8.1 engine transmission options

boomer 33 · October 2, 2003

When you order, their are two options on the 2500 Ykon XL with the 8.1 liter, both describe an HD transmission with cooler, but there are two options. Anyone know what the difference is between the two?

sierra8.1 · October 2, 2003

boomer 33:

the only thing different in the tranny's is one is mt1 and the other is a mn1. when you select the trailering package on the build it yourself site, it defaults to mn1 making me thing that it maybe has a larger clutch pack and beefier gears in it. otherwise probably the same tranny's.

Larry

boomer 33 · October 2, 2003

Makes sense to me, I got the trailer package, I guess the Allison only comes with the Duramax ?

CMNTMXR81 · October 2, 2003

You missed that he's driving a Yukon XL. Not a pickup.

8.1's and D-Max's in the pickups get the choice of Allison or 6 speed manual

8.1's in the Suburban's and Yukon XL's get the Hydramatic 4L85E with trans cooler.

The 4L80/85E is a stronger unit than the standard 4L60/65E hence the term "HD"

sierra8.1 · October 2, 2003

boomer 33:

You can have the Allison behind the 8.1 gas but only in the 2500HD or 3500 pickups. I believe that due to the Allison's size(height) it won't fit in the Yukon. That's the reason the 2500HD and 3500's have the body raised up about 2" off the frame from the factory , so there is room for the Allison tranny. One more thought as to the difference is that there might be a difference in gear ratio's also. Maybe lower gear ratios to get the weight moving(as in trailering) when pulling a heavier load.

by the way the Allison is M74 rpo #. Larry