Been a bit since posting any updates. The truck is still running great - totally pleased with the engine and transmission.

The highway speed vibration is still around and shaking the patience out of me. Every moving part of the front end has now been replaced, bushings, control arms, steering, shocks, steering gear, etc. Alignment was done and I won’t have to think about that for a long time.

The tires are new and were re-balanced. Driveshaft has been in and out several times and re-balanced. The transmission extension bushing and seal replaced.

I tried to get the tires road force balanced today but apparently the steel wheels were too out of whack to run them. I watched as all 4 were spun up and two looked noticeably bad. So the simplest thing seemed to be the thing. I’m now trying to find a good set of steel wheels, 16”x7”, 8x6.5” hole pattern. I want to keep the hubcaps and steel look for the truck. Wheel Vintiques has some with those specs but 8-10 week wait to get stock, so that’s not a great option.

Aside from the wheels, the vibration seems to change when coasting or slowing. I theorized the rear end gears could be a factor there, but not too sure.

Looking forward to getting this sorted and taking it for some long road trips this summer!
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Old furd vans have that 16x7 pattern and fit our hubcaps.
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Re: 72 C20 LS Swap/Build
 

How's your pinion angles? I have heard that issue on a fair amount of LS swaps and it turned out to be that.

Re: 72 C20 LS Swap/Build
 

Update on the truck since it has been ages and ages. Some of the long lasting sagas in sorting things below...

I've mostly eliminated all of the highway vibrations after ordering a new set of steel wheels. One of the four (new from a tire shop) turned out to be out of alignment and they had to order in 4 others to find one straight replacement. This was after I decided to get them powdercoated white. Live and learn that it is worthwhile to spin up the wheels themselves to check first. They are really basic 16" x 6.5" steel wheels since I wanted to run hubcaps. The closest alloys that I thought would have been tolerable were the 8 hole Pro Comps.

Once I had the wheels all set, the tire shop discovered that one of the tires was out of spec. They are Coopers, purchased in 2020, with very low mileage. That tire was replaced under warranty and I got it road force balanced along with the others.

Oh and I also removed the new polyurethane engine and trans mounts and put rubber ones in their place. And found a spot or two where there was interference between a heat shield and the frame and corrected that.

There is still some minor vibration at 70+ mph but I can live with it now.

After that, I managed to find a set of 72 hubcaps on ebay and my dad painted them up with blue bowties to match the truck. Will have to do new photos this summer.

I also found a set of oem 72 sport mirrors on ebay and recently installed those.

My power steering caused all sorts of issues in the last 10 months. I am trying to recall the sequence since it was such a saga. I think when the front end suspension was all replaced, the steering box was in need of rebuilding or replacement. I ordered a rebuilt Cardone from amazon. Seemed fine until coming home from a camping trip last summer when it blew the upper seal on the drive home. Rather tricky driving and especially parking it like that! It was sent back and I found a local rebuilder for the original box. They had a rebuilt one on the shelf, so I exchanged mine and installed it. That one was extremely sloppy with inches of play at center, so I had the shop rebuild mine. It was still sloppy, just not as much. I learned more than I care to know about steering boxes.

Somewhere along the way, the pump went as well and I learned that perhaps the LS power steering pump puts out too much pressure for the original box. I ordered the Borgeson 899001 pressure reducing kit to try that out. I think the pump was cooked when the box went, so a rebuilt one went in from the same shop.

My rebuilt box was still sloppy and adjusting the nut on top only made it harder to steer without actually reducing the slop. The shop insisted that the internal bearings do not wear out, however in speaking with Red Head Steering, they said that they size new ball bearings for each rebuild to eliminate play. Being in Canada, it wasn't really cost effective to send my old box to them and so I hemmed and hawed for months about dropping $800 CAD on a new Borgeson 800132 steering box and 990012 coupling/rag joint. Finally bit the bullet recently and installed it last week after getting a $50 off deal at Jegs. Now that is how it is supposed to steer! It has no slop, responds nicely and overall it drives on the highway without requiring any thought or constant corrections.

Oh yeah, had a frustrating day back in the dead of winter. I was running errands all day, picking up lumber, fasteners, etc. and on one of my last stops, it would not start. I could hear relays but no crank. I had power, pulled and checked fuses, checked the fuseboard and swap wiring and thought it could be a dead starter. Was a couple doors from a parts place, so got one of those and spoke with my dad about all this. He decided to drive up to see if we could install the new starter in the truck to get it going. I walked to a coffee shop to stay warm and my partner came to keep me company. She drove us back to the truck and I was texting with a friend about it. He suggested the neutral safety switch and sure enough, I threw it in neutral and it started right up! My dad arrived a few minutes after that and I bought him a burger for his troubles.

Other than all that, it is still running great and is better than I expected from a LS swap. Wouldn't hesitate to do it again even after all the fuss.