Opinions on budget build K20

[Rustic_k20]

Hey ya'll!

New member here. Im sure ya'll get this question alot but what are ya'lls opinions on running gear and suspension setup for my 81' K20. I'd like to have it very capable off-road crawling, some muddin, and also be able to take her out to town now and then. She's all torn apart at the moment but I still have all the original 4 bolt main 350, th400/np208 and corp 10 bolt front and 14 bolt rear i believe, May have to double check on that. She's sitting on 315/75r16's (basically 35s) with stock gearing (whatever that may be). But ive recently picked up a Sm465/np205 full manual swap that im gonna be goin through here in a couple days. What are ya'lls thoughts on a doubler or different axles or gearing, steering boxes, 4 linking, etc. Im open to anyones suggestions as long as it dont cost an arm and a leg. Not a great welder but im sure this project will make me very familiar with welding lol. Rather put in alot of elbow grease than break the bank. Shoot me some pics of ya'lls rigs. Here's mine at the moment.

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[Shorty81]

Welcome from the Buckeye State

 

[HotRodPC]

Welcome to GMSB. You've got a ton of questions there. I'd start a build thread about it in the Under Construction Section since you're asking for opinions on a build. For now I'll respond to the SM465/NP205 suggestion. You mentioned you want to to do some crawling. Not many crawlers are using manual transmissions at all. Depending on how aggressive you get in some crawling situations, I assume you mean rocks and not mall crawling, using a clutch can get sketchy.

 

[Arkansas_V8]

Welcome aboard.

I went with rough country 4" springs and ORD zero rates. The front axle is 1.5" forward. The springs have enough flex for me to get around in the rocks. I run 37x13.5x17.

If money wasn't an issue than coilovers would be my direction.

 

[Arkansas_V8]

Dont try and build it to the best at anything, but rather good at everything.

 

[Arkansas_V8]

Rear setup-
https://www.offroaddesign.com/complete-rear-coilover-conversion-system-for-67-87-91-gm-trucks.html

Front setup-
https://www.offroaddesign.com/complete-front-coilover-conversion-system-for-67-87-91-gm-trucks.html

Doubler kit-
https://www.offroaddesign.com/np203-np205-doubler-kit.html

Crossover Steering-
https://www.offroaddesign.com/catal.../gm-d44-and-10-bolt-crossover-and-high-steer/

Knuckle for crossover-
https://www.offroaddesign.com/catal...8/s/reid-racing-dana-44-and-10-bolt-knuckles/

Bolt in steering brace-
https://www.offroaddesign.com/bolt-in-steering-box-brace-for-81-91-gm-4wd-trucks.html

Weld in-
https://www.offroaddesign.com/weld-on-frame-repair-kit-for-73-91-gm-trucks.html

 

[Arkansas_V8]

I would go with these, but I am old and like leaf springs.

Front-
https://www.offroaddesign.com/ord-lift-custom-front-springs.html

Rear-
https://www.offroaddesign.com/ord-lift-custom-rear-springs-without-bushings.html

Zero Rates-
https://www.offroaddesign.com/1-zero-rate-add-a-leaf-kit-2-1-2-wide.html

These could be used if your rear springs are good.

4" shackle flip-
https://www.offroaddesign.com/4-shackle-flip-kit-for-73-up-straight-axle-gm-k5-1-2t-3-4t.html

2.5" shackle flip-
https://www.offroaddesign.com/2-5-shackle-flip-kit-for-73-up-straight-axle-gm-k5-1-2t-3-4t.html

 

[RoryH19]

Welcome from TX.
Personally I would keep the TH400. I had a k20 with a Sm465 and hated shifting gears while mudding/off-roading.
Too easy to loose wheel speed when shifting.

Assumed you have a lift kit if running 35s but you mention stock gear.
I like Tuff country for the lift kits. You can go full spring or as @Arkansas_V8 mentions a shackle flip in the rear.

I would make it a reliable runner; engine, trans, transfer case, axles, etc.
Then I would take care of the metal work and body.

 

[Rustic_k20]

Welcome from TX.
Personally I would keep the TH400. I had a k20 with a Sm465 and hated shifting gears while mudding/off-roading.
Too easy to loose wheel speed when shifting.

Assumed you have a lift kit if running 35s but you mention stock gear.
I like Tuff country for the lift kits. You can go full spring or as @Arkansas_V8 mentions a shackle flip in the rear.

