Could someone please shed some light on this confusion.. Seems Chevrolet liked to confuse people with multiple RPO codes for transmissions. my understanding is that the MX0 is a RPO used to refer that one selected an automatic 4 speed transmissions. However the 2010 Camaro seems to use this as a Generic RPO for the Auto 6? Upon further documentation (Restoration kits, Books, Magazines, and online sources) there are even more RPO codes for various Transmissions throughout the year referring to the same transmissions.. For example the following shows reference of two RPO codes for the same transmission Example: 5-speed Manual M49 & MM5 4-speed Auto MD8 & MX0 6-speed Manual M28 & MN6 (Same MN6) 6-speed Manual M29 & MN6 (Same MN6) MB1 & MM5 M39 & MM5 MK6 & MM5 And many others thought the years.. Going by this it SEEMS to indicate that : - MM5 was the code to refer that a Manual 5-speed had been selected - MN6 was the code to refer that an Automatic 6-speed had been selected But other years become more puzzling. 1. Which of these would show up on your RPO decal? Both M49 and MM5 ? Referring to the restoration kits make it even worse because of one part they list for example M49 as the transmission for a given engine, and yet other pages mentioning the same indicate MM5 then an RPO list show the transmission as being M49, then another RPO list somewhere else might show it being M49. 2. How exactly can you easily understand what the transmission codes refer to? (Whether they are those above, or others from other years as there are more that I have yet to mention) How do you know which is for the "Denoted selection of a TYPE of tranny (i.e.. a 5-speed manual)" and which refers to the ACTUAL SPECIFIC transmission? Thanks, Paul

The MX0 RPO denotes an automatic transmission on the order sheet. Now the actual automatic tranny for that vehicle could be a MD8 (700R4) or an M30 (4L60E), etc. The same for the MM5 or MN6. Those are the checklist RPOs for 5 or 6 speeds. The other numbers correspond to the actual tranny for that vehicle. The 5 speed for a Fiero 4 cyl will have a different RPO than the 5 speed for the Firebird.

For both of my 1988 GTA's (305 V-8/5-speed), I show on the RPO list:

MK6: Transmission, 5-speed manual and
MM5: Transmission, 5-speed manual

For my 1989 Firebird (2.8L V-6/ 5-speed), I show on the RPO list:

MB1: Transmission, manual 5-speed (Borg-Warner) and
MM5: Transmission, manual 5-speed provisions

On my 1984 Trans Am (based on the ThirdGen RPO Decoder), I show:

MD8: Transmission, auto 4 spd, THM 700 R4

I Believe the MK6 and MB1 refer to the actual transmission. The MM5 refers to the peripherals.

hth.

Gary.

gm is good at re-using codes over the years

you have to be careful

and RPO codes like GQ1 and MXO and such are general/standard codes