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My brother in law, just got a 2012 2500HD gasser. He has the 6.0 engine, 3.73 axles, and 6spd auto tranny. From what I can find the RPO code for the Allison is M74, and he does NOT have that. However, it does have tow/haul mode and the manual mode, just like my '06 Duramax.

So what tranny do they have? I know the Allison was available with some gas engines but he does not had the M74 RPO. He does have the same G80 axle I have though.
 

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cunts
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6L90E

Sent from the land of teepee's and buffaloes
 

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I was also looking for the RPO code for the trans in my '08 Silverado 1500 Z71. The window sticker lists a "4-speed Super Duty trans" as part of the 6.0L motor option. I have the build sheet and it lists an M70 code. So is that a 4L60E or other version?? I think there is a 4L80E trans.

I'm sort of confused by the "G80" code too. G80 points to a Positraction diff, but the window sticker lists a "Locking rear differential" under the LTZ trim items. I have read where the G80 code for passenger cars is a positraction diff but for trucks, the G80 is for the Eaton Locking Differential, Sound right??
 

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cunts
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Not sure on RPO code, but 6L90E is the only 6 auto speed trans in a 6.0 HD.

Your 08 is most likely a 4L65/70E.

Sent from the land of teepee's and buffaloes
 

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Should be RPO MYD.
 
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