@Tatertot /
@Anak
Agreed, the K2500 series burbs are heavy... over 5700 lbs! before you start loading them up. The 8.1 I think is closer to 6k lbs!
Larger than stock tires without re-gearing the axle(s) makes even slower off the line.
Also the biggest restriction to "off the line power" is the transmission they put in these rigs. While the 4L80/85e series trans are great in their own right, it has a max input torque rating (440lb/ft) that they have to work with.
The 6.0L is a decent engine but thirsty compared to the 5.3L for the additional power you get from it. The 8.1L is a beast (455lb/ft)! But when mated to the 4L80/85 series trans they really need to dial the engine back to keep it under the max torque rating of the trans. The later 03+ 8.1 was detuned further to keep the trans happy. In the pickups, they had the Allison 5 speed (520 lb/ft) behind the 8.1L and while the pickup might weigh a little less, those rigs definitely have more power off the line since they do not need to limit the torque like they do when mated to the 4L80/85.
If GM would have put the Allison in the burbs then we could have had the same fun as the pickup guys. but Allison is 100+ lbs heavier then the 4L80 and with the 2500 burbs getting an 8600lb GVWR they needed to keep the component weight down so that payload capacity could be competitive. The Pickups had a higher GVWR (9200lb) so they could afford the additional weight of the allison.
I've driven a couple 8.1's with the BlackBear treatment and they definitely wake up that motor, but I feel its a matter of time for the trans with that additional torque being thrown at it. If you address the trans then you should be good to go.
That 8.1L was designed and built to be used and abused for 250k+ miles. Probably one of the most durable gas engines GM has built in recent years.
Good luck with your rigs and I'm glad to see the GMT-800 crew who appreciates these rigs for what they are.
