IIRC, the allison was upgraded in all '04's to handle the LLY's output. So, if I am understanding this correctly, my LB7 has the upgraded allison behind it. Would this be correct dmaxallitech, gmcsid, other techs/people in the know?
The one by Mic_ a ways down the page, the upgrade is in all Allisons, but is not functional with anything but the 8.1 gas and the LLY. According to what he copied, which I'll paste part of here, functionality with the LB7 is specifically excluded:
The valve body for the Allison® Series 1000 transmission has been revised for the 2004 model year to add modulated main pressure control. This revision will provide additional transmission oil cooler flow and reduced pump load during certain low speed operating conditions. The revised components will be installed on all 2004 transmissions and will be functional on the L18, 8.1L gas engine and LLY, 6.6L diesel engine but not on the LB7, 6.6L diesel engine.
That's just part of his post. I know Eric has said something about them all being upgraded, and I don't know where Mic_ copied this stuff from. Maybe one of the techs has more info.
My dad has an '02 D/A EC 2500HD 4x4 and I just purchased an '04 D/A CC 2500HD 4x4. I have the LB7 engine and I assume he does as well. The difference I can see in the allison is almost like a gear ratio difference. We both have 3.73 rear ends, but mine runs about 150RPM higher than his at 70mph.
I don't understand why that would be unless there was an intentional change in the transmission to compensate for the in weight difference? I have the crew cab and he has the extended but I would think this would be trivial to the D/A powertrain.
Not sure, but just an interesting observation. Would the upgrade for '04 Allison have any bearing on this? Maybe there were also changes to the Allison between the '02 & '03 that would explain the difference?
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