Thanks for the commiseration on the rivets. I went back to the plasma and the air chisel. I still have another 4 (or 6?) to go, but got through about 9 yesterday. I swear they are stronger than the average rivet. The grip on the rivet shank is like it is melted to the steel around it.
Get ready for a wall of text!
So I wanted to lay out my plan for the rear suspension now that I have everything ordered, and made all of the hard decisions. I have devoted more effort than I probably needed to, but I think the end result will be worth it. I hadn't planned any of this going in, when I pulled the truck in the garage and restarted this thread a couple months ago, but I ran into major roadblocks that necessitated doing this job now. I have learned a lot planning this all out, and a lot about how to make these old trucks handle (thanks to this forum and others). The biggest thing that I have learned is that if someone else is planning on converting from a C20 long bed to a pro-touring-lite C10, you must REALLY want it. It is better to just start with a C10, as most of the information you find will be C10 specific and all of the aftermarket is geared towards C10s. If the application says "'67-72 Chevy Truck", they really mean 69-72 C10 SWB. The frames, brackets, fittings, mounts, etc. are all different, and the huge wealth of info online is mostly focused on the 1/2 ton trucks.
Starting goal:
Limited slip rear with 3.7+/- ratio and disc brakes
What I decided on:
Currie 9" (63.5" WMS to WMS), 3.5:1 with Eaton Truetrac and Explorer disc brakes. One of the earliest major setbacks in my original plan, was that the QA1 coilover setup required light duty spindles (even with HD brakes) due to the ball joints. No one makes an 8 lug spindle/hub for a 1/2 ton ball joint application. This triggered new wheels, spindles, rotors, etc. This also meant that the rear would need to change as well, oof. I looked at all of the possible fixes before deciding on biting the bullet for the Currie 9":
- New 5x5 wheels to match the old wheels (bought some and sent them back)
- 8 lug wheel adapters for the front (nope), 5 lug adapters for the rear (nope),
- Buying an 8 lug Dana 60 that I thought I could convert (nope, still sitting rebuilt in the backyard waiting to be resold)
- Looking for an old 5x5 12 bolt to rebuild (nope, looked for a month and couldn't find one locally)
- and I'm sure I am forgetting some...
For anyone else who may be doing this, here are the brake lines I ordered from
- Rockauto and Jegs:
- Parking brake cables - RAYBESTOS BC96022
- Outer flex hose - CENTRIC 15066321
- Center Section - Reuse old one for now
- Hardlines - Jegs 555-635822 NiCopp Brake Line [3/16 in. x 20 in.] (3/8" flare fitting)
There is also the need for C20 owners to replace the rear most universal joint with a 1330BC to 1350 conversion (and special 1.125" u-bolts). Strange Engineering makes them, as well as Neapco. I bought the Strange version from Jegs.
Starting Goal:
Drop 3" front and ~5" rear, no C-notch (for now)
What I decided on:
I ended up with the QA1 front adjustable coilovers and 2.5" CPP drop spindles (if you need to replace... always upgrade).
In the rear I went through the following iterations:
- Stock shocks/springs with lowering blocks (what the truck came with, it was all totally blown out)
- New stock shocks with HD 450lb 4" lowering springs (Came to learn that the stock rear shock location doesn't really work for controlling motion)
- DIY shock relocation (was planning to copy/buy the NLE design) with HD 450lb 4" lowering springs (Found that the trailing arm and high unsprung weight of these trucks means that you need a very light spring to keep the tires in contact with the road, and the layback of the shock would mean that you would get a digressive compression at full travel. A shock is meant to control motion in one direction, and is best able to do so when the impact is orthogonal to the shock- it is fine to deviate from this when you can control for the compression and rebound curve across the range of motion- but most the available shocks do not provide this info or design for it. Picking the right shock would always be a guessing game)
- QA1 rear coilover kit (Expensive and single adjustable ($1k), and I had already bought the low roll panhard bar with the rear end)
- NLE trailing arm setup with double adjustable coilovers (Didn't want to replace my trailing arms)
What I decided on:
You can see my thought process in this list as I learned more and began to think through my past MX-5 experiences, and also that my budget isn't huge. I had built a miata as a track car a number of years ago, and I began filtering the big heavy truck plan through that info. If I ever wanted to make this thing handle, I needed to reduce the unsprung weight (#1), have double adjustability for when the bed is empty/full, autocross, or drags, and have as much suspension travel as possible. I ended up with a DIY plan to use the stock arms with poly bushings, stitch weld reinforcements, and a general clean up. For the suspension, I have decided to go with engineering my own lower trailing arm mounts for the NLE spec'ed Viking double adjustable coilovