my car won't shift down

i have a 1994 olds cutlass supreme and it won't shift down when i stop. i have to manualy shift it down as it stays in high. i put in low and start down the road it shifts up to 2nd then as i get faster i shift to drive. but when i slow down or stop i have to shift down or it won't go. when i was changing the starter i found transmission fluid in my modulator valve and line going to my motor, i went and got another modulator valve and now it won't shift down. what i find really strange is i got the valve for $20 at one store and some part stores wanted $75 to $100 for one. do you think i got the wrong modulator valve? or will that even cause my trouble? thank you for any help.

Normally the modulator will not cause this, stuck solenoid is one possiblity or valve in the valve body, a scan with a trans function scanner will find the problem. Try disconnecting the hose, manually upshift the car then see if it drops down to 1st.

what hose should i disconnect? and where is the solenoid? i've heard of valves but not a solenoid for transmission. thank you for your help.

All the shifts are commanded by solenoids in the valve body as well as modulator functions, disconnect the hose to the modulator for testing the down shift, manually upshift as you have been then see if it downshifts, Remember as I said the pcm controls the shifting here.

All the shifts are commanded by solenoids in the valve body as well as modulator functions, disconnect the hose to the modulator for testing the down shift, manually upshift as you have been then see if it downshifts, Remember as I said the pcm controls the shifting here.
My 95 Olds Cutlass Supreme wouldn't shift into 4 (overdrive)? and the back-up lights wouldn't work. The problem was a completely worn out transmission position switch (TPS)? It seems to play a part in transmission shifting. Replaced the switch and the transmission shifting is back to normal.

Correct, the pcm has to see what gear you selected to determine solenoid and shift functions.

thanks, i'll try that. called my local parts store, they have them for $35.00

i went to the parts store today and i don't know if they gave me the right part. the part they gave me was about round as a quarter and flat with a tit along the side where the wires plug on. the part they gave me went right across from the throttle cables. i did notice another sensor on top that was much larger but don't know what it goes to. well i put it on and it still won't shift down, i put it on crank the car put it in drive........ nothing had to put it in low to take off. any more ideas?, i sure could use them. i just got told by a another friend that i might need a vehicle speed sensor, that it helps shifting too. thanks for any help.

Vss also controls the speedo, the sensor is a large unit on top of the trans where the linkage connects, as I said without a proper scan which can check the sensor, you will be throwing parts at this.

well i found my trouble, its the modulator valve. a friend loaned me his off his car to try, it shifted up and down good. so now i'll go get one and hopefully have it cured. i just checked the online part places and there sure is a big difference in prices on modulators. oreilly's has 2 that supposed to fit one is $20 the other $60, now i called and they told me either will fit. my transmission is a TH4T60E 4 speed, they said that both fit. i called my local store they have 2 one is $25 the other is WHAT#$#$..., i can't believe it they said $148.00. they also said both will work. i don't believe it, if yall could help i would be gratefull. i can't see that big of a difference without it being for different trans. thanks for any help

Can somebody explain where the modulator valve is located on a 95 cutlass?
Thank You

Look at the drivers side front of the trans should be a vacuum hose on it.

Look at the drivers side front of the trans should be a vacuum hose on it.

Look at the old modulator,,,,,the new modulator must have the same length,,,same stack-up that inserts into transmission,,,there is several different versions of stack-up,,,if wrong will cause shift issues

When working correctly,,modulator only controls line pressure,,,,shift feel. When out of peramiter will cause 2nd gear starts.......
The 20.00 dollar one should work as good as the 100.00 one except someone made a s+it load more money !!!!!