher than stock line pressure and has had other internals modified to make the 1-2 shift a bone crusher. The 2-3 is pretty hard too, but not like the 1-2. The trans loves it, but if you listen real close, you can hear the u-joints screaming for mercy.

[DozerDan]

The programmer is a Diablo Sports Predator. Even with the +60hp trans setting at stock shift, it still is a neck jerker.

[texascadillac42]

Maybe it has a Sonnax kit to modify shift points and firmness. (Actually it might have a generic version of the Sonnax kit) When these kits are installed improperly or cobbled together with different springs, the shifts can be too harsh, too soft, too slow, too fast....blah blah blah. Any way to get the history and find out if a trans kit was put in?

[paul_arc]

the previous owner probably burned up the trans and had it rebuilt. my dad has an 01' f250 and when he had his trans rebuilt he got it so that there is no slippage between shifts. first and second are hard then third and so on arent that bad. Its way better for the trans and will last longer that way.

[Danger Ranger]

does it hesitate before it shifts? do you find yourself anticipating it and letting off the throttle? Sounds like the clutches slipping and the *bang* is when they engage...

[IDASHO]

The programmer might have the TC locked.

That would certainly make for rugged shifts

That said, my '96 PSD with a rebuilt trans and a generic 'shift kit' hits pretty hard on the 1-2 if my foot is into it.

[72blazer]

Originally Posted by Mechanos

if you listen real close, you can hear the u-joints screaming for mercy.

[-SHC-]

If you changed tire size the valve body on the tranny may have been set up for a larger tire this would effect shifts. The diablo programmer could be the problem. My buddy has one on his manual 7.3 and is gonna throw it away because it keeps erasing the PCMs programming.

[mike holt]

My 03 psd shifts very hard between 1and2 shift, too hard imo. I can prevent it by starting out in 2nd but sometimes this is not possible when towing. I was told by the dealer that my pump pressure is low? Not knowing the internals of automatics I don't know where to turn. keep me posted if you should find the problem or figure out a solution. Thanks

[MR4WD]

Not quite the same, but my hard shifting allison (roasts tires in all gears, barks tires on 4-5 shift) busted the flexplate, torque converter and pump a few days ago. Doing 70 (mph) up a snowy hill on the highway, passing a semi, tires broke loose towing a trailer. Shifted from 4-5, tires broke loose and grabbed. Clang clang clang! Pulled over and sawing the tranny pouring blood. Got towed and found the broken parts.

I've never busted a driveshaft or u-joint even though the trucks got 100,000 miles on it, 33" tires and 600 horse.