Chevrolet Cruze Forums banner

1 - 11 of 11 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter #1
I am trying to find out some information on my cruze. My transmission went out on my car and i have a salvage transmission out of the same make and model vehicle. I would like to know it the TCU / TCM needs to be programmed if it came out of the same make and model? Also, where is the TCU / TCM located on this vehicle? I think it is right next to the ECM in the engine compartment but i want to confirm a few things before going under way with replacement of the transmission. Thank you guys!
 

·
Registered
Joined
·
1,213 Posts
The TCM is integral to the transmission. It SHOULD be programmed but sometimes they work without programming. Of note is that the VIN is stored in the TCM, and you can't change it with GM software. Even if you were to programming it is using GM Tis2Web software you'd only be programming it to the software it requires, not your car.

There's a slim chance that installing a used trans will make your car undrivable until you replace the TCM.
 

·
Registered
Joined
·
17 Posts
Discussion Starter #3
The TCM is integral to the transmission. It SHOULD be programmed but sometimes they work without programming. Of note is that the VIN is stored in the TCM, and you can't change it with GM software. Even if you were to programming it is using GM Tis2Web software you'd only be programming it to the software it requires, not your car.

There's a slim chance that installing a used trans will make your car undrivable until you replace the TCM.
[/QUOTE
what is the TCU then? What is it’s purpose? It’s mounted in the engine bay next to the ECU?
 

·
Registered
Joined
·
1,213 Posts
You have a diesel , don't you? My mistake. Your omission LOL.
Yes the trans module will need to be programmed when you install a new transmission. If you install a different transmission and don't program the TCM with the proper info the car won't shift properly
 

·
Registered
Joined
·
17 Posts
Discussion Starter #5
You have a diesel , don't you? My mistake. Your omission LOL.
Yes the trans module will need to be programmed when you install a new transmission. If you install a different transmission and don't program the TCM with the proper info the car won't shift properly
It’s not a new transmission though, it’s a salvage transmission. Does that make a difference?
 

·
Registered
Joined
·
1,213 Posts
No, it doesn't. The transmissions have calibrated solenoids and valves inside them, this calibration information is stored in GMs servers, the car needs to be programmed with the calibration data for the transmission it has installed in it. New or used trans doesn't matter, you'll need to have the TCM programmed with the "transmission unique number"(TUN) in order to have proper shifting. The TUN is the 16 digit number on the bottom of the trans ID tag. Be sure to document this number so it can be input into the software when programming the trans control module(TCM, TCU, whatever you wanna call it)
 

·
Registered
Joined
·
965 Posts
New or used trans doesn't matter, you'll need to have the TCM programmed with the "transmission unique number"(TUN) in order to have proper shifting.
I'm not sure I understand the ramifications of this. Does this mean that the old transmission will work in the new car even though the VIN in the tranny doesn't match the new car's VIN?

Of note is that the VIN is stored in the TCM, and you can't change it with GM software. Even if you were to programming it is using GM Tis2Web software you'd only be programming it to the software it requires, not your car.
How does this affect using the old tranny in the new car?

Thanks.
Doug

.
 

·
Registered
Joined
·
1,213 Posts
The trans in the diesel has an external discrete transmission control module. It stores the VIN and other data. The trans doesn't store anything. But the transmissions each have unique internal mechanical characteristics that are programmed into the TCM. If you swap trans without updating the TCM and telling it the ID of the installed trans, the vehicle will have unexpected and likely undesirable shift quality.
 

·
Registered
Joined
·
17 Posts
Discussion Starter #9
The trans in the diesel has an external discrete transmission control module. It stores the VIN and other data. The trans doesn't store anything. But the transmissions each have unique internal mechanical characteristics that are programmed into the TCM. If you swap trans without updating the TCM and telling it the ID of the installed trans, the vehicle will have unexpected and likely undesirable shift quality.
I am having the transmission swapped by a shop would it hurt anything to drive it a couple miles to the dealership to have it reprogrammed?
 

·
Registered
Joined
·
1,213 Posts
I am having the transmission swapped by a shop would it hurt anything to drive it a couple miles to the dealership to have it reprogrammed?
Very unlikely there'd be any lasting effects from driving just a few miles. Just don't be concerned about the trans' shift quality or operation until you get the TCM programmed.
 

·
Registered
Joined
·
965 Posts
The trans in the diesel has an external discrete transmission control module. It stores the VIN and other data. The trans doesn't store anything. But the transmissions each have unique internal mechanical characteristics that are programmed into the TCM. If you swap trans without updating the TCM and telling it the ID of the installed trans, the vehicle will have unexpected and likely undesirable shift quality.
Thanks for the reply. It makes sense now - for the diesel the TCM stays with the car, so no issue with the VINs matching.

The cal data matching the donor tranny's TUN number gets downloaded from GM and loaded into the TCM thereby mating it to the "new" tranny.

Thanks again.

Doug

.
 
1 - 11 of 11 Posts
Top