Allison tranny holdback is week

[ervschroeder]

When first purchased my 2007 Silverado Classic with the 2006 engine and allison tranny and put it to the test, this tranny would not grab gears let alone holdback. Dealer flashed and reinstalled software and now the tranny will grab gears but not first gear. It does hold back but not very aggressively.

I am wondering if an any one else is experiencing this problem. My 2002 was set up similarly to haul the same fifth wheel camper, but I also installed an exhaust brake, so my comparison is not apples to apples.

My 2002 would grab all gears including 1st gear, but would kick out of the holdback when slowing below 20 MPH. This 2007 won't even grab 1st gear.

[weatherman410]

I have the 2006 GMC Sierra 4X4 crew cab pick-up with the 6 spd Allison 1000 tranny. I regularly tow a 12'x8' dump trailer that hauls 4000lbs of cargo plus the wieght of the trailer of 2000lbs and the truck GVW is 9200 Plus I have an extra large fuel tank of 45 gal. THe combined weight is around 15,500lbs.

I use the tow/haul swtich on the shift lever when hauling and the tranny does a fine job of holding back the load on steep grades. THe trailer has electric brakes and the comination of tranny and braking is very easy and controlled. I don't need to use the brakes to slow my descent untill I need to come to a total stop at the bottom of the hill.

THe combination is very effortless.

THe RPMS on the LBZ can get fairly high on the downshift but it slows my speed efficiently.

[jeepgeek]

The tranny on the 05 and later will not go into 1st gear, but will downshift to and hold 2nd gear. The transmission does not lock up fully in 1st and will lead to excessive slippage and overheat. It happened to me when I downshifted manually to 1st pulling my 5th wheel toy hauler down from Big Bear.

There is no exhaust brake yet from Banks for the LLY and later engines due to the VV turbo according to banks. They are working on one that will use the VVT to create the backpressure to slow the vehicle. One bonus to this system will be if you get to the bottom of a hill and need to climb again right away, the turbo will already be spooled up and ready.

George