4L60E slipping and won't lock up

Hello, I have a 94 Chevrolet 1500 (4X4 – 5.7 liter) with the 4L60E tranny.  I had the tranny rebuilt a couple months ago.  At the time, I had the upgrades done (servo, 3-4 clutch pack) to minimize the normal problems the 4L60E has been known to have.  However, none of the electrical components were replaced.  So, they are from my previous tranny that had 200,000+ miles on it.

A couple weeks ago, while driving at 75 mph on the freeway, the tranny instantly began to slip.  As I slowed down, I found that 3rd gear was also slipping.  After reaching slower speeds (against my desire at the time), I found that manual 1st and 2nd were fine.  After getting off the freeway, I played with it and found that I could shift from manual 1 to manual 2 with no slippage whatsoever.  I also found that occasionally I could accelerate to 45-50 mph (with the throttle under even pressure) in manual 2 and then I could shift into overdrive and the tranny would operate normally.  This was occasionally.  Most of the time, no matter what I shifted into from manual 2 it would simply slip (allowing the truck to accelerate to a max speed of 55 mph at 3500 rpm).

The tranny is under warranty.  But, I’ve had limited success in getting an appointment to have it looked at.  So, I’m forced to forge ahead on my own.  I have driven the truck very little since the tranny failure.  But, I have noticed that the times I have driven it the problem has gotten worse.  In fact, this morning manual 1 and 2 were also slipping badly and my top speed was 25mph in all gears.

In talking to the guy that rebuilt the tranny, he suspected that the problem was electrical (this was based on the problem being intermittent).

Any ideas of what electrical component could cause the described problem?  Thanks in advance for your input.  

I think your rebuild man is full of BS if you paid for a rebuild that includes all parts elec included unless it was only select parts that you specified.I'd tell your rebuilder to get his head out of his backside and do the job he was paid to perform.Tell him to save the BS for someone else.This is the number for my tranny man 716-373-8726 ask for kevin or brad very helpfull and honest very good men.People literally send tranny's from hundred's of miles away they are that good.Tell you a little story had them build me a 700r4 ror my 90 chev 1/2 ton 4 wheel drive while trying different valve bodies we were testing we had it spinning 60-70mph when the pin broke in my pinion gear.Net result was it shattered the rear end shattered the sprag ie wiped out the tranny shattered the torque convertor and snapped my crank shaft a 4340 3.75 stroke eagle as engine is 383 ouch.What these guy's did was find me a replacement rear end for 800 dollars with 12000 miles posi from a rolled truck then they built me a new tranny and convertor for free as they felt i had taken enough of a beating.The special part is this was the first time i had ever done bussiness with them.How's your tranny man compare to that.PS i was standing beside the pass side rear tire when it happened my exact words at the time were Pease God let someone else have a turn.  

I tried to get hold of my tranny people today but apparently they're still on holiday.I'm not sure but doe's your trans have a detent cable(kickdown cable)i know on my 700r4 it is important that this be hooked up properly if your trans is supposed to have one and it's not hooked up that would fry your trans.  

It sounds like the solinoids are acting up, With that many miles on them changing them should have been a no brainer. and also, with the lockup not working the trans will overheat and this will cause problems too.