3/4 ton axle swap

[Ricky vegas]

i am planning to swap to a 10 bolt 8 lug for the front and a 14 bolt semi float rear. Was wondering what all lines up and what doesn't. So far what I found is the pitman arm and possibly u joints. Just wondering who's done it and what they did to fix it. Thanks

 

[Honky Kong jr]

i am planning to swap to a 10 bolt 8 lug for the front and a 14 bolt semi float rear. Was wondering what all lines up and what doesn't. So far what I found is the pitman arm and possibly u joints. Just wondering who's done it and what they did to fix it. Thanks

For the front all you have to switch is the backing plates and rotors and K20 calipers have a slightly larger piston. Other then that K10 and K20 10 bolt are the same chicken your gearing would have to be swapped to match the back rear. And welcome to the site.

 

[4WDKC]

the 3/4 ton uses a device to adjust how much rear brake is applied depending on weight on rear suspension, 1/2 doesnt have this, so your flexible line will be different and require modifying the rear brake lines.

If they are the exact same why are there so many different parts listed for the front of the 1/2 and 3/4 ton trucks? I still have to swap my front axle.

 

[Honky Kong jr]

the 3/4 ton uses a device to adjust how much rear brake is applied depending on weight on rear suspension, 1/2 doesnt have this, so your flexible line will be different and require modifying the rear brake lines.

If they are the exact same why are there so many different parts listed for the front of the 1/2 and 3/4 ton trucks? I still have to swap my front axle.

Only difference in the axle itself not suspension is backing plates, rotors and calipers. That's why it's kinda funny when people pick on the 6 lug 10 bolt and say they are going to a K20 front rear.

 

[4WDKC]

I did it cause its cheaper than swapping gears.

 

[Honky Kong jr]

I did it cause its cheaper than swapping gears.

There is that side as well.

 

[Ricky vegas]

Axles are complete hub to hub. No probalm with u joint or pitman arm?

 

[Maaac1789]

Mine were already swapped when I got the truck

 

[Maaac1789]

I had to get one of those bastard u joints for the rear, front worked ok

 

[Honky Kong jr]

Axles are complete hub to hub. No probalm with u joint or pitman arm?

Not it the front but you will need some drive shaft work in the back and or a conversion U-joint

 

[Craig 85]

I did a 79 K15 (350,TH-350, NP203) and it was pretty straight forward. I did it because I wanted a gear change. My axles were out of an '82 3/4 ton with semi float rear. The front was pretty a direct bolt in. I did find the old raised steering arm was cracked so I purchased a new arm. The rear you will need 3/4 ton U-bolt spring plates and U-bolts for the larger diameter rear axle. The e-brake cables were torched off on my axle, so I purchased new ones. I did have to shorten my intermediate cable. I used a master cylinder for a '79 3/4 ton. I had to swap the brakes lines at the MC as the reserviors were reserrved. Here's some part numbers of the items I used. Your's may be different of you have different transmission and transfer case. I also know the rear drums and backing plates changed on SF 14 bolts around 83 or 84. The drum has a deeper dish to them than mine.

Rear U-joint
Spicer 1310-1350 Part# 5-460X or O’Reilly’s – Precision U-joint Part# 348
3.219"/ 1.062" to 3.625"/ 1.188"

Steering Arm Washers GM #3965138
Master cylinder Napa NMC M2085 - 1979 GMC K20 w/“JB7” 13” rear brakes
Front brake caliper Napa CAL SE4674 (LF)
Front brake caliper Napa CAL SE4673 (RT)
Front brake pads Napa UP UP7084AM
Rear brake shoes Napa UP UP451R
Rear brake drum Napa ND 4401348
Rear brake cylinders UP37290
Parking brake cable Napa UP93228 (LF)
Parking brake cable Napa UP93228 (RT)

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[Seth Arrowood]

going to jump on this thread to see if I would be better off doing a complete axle swap on my k10, or would it be better to just swap the guts out. just wanting a lower gear.. 3.08s to 3.73

 

[bucket]

going to jump on this thread to see if I would be better off doing a complete axle swap on my k10, or would it be better to just swap the guts out. just wanting a lower gear.. 3.08s to 3.73

If you really like your current wheels and tires and don't need the strength of an axle or brake upgrade, you may want to stick with a gear swap.

 

[VAL]

My truck had factory 3.08s, I swapped front and rear axles from a 1989 k10 suburban with 3.73s. Everything was a direct swap, and I kept my nice 6 lug wheels. There is big difference in power to the ground between 3.08sand 3.73s, especially if you have tall tires. I have a thread on the swap somewhere on here.

 

[HotRodPC]

Axles are complete hub to hub. No probalm with u joint or pitman arm?

Nope, bolt the bitches in and be done. Only issue you're going to have is the rear driveshaft length. That load level brake adjustment needs to be bypassed per GM Technical Bulletin. I'd just use the same lines as your current 10 bolt on the rear.