2002 4.8 and auto trans issues

[Yukon6.2]

Hi All
i have a gasser p/u that i got from auction.
Now that the weather has turned colder the tranny has an issue...
When i start the truck in the cold if i go to backup it takes a while before reverse kicks in.Forward gears are fine the engage without any hesitation.
Idea's or direction please...
Thanks All

[trbankii]

First check would be fluid level and condition - is it where it is supposed to be and is it clean?

[Yukon6.2]

Yup it's good

[More Power]

The Allison in my 2001 GMC set the "MIL" warning lamp following the coldest overnight low we experienced last winter. The MIL would come right back after clearing the codes - I cleared them many times - they always came right back. The fluid level and color/condition were great.

The solution came as a result of what we always recommend as a first step when troubleshooting most transmission problems... a full service. Changing both fluid filters, along with what fluid drained as a result of changing the filters, solved the MIL problem. A series of trouble codes had been set. I'll have a short tech page soon that talks about the codes and the trans service.