Re: Do gas prices affect your towing speed?
Your tranny will change or not change at specific RPM depending on the load you have. It is actually noticeable with a full load of people and luggage and nothing on the back.The cooler it runs the better as well. I have an additional tranny cooler on our Trailblazer for that reason.
Well in typical cars the TCM shifts based on target speed (throttle position) and actual speed, plus a million different calculations between those two numbers. ie. quick increase in target speed and slowing actual speed = downshift, when approaching a hill etc etc.
My point was that I could not get the thing to up-shift when taking my foot almost off the accelerator, it still continued to increase rpm till it reached a specific number, NOT a specific speed or level of acceleration. I know what you're trying to say about load, but usually if you've got it mashed down and need to coast or stop increasing speed, taking your foot nearly off the pedal always results in an up-shift (at least if you're already over 3-3.5krpm!). Some of the guys on the rover forums hinted that the TCM senses load and calculates the required shift points so that the vehicle can achieve adequate acceleration in the NEXT gear after the shift is completed, but that the calculation is directly related to weight and not pedal position.
It does have a decent sized cooler from the factory, but fortunately it will also change shift maps if temperatures become too hot.
As far as TC lock-up is concerned, this is the only info I could find (from Jaguar but it has the same ZF 6HP trans I guess)
The TCM controls how the TCC is engaged as a function of the accelerator pedal position, OSS, TFT, gear selected and shift program. Lock-up is possible in all forward gears, but usually it is restricted to fourth, fifth and sixth gears. To make use of the comfort enhancing effect of the torque converter, the TCC can be disengaged prior to a downshift or upshift. The TCC is always modulated to allow controlled slip, to further improve the shift quality. Towing: When the TCM detects reduced vehicle acceleration for a certain percentage of throttle opening then this mode is automatically engaged by the TCM. When this mode is engaged a new shift map and TCC map is selected. This new shift map is designed to reduce the number of gearshiftswhen towing a trailer or with the car climbing a steep hill. The shift map will cause the transmission to hold on to gears for longer this increases acceleration and reduces the number of gearshifts. This mode can also give an advantage when driving at high altitudes, where the torque produced by an engine is greatly reduced by the effects of reduced ambient pressure and airflow.
I believe the vehicle sensor inputs and TCM software is a little more complex in the rover over the jag because it also has input data such as rear shock air pressure etc to determine load, but finding these internal component PDF documents is hard!
