Help with a RPO number

[dgodecke]

I am looking at the service parts identification sticker found on the left inner fender on my 73 GMC.

It has a code 1ZN8 for an optional axle ratio. I can't find that code any place and I have searched the net up and down. Can anyone help me with this code?

Thanks all.

[Keith Seymore]

I'm full of information, but none of it helpful...

First, the "1" is a dummy character (I assume there is a "1" in front of every RPO on your label), so the actual code is "ZN8".

Having said that, I also did an internet search, as well as looking through some of my old books, but the only "ZN8" I came up with was a Sequence/Delivery RPO for Grumman-Olsen (a body builder company) - so I like the description on your SPID label better than that.

Also - axle ratio RPOs are usually in the "G" series (ie, GQ1, GU6, GT4) with an occasional gust up into the "H" zone ("HC4"), so this doesn't strike me as a standard format. Are you sure you read it right? I see a "GM8" for a 2.56 rear axle ratio.

Lastly, RPOs do get reused, so a "ZN8" in 1973 could legitimately be very different from a "ZN8" in 2003. We see this commonly with engine RPOs, probably since they are a bit more recognizable (ie, LS6 was a monster big block, now a GEN series smallblock).

Sorry I couldn't help more. I'll keep my eyes peeled and look forward to what some of the other guys might be able to come up with.

K

[dgodecke]

Originally Posted by Keith Seymore

I'm full of information, but none of it helpful...

First, the "1" is a dummy character (I assume there is a "1" in front of every RPO on your label), so the actual code is "ZN8".

Having said that, I also did an internet search, as well as looking through some of my old books, but the only "ZN8" I came up with was a Sequence/Delivery RPO for Grumman-Olsen (a body builder company) - so I like the description on your SPID label better than that.

Also - axle ratio RPOs are usually in the "G" series (ie, GQ1, GU6, GT4) with an occasional gust up into the "H" zone ("HC4"), so this doesn't strike me as a standard format. Are you sure you read it right? I see a "GM8" for a 2.56 rear axle ratio.

Lastly, RPOs do get reused, so a "ZN8" in 1973 could legitimately be very different from a "ZN8" in 2003. We see this commonly with engine RPOs, probably since they are a bit more recognizable (ie, LS6 was a monster big block, now a GEN series smallblock).

Sorry I couldn't help more. I'll keep my eyes peeled and look forward to what some of the other guys might be able to come up with.

K

Thanks this one is a weird one it looks like. I am looking at the photo I took of it right now and it really does say 1ZN8 and the description defiantly says "Optional Axle Ratio" I don't see any G or H codes on the photo at all???