Transmission Will Not Shift into 3RD Gear and High RPM Overdrive

2002 Avalanche Z71, 243,000 miles.......I Have had my tranny rebuilt 3 times since 2003, the last one about 1-1/2 years ago. New torque converter, and full rebuild twice. About 6 weeks ago it was put into shop and they replaced the Valve Body, new filter, and fluid. It has been driven about 900 hundred miles since. I put a new DelCo TPS sensor on 3 days ago, did not help. Last week I found 4 wires coming off of the transfer case, 3 of them with no insulation on them, and one broke. I put heat shrink obut if I have to stopn the wires and repaired the broken one and put in  a new 15 amp fuse. The 4-wheel drive lights on the dash were not working. 4-wheel drive and lights now work.

PROBLEM------When I drive at about 30-35 MPH, the tranny will not shift into 3rd gear and when it goes into Overdrive, it starts tacking 3000 RPM or higher, in Overdrive, depending on what speed it is going. Taking off in 2nd gear manually, and  shifting into 3rd gear, it will go into neutral. Manually shifting into Overdrive the truck will shift, but the RPM's are 3000 or more. I am totally flustrated. Any help or solutions would be appreciated. I am trying to avoid putting it into the shop again. I do most of the maintenance on my Av, but do not know a lot about transmission.
NOTE: Periodically, When the engine warms up, if I drop the shifter into 2nd gear, then into 3rd, the tranny will work perfect, when shifting into overdrive, but if I stop it will not work. I am thinking,maybe an electrical problem.
Thank You 

I say put it back in the shop.  They usually offer some kind of warranty on the work and they know more than I do about it. 

I've been using the same shop to rebuild by tranny and transfer case, and when the shifter cable ended up wearing down from being hit by the drive shaft, they replaced it all for free.  Guarantees are a great thing.

That's what I would do, except I am 600 miles from my home in SC. Spending winter in FL Keys. No Transmission shop within 60 miles. Thanks anyway  

I would suspect the 2-3 shift solenoid and/or the valves immediately in line with it, the 2-3 shuttle and 2-3 shift valves, which may be sticking or leaking.  These can be accessed by dropping the tranny pan.  I'm not a transmission expert, but I have rebuilt a couple of these.  When you are starting out in 2nd, pressure is applied between these valves to force them to opposite directions in their common bore, vice going in the same direction depending upon what the 2-3 solenoid is doing.  That may be why you sometimes get it to work correctly when starting out in 2nd, then manually shifting up to higher gear.