RPO Codes are a system that GM uses to identify which parts and options are on any particular vehicle that they manufacture. RPO codes are typically placed in the glove compartment, which allows you to view the options on your vehicle without ever cracking the hood, or crawling under the car. GM Transmission RPO Codes start with the letter M.
General Motors Transmission RPO Codes |
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| RPO Code | Transmission Name | Auto or Manual? | # of Forward Gears |
| M08 | Borg Warner- 4 Speed | Manual | 4 |
| M13 | 4T60-E | Auto | 4 |
| M15 | 4T65-E | Auto | 4 |
| M17 | Muncie- 4 Speed | Manual | 4 |
| M20 | Muncie- 4 Speed | Manual | 4 |
| M21 | Muncie- 4 Speed | Manual | 4 |
| M22 | Muncie- 4 Speed | Manual | 4 |
| M26 | Muncie- 4 Speed | Manual | 4 |
| M27 | Getrag- 5 Speed | Manual | 5 |
| M28 | Borg Warner- 6 Speed | Manual | 6 |
| M29 | Borg Warner- 6 Speed | Manual | 6 |
| M30 | 4L60E | Auto | 4 |
| M31 | TH250 | Auto | 3 |
| M32 | 4L65E | Auto | 4 |
| M33 | TH350 | Auto | 3 |
| M34 | TH125 | Auto | 3 |
| M35 | Powerglide | Auto | 2 |
| M38 | TH350 | Auto | 3 |
| M39 | Borg Warner- 5 Speed | Manual | 5 |
| M40 | TH400 | Auto | 3 |
| M49 | Borg Warner- 5 Speed | Manual | 5 |
| M49 | TH350 | Auto | 3 |
| M50 | NVG- 5 Speed | Manual | 5 |
| M51 | Isuzu- 6 Speed | Manual | 6 |
| M62 | 3 Speed | Manual | 3 |
| M63 | ZF | Manual | 4 |
| M64 | 3 Speed | Manual | 3 |
| M73 | Isuzu- 4 Speed | Manual | 4 |
| M75 | 5 Speed | Manual | 5 |
| M77 | Borg Warner-4 Speed | Manual | 4 |
| M79 | Isuzu 5 Speed | Manual | 5 |
| MB1 | Borg Warner- 5 Speed | Manual | 5 |
| MB4 | Borg Warner- 5 Speed | Manual | 5 |
| MB6 | Borg Warner- 5 Speed | Manual | 5 |
| MC0 | Getrag- 4 Speed | Manual | 4 |
| MC4 | Borg Warner- 5 Speed | Manual | 5 |
| MC5 | Borg Warner- 5 Speed | Manual | 5 |
| MC9 | Borg Warner-4 Speed | Manual | 4 |
| MD2 | TH180C | Auto | 3 |
| MD3 | TH180 | Auto | 3 |
| MD5 | Getrag- 5 Speed | Manual | 5 |
| MD8 | 700R4 | Auto | 4 |
| ME2 | 5 Speed Manual | Manual | 5 |
| ME2 | 6 Speed Manual | Manual | 6 |
| ME9 | TH440 T4 | Auto | 4 |
| MF2 | Borg Warner-4 Speed | Manual | 4 |
| MG1 | Muncie- 5 Speed | Manual | 5 |
| MG2 | Getrag- 5 Speed | Manual | 5 |
| MG3 | Muncie- 5 Speed | Manual | 5 |
| MG4 | Isuzu 5 Speed | Manual | 5 |
| MG5 | Getrag- 5 Speed | Manual | 5 |
| MH2 | Borg Warner- 5 Speed | Manual | 5 |
| MH3 | Borg Warner- 5 Speed | Manual | 5 |
| MH5 | Doug Nash- 4 Speed | Manual | 4 |
| MH6 | 6T75 | Auto | 6 |
| MK2 | Doug Nash- 4 Speed | Manual | 4 |
| MK4 | Borg Warner- 5 Speed | Manual | 5 |
| MK5 | Borg Warner- 5 Speed | Manual | 5 |
| MK6 | Borg Warner- 5 Speed | Manual | 5 |
| ML2 | Borg Warner- 5 Speed | Manual | 5 |
| ML3 | Borg Warner- 5 Speed | Manual | 5 |
| ML6 | ZF | Manual | 6 |
| ML8 | Borg Warner- 5 Speed | Manual | 5 |
| ML9 | Muncie- 4 Speed | Manual | 4 |
| MN8 | 4L85E | Auto | 4 |
| MR2 | Muncie- 4 Speed | Manual | 4 |
| MR5 | Isuzu- 5 Speed | Manual | 5 |
| MR6 | Isuzu- 5 Speed | Manual | 5 |
| MR8 | Isuzu- 5 Speed | Manual | 5 |
| MS7 | Toyota Auto | Auto | 4 |
| MT1 | 4L80E | Auto | 4 |
| MT2 | Isuzu- 5 Speed | Manual | 5 |
| MT8 | NV4500 | Manual | 5 |
| MV4 | TH350C | Auto | 3 |
| MV9 | TH200C | Auto | 3 |
| MW1 | Borg Warner- 5 Speed | Manual | 5 |
| MW3 | NV4500 | Manual | 5 |
| MW4 | Getrag- 5 Speed | Manual | 5 |
| MW9 | 200-4R | Auto | 4 |
| MX2 | TH350C | Auto | 3 |
| MX6 | Muncie- 4 Speed | Manual | 4 |
If you see any errors, or would like to add an RPO code, just leave it in the comments and I’ll throw it on. There’s no definitive place to find these. Hopefully with enough input, that can change.