Modulating Vlv Location

I have a 90 Suburban auto tran that will not shift out of 1st. I was told to change out the modulating valve first and see if that fixes it. I looked all over the tarn and have not found the valve and looked at numerous manuals with no luck. I have't pulled the pan yet so it might be in their. ANy suggestions?

I think the valve you are reffering to is simply mounted on the side of the transmission. No need to drop the pan.

700R4's don't have a modulating valve

This trans is a 700R4. Any suggestions on what to check to see why it will not shift out of 1st?

Does Reverse work at all?

Does it stay in 1st and not shift at all or does it shift from 1st to Neutral (i.e. slips)?

//2000CAYukon

I runs in reverse and will not shift out of 1st. I have tried to downshift to 1st and when I get fast enough to shift into 2nd manually shift to 2nd but it will not shift. I have not had any warning signs of tranny problems. Drove it on the highway and parked it overnight and the next day it would not shift. This is tanny is only 5 years old.

Looking at my factory manual for 700R4 not upshifting out of 1st:

- Governor Assembly
- 1-2 Shift valve sticking
- 2-4 Servo Assembly
- 2-4 Band Assembly

//2000CAYukon