Help with Trans Tag Decode [Archive] - Forum


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12-14-2013, 12:36 PM
Need some help guys, so I'll try to make a long story short. I just picked up an 04 GT that needs a trans. The people I bought it from had already bought a new trans to swap in, but decided it was too big of a job for them. So they gave me the trans they bought when I bought the car. But my concern is that it has the wrong gear ratio. Short of disassembling the trans, I was hoping that someone might be able to tell what gear ratio this trans has by looking at the ID tag.

If this is a 3.05 ratio, all I need to do is get the PCM programmed for a regular SE car correct? The trans that they gave me is a low mileage trans with only 38,000 on the clock. I may just swap the gears out, but by the time I take everything apart and have to replace the seals on it, that may cost more than just having the PCM tuned.

Here's the pic and thanks for the help.


12-14-2013, 02:32 PM
I'm not sure if you can tell from that tag. It doesn't look like there are any RPO codes on there. There is a code for the transmission (MN5) and another code for the drive ratio. Your final drive would be 3.29 which would be RPO code FR9. It should be on the under side of your spare tire cover. You'd be able to tell the final drive in the donor transmission if you could look at the rpo codes from the car it came from. Otherwise, I'm not sure if there's a way to tell. Are there any other tags on the trans anywhere?

12-14-2013, 03:48 PM
I have no access to the donor car, its long gone. As for any other tags, I'll have to go back out and check on the case to see if I can find anything.

12-14-2013, 05:55 PM
Look for a partial VIN stamping on the case somewhere. I don't remember how many digits are usually there, but if you're lucky there will be eight. Your friendly local GM parts department references vehicles by last eight, so you can call them up and they can give you all the dirt on the donor.

Places to check include the bellhousing flange left of the electrical connector on the front, or maybe around back on the barrel near the left output shaft.

You may also find a Hydra Matic plant tag on there somewhere, which may be of some use.

12-15-2013, 02:34 PM
I did find the number stamped on the trans, it was pretty difficult to read though. Here is what I found: 25M116475

12-18-2013, 11:11 AM
I was able to take the last 8 of the vin I found on the trans to a dealership and they told me it came from a GA SE. And with that they also told me the trans had a 3.05 FDR.

So I think I'm going to have the PCM reflashed for the SE car. This should work right? It is cheaper to have the PCM flashed than it is to have a Trans shop swap the gears for me.

12-18-2013, 02:01 PM
Should work, yes. It's going to make your car a little slower, but you it should give you a tiny bit better gas mileage too.

12-18-2013, 04:12 PM
Thanks Aaron, I'm not too concerned with making it slower. I'm just trying to get it back on the road. This is just going to be my "beater" so to speak. Its really too nice of a car to call it a beater, but its going get me from A to B.

With this super low mileage trans and rebuilding the motor, I should have practically a brand new drive train.

Do you guys recommend anyone to do the computer re-flash? I see I can buy a used pcm from flea-bay flashed with an OEM tune, all I have to do is give them the vin number I want flashed all for $75 with free shipping. Does anyone do a performance tune for that price?

12-18-2013, 05:54 PM
Problem with getting a flashed PCM through the mail is that you still may have to go to the dealership to get a CASE learn done (this is for correcting the crank position accuracy below 1600 rpm). Any time you change the PCM, reflash the PCM, or remove/replace the crank pulley, that needs to be done. I'd just go to the dealer and ask how much they would charge. They would need to upload the V6 SE file to your PCM updated with your VIN, and do the CASE learn.

12-18-2013, 07:30 PM
I do have a scantool capable of doing the crank re-learn on my laptop. Its just too bad that its not capable of reflashing the computer.