T slow speed slow take off hunts between 1-2 gear if i take off fast shifts normal also air conditionor somtimes goes into defrost on take off

just 1 possibility is this, Mercedes Benz Actros Replace gear sensor the other is you are just going to fast for the gear.

look for a vacuum leak in the hose to the actuator
run the fault codes and look for a problem servo/ solenoid

well gee, there are 50 reasons.
did you scan the PCM yet, if not ,why not?
when the idle surges, that means.
NO RPM ranges stated, if super low rpm check EGR.

1: engine lean and ISC dead, or cant handle the huge engine power drop..The PCM can even make this worse!, buy hunting the ISC to find spec, idle and failing... to...
2: or any of 50 other things causing huge engine power drop and PCM can't maintain idle controls.
super lean burn.(bogging)
super rich burn, misfire for 50 reasons.

i cant hear your engine,nor feel it, or see it shake from gross misfiring.
no can i drive it and see/feel power loss,
can I?
asking net bunny's this (blind as bats)
is "OVER THE TOP" no?
so here , ill toss the dice for you
and guess gross misfiring.
ever get a tuneup this decade, if not bingo , no?

and the others...

http://jeepdied.com/Misfire101.html

link even has the 50 cause list, to show the futility of guessing!
we do 1 to 10 tests. and find it.
for sure.

as you can see EFI systems are complex.
gue$$ is not only expensive but can net you 2 problems easy.

D4, that is overdrive in a 4 speed automatic. It should go into 4th gear at about 45 mph, although you may not feel it shift. The only reason to use D3 is if you are driving slow, like in city traffic, and the D4 keeps shifting in and out (from 4th to 3rd and back), as if it is "hunting gears". Most people just put it in D4 and drive away.

O/D is "Over Drive". This is the recommended transmission setting when driving normally. You should disable O/D when towing a trailer, when climbing hills or when the transmission is "hunting" (shifting back and forth over a very short period of time).

O/D provides maximum fuel efficiency by allowing the transmission to shift to the highest gear, quickly. When O/D is disabled, the transmission may not shift to the highest gear range and it may take longer for the transmission to shift into the highest gear supported.

You can see / hear this by looking at your tachometer (or listening to the engine rev if no tachometer) with the O/D on at any speed. Shutting it off should cause the tachometer to jump up noticeably (or hear the engine rev up) and the car should begin to slow almost immediately. You'll need to step on the gas to maintain the speed when you switched it of. This additional fuel is what you saved when in O/D. The up side of O/D off is more responsive acceleration - but at the cost of fuel efficiency.

I hope this helps :-)

Depending on the indicator rapid acceleration will downshift for passing this is normal.

my car is a 2002 saturn sl1 i was woundering if you can help me with my car when i drive on the freeway up hills my car goes from fast to slow so i have to shift from 5th gear to 2nd or 3rd gear and i have to go like 40 mph on a 65 mph speed limit all the way home how do i fix that problem

try to reset the computer if that doesnt work reset the idle speed it may have picked up bad codes

The fast idle valve is inside the throttle body. Sometimes it backs out and needs turned back in (it's threaded). This will cause the loping idle.

Get transmission filter changed with new fluid. Honda does not recommend transmission flushing.

With normal acceleration the 1st to second shift point should be around 2500-3000 rpm. Most of your shifts under moderate acceleration will take place at this same point or when there a light load on the transmission. Under hard acceleration the RPMs will climp higher due to increased power needs and the computer will shift when less power is needed or the RPMs climb to an unsafe speed say5000-6000rpms (depending on where yours redlines). Also going up a steep hill will raise the RPMs higher and goind down a hill will cause a faster shift at lower RPMs. These can always be altered by an individual owner by adjusting shift points, using performance parts and if you have problems (low tranny fluid/trans issues). Your trans RPMS are fine and will vary depening on how your foot accelerates. The shift pattern should be the same every time you drive slow/medium/fast/, look for changes in those patterns you will also catch a problem early.