I have a 1999 Chevy Silverado z-71, My trans lost 4 th gear and checked and found out the 2-3 shift solenoid was bad in the proccess the bearings fell out of the valve body and I put them where I thought they should go, All I have now is all forward gears, even in reverse and nuetral. Where do the bearings go.

There are a few potential causes for the issue you are experiencing with your 2006 Chevy Silverado 1500 4x4 and the 4l60e transmission. Here are a few possibilities:

1. Clogged or dirty transmission filter: If the filter is clogged or dirty, it can cause problems with the transmission, including a loss of reverse gear.
2. Faulty solenoid: The solenoid is responsible for controlling the flow of transmission fluid, which in turn controls the shifting of the gears. If the solenoid is faulty, it can cause problems with shifting, including a loss of reverse gear.
3. Wiring issue: There may be a problem with the wiring that connects the transmission control module (TCM) to the solenoid.
4. Faulty TCM: The TCM is responsible for controlling the transmission, so if it is faulty, it can cause shifting problems.

To diagnose the issue, it is recommended to have a mechanic or dealership technician take a look at the car. They will have the necessary tools and expertise to properly diagnose and repair the problem

in reverse there is no solenoid involve. so I think the servo seal or 2/4 band. look to 2/4 servo can be done without trans removal. have look to this; http://www.youtube.com/watch?v=YfPgBUH6Ru0
hope it helps

Sounds like a clutch is slipping.
Does it feel like it shifts from second to third gear ?

rebuild or put a used trans in it they have hd zpack made for 3and 4 gear

If fluid level in trans is ok it sounds like clutches in tranny or internal pressures are going bad.

Shift solenoid is where the wire clip connects to the transmission.

Put a transmission line pressure gauge or visit a local trans shop, on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.500" boost valve (easy fix in pan).
“3-4” clutches are worn out or 2-4 band is slipping. Servo seals may be damaged (can be fixed without removing trans. Otherwise, 2-4 band is worn out. R&R.
Soft shifting, gradual performance degradation: Poor line pressure rise due to leaking boost valve, clogged EPC filter screen, failing EPC solenoid, or worst case: leaky seals throughout the transmission.
Most transmission shop test drive and hook up a scanner to see what condition your transmission is in. Call around and if they do charge for the inspection, call another place that will. 4th gear slip sounds like ether line pressure issues from a bad boost valve or a bad EPC and if your lucky, it's might just be a simple TPS that has a bad spot which controls your EPC valve. EPC (electronic pressure control) Valve. TPS (Throttle Position Sensor)
Good luck and keep us posted. http://www.hotrodders.com/forum/attachment.php?attachmentid=27867

FIRST CHECK TRANNY FLUID LEVEL. IF ALL GOOD. HAVE IT SCAN CHECK 1 -2 AND 3 - 4 SHIFT VALVE SOLENOIDS.TO SEE IF THEY WORKING OR FUSES BLOWN.

u need to have the system tested for trouble codes, but u most likely have a defective trans 1-2 shift solenoid. to replace this u will need to pull the trans pan off the solenoids are attached to the valve body, also check the trans connector for water or corrosion.

transmission shift solenoid is stuck open this is a common vehicle issue in automatics and not particular to any make or model vehicle 15 dollar part and arm and leg for labor if taken in

heres an idea to try
take out the transmission filter and replace with new one make sure to take not of any metal debry in trans pan this indicates the trans had sheered its gears down and a trans rebuild is needed
the transfilter needs to be changed at a certain milage interval they can get clogged up
there is a kit you buy for your truck at any parts store
its an easy change hour of time unbolt trans pan unbolt trans filter and put new one in
kit comes with new seals less than an hour you can do it yourself

to overdrive you would feel a difference in shift badley if it was that something to keep in mind