Allison Shift Points

[JCM5]

Looking at changing my partial upshifts and downshifts for tow haul mode only.

Camper pulls better in regular mode.

In tow mode does line pressure go up?

If I decrease my tow mode to look closer to standard but with a % increase in shift points is there any risk?

I read some were that the ECM needs to be re-tuned? Im confused on this one, I guess I dont understand why.

Basically in tow mode the shift points are to high for a 7K camper. In standard mode the truck runs better. I was just wondering about line pressures higher in tow mode and a slight increase in shift point would be better.

thoughts?

I have the EFI Live and know were to change the points - just looking for pros and cons on this.

 

[JoshH]

I wouldn't mess with it, but if you insist, there's nothing special about it. The only things that change with T/H mode are shift points and converter lockup. I would not make the shift points the same as normal mode because you'll end up lugging the engine because of the converter being locked earlier in T/H. There is no need to retune the ECM.

 

[JCM5]

Shift Points

Good to know about the ECM

I dont want the normal and tow mode to be the same, I just want to reduce the tow mode by say 15%. The shift point are really to high for my application.

I could and usually do just run in normal mode. But my question is - is the line pressure in the trans increased for the added strain on the trans in tow mode?

If so then I would rather run in tow mode while pulling but just reduce the shift points by a percentage.

The shift points in tow mode are to high for this trailer weight and yes I understand it probally was adjusted for the max tow capacity. But for my current application I would like it more driveable while pulling.

 

[JoshH]

There is no increase in line pressure. The 2010 and earlier Allison transmissions have no way to control pressure electronically. If you want to get technical, the line pressure is actually less in T/H on a stock transmission due to pressure drop during lockup, but the benefits of lockup outweigh the loss of pressure.

 

[Mike L.]

Pressure drops 100 psi when converter locks.

 

[JCM5]

THx for the info

Im going to reduce the tow mode by 20% of the differential between the standard and the tow. This will keep the relationship of the curve the same.