I have an 02 2500HD 4WD Silverado with and auto trans.Today while driving home from work it felt as if the trans slipped or down shifted funny 2 times.I had the trans fluid changed (not flushed) at the dealer 3k ago and the fluid level is good.

I just put new tires on the truck before I went up north to do some ice fishing.The tires on the truck were the original size LT245/75R16 and I went to Cooper Discoverer ATRs
LT265/75R16,a slightly larger tire.I havent had the tire size change adjusted in the computer yet.

I know the size difference will cause the speedo to read off a little but will it also cause shifting issues in the trans?

 

No the tire size won't affect the trans.

There's a good chance the clutch packs are worn. It's an all too common problem with the 4L60e's.

But now I'm seeing you said HD...do you have the 80e?

 

I'm not sure.It does have the tow package and the 6.0L engine.Where can I find the trans info?

 

Look in the glovebox at the RPO sticker...

M30 is a 4L60-E
MN8 or MT1 is a 4L80-E