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I am having a problem where my transmission doesn't want to shift into fifth. I am in a cool climate and when the engine is at 190 degrees the trans temp hardly moves at all. If I stop moving for a few minutes the tranny temp will rise a little and then when I take off again the thranny will shift into fifth. I think I noticed this in warmer weather also where the fifth gear shift only came after the tranny temp was off of the cold end of the gauge. What are some of you seeing on the tranny temp gauge in similar situations. At 20 degrees outside mine hardly moves. I am assuming I could have a bad temp sensor causing my problem. A have a 2001 6.6 with a allison and 148000 miles. Other than this problem the tranny works fine.

 

[DangerousDuramax]

That is a safety feature built into the Allison to keep it from being damaged. Here in Houston my tranny will barely get warm in the morning driving to the office. Needle will only move 2 marks which is only about 120*. I have to drive for about 5 miles before it finally shifts into 5th.

PS- Create a signature to list your truck and mods so that the experts will know what you have an can chime in.

 

[Josh61513]

Adding the GM vinyl cover in front of the grill will help your engine heat up quicker, as well as significantly heat up the transmission.

 

[Barkbuster]

I recently added a grill cover and had both pieces on yesterday with temps in the upper 20`s. Trans warmed up to a nice warm 150 @60mph into a 10-15mph nw headwind. My route turned directly into the wind for the last 10 miles of the 55 mile trip and I upped the speed to 70, which brought the trans up to about 170. Comming home I did the same speeds with the wind pushing me and the trans. never topped 150. without the covers the trans temp would have barely moved the gauge past the 1st mark. engine temp stayed around the 200 mark and fan never kicked on. Heat in cab was very toasty warm:

 

[DuramaxxedLBZ]

On the five speed allisons it is normal for this to occur, such as Danger said, it helps things heat up quicker and gets the tranny fluid warmed up to better lube it. Both of the 5-spd allys in my family do it, it is a normal thing.

 

[Josh61513]

Also, it's not that the transmission isn't shifting into 5th, it's that it won't lock the torque converter.

An unlocked torque converter can create a LOT of heat since less of the input (mechanical energy) is transmitted to the output (mechanical energy), the loss is all in heat.

 

[Machinator]

This link should answer your question:

http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3931EN.pdf

 

[DuramaxxedLBZ]

Also, it's not that the transmission isn't shifting into 5th, it's that it won't lock the torque converter.

An unlocked torque converter can create a LOT of heat since less of the input (mechanical energy) is transmitted to the output (mechanical energy), the loss is all in heat.

I understand what you are saying...heat will be created due to that. But that is what the Allison is designed to do to warm up the tranny fluid. No worries about it. Click on the link that machinator posted and read page 3, specifically the right side of it. I believe this will clarify things for all of us.

 

[DuramaxxedLBZ]

Nevermind that prior remark josh, i didn't carefully read what you said. you said the same thing i said just with more depth.