sbarto

My 2003 silverado 4.8 while idling with ac on upon driving, the transmission acts like it is overheating if you sit and idle for more tha 3 or 4 minutes.

MT-2500

What are your symtoms of acting like overheating?
What is it doing or not doing?
Is the engine overheating at stop light?
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

sbarto

The engine doesn't overheat. The transmission takes a long time to shift, almost like it is slipping. But then after you have driven a few miles it is back to normal.It does this when it fairly warm outside and you sit and idle for 5 minutes or longer.

MT-2500

Is it at idle in or out of gear?

Usually transmission does not overheat unless engine overheats.
What is the mileage?
Has transmission ever been serviced?
How is fluid level and fluid and filter?

I would get a good transmission capable scanner on it and read out all engine/transmission data and shift time and shift adaptives and watch for any slipage.
Check for transmission or engine running codes.
Engine has to be running good for transmission to shift good.
Post back any codes.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

j cAT

check fluid level and condition with engine at operating temp....on level ground ....if fluid is discolored and grayish on white cloth replace fluid and transmission filter....this means dropping the pan and carefully cleaning and inspecting for debris....as fluid gets hot pressure drops this MAYBE your problem....

sbarto

Why would the transmission do this only when the ac is on and sitting still for more than 5 minutes, then is normal after a couple of miles is driven? This si the only time this occurrs.

MT-2500

The answer to that can/may be found by proper testing and giving us more info.
Does it do it sitting still or at stop light in gear?
Any check engine lights?
Mileage and has it ever been seviced?
As j caT says fluid level hot in park and on level.
And fluid condition.
A good transmission/engine capable scanner check should have a lot of information about transmission shifting and operation.
This could also be a engine running problem to.
Need to check engine and transmission both.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

sbarto

Doesn't do it at stop lights, no check engine light. I will check fluid and get back, thanks so much.

j cAT

this is because when stopped in gear a/c on added heat is created by engine/transmission and lack of air flow acrosss the radiator...this added heat is transferred to the transmisson this then reduces the pressures required to allow the transmission to function properly...

if your engine idle rpm is too high like over 700rpm this too will quickly heat up and damage the transmission fluid...if your idle is over 700rpm and this has been going on for a period of time you may need a rebuild on transmission...what does the fluid look like??????