I have a 2006 yukon the engine is missing and the trans is shifting hard when u drive easy but if u get on it, it shifts perfect,i took it to shop they can't figure it out ,every where i take it the only thing that they can tell me is the engine has a mis fire on the #1 cylinder. even took it to the dealer and they was stumpted could not help me

SOURCE: WHATS INVOLVED

No that hard, but your going to have to drop the Transmission pan, there are two identical solenoid at the back of the valve body with the pan removed.
The "B" (2-3) solenoid is the closest to the passenger side,"A" (1-2) is closest the driver side.I would go ahead and replace both as they are not that expensive.Spring clips hold them in place that can be removed with a small screw driver.
The "slipping" you're noticing,is most likely just the transmission shift pattern getting screwed up due to the malfunctioning solenoid.Probably more like a 1-2-2-1 or a 4-3-3-4 pattern depending on which way the solenoid is failing,or maybe it feels like it is starting out in 2nd or 3rd gear. 

Once you get the solenoid changed and transmission fluid and filer changed, here is a little added performance you can do. Have the Servos replaced with the Corvette servos, the part is only $45.00 and take about 30 min to replace but less for you since you have the truck up on a lift already. 
Good Luck and here is a link for the 4L60E improvement. http://s-series.org/component/option,com_tech_article/Itemid,/item,6/task,item/

SOURCE: 97 yukon 4wd. Jerks and makes noise like its

Hi amberdawn_84

My 97 yukon did the same thing (I believe). The valve body in the transmisson wears out (design problem) and causes the transmission to shift really hard. My repair was about $500 (nondealer).
LOVE MY YUKON!

SOURCE: i have a 97 gmc jimmy 4x4. the transmission goes

I need the CODES this year has valve body problems for tcc slipping on these & shift timing need more information

SOURCE: engine code p0307 miss fire cylinder 7 ?

A code P0300 may mean that one or more of the following has happened:

• Faulty spark plugs or wires
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector(s)
• Burned exhaust valve
• Faulty catalytic converter(s)
• Stuck/blocked EGR valve / passages
• Faulty camshaft position sensor
• Defective computer

Possible Solutions If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak
in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

SOURCE: 03 yukon with 125000 miles wont shift into 3rd

yes but you can get it less becauses the kit cost only 72 to220$ for it and its a half day labor onit any ? you can call 863 261 6116 if no answer leave a message