Tow vs daily driver?
Butt-Head
Joined: Apr 2004
Posts: 9,444
Likes: 2,933
From: Reed Point, MT
The tow program has sightly raised low-accelerator pedal upshift speeds, raised downshift speeds and raised torque converter clutch apply speed in 3rd compared to the daily which leaves those things mostly stock. The reason for this is to keep the RPM up (more usable power) and avoid lugging the engine.
A few fuel rate changes (tow "comes alive" slightly little later than daily) and a couple other changes related to smoke control are a couple more differences.
Some people (me included) prefer "tow" or "performance" - oriented calibrations simply because stock programming (and hence many "daily" tunes) shift way too early for our tastes. You can use either interchangeably and see what suits you the best. My biggest peeve with the tuning used by many vendors (in your case likely TNAA4S2; also known as VDH2) is they use a modified version of a PMT1 shift strategy which has nearly no delay in the release and reapply of the torque converter clutch on a 4-3 downshift which can be harsh at times. Your stock VDH4 (as well as a stock VDH2) did not do that as there is a torque-based time delay in the converter clutch reapply after the downshift. This can be annoying but it is far easier to live with.
A few fuel rate changes (tow "comes alive" slightly little later than daily) and a couple other changes related to smoke control are a couple more differences.
Some people (me included) prefer "tow" or "performance" - oriented calibrations simply because stock programming (and hence many "daily" tunes) shift way too early for our tastes. You can use either interchangeably and see what suits you the best. My biggest peeve with the tuning used by many vendors (in your case likely TNAA4S2; also known as VDH2) is they use a modified version of a PMT1 shift strategy which has nearly no delay in the release and reapply of the torque converter clutch on a 4-3 downshift which can be harsh at times. Your stock VDH4 (as well as a stock VDH2) did not do that as there is a torque-based time delay in the converter clutch reapply after the downshift. This can be annoying but it is far easier to live with.
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