Can somebody school me on the workings of a 2008 Sierra speedometer. I read the transmission speed sensors send a signal to the TCM which relays to the ECM and then to the dash. is this correct? if so whats the point of the VSS on the transfer case?
Speedometer
- Thread starter Diezel
- Start date
My guess would be for actual speed of the drive shaft vs the transmission, so it know by the speed differential if its in low range.
That’s what I thought, long story short trying to get the speedometer to work without an Alison tranny. Planning on a Zf6 swap soon. It’s been done but I can’t find the info on how it was done.
VSS is the what the actual speedometer displays as it will be accurate for all gears and ranges (if 4x4 equipped).
The TCM reads the other sensors to determine torque convert clutch (TCC) slip, determine actual gear ratio received, and to also detect a slip in any of the gears. The truck knows at XX vehicle speed I should be at XX reading on the other sensors in the trans.
The TCM reads the other sensors to determine torque convert clutch (TCC) slip, determine actual gear ratio received, and to also detect a slip in any of the gears. The truck knows at XX vehicle speed I should be at XX reading on the other sensors in the trans.
Sweet. Plan is to leave the TCM in place and set the NSBU to neutral and tie that up to the frame some where and then everything should work.
Better off finding the segmented tune I think Ben Tyler did or someone in the tuning game did for the lmm. Years ago someone did a zf swap into a lmm and the tune was made.
Doing what you did has its issues but can’t remember what they were.
Doing what you did has its issues but can’t remember what they were.
Know where I could find anymore info about it? I called a few tuners, and was told I would just need to get a tune to delete all the DTCs that will pop up.
This is what I did with my lly when I swapped it to a zf6. Everything worked fine and i just turned off all the dtcs as they popped up. As long as the the speed sensor in the t-case is hooked up and it thinks the trans is in neutral you're good. You'll have to get a little creative with the neutral switch. It is internal on 6 speed Allison's. 5 speeds are easy, just unbolt it and move it to N.
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I called PPEI yesterday and was told everything should work as with fooling the tranny to be in neutral but will need a tune to get the DTCs to go away. Gunna start sourcing out a trans hopefully can’t find a ZF6 if not I’m go with a built NV4500