Hard Shifts, But just for 1 day.. wtf?

[WoR]

A few weeks ago i was driving my '91 ga Quad 4 and she was shifting like a built 350turbo. I really really like it, didnt seem to shift hard enough to prematurely wear the thing out but was a nice good shift. Im just wondering why it would only do it for one day, then the next day its back to switching like a lazy lazzy trany? Is this bad? I would actually like it to do that all the time, i cant stand the way it shifts normally, way too soft.

[rixGAphx]

My *guess* is that the entire engine and tranny, both controlled by the PCM, were in the 'limp-home' mode.
You noticed the difference in tranny shifts, but not the slightly different engine performance.

Without the SES light coming on to show a code, there are certain times when the PCM gets 'goofy' codes from the sensors.
It says to itself, "something is wrong, and rather than react to this goofy data, I'll set my ignition, FI mapping, and tranny shifting to the built-in defaults" so the driver can limp home.

The number one sensor that the PCM will ignore is really bad signals from the O2 sensor.
It defaults to 'rich and polluting'.
It defaults the ignition timing.
And, it defaults the tranny shifting.
So, your PCM might have been getting a goofy code, whether from O2 or elsewhere, and defaulting.

It is illegal to deliberately by-pass an emission-control feature (like the O2 circuit) for a street vehicle, but I'll bet if you unplugged the O2 sensor on the track you'd find that same 'sporty' shifting had returned.
'Course, the rest of the engine would be on 'default' too, so your overall performance would suffer.

Anyhow, that's one way you may have felt a difference in shifting.

-Rick

[Brad97GS]

Would this work for a '91 though? GM trannies weren't computer controlled till the mid 90s AFAIK. But let me know if I'm wrong - it'd be good info to know!

When the front engine mount went bad in my old '89 GA (Q4), the tranny felt like it was ready to die because you could feel the shifts so much! I replaced the mount, and everything smoothed out considerably, including much less vibration in Reverse.

[WoR]

This trany isnt computer controlled. The only thing going too it is for the lock up torque converter which i have disconnected cause the dam thing sticks after driving it on the highway for more than 2 min. Ive had this problem with 2 of my quad cars (the sticky torque lockup)

[rixGAphx]

Never mind. :roll2:

-Rick

[WoR]

Thanx anyway for your help rixGAphx, still interesting even if it doesnt apply to my year.

[RomeoGAOC]

my car shifts hard thru every gear lol. i like it tho so i dont complain. one of my friends thought i put a shift kit in it heh.

[WoR]

Well dam, the car teases me for one day then sais f**k You.... wonderfull

[RomeoGAOC]

:lol: