454ci Engine RPO code

[mntoy]

Can anyone tell me where to find the RPO codes or how to get information about this 454ci engine? The RPO code in the engine compartment on the factory sticker is 1LF8. It is in a 1974 C-20 truck. I am also interested in finding out what the rear end gear ratio is, and the RPO code is 1G80? Is there a code or how do I figure it out?

[b454rat]

The G80 is a factory locker, but it 74 it would be an Eaton posi, the Govlok didn't come out till the late 70s. Is the RPO tag in the glovebox?? If it's still there it will list what motor it is and the RPO code.

[mntoy]

Thanks for the information but how do I tell what the gear ratio is in the G80 factory locker? Or more details other than the engine is a 454ci?

[lilpup69chevy]

there should be a rpo code in the glovebox with like a GU6 which is 3.42 i think and GT4 which is 3.73 just for an example i think all rearend rpo codes start with a G but i'm not positive

[Ironclad454]

I have a 73 so im not sure if the RPO's are gonna be different or not but according to my literature,the standard gear ratio for a C/20 is 3.73's, a ZN7 code means that you've got 3.21 a ZN8 means you've got 4.10 and a ZN9 means you've got 4.56, those are the Optional ratios. A stock 454 is gonna be around 240HP 360LBFT torque. And b454rat is correct G80 in your case would be an eaton locker seeings as its a 3/4ton. I hope this helps. And if im wrong on anything, someone please correct me.

[mntoy]

Thanks again guys for all your help, but I am unable to find the RPO code listing in my truck, there is not listing in the glovebox of my truck. Would it be somewhere else? or is there a way of getting the information from GM by using the VIN number or a different number on the truck?

[Ironclad454]

On mine, the RPO list is in the engine compartment on the drivers side inner fender. Have you checked there?

[mntoy]

Yes that is where I found the G80 code for the rear end, but it does not say anything about a gear ratio. Do you know what the ration is for this G80? Thats why I keep asking this question. Can you help?

[Ironclad454]

Thats the RPO list then. the G80 is the factory code for a locking rear differential, it has nothing to do with the gear ratio as it can be installed with different gear ratios. If it doesnt have any codes my guess is that it would be the standard 3.73 gears then but thats just my best guess. If you'd like to get an info packet from GM heres a link with how to get one. Please note this is just general information like options codes and not info on your specific truck, but is still really helpfull in decoding your RPO list.

http://www.73-87.com/7387info/7387info_packets.htm