84 K20 Build Help

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Hottytoddy06

Junior Member
Joined
Nov 24, 2014
Posts
14
Reaction score
3
Location
MS
First Name
Matt
Truck Year
1984
Truck Model
K20
Engine Size
350
Hello all! I have a 1984 K20 with a newly rebuilt sbc 350. Not sure on the new total hp but motor was bored .40 over, mild cam, new carb, intake, long tube headers, etc.

My current setup is the Sm465 and Np 205 TCase. I recently had both of those re-kitted with all new seals/gaskets.

I recently freshened up the front end myself with all new tie-rods, inner and outer wheel bearings, and also upper and lower ball joints (<—— pain in the ass might I add!!) on both sides.

I tore into the rear end (14b SF 9.5” open diff) yesterday with intentions of replacing the wheel bearings only to find two teeth broken/chipped on the ring gear. I pulled the r&p gears and carrier and was surprised to find a 3.23 gear ratio (wth??).

Now I’m planning on regearing and was curious to know your recommendations. This truck is a farm truck and I sometimes use it to pull my 30-35hp tractors. Currently has 35” buckshots and has seemed to do well in the past. I plan to eventually put 6”-8” lift and possibly run 37”-38” tires.

Not much highway driving or off roading other than at deer camp. This was my late grandfather’s truck who passed it down to me and one that I will never part with. It is more of a fun project and way that I can remember spending time with him when I’m working on it.

Was looking at going back with 4.11, 4.56, or even 4.88?? Also considering throwing in a Detroit true trac Torsen locker while I’m there. Plan on tackling the front (GM corporate 10) next as I have not yet busted the cover off yet.

What do you guys think?
 

Craig 85

Full Access Member
Joined
Jan 25, 2017
Posts
3,889
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4,024
Location
Nashville, TN
First Name
Craig
Truck Year
1985
Truck Model
K30 SRW
Engine Size
454/TH-400/NP205
Used FF 14 bolts are probably cheaper than buying all the parts you need for the SF 14 you have. Most will probably have 4.10's and a Govlock. The only reason I bought the SF 14 for mine is it was cheaper to axle swap than up grade gears on the 1/2 ton stuff I had. I got a pair of axles for $400.
 

TubeTruck

I'm from Boston. Deal with it.
Joined
Sep 4, 2019
Posts
1,417
Reaction score
2,135
Location
East TN
First Name
Denis
Truck Year
1978
Truck Model
Suburban K10
Engine Size
LQ9
What Craig said. Find a 14b FF. You will be happier in the long run. Parts are cheap and easy to set up in those too. No playing with shims. If you've got some fab skills find a 14b FF off a 2001+ 2500hd with a 6.0L.(not diesel, those are a 11.5 ring gear. Look for an AAM 10.5) Comes with factory disc brakes and you just have to move the perches.
 

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