I would make it a reliable runner; engine, trans, transfer case, axles, etc.
Then I would take care of the metal work and body.

Sorry, i forgot to mention i got a 4 inch rough country lift (blocked in the rear). I picked up the Sm465 because of the low granny and thought it'd work wonders off-road while crawlin through the trails and paired with the very considerably stronger np205 compared to my np208 although with the downside of losing the low low gearing but thats why i asked opinions on the doubler. Thankyou for ya'lls input. Im reading all this and doin my online surfing.

 

[shiftpro]

Rear setup-
https://www.offroaddesign.com/complete-rear-coilover-conversion-system-for-67-87-91-gm-trucks.html

Front setup-
https://www.offroaddesign.com/complete-front-coilover-conversion-system-for-67-87-91-gm-trucks.html

Doubler kit-
https://www.offroaddesign.com/np203-np205-doubler-kit.html

Crossover Steering-
https://www.offroaddesign.com/catal.../gm-d44-and-10-bolt-crossover-and-high-steer/

Knuckle for crossover-
https://www.offroaddesign.com/catal...8/s/reid-racing-dana-44-and-10-bolt-knuckles/

Bolt in steering brace-
https://www.offroaddesign.com/bolt-in-steering-box-brace-for-81-91-gm-4wd-trucks.html

Weld in-
https://www.offroaddesign.com/weld-on-frame-repair-kit-for-73-91-gm-trucks.html

This info should be pinned.. How many times have we dished this recipe out in the last 8 months?

 

[HotRodPC]

Sorry, i forgot to mention i got a 4 inch rough country lift (blocked in the rear). I picked up the Sm465 because of the low granny and thought it'd work wonders off-road while crawlin through the trails and paired with the very considerably stronger np205 compared to my np208 although with the downside of losing the low low gearing but thats why i asked opinions on the doubler. Thankyou for ya'lls input. Im reading all this and doin my online surfing.

I'm still leaning toward sticking with the Th400 if you want to go crawling. Keep in mind, if you need LOW, you have 4Low. That K20 probably has 3.73 or 4.10 gears so with T case in Low, with the NP208, I can't imagine you'd need lower gear than that. Don't discount the NP208. There's pros and cons to both the NP208 and NP205. Many people run the NP208 without major problems. The big key is to always make sure your mounts are in good shape so it don't jump around and crack the aluminum case.

 

[77 K20]

I have a similar setup on my truck- running 315/75R16 tires on the stock 4.10 gearing except I have the TH350 and the NP203. I wish I had lower gearing for descending steep hills when out on the trails. In 4 low and 1st I have to rely on my brakes- and this gets dangerous. I wish I had a doubler or an atlas transfer case. The other offroad guys I wheel with all have low crawl ratios and go down these steep hills without touching the brakes. Way better/safer control.

I'm a big fan of removing the front sway bar which greatly improves the articulation and the ride. I remove the factory front shock mounts and instead use the ford shock mounts. This moves the shock mount upward giving more suspension travel (not shock limiting)

https://www.offroaddesign.com/extended-front-shock-mounts-pair.html

My rear springs were shot- and I wanted to remove my 3" blocks as I was getting wheel hop in the snow. My rear springs were 52" so I ordered the stock longer 56" springs. I ordered the 2.5" shackle flip kit. It rides nicer- but it moved the front axle forward too much for my liking. I ordered the 1/4" axle relocation plates to shift the axle rearward again. The pic below shows how the rear tire isn't centered.

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I'm going to be going up to some 37" tires in the near future. I'm just running the D44 in the front. I did buy some chromoly axle shafts to get rid of the weak necked down area of the stock shafts.

https://www.tenfactory.com/

ORD makes greasable bushings for the leaf springs and even the front upper shackle hanger. Allows the suspension to move/flex better.

Front/rear lockers are recommended (at least a rear). Instead of locking the front axle where you can lose some steering or break stuff I put an Eaton Truetrac in. Been impressed with it. Have a detroit locker in the rear.

And a steering brace like what Arkansas said.

If you are going to be going places where the front axle articulates a lot then crossover steer is the way to go. I'm slowly going that route. Installed the Reid racing knuckles on the front for the passenger side mount but haven't bought the 2wd steering box or the crossover linkage yet.

Might look into some differential protection also. Either new covers or they even make a "cage" that can fit over the stock cover.

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