14 bolt FF 3.73 SRW/ 10 bolt front 3.73

[roundhouse]

14 Bolt FF SRW 3.73

10 bolt front axle 3.73

$500 for the pair

pulled from 79 K20

in Atlanta

 

[campfire]

Pics of the front? I would have thought that a '79 would have a D44 front.

 

[thatK30guy]

Pics of the front? I would have thought that a '79 would have a D44 front.

10 bolts started mid-year '77 with the 2nd design axles. D44's were in the phasing out stage of which they ran up to '82 in GMC trucks.

 

[roundhouse]

Started pouring down rain before I got pics of the front

these axles are currently in a shortbed K-10
so theyve been swapped in.

I thought they were 4.10, dumbass me, listening to the seller.
should have pulled the covers and checked before I bought the truck

was planning on putting them in a 77ish K-10 with a NV3500 5 speed OD and 35'' tires
figured 4.10 would be just about right, but 3.73 may work ok for that.

I have 4.11 and 35's on my 74 Bronco with EFI and a NV3550 5 speed, and its just about right, I think 4.56s would be soo high RPM on the hwy

 

[campfire]

10 bolts started mid-year '77 with the 2nd design axles. D44's were in the phasing out stage of which they ran up to '82 in GMC trucks.

Thanks for filling me in! I hadn't realized that 10-bolts started that early (my '79 axle pair had a D44 front, so I had assumed the transition point was later on). What are "the 2nd design axles" you refer to?

 

[thatK30guy]

Thanks for filling me in! I hadn't realized that 10-bolts started that early (my '79 axle pair had a D44 front, so I had assumed the transition point was later on). What are "the 2nd design axles" you refer to?

GM has two different types of axles: the "first design" and the "second design". For those who dont know the difference, the "first" goes from 73-76. The "second" goes from 77 to 91. Some differences are:

1. Backing plates are ALL diffferent. Both 1/2 and 3/4 ton for both designs are NOT the same thing. 3/4 tons are larger diameter than the 1/2 tons. There are currently 6 different types of backing plates. The 1/2 ton has the 73-76, 77-80, and 81-91. 3/4 ton is the same years, but only bigger around.

2. Bearing hub and rotors are different. There are 4 types. 73-76 use a smaller wheel bearing on both the 1/2 and 3/4 ton. The 1/2 ton bearing hub is an internal drive. 3/4 tons were available in both the internal and external drives. 77 and newer bearing hubs are the same size wheel bearing. 1/2 and 3/4 tons are all internal drives. The differences in the rotor diameter is the fact that the 3/4 tons are larger around than the 1/2 tons. This is why the backing plates are larger around than the 1/2 tons. If you use a 1/2 ton backing plate on a 3/4 ton rotor, the caliper will NOT even align up with the bolts. If the 1/2 ton rotor is used with the 3/4 ton backing plates, the caliper will NOT have enough pad contact with the rotor.

3. Spindles. 73-76 are one type only. They are "first design" small bearings. 1/2 and 3/4 ton spindles are interchangable. 77-91 spindles are "second design" and all interchangable between 1/2 and 3/4 tons. You cannot use a first design spindle with a second design bearing hub & rotor. The hub will wobble in place. If the second design spindle is used with a first design bearing hub, the hub will not even go on at all.

4. D44 and 10B axle shafts are not interchangable. The D44 shafts measure: right - 36.13"
left - 18.31"
10B shafts measure: right - 35.46"
left - 19.15"

5. Steering knuckles. Some pre 76 D44's have the infamous "flat top" knuckles on the passenger side. These are good for the crossover steering for where the steering arm is mounted on top of the knuckle after machine work and drilling has been done. The 10B knuckles have NO flat surface whatsoever. Machine work would be excessive to make the crossover work and therefore would be easier and cheaper to locate the correct knuckle off a D44.

All in all, when doing a swap like this, try to round up the parts off one truck to use on the other. Such parts to swap over would be: backing plates, spindles, bearing hub & rotors, and if desired for crossover steering, the knuckles.

The knuckles do NOT need to be changed if you do not plan on the crossover steering.

It all boils down to this: D44 and 10B parts ARE interchangable from the knuckles out. Anything else from the knuckles in is NOT interchangable.


ALL calipers on both D44 and 10B are compatible with either axle. Even the first and second design axles are compatible with BOTH 1/2 and 3/4 ton calipers. So, whatever swap you plan on doing, you can retain your stock calipers.
When stepping up to the big D60, this is a whole different ball game. Nothing is interchangable from the D44 and 10B to the D60

 

[campfire]

GM has two different types of axles: the "first design" and the "second design". For those who dont know the difference, the "first" goes from 73-76. The "second" goes from 77 to 91.

Thanks again! Nice summary! I have heard much of that (and swapped some of these parts around between axle eras), but for some reason I was thinking of first/second REAR axle design. Which is where I got confused.

 

[roundhouse]

Pics of the front? I would have thought that a '79 would have a D44 front.

from 77 to 81 GM just used whatever axle was handy

this back axle is a 1 ton FF , dont think they were available in K-10 or K-20 or in single rear wheel ?

must have had the perches and shock mounts relocated to fit ??