Pex68
07-19-2005, 11:10 PM
All,
Been lurking around since just before I decided to buy my 2500HD and see alot of people (and alot not) having issues with overheating/fan noise(wrrr)/high trans temps while towing. While I've yet to break 1000 miles on my truck and only towed with it once, I've yet to see any issues but found this site with FAQ's and alot of good info on just how the allie works. It seems it's mostly related to the older trucks as per year but I think the allie has remained mostly the same even with the LLY. I know it's not the cure-all to all the problems mentioned, but maybe it will help solve some peoples issues the next time their towing. The thing I got out of it the most was that it seems every time you tow, you need to be in the tow/haul mode because:
Tow/Haul (T/H) shift mode significantly changes the transmission's shift pattern to reduce shift cycling and to deliver better performance, control, and cooling when towing/hauling heavy loads. For instance:
1. Upshift points are raised at light to mid throttle position to use more of the engine's available power for accelerating.Downshift points are raised to enhance engine braking to help slow the vehicle.
2. During deceleration, the torque converter clutch (TCC) remains applied at closed throttle to much lower vehicle speeds to significantly improve the effect of engine braking.
3. During acceleration, the TCC is applied in 2nd range and remains applied in 3rd, 4th, and 5th. This improves the drivetrain efficiency and significantly lowers transmission sump temperature when towing heavy loads. In Normal mode, TCC generally applies only in higher ranges and is dependent on throttle position.
Anyway, enough of my :blahblah: , here's the link to the site and thanks for all the great info on this forum!
http://burt.com/commtrucks/AllisonFAQs.htm
Thanks Again, Chris.
Been lurking around since just before I decided to buy my 2500HD and see alot of people (and alot not) having issues with overheating/fan noise(wrrr)/high trans temps while towing. While I've yet to break 1000 miles on my truck and only towed with it once, I've yet to see any issues but found this site with FAQ's and alot of good info on just how the allie works. It seems it's mostly related to the older trucks as per year but I think the allie has remained mostly the same even with the LLY. I know it's not the cure-all to all the problems mentioned, but maybe it will help solve some peoples issues the next time their towing. The thing I got out of it the most was that it seems every time you tow, you need to be in the tow/haul mode because:
Tow/Haul (T/H) shift mode significantly changes the transmission's shift pattern to reduce shift cycling and to deliver better performance, control, and cooling when towing/hauling heavy loads. For instance:
1. Upshift points are raised at light to mid throttle position to use more of the engine's available power for accelerating.Downshift points are raised to enhance engine braking to help slow the vehicle.
2. During deceleration, the torque converter clutch (TCC) remains applied at closed throttle to much lower vehicle speeds to significantly improve the effect of engine braking.
3. During acceleration, the TCC is applied in 2nd range and remains applied in 3rd, 4th, and 5th. This improves the drivetrain efficiency and significantly lowers transmission sump temperature when towing heavy loads. In Normal mode, TCC generally applies only in higher ranges and is dependent on throttle position.
Anyway, enough of my :blahblah: , here's the link to the site and thanks for all the great info on this forum!
http://burt.com/commtrucks/AllisonFAQs.htm
Thanks Again, Chris.