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**hatzie** · 04-19-2021, 03:34 PM

It's all electronic including the go pedal.
Hit the tow-haul button. The shifting behaviour changes.
I often put the shifter in 3 when I'm towing something heavy to keep my 4L80E from hunting or lugging the engine by staying in 4th gear when it really should downshift.

If she figures it should be in a lower gear and it isn't going there pull the lever down a notch and drive.

04-19-2021, 03:34 PM	#2
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,916	Re: Duramax/Allison downshift? It's all electronic including the go pedal. Hit the tow-haul button. The shifting behaviour changes. I often put the shifter in 3 when I'm towing something heavy to keep my 4L80E from hunting or lugging the engine by staying in 4th gear when it really should downshift. If she figures it should be in a lower gear and it isn't going there pull the lever down a notch and drive. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.