Truck 10 (89') vs Truck 12 (79)

[Vbb199]

OK. So while I've got two axles to be built in my possession, I thought it be appropriate timing to measure some things for a real deal shootout of the famed truck 10 and 12 bolt axles


The units used in this research involved are as follows
OEM 10 bolt, G80 carrier (oem 3.42)
OEM 12, open diff (oem 3.08)
Aftermarket 10 bolt locker (yukon duragrip)
Aftermarket 12 bolt locker(Eaton truetrac)
Stock axle shafts.
Stock gear sets
Aftermarket Gear sets from Yukon HP

I'm measuring these with the very calipers I pay my bills with, so I don't doubt their accuracy within +/-.002

They're guessing sticks, and I'm not breaking our my micrometers for this.



Posted below will be the measurements of comparison, if you see something you'd like to add, by all means, suggest an edit. BUT I want to note I'm currently building the 10 bolt, so the only thing I'll have after is a stock carrier, 1 oem gear set, 1 Aftermarket gear set after I'm done.



Heres the info, and I'll edit it upon my new 12 bolt gears' arrival.

LEFT will be 10 bolt
RIGHT will be the 12 bolt

OEM Large Pinion OD 1.625 / 1.4375
OEM Small Pinion OD 1.312 / 1.312
Aftermarket Pinion Large OD 1.625 / 1.4375
Aftermarket Pinion Small OD 1.312 / 1.3125
Pinion Length (Tape measure, end to end d) 9" / 8"
Thread OD .865 (was the same on all)
Stock Carrier Journal OD 1.625 / 1.785
Aftermarket Carrier Journal OD 1.785 / 1.785
Stock Carrier ID (axle hole) 1.312 / 1.312
Aftermarket Carrier ID 1.312 / 1.312
Ring Gear OD 8.5 / 8.875
Stock Outer Axle Bearing Seat 1.615? / 1.625
Spline OD 1.290 / 1.265
Spline Count 30 / 30

 

[Vbb199]

Here's some side by side Pics. Explanations will be with the pic.


Truck 10, OEM left, Yukon on the Right

3.42 / 4.10 pinion shafts.

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OEM 10 bolt left, OEM 12 bolt right

3.42 / 3.08

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Truck 10 shaft next to Truck 12 (right)
Notice the 10 bolt tapers down.

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Truck 10 next to Truck 12 (right)

Again, notice the 10 bolt tapers down.

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Left to right:
Yukon duragrip (10b)
Eaton Truetrac (12b)
Oem g80 gutted (10b)
Oem open carrier (12b)
A open diff d60 front carrier for giggles.

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[Vbb199]

I want to additionally focus your attention to the quality of the 79 shaft vs the 89 shaft.
And this is where my tool maker eye comes in, because I like quality. It makes money. Better quality than this, but still quality, nonetheless


The 12 bolt shaft is pretty rough cast, and the splines' raised teeth are a little flat in comparison to more modern, machined 10 bolt shaft.

The 12 bolt shaft almost looks crooked, it's poor casting.

I wonder how many 30" drag slicks launches it'll take ?

 

[Vbb199]

Overall, the obvious here is, while the 12 bolt DOES have a smaller LARGE OD pinion shaft (on oem), it's a shorter pinion shaft in the 12 bolt PLUS it's not necked down like the oem 10 bolt is.

The necked down portion of the OEM 10 bolt pinion shaft measures 1.415 at its smallest point.
That's SMALLER than the LARGE PINION BEARING OD surface of the 12 bolt.


When I get the new set of 12 bolt gears next Wednesday, I will punch in their data for additional discussion and comparison

I just wanted to finally lay this to rest that 12 bolts arent the junk they are made to be. Maybe not world's better, but not just bottom of the barrell


The 88?-91 8.5" 10 bolt is the more desirable units to have being as they are 30 spline, but after this shootout, I'd rather take a truck 12 any day.


When the gears arrive Wednesday, ill compare them to the aftermarket 10 bolt gears I have sitting in the shop that got destroyed recently.

 

[Vbb199]

I think failed to add the most important thing, these are both rear differentials.

I thought that'd be implied, but I need to be clear.

 

[Vbb199]

Back again gentlemen.
Maybe a moderator can bump this post up the line below the photos I posted.
(Max is 5 per post)

I am mid installation of my 10 bolt I built for my suburban (the same 10 bolt in this writeup), and stepped inside my workshop for a beverage in the AC to notice, this other gear set I have for a 10 bolt is from Richmond (it's part of the gear set that got destroyed in my recent travels) and its design is actually different than OEM and Yukon.
Yukon Addresses all the weak spots and adds beef as needed, Richmond for whatever reason added a concave that dips down to 1.4735 (same as a OEM truck 12)

Attached you'll find a Richmond 4.10 pinion (left) next to a OEM 3.42 pinion for a truck 10

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[Vbb199]

Here we are with the final piece of the puzzle.
Aftermarket 12 bolt gears.

Here it is next to the OEM 3.42 12 bolt pinion.

Not much changes.


I updated the other info, this shootout is complete

(Sorry to take so long)

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[Big Chip]

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Problem solved...except maybe for the G80.