I am new to GM and looking into buying an used 3500 Duramex/Allison , 2001-2003, dualy,L/B to tow 5th wheel 12000LBS.
Are there any differences in theese models?If yes which?what ratio is recomended?
Any other remarks,suggestions or advise will be welcomed.
Thanks,
Danny

Somewhere between 02 and 03 there was suppossed to be an injector model change. 2001-02 have injector warranty out to 200K. Chevy underwent major cosmetic surgery in 03, GMC was far more subtle. Updated interior & heater controls in 03 as well. Power numbers were all identical from 01 to 04. 3.73 is the only ratio available with the diesel. A six speed (if you want one) will be relatively difficult to find.

DanShula,

Both makers are GREAT for what you want to do. Platform the same for all those years. Cosmetic differences between GMC and Chev. Styling will be your preference.
Do not be afraid of a good used 01. Very nice. Looking at all the trucks every year that they have been released, I still prefer my 01. Simple, not a lot of bells and whistles that ultimately can be problems and more grief. I always believed in the K.I.S.S. principle. I have pulled trailers up to 15K down to 3K. Towed with out issue.
If buying from private party check a fuel filter or ask for maintenance records.

Have fun and Good Luck

If I can be of any other help, just let me know