Anybody carry a spare TCM with them?

Nov 11, 2012
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This may be the dumbest of dumb questions, but after having my first TCM go out on me I'm scared to death of having the current one go out on me out in the middle of nowhere. I figure it would be cheaper to carry a spare TCM than wait for it to go out on me in the middle of nowhere while hooked up to my camper trailer. So I ordered a new one from my local dealer (although nobody knows when - if - it will ever come in).

So...and I'm ready for all the "noob" comments to fly...is it possible to either clone the current TCM or flash the new TCM such that the new TCM can be "plug and play?"

Assuming it's possible, how would I go about it?

Thanks!
 

2004LB7

Well-known member
Dec 15, 2010
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Norcal
Yes. The dealership can program the TCM with your calibration and vin so it would work out of the box.

The good thing is, even if the TCM fails, it will default to 3rd so you can still make it to a shop

It's pretty rare to have one go out. What about carrying a spare transmission? The clutch packs or converter are more likely to fail. Or complete harnesses, or solenoids, etc. What about pistons, crank or other engine parts. Maybe a spare engine. You know towing a spare truck with you would be easier. I'm kidding. Just busting your balls. If it makes you happy then go for it.

For a while I carried a spare front CV axle as mine would break them really easy until I found the problem.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
This may be the dumbest of dumb questions, but after having my first TCM go out on me I'm scared to death of having the current one go out on me out in the middle of nowhere. I figure it would be cheaper to carry a spare TCM than wait for it to go out on me in the middle of nowhere while hooked up to my camper trailer. So I ordered a new one from my local dealer (although nobody knows when - if - it will ever come in).

So...and I'm ready for all the "noob" comments to fly...is it possible to either clone the current TCM or flash the new TCM such that the new TCM can be "plug and play?"

Assuming it's possible, how would I go about it?

Thanks!

its very rare for those TCM's to die. i wouldnt carry one. Depending on how the TCM fails, it may not default to 3rd gear BUT if you unplug the big harness connector at the very back of the trans on the pass side, the trans will go into hydraulic 3rd the moment you shift out of park. that will get you where ever you need to go, albeit slowly, you will get there lol.
 
Nov 11, 2012
5
1
3
Yes. The dealership can program the TCM with your calibration and vin so it would work out of the box.

The good thing is, even if the TCM fails, it will default to 3rd so you can still make it to a shop

It's pretty rare to have one go out. What about carrying a spare transmission? The clutch packs or converter are more likely to fail. Or complete harnesses, or solenoids, etc. What about pistons, crank or other engine parts. Maybe a spare engine. You know towing a spare truck with you would be easier. I'm kidding. Just busting your balls. If it makes you happy then go for it.

For a while I carried a spare front CV axle as mine would break them really easy until I found the problem.
Thanks, Jason.

Working on the trailer to carry the spare engine and transmission right now...🤣🤣🤣
 
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Nov 11, 2012
5
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3
LML tcms fail a lot. We sell at least a dozen a year. Good luck getting a spare though. Gm has yet found a supplier to make them. I’m getting 2500-3000 for used ones.
That's what the parts guy at the dealer told me, too (about the manufacturing part). Also said that GM was having some supply chain issues with their vendors being able to source component-level parts for the PCBs. Don't know if that's true or not - I have no evidence to go either way.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,690
5,847
113
Phoenix Az
its very rare for those TCM's to die. i wouldnt carry one. Depending on how the TCM fails, it may not default to 3rd gear BUT if you unplug the big harness connector at the very back of the trans on the pass side, the trans will go into hydraulic 3rd the moment you shift out of park. that will get you where ever you need to go, albeit slowly, you will get there lol.

Ok, for some damn reason i though the OP's truck was an LLY. I retract my prior statement about the TCM's being rare to die BUT the new t14 TCM's ive not heard of them having issue???