Hi all. Old thread but was looking to solve why my shift tables didnt match real world speeds and thought I would post here as I couldn't really find anything else on the web
I have an 06 LBZ and with Allison 1000/A40 swapped in a Nissan Patrol with 4.1 diff ratio and 33" tyres.
Have made improvements to shifts by altering shift tables but it always annoyed me why real world speeds didn't match the tables but put up with it for years as it was shifting nicely anyway.

I experimented with altering diff/axle ratios and tyre sizes but made no change.

My 5-6 upshift at low throttle was set to 85kph but real world was 90kph. This is a 5.7% difference.
So I put axle and diff ratios back to stock 4.10/3.73 (to ensure inaccessible tables aren't referencing these figures) and reduced vehicle speed ratio by the above 5.7% and now my shifts are near bang on real world
I kept the tyre revs per km the same as the figure I entered into the ECM as this gives the vehicle speed PID accurate to GPS, I did this by inputting the measured diameter from the ground to the top of the tyre in the EFI live speedo calculator and using the calculated value. Keeping the TCM tune the same as the ECM tune makes sense to me even though I proved earlier changing this value in the A40 calibration didn't make any difference.

So if anyone reading this wants their real world speeds to match the shift tables, work out what the error is and alter the H0137 table by the same amount

My settings below


{H0102} Vehicle Speed Sensor Pulses per Revolution 40
{H0103} Final Drive Ratio 4.10
{H0105} ECM Pulses Per mile 4000 count/mile
{H0122} Axle Ratio 3.73
{H0136} Tire Revolutions Per kilometer 397 rev/km
{H0137} Vehicle Speed Ratio 248 rev/km
{H5061} Transfer Case Ratio 2.72 :1