Help w/ RPO on E/C Sequence Sheet
 

Good afternoon everybody! A previous owner removed the glove box RPO sticker, however I found a sheet under the bench seat titled "E/C Sequence Line Up No....". It's front and back, with 18 total lines. Is there any way to read this and figure out if this sheet points out which build is my truck? Three lines are not crossed out by red pencil. Any help you can provide would be greatly appreciated.

Re: Help w/ RPO on E/C Sequence Sheet
 

If that build sheet is from your rig the build date should match the door pillar plate.
The complete VIN on this sheet should match your truck too.

Re: Help w/ RPO on E/C Sequence Sheet
 

hatzie, i appreciate the quick response...I was scrambling this afternoon, found it, but I was thinking the red penciling scratch meant something....matched the VIN on the sheet! Now onto taking the 14 bolt rear apart and checking the brakes. Have a great day!

Re: Help w/ RPO on E/C Sequence Sheet
 

The red pencil may mean something. Keith Seymore would be the guy to ask since he worked in the assembly plants. Maybe he'll pipe up.

There are RPO definitions in some of the parts books. Look in the manuals link in my signature for download links to the parts books.

Re: Help w/ RPO on E/C Sequence Sheet
 

After reading through the RPOs, now I have to figure out how the truck was switched to a manual transmission...RPO codes say the truck came off the line with a Hydramatic Auto 3 speed. The truck has a 4 speed manual now, and who ever switched this out did a great job making it look factory. Also, RPO says JB6 brakes, however the rear drum measures over 13in...making me originally think it was JB7 equipped...alright, time to crawl around under it and get some more info...Thanks hatzie!

Re: Help w/ RPO on E/C Sequence Sheet
 

JB6 is 7200 GVW JB7 is 8400 GVW

1978 3/4 & 1 ton JB6 & JB7 SRW used 13x2.5" shoes while 1 ton SRW with Hydroboost JB8 is slightly wider at 13x3.5" on the 10.5" 14 bolt full floating rear axle.

Only the 1/2 ton trucks and 1980's 9.5" semi floating 14 bolt got the 6 bolt wheels and tiny 11" drums.

JB6 & JB7 used a dual diaphragm booster and master cylinder specific to the RPO package. You can update your 3/4 ton JB6 to JB7 brakes by swapping the master and booster as a set.

Re: Help w/ RPO on E/C Sequence Sheet
 

Ahh that makes much more sense. I must have had my head upside down under the dash when I mistakingly read that about the JB6. I def know it's got a 14 bolt back there. Hatzie, I really appreciate your info and time on this! Thank you.

Re: Help w/ RPO on E/C Sequence Sheet
 

The red lines indicate that truck has been built and passed by (like a "check mark"). It's really easy to lose your place, especially when you are "in the zone" and not really paying attention.

That piece of paper is actually the build "manifest", which is a summary of the various build sheets. An operator who has to look for specific low running RPOs, like manual trans or cab running lights or whatever, gets a complete set of sheets of what is going to be built that day so that he can plan ahead and be on the lookout for those specific trucks.

If your truck is on there then you have truly hit the gold source. It will describe the actual RPOs your truck came with by definition. However, since you have some suspicions you might be the victim of a VIN swap, or more likely a cab swap. The content would then match the cab but would not necessarily match the chassis/powertrain that you have.

K

Re: Help w/ RPO on E/C Sequence Sheet
 

You can look at your high hump trans cover and see if the 4 speed hole was a non factory cut to explain the changeover from auto to manual.

Re: Help w/ RPO on E/C Sequence Sheet
 

Wow, thanks guys, this is a lot of great info. A cab/chassis swap would make a lot of sense...the frame has been sprayed with an undercoating, and there's no overspray Ive seen anywhere on the body, which doesn't fit the type of work the truck has seen from the previous owners...a bit too clean, if you catch my drift. Either way, it's been a great project so far, and it's definitely kept me on my toes. Thanks again everyone.

Re: Help w/ RPO on E/C Sequence Sheet
 

Check that the vin on the build sheet matches you truck...if not your seat may have come from another truck...with its build sheet.