MY 1993 BUICK SHIFTS HARD FROM 1ST TO 2ND AT MEDIUM AND FAST SPEEDS

Need more info is the truck stock or purchased used? sounds like someone put a shift kit into the truck at some point. Has it always done this? Is this something recent out of the blue?

my friend you are having valve body problems, the 1-2 shift acumulator valve is probably stuck, you have to service the valve body or replace it

When the O/D light is blink is warning of lube overheat (initialy). Check it.

Good luck.

Did you change the transmission filter and gasket as well as the transmission oil before running your truck.

It sounds like your input clutch seals are rolling. Is the check engine light on. It could also be the pressure control solenoid could be causing the problem aswell

Sounds like you have a bad shift solenoid. Not sure if the Chevys are a solenoid pack, or seperate, but it will need to be replaced.

No, the modulator on a 4t60e only will adjust shift feel, not shift points. Does the trans not shift up or go it to neutral instead of 2nd? Does you speedo work? The pcm needs a speed input to shift the trans. You might have a bad VSS

Hello;
I need to know the codes so I can properly diagnois your problem. Here are a few tips though. Your electronics inside the transmission may be going out. You should start by changing the fluid and the filter. Let me know if there is a lot of metal or fiber shavings in the pan. Put new fluid in and clear your codes. See how it shifts and then let me know what is going on with it. Hope this helps.
Thanks;
Rich
RPM Northwest

SHift solenoid pressure switch

The blinking overdrive button is telling u that a serious fault has occurred in the electronic controls or a mechanical fault such as excess slippage is occurring.