1997 Silverado 4x4 4L60E Shift issues, HELP!

Ok, I read some stuff on here and hoping there is some help for me.

1997 Z71 with 239,000 miles. Auto Tranny juice looks good, but low. Shifts hard from 1st to 2nd, won't shift to 3 or OD. Manual shifting from 1-2 works well if I let off the pedal and shift manually. Added two quarts of Dextron III rated tranny juice, inspected for leaks...leak was from the pan. I looked for the old vacuum modulator and guess what? We're all electric now!

Looks like 3 or 4 solenoids on it. Anyway, some other info.....
I recently had the intake manifold replaced, as I cracked it trying to remove the heater hose coupling. Got it from the shop and the guy says my brakes are spongy and heater core leaking. Brakes were fine when I took it in and it wasn't leaking, so I figure he stepped on the heater core outlet pipe near the firewall while he was working on it. The few times I drove it, a hard right turn caused my brakes to hit the floor board and felt like it was jumping a curve. Go straight or left, no problems with the brakes. New pads, no air in lines, no brake warning light. Could that be connected to my tranny issue? Any help appreciated. Thanks!

May have lost the direct clutch, or the solenoid(s) actuating it. A scan with a powertrain capable scanner and/or measuring resistance of the solenoids (can be done externally) might be a good first step.

Brakes and transmission and heater core are all seperate pronblems.

Get the brakes fixed first before you run over someone.

Are you going to DIY it or getting a repair shop to fix it?

I know the heater core is seperate issue. But wondered if the brakes/ABS might somehow send a conflicting signal to the computer, telling it that I was braking and consequently sending a signal to the tranny to downshift? Just wondering.
I'm going to get the parts and do it myself unless it needs a major valve body cleaning and rebuild or clutches. Any tips on the solenoids? Thanks for posting...
JMR

Seperate problems but You.
Might check the ign switch and transmission and ABS computers for codes or problems.
MT

BTW, I just did the brakes before I had the intake manifold done at the shop. Rotors are fine and new lifetime pads in front. Rear shoes not worn that much, drums look fine. Also, due to the rotor over heating issues, I not only replaced the rotors last year, but I now completely drain my master cylinder with a turkey baster and start with fresh brake fluid, bench bleed the master cylinder and then the brake lines. There are no leaks at the calipers/cylinders and the only time I experience the brake issue is on a right hand turn. I suspect that when the manifold work was done, something got dislodged, replaced wrong, I don't know. The brake vacuum booster checks out, vacuum hose has no cracks and I can't fathom any way that the metering/proportioning valve would act this way. As I said, the brakes were GREAT before I took the truck in for the intake manifold work, which I would have done myself if it wasn't freezing outside at the time.
On the tranny issue, I am getting a master solenoid kit which includes the 1-2 solenoid, 2-3 solenoid, 3-2 downshift solenoid, lock-up solenoid, PWM solenoid and force motor. The force motor can be adjusted for harder or softer shifts, but I am wary of replacing that one if I don't need to as I have no way of checking the line pressure. Ya think I should leave that one alone for now? Thanks for posting.
JMR