2007 2500 hd TCM location

poreda · February 24, 2015

I have a 2007 gmc 2500 hd with what i suspect to be a tcm issue. Must things i have read show the location on the radiator shroud but it is not there. any suggestions where it could be?

newdude · February 24, 2015

If it is a 2007 "new" body style (2007-2014 body) HD with a 6.0 and the 6L90, the TCM is internal to the transmission. If it is a "classic" body style 6.0 4L80E truck (1999-2007 body) its under the battery tray, driver's side of the truck.

2007 classic with Duramax its left side, upper fan shroud. If its 2007 new body Duramax, its in the same spot.

Edited February 24, 2015 by newdude

poreda · February 24, 2015

It is the newer body style. It's a gas engine with an Allison transmission. Not sure if that changes location.

newdude · February 24, 2015

It is the newer body style. It's a gas engine with an Allison transmission. Not sure if that changes location.

Gas engine does not have the Allison its a Hydramatic 6L90. Its in the transmission. If you drop the pan its attached to the valve body.

poreda · February 24, 2015

Definitely has an Allison I believe it's an 8.1 gas engine

poreda · February 24, 2015

Not sure that the TCM is even the issue. It doesn't crank. There is no line under the shift selector and I cannot get any communication with my scan tool. If I cycle the key enough I can get the line and it will start for a few seconds the die. Read a ton and was hoping for a bad ground in the TCM

newdude · February 24, 2015

Definitely has an Allison I believe it's an 8.1 gas engine

So its not a "new" body 2007-2013 its a 1999-2007 body with an 8.1 and Allison...drivers side of the fan shroud almost under the upper radiator hose.

If its not there...I have no clue lol.

If you have no line under the PRDNL the internal mode switch/range position switch on the drivers side of the transmission could be shot and it can't detect gear position and won't let it start. Older Allisons had a different switch set up (Neutral Safety Back Up switch) that would fail (corrosion, swell and crack) and would cause all sorts of issues.

If that is bad, the valve body has to be dropped to change the switch.

poreda · February 24, 2015

Any clue why it has no communication with scan tool?

Silverado4x4 · February 25, 2015

The 8.1 and Allison trans was not available in the 2007 HD, only the Diesel's came with the Allison. The 8.1 with the Allison ran from 2001 to 2006.

Edited February 25, 2015 by Silverado4x4

poreda · February 25, 2015

Not sure on motor but was told its a gas with Allison its a 2007 and I do believe it's the new style. What would be the tell tale sign of an Allison vs standard trans?

Edited February 25, 2015 by poreda

gmtech4 · February 25, 2015

Not sure on motor but was told its a gas with Allison its a 2007 and I do believe it's the new style. What would be the tell tale sign of an Allison vs standard trans?

Omg dude just take to a shop !!!!!! You don't have a clue what you're doing , except wasting money , STOP IT NOW !!!!

poreda · February 25, 2015

You have no clue what I know. Obviously this is not a place to get help!

newdude · February 25, 2015

You have no clue what I know. Obviously this is not a place to get help!

No it is a place to get help but when we have to pry the info out of posters its a problem. Do you have a VIN number? That would be worth gold for one of us to help.

poreda · February 25, 2015

It's a friends truck so I apologize for not having all the info. I will get the vin and post it. It's be to the dealership 5 times with no solution. I have seen these forums do wonders to help when the dealership cant. The original problem started with the truck going into limp mode and has progressed into a no crank situation.

newdude · February 25, 2015

It's a friends truck so I apologize for not having all the info. I will get the vin and post it. It's be to the dealership 5 times with no solution. I have seen these forums do wonders to help when the dealership cant. The original problem started with the truck going into limp mode and has progressed into a no crank situation.

Its all good sir. If you have the ability to private message the VIN if you don't want to post it thats fine. Not sure if there is a post limit before you can.