may be stupid question changing pcm (vcm)

[skychair]

my 5.7 vortec Yukon will be 'down' while I get it programmed (mail in)... I have another VCM from a donor that had same engine/trans, Question.... can I run this VCM until I get mine back?
Any down sides to this, can I damage any thing? Any irreversible issues ? Dont do it? etc.
Ron

 

[upper_tanker]

Is it the same year? Same rear gears? I don't see why you would have an issue, other than your speedo may be off. I could be wrong though.

 

[skychair]

Is it the same year? Same rear gears? I don't see why you would have an issue, other than your speedo may be off. I could be wrong though.

Not sure about year/rear end ratio, did have 'R' in vin# translates to 5.7 and should have 4160E?
Glove box was gone, I'm assuming 3.42 rear and 4160E, what will it hurt to try?

 

[skychair]

Is it the same year? Same rear gears? I don't see why you would have an issue, other than your speedo may be off. I could be wrong though.

Here are the 2 VCM's, the first 2 pictures are my VCM, the last 2 pictures with an 'X' marked on them are the donor part, looked close to me.
Any comments?

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[PlayingWithTBI]

Looks like they're the same CMUF chip. As long as either hasn't been tuned differently, it should work fine.

 

[upper_tanker]

As long as they're both out of a truck with a 5.7 with the same injection (OBD2, they are since TBI didn't have those pcms), and the SAME transmissions (4l60E), I'd say you're fine. I'd be willing to bet that the worst that would happen is your speedometer will be off if it's programed for different gears than yours. However, if they're both for the same engine/trans, the fuel tables and AFR should be the same.

I'm sure someone will chime in with more knowledge. I'm just a peasant.

 

[df2x4]

Like others have said, if the spare PCM is from a truck with the exact same engine and trans it should work. If not, you're going to have major running/driving issues. The only big thing I'd be worried about is if the other PCM is tuned for a 305. If that's the case it will start and run, but you'll probably be running lean. I'm not sure if running a 305 tune with a 350 would cause lean enough conditions to damage anything, but personally I wouldn't want to chance it.