I bought the Superchips handheld tuner for my 2004 Sierra and I set it on the "Performance" setting but it seems like ever since I did this my rear diff. makes a clunking noice when I take off from a stop... what's causing this??

Also as I was putting the tune into the computer my dispaly by my guages read " Reduced Engine Power" and "Service 4WD" is this normal? cuz I haven't seen those messages while driving it at all only while the tune was being entered.

Any help is appreciated!

 

I had the same problem when I had a power programmer for my truck, not too sure why it did it. But ever since I got a mail order tune from Nelson Performance it hasnt happened since. The power difference between the two is night and day. IMO get a custom tune.

 

the reduced engine power and service 4wd messages are normal, they both flashed up when i installed my superchips programmer. everyone here will reccomend switching to a custom tune and i will be soon as well.