I have a '98 Bonneville SLE 3800 with a little over 100,K I bought the car used and after it warms up it shifts like it has a shift kit.

That can't be good.

Has anyone else had this problem ?

Does anyone know what causes this ?

Any help would be appreciated. Thank you,,,,,,,Doug

Common problem with the 4t65e. You need a new pressure control solenoid inside the side cover of the trans. Part is about $40 but it is 4 hours of labor to change it. Hope this helps.

Check the trans fluid level, also...car driven around through all gears, fully warmed up, then check dipstick on level ground with engine running and trans in park (or neutral with park brakes on).

Make sure you're not over or under full.

The PCS is a known issue for harsh shifts, but not the only cause. Make sure you rule out simple things like a fluid and filter change, proper levels, etc., (as mentioned) before you spend big bucks on something that may or may not be needed.

Yes I also thought the fluid was the cause so I had the trans. flushed and filter changed.
It stills shifts hard.
Thank you for your responses.

1997SESC when you worked on the Pontiacs at G.M. did you ever work on any '68 Firebirds ?
I have one of those to.
I think Pontiacs Rock !!

try a bottle of Lucas tranny fix (no flames please). Won't hurt, should help

If the Lucas doesn't - try a bottle of Seafoam'* TransTune. That has freed up some sticky solenoids.

o.k. dudes.
I will let you know how it work'* out.

sounds like the same problem I have, the pressure control solenoid. you might not have to worry, your trans is not toast if that'* it, just change that solenoid. hope that helps a little