9" Chunk Interchange

[Lando375]

Buy once cry once. I'm in the same boat as you. I'm rebuilding my 9" because I'm upgrading to 31 spline axles. I thought this would be a good time to upgrade to the Daytona pinion support but decided to also go with a nodular iron case as well. I ended up going with this one from Quick Performance. Its definitely overkill but why not. It may be something to think about.

https://www.quickperformance.com/Ford-9-Nodular-Iron--Pro-N--Dropout-Case_p_22761.html

 

[pcf_mark]

Thanks guys I'll do a dry fit before I completely clean the case for the final time. That would really stink to have to grind on something I just spent hours cleaning.

All the bearings are being replaced I'll be setting it up from scratch. Amazing what sort of damage can happen when a side bearing comes apart.

 

[crashnburn]

Both my 77 and 79 F150 4x4 trucks had trac-locs with 31 spline axles.

I have a theory that I can't prove that SOME 77 broncos came with 31 spline axles... I have a 77, and swear thats what I had before going to 35 spline but i solt the center chunk and axles a few years back... Can you PROVE me right and count your 77 spline count????

 

[DirtDonk]

Sounds like they were speaking of both vehicles being F150s.
If that’s correct then it’s natural that they had 31 spline axles.

Although I won’t argue against some 31s coming in Broncos as well in that last year.
It’s not likely, but how many times have we said that and then been wrong because Ford did something weird?

 

[jamesroney]

Sounds like they were speaking of both vehicles being F150s.
If that’s correct then it’s natural that they had 31 spline axles.

Although I won’t argue against some 31s coming in Broncos as well in that last year.
It’s not likely, but how many times have we said that and then been wrong because Ford did something weird?

I'll argue it. I have seen exactly zero evidence that any optional axle was provided in the 1977 Bronco. Nothing in the MPC, nothing in the Service manual, nothing in the warranty literature. There is no way that the Factory could "sneak" a 31 spline axle into a 77 Bronco. Just like the Hybrid D44/D30...there would have to be a DSO, along with a Bill of Materials change, and some way to procure the item. Logistics and MRP would be a nightmare. The Service Department and after sales support would be problematic. Can you imagine being in the service department at Ed Chovanes Ford, and some guy needs a warranty axle, and you pull the shaft and find it is a 31 spline axle with no part number, no source, no cost, no reference material, no corresponding axle side gear? It would be impossible to service. It just doesn't happen.

The general public just doesn't understand what it takes to run a manufacturing plant with a 90 second TAKT time. The engineering that goes into a running change at the plant level is significant. The only wierd stuff that happens is stuff that could be done by human error. NOBODY wakes up and goes to the plant and says: I'm going to visit my Tier 1 sub-assembly factory, forge an axle shaft, machine it to a new specification, build it to a undefined length...add it to a normal RPO delivery, get those shafts married to a non-conforming differential from another application, and create a new axle assembly. I will have this axle assembly identified with a standard Ford part number, and ship it on the same purchase order (or factory work order) and I will do ALL of this at no cost, with no change to any logistics, inventory, FIFO, or buffer. No one from Engineering will know. No one from Quality will know. Just little ol' me.

Even if @crashnburn did find one in a 77, it is FAR more likely that someone in the warranty department or aftermarket did an upgrade. It is possible that Ford sent a Bronco to a specialty service provider, like Shelby, Stroppe, KarKraft, etc. But there would be documentation. People don't do work without getting paid. So I'm going to say it didn't happen.

 

[toddz69]

I'll argue it. I have seen exactly zero evidence that any optional axle was provided in the 1977 Bronco. Nothing in the MPC, nothing in the Service manual, nothing in the warranty literature. There is no way that the Factory could "sneak" a 31 spline axle into a 77 Bronco. Just like the Hybrid D44/D30...there would have to be a DSO, along with a Bill of Materials change, and some way to procure the item. Logistics and MRP would be a nightmare. The Service Department and after sales support would be problematic. Can you imagine being in the service department at Ed Chovanes Ford, and some guy needs a warranty axle, and you pull the shaft and find it is a 31 spline axle with no part number, no source, no cost, no reference material, no corresponding axle side gear? It would be impossible to service. It just doesn't happen.

The general public just doesn't understand what it takes to run a manufacturing plant with a 90 second TAKT time. The engineering that goes into a running change at the plant level is significant. The only wierd stuff that happens is stuff that could be done by human error. NOBODY wakes up and goes to the plant and says: I'm going to visit my Tier 1 sub-assembly factory, forge an axle shaft, machine it to a new specification, build it to a undefined length...add it to a normal RPO delivery, get those shafts married to a non-conforming differential from another application, and create a new axle assembly. I will have this axle assembly identified with a standard Ford part number, and ship it on the same purchase order (or factory work order) and I will do ALL of this at no cost, with no change to any logistics, inventory, FIFO, or buffer. No one from Engineering will know. No one from Quality will know. Just little ol' me.

Even if @crashnburn did find one in a 77, it is FAR more likely that someone in the warranty department or aftermarket did an upgrade. It is possible that Ford sent a Bronco to a specialty service provider, like Shelby, Stroppe, KarKraft, etc. But there would be documentation. People don't do work without getting paid. So I'm going to say it didn't happen.

A great explanation of how 31 spline axles were well nigh to impossible to have been installed in '77 Broncos.

That said, I remember back in the pre-internet days, there was at least one, maybe more '77 owners in the EBR newsletter claiming their '77s had 31 spline axles and they were the original owners, blah, blah, blah. Always wondered about those.

Todd Z.

 

[Broncobowsher]

Some parts books will also list the '77 as having optional full time 4WD and 400 engine. That would be a '78. But some of the old books were off by a year. Production of the '78 did start in '77, maybe that is what confused them?