Hi guys!
We just went live with our GM RPO Decoder and database! It was a bunch more work than I thought it would be but after a few days and some attention to detail it is done now and open for all to view and use, for free (no account necessary). It took a bit honestly, and we ended up with north of 24,000 + RPO Codes that were GM sourced and verified.
Yes I know - there are other sites that do this, and it’s not something new. The difference with ours is that we tracked how the codes actually changed over forty years, and kept every entry we found along the way.
Type G80 into most RPO lists and you get one line:
G80: Axle, Rear, Positraction, Limited Slip.
The problem is that G80 has been in use since the 70s and it did not stay still. It started as Positraction, went through limited-slip, and on current trucks it is an automatic locking differential. One line cannot be right for all of that!!
Put G80 through the FullSizeChevy decoder and you get:
G80 = one of the following, not resolved:
- Positraction rear axle (1973, GM sourced)
- locking rear differential (1990, GM sourced )
- P, AXLE POSITRACTION, LIMITED SLIP (1991, GM sourced)
- rear limited-slip / Positraction axle (2000, GM sourced)
- limited-slip / Positraction rear axle (2007, GM sourced)
- Auto-locking rear differential (2022–2023, GM sourced)
- automatic locking rear differential (2026, GM sourced )
Enter your model year and it narrows to the ones that fit your truck. Every line says where the meaning came from, so you can tell a GM document from something that has just been copied around the internet.
We’re also not requiring you to download some dumb app, you can literally read your glovebox RPO code from the web browser on your mobile phone. Simply take a photo, or upload a photo you took earlier of your RPO codes.
I tested it earlier on desktop and mobile with great success. The honest take I have is my GMT900’s RPO list has seen better days, and it still did a pretty good job. I’ll take it as a win that we only missed a few with my quick picture taking. If you can take a perfect picture of your RPO code in good light, I’m sure it will work better than the GMT900 pic did.
| Label | Picture Condition | Desktop | Mobile |
|---|---|---|---|
| 1997 GMT400 | sideways, shadowed | 79 / 79 | 78 / 79 |
| 2002 GMT800 | sideways, edge clipped in frame | 81 / 82 | 82 / 82 |
| 2007 GMT900 | dark, angled, worn label | 93 / 95 | 93 / 95 |
| 2014 K2XX | clean | 97 / 97 | 97 / 97 |
| Total | 350 / 353 | 350 / 353 |
Same photos, same result on a phone as on a desktop. The handful of misses are single characters on worn or damaged text — an I read as a 1, a B as an 8 — and when it can't be sure it says so rather than guessing. Call it right around 99%.
I have to figure out how to build the QR one for the newer trucks, that will likely come in time but for now this will work up to the last K2XX’s.
The full database is here (and not locked behind some dumb paywall): GM RPO Code Database
If you want to scan your RPO codes and get your truck’s list, you can check that out here:
Any issues, comments or concerns you can post over in the RPO Decoder thread.
Anyways, hope its helpful!
Todd