i haven't had that problem. but mine shifts hard the first couple of times when it is cold and then goes away when it warms up

 

I have also yet had this happen and I regularly see temps down to -30 or lower.

I do know that the Allison does not allow certain shifts to occur if it is too cold however I have never seen it happen.

Perhaps it is because I let mine warm up when it is that cold.

Are you sure it wasn't just your converter not locking up? You would not see rpm's that high from the conveter not locking up but you will see them higher then normal.

One other thought, are you sure that you didn't have the OD locked out? A lot of people don't know how the OD lockout works and they lock it out accidentally while trying to put their truck in tow/haul mode. That would also explain why it corrected after restarting your truck.

 

According to the chart in the link below, all ranges should be active when the sump temp is +5 F and above.

http://service.gm.com/gmtechlink/images/issues/aug04/TLaug04e.html




Gary

 

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One other thought, are you sure that you didn't have the OD locked out? A lot of people don't know how the OD lockout works and they lock it out accidentally while trying to put their truck in tow/haul mode. That would also explain why it corrected after restarting your truck.

can you expand on that. what to do/what it does/ect...?

 

check this out:

Q. Shift Delay - Why does my transmission seem to "hang" or delay upshifts when cold? (Diesel powered trucks only)
A. On diesel powered trucks, the Allison transmission has a feature to shorten engine / cab warm-up times. This feature is called Heater Performance Mode. This feature raises part throttle upshift points (2-3, 3-4, 4-5) to increase engine speed when cold weather conditions are detected. In addition, the torque converter clutch (TCC) will not apply below a transmission sump temperature of 31°C/88°F. This also aids in warming the cab more quickly. Under these conditions, it is normal to experience upshifts that seem to "hang" or be delayed.

taken from:http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11#232

 

can you expand on that. what to do/what it does/ect...?

If you tap the tow/haul button it just puts it in tow haul mode, there is a little trailer symbol on the dash. If you hold it a few seconds it locks out overdrive. There will be a symbol on your dash of a D with a slash through it. So no fifth gear. Hold it 3 seconds again to let it go into 5th again.

 

If you tap the tow/haul button it just puts it in tow haul mode, there is a little trailer symbol on the dash. If you hold it a few seconds it locks out overdrive. There will be a symbol on your dash of a D with a slash through it. So no fifth gear. Hold it 3 seconds again to let it go into 5th again.

ahhh i see. thanks

 

I have been trying to get this info for a while now . My questions are , the GM tech site says all ranges at +5 sump temp. , TCC at 86 ( for diesel ) . Now our tranny temp gage only goes down to 100 , how do you know when it's ok to work the tranny ? Also where is the sesor , in the sump or in the cooler line?

 

You can work the trans when engine temp is at normal operating temp. The trans temp sensor is on the pressure switch manifold on the valvebody (in the sump).
mike