RPO Codes

[justcuz]

I looked around and could not find the answer. My 1973 Suburban has a couple of RPO codes I can't decipher. All of the codes are preceded by the number 1. The ones I want to figure out are 1G86 Eaton lock and Diff. Is this the same as a G80? The other is 1ZN8 Optional axle ratio, what ratio is it?
Any help is appreciated, Thanks.

[LONGHAIR]

I'm pretty sure that the G86 is the bigger version used in 14 bolt differentials. Basically the same as the "Gov Lock" G80, just bigger.
AFAIK the NZ8 is 3.73-1 gears

[justcuz]

Ok thanks, I'll confirm all this when I pull the rear cover, but this vehicle is not on my short list of things to do. Actually I was just doing my once every 3month hood hinge lube to prevent bending the hood. I decided to check the fenderwell tag. I forgot to mention that this is a C20 Suburban (3/4 ton 2wd).
I am familiar with the G80 and GM now uses it for everything regardless of model. However 1973 was the first year for the 14 bolt corporate rear axle and I wondered if it may have had a different RPO code that first year. i was also kind of hoping it meant a No-Spin Detroit locker in spite of it clearly sayiing Eaton on the tag. The difference between the 3.73 and 4.11 is not too great, but every little bit helps these days. It will probably get a 700R4 down the road anyhow. I also have a way to eliminate the flyweight and gear mechanism, add frictions and shims to make these G80 rear ends completely trouble free. When I do another one I'll post a thread.

[rick1956]

I've got a master listing of the RPO codes (not sure where I got it originally), and I don't see any with a "1" preceding the 3-letter designation.

For anyone that wants the PDF file, here's a link to it

[b454rat]

The Eaton is acutally a posi, whereas the newer ones are the Govlock...