do the 03's have a limp mode setup? After working the truck real hard plowing snow i pulled out of the lot and it shifted into overdrive at 30mph. Stayed there for about 2 miles then worked fine, happened twice now. Only would kick down if over half throttle then as soon as i let up the pedal right back to overdrive.

 

Mine kicked in to limp mode but only when the check engine light came on.

 

You may be experiencing this because of the change in final drive ratio that is a result of the 315 tires. Are you running 3.73 or 4.10? If 3.73, you may need 4.10

 

If you haven't had the dealer recalibrate for the larger tires you need to, the info you need to give them is 601 rpm's (revolutions per mile) only a dealer can do it with there DRB tool, takes 2 minutes.

 

The only limp mode I know about is that the OD will drop out if the tranny fluid gets too hot. When it cools back down, then you can engage OD again.

With yours going into OD at 30 MPH I wonder if some wiring got wet from your snow plowing?

 

Man if that is the case I would get that fluid changed, cheap insurance, in my 01.5 I changed it every 10000 miles, but still as I suggested with the 601 rpms your tranny is thinking it running a higher gear. Its a must do.

 

Thanks for repling goes in on monday to recalibrate and 2 recalls. I'll let you know what happens

 

Check the colour of the fluid, if it needs to be replaced HAVE THEM ONLY DO A FLUSH not a drain and fill. Flush gets 96% out, A drain you are lucky to get 70%.

Good Luck

 

Like SBishop says, I'd bet on either wet wiring or maybe even some snow/ice lodged in the linkage somewhere.