1978 Chevy K20 longbed with nearly 500,000 miles! LS Swap begins!

[Nick_R_23]

Rear wheel hubs after a couple rounds in the hot tank and a fresh coat of paint!

[Nick_R_23]

New bearings installed in the wheel hubs!



I need to pick up a press to install the wheel studs through the hubs and drums.



I scored a pair of early 13” backing plates! These were hard to find because they used the bolt in style parking brake cables.



Old junk removed!





Brakes completely redone on passenger side!





And brakes completely redone on the drivers side!

[OutlawDrifter]

Brass hammer and punch will get those studs driven in, but a press is nice to have as well.

[Nick_R_23]

Picked up a new toy!



All assembled! I’ve been needing one for a while and finally bit the bullet.



Pressing in the wheel studs



All the studs are installed



New wheel seals installed



Hub and drum assemblies completed!



Assembly installed and hub nuts torqued!



Cleaned and painted the axle shafts



As well as the axle flange hardware.



Axle all complete!



Picked up some new hardlines for the rear brakes



Also some retaining clips for the parking brake cables.



New hard lines on rear axle





New hardline for the rear frame also





New shocks for the rear!



Installed!

[OutlawDrifter]

Looking good!

[Nick_R_23]

I had quite the lame weekend on this one. I finally got the parking brake cables in, and intended on bleeding the brakes and installing the wheels, and maybe even getting a test drive in! The front parking brake cable went well, but the intermediate one turned out to be for a shortbed wheelbase, so I ordered the next size up.

Then, bled the rear brakes only to not get that great of pressure out to the rear. After vacuum bleeding the rears, and various troubleshooting, I could sometimes get pressure at the rear, and sometimes not. The proportioning valve was replaced quite a few years ago, but it’s acting like it’s sticking to one side now. I ordered up a new one and will try again next week!

[Nick_R_23]

Alright, after messing with it for a bit, this is where I’m at.

Went to adjust the rear shoes. I can tell the new drums are slightly out of round, as they drag slightly on the shoes on only about 1/2 of the drum. Both sides do this. However, at the adjustment sight windows at the bottom of the backing plates, the shoes have a small gap and don’t touch the drum. I could likely crank on the adjuster and force them to, but the drum would be locked up. It feels like the shoes touch the drum at the top before the bottom. The driver side is slightly better than the passenger side. Currently, I have it adjusted where there is some slight drag.

After attempting to bleed the brakes, the front worked fine. I could not get consistent pressure to the rear, although the rear brakes did work really well once sporadically. I determined the proportioning valve was shot. Ordered a new proportioning valve and the bleed lock tool for it. Installed both of those and had better results, but still inadequate pressure in the rear.

Warrantied out the brand new master cylinder for another one and rebled the system. Now I have good pressure to the rear. However, the hose from the frame to the axle was machined incorrectly, and the hard line wouldn’t seat and kept leaking. This damaged the new passenger side hard line. I warranted out the hose and reflared the hard line and replaced the fitting. Went to install and the drivers side threads pulled right out without even tightening down, damaging the driver side hard line. Replaced the hose again, with a different brand, and reflared the other hard line and replaced that fitting. Installed the new line and rebled the system again. Removed all the air and the pedal feels good.

However, if I have the pedal pressed I can still turn the rear drums by hand. They definitely drag more than what my adjustment was, but they definitely don’t work. Front seems to lock up solid and work great. For an extra brain scratcher, if I manually pull the parking brake cables by hand, both rear brakes will work perfectly via the parking brake.

Not sure what the issue is, but I think I’ll have to dive back inside one of these upcoming weekends.

At least I had some help, lol.





This was…interesting.



New proportioning valve installed



New wheels mounted in the front!

[OutlawDrifter]

Brakes can be very frustrating!

Sounds like the drums need turned to true and balanced before you chase any other issues.

Or just swap to rear discs?

[Nick_R_23]

Had to at least see what the wheels looked like on it!



I’ve been messing with the brakes more on and off. Ended up taking the drum assemblies apart to double check that everything was okay. Shoes appear to fit perfect.





I did notice that the shoe material stuck out past the metal portion, so I ground that down in case it was causing the shoe to not sit flat on the backing plate.





Still not satisfied with the brake performance, I hypothesized that I needed a K30 master cylinder instead of the K20 unit, which gave me 1-5/16” bore instead of the 1-1/4” bore, meaning I would have a higher volume output, stiffer pedal feel, and less pedal travel, which is what I think this truck needs. So I picked up a K30 unit.



Painted!



Bench bled the unit



Just out of curiosity for comparison - it appears the K20 and K30 units are slightly different depths.





After all of this, I’m still not completely satisfied. I’ve also determined that the hydroboost unit doesn’t appear to be always working as it should, so I’ve ordered a new replacement. Unfortunately, it has an up to 90 day lead time.

[Nick_R_23]

Made an unexpected score today! I found a rust free hood on Marketplace for $75!



Not perfect but damn close!

[OutlawDrifter]

Awesome find!

[Nick_R_23]

Alright, I’ve finally admitted defeat on these brakes. I’ve been through this system a hundred times and can’t come up with any reason why it won’t function. The new hydroboost unit should be here soon, and I ordered a Lugnut 4x4 rear disc swap kit with the larger 76-78 Eldorado calipers and all the upgrades, as well as a new Leeds disc/disc proportioning valve. I’ll have to swap out the master cylinder again too, but I hope this will be worth it to finally get the brakes where they should be.

[Nick_R_23]

The Lugnut4x4 kit showed up today!



As well as the Leeds disc/disc proportioning valve.



I’m waiting on the hydroboost to show up before I get a master cylinder, but I’m planning on moving to a 99-07 hydroboost master cylinder with a shorter 2000 S10 reservoir.

[Nick_R_23]

Stripped the axle back to a bare spindle



Pressed the studs back out of the hub and removed the drum



Reinstalled the studs with the brake rotor



Updated seal installed



Hub mounted and spindle nuts torqued and adjusted.



Caliper mounted





Passenger side also completed

[OutlawDrifter]

Looking good, brakes for as simple as they are, can be quite frustrating!

[Nick_R_23]

Picked up some new axle shaft seals and short brake lines.



Axle shafts reinstalled





Welded on the tabs and installed the hoses





Bent new hard lines





Installed the new disc/disc proportioning valve



Upgraded the rear exhaust hangers while I was under there.

[Nick_R_23]

Today, we FINALLY have *progress*! Over a year later, my new hydroboost setup has arrived. This came from Sweeting Performance and is setup for an LS pump. I DO NOT recommend them. Their communication is terrible, and my initial “90 day lead time” turned into almost 400 days to actually arrive. However, the product looks good and hopefully solves my brake issues.

Starting with a 2002 Silverado 1500HD (disc/disc) master cylinder and a 2000 S10 brake reservoir.





As you can see, the reservoirs are a direct swap.



The new style master cylinders do not fit the OE units.





New unit with new master cylinder installed.

[Shark_13]

Looks great, so close!

[Nick_R_23]

Old hydroboost removed



Adapter plate installed.



New hydroboost mounted



I found a brand new set of master cylinder and front wheel brake lines on Marketplace for $40!





All lines installed.



New master cylinder bled and installed!



So I’m very happy to report that all four brakes FINALLY work! I still need to install the parking brake lines and fix a front pinion seal leak, but I think it’s about ready for the road!

[Nick_R_23]

I didn’t like the universal set of parking brake cables with the kit, so I did some research and found a stock set that I can work with. I believe these were for an 85 K20, two RH cables.



I trimmed off approximately 1/4 of the spring to work with the travel of the caliper arms.



Cables ran!





I just need an intermediate cable and the brakes should be done. I’m measuring 102”, my two OEM options appear to be ~95 Dakota or Ram Van (102”) or ~85 Chrysler New Yorker (101.35”). Both are out of stock so I may just have one made.

[Nick_R_23]

Ended up making my own cable at 102”. Installed and adjusted the cable, the parking brake works great, along with the regular brakes! I reinstalled the brake switch and tightened down all the linkage hardware, and put the wheels back on. It’s about ready for an alignment now!

[OutlawDrifter]

Get that stuff out from under it and take it for a drive!

[Nick_R_23]

Alright, here’s the major update!

Finished under hood product!



Cleaned out in and around the truck!



Brought it outside and wiped everything down!



Loaded on the trailer to take it in for alignment!





Back home from alignment!



The truck needed a few final touches. The original starter was hanging up, and the tensioner/pulleys were squeaking, so I bought a new OEM starter and picked up a tensioner/idler/belt kit.





Back from its first official test drive!





So now that I’ve put about 500 miles on this truck, I want to give an honest review of it - and to be honest, overall, I’m not super happy with it. I think I set my expectations too high. The engine is a GREAT addition, the turn key running is amazing, it has quick, smooth power delivery, good acceleration, and is definitely what this truck needed! However, everything surrounding it is so outdated that it still feels like a chore to drive.

The biggest drawback is the SM465 - I wish I would have swapped this out with a NV4500 or the new TR4050. Hell, even a 4L80E would’ve been a good compromise, but the clunky, partial-synchro shifting and lack of OD gear just really feels disappointing when it’s behind such a great engine upgrade. 10/10 for keeping the nostalgia factor, but 2/10 for daily driving and practicality. Also, even rebuilt, the NP205 remains difficult to shift in and out of gear.

The other big drawback is really the chassis itself. I thought with all new steering and suspension, it would improve things quite a bit. It did in a way, things feel tighter, and I do like the faster ratio of the Borgeson steering box, and the brakes have never felt this good, so I feel like the quick ratio box and the rear discs are 100% worthwhile upgrades on these trucks. However, I think some issues are just by design - the truck still feels floaty at highway speeds, bumpsteer still exists, and the suspension is still jarring. The frame feels flexy while taking corners, and overall it just doesn’t feel solid or smooth to drive.

So I’m left at a crossroads - the truck is “done”, and driveable. I can keep it as is and try to enjoy it, although I’m not very excited to drive it as is. I can make some more upgrades, mainly the transmission and possibly the transfer case. I’m not sure if there’s anything I could do to improve the chassis at this point. This would solve the worst parts, but I’m still left with SFA and a flexy frame. Costs would probably be ~$7500 to upgrade just the drivetrain.

However, I may have found a completely new avenue to take with this truck. I was given a 2002 GMC 2500HD 4x4 with a Duramax and Allison. The engine needs a pump or injectors, but apparently was well maintained to that point and they decided to buy a new truck. The body is rough, and the chassis is an extended cab shortbed, so I’m not sure if that’s equal enough to a regular cab longbed, but that’s not hard to solve. I’m considering just doing a body swap onto this newer chassis, and gaining EVERYTHING modern, plus additional capacity.

What’s everyone’s thoughts?

[OutlawDrifter]

Tough to meet expectations the brain puts on a project. Been there with similar results.

If it were me, I'd swap in an overdrive. That in itself will increase the driving enjoyment. Suspension is tough, unless you go with some ORD Soft Ride springs or something like that, there isn't much you can do with these pickups. My '79 K10 had the snowplow package and rode like a lumber wagon.

Save the diesel and running gear for something else.

[Honest Bob]

Ive done nearly what you have (except I went with a 4l80e) and agree with you on the suspension, ride quality, and creature comforts.

Part of the mushy feeling is probably the big tires on little rims and there is no way I am putting anything larger than MAYBE a 17" wheel (Im guessing you are running a 17" though?) on a squarebody.

Do I want the truck to ride better? Yes, and as mentioned the offroad design custom springs are supposedly the ticket but then I'm lifting the truck and messing with the load capacity both of which I dont really want to do. Im sure a 2" lift wouldnt be horrible but I am gonna be tempted to go with larger tires which is gonna make it feel even more floaty.

The windshield wipers are another area in need of improvement but the kits to fix it are super expensive.

The 2 wheel drive squarebodies drive so much better, the 4x4 ones just are what they are.

I dont remember if you went twin stick on the np205 but that in combination with the adjustable shift detent kit improves the np205 shifting to be as good as its gonna be (less finicky). An NP208 has a lower low gear and is alot easier to get in and out of 4x4, I kinda with I went that route.