Engine/Transmission (1998.5 - 2002) correct idle rpm

[99slt]

I recently had my transmission overhauled, and one of the suggestions made by the shop was to lower my idle speed because he felt it was to high. My truck is a 99 4wd automatic. The first picture is in park at operating temp, second picture is in gear at operating temp. Is this normal? Or does it really need to be adjusted lower?

 

[SSage]

If I remember right your engine data plate will say 850 rpm. Looks good to me. I would expect 750 to 850 rpm on most trucks, depending on temp, air conditioner etc..

 

[Grizzly]

You can lower it slightly, maybe 100 rpm.

 

[99slt]

How does one go about adjusting the idle? Can it be done myself or is it done through a scan tool at a dealer? I'll try and lower it about 100rpm I guess if it makes this shop happy. I don't need any hassles from them if I have a warranty issue with my trans in the next year.

 

[SSage]

Why would it matter? I don't get the issue. Maybe the 24 valve is different than mine. My 3rd gen doesn't idle any lower. Even with a built trans I don't creep at red lights in gear. On my old 12 valve things get rough below 700 rpm or so, when I did my DTT upgrade I had to raise the idle on my P7100.

I have a billet DTT built trans in my 2nd gen and its really strong off idle. I have no issues with my idle at 900 rpm in park. With the air conditioner on in gear it will come down to 700 rpm, but my 12 valve is mechanical. Maybe the later versions don't pull down 200 rpm in that situation. I can idle my heavy trailers around on flat ground. In slippery winter conditions neutral is required at red lights, but only when its really icy out.

 

[99slt]

When he was done with the rebuild he said he felt like it would lurch forward at a stop because it was idling to high. I blew him off but I just dropped it off for the 500 mile recheck and the first thing they asked was if I corrected the high idle.

 

[SSage]

The fellow does not have much knowledge with our trucks then, your idle is normal. Thats why I used a well known diesel transmission specialist, DTT did mine in house. They told me what to expect and how it would drive differently.

Depending on what torque converter you have, the truck could idle roll some. If you want the truck to run like stock, then you just choose a TC with an OEM stall speed. My old 43' toy hauler weighed 15,886 dry and I could idle it right out to the main road most of the time if it was flat pavement. I down sized since, that sucker was over 18K easily loaded and the built trans handled it well. I have a billet single disc from DTT, its very tight at idle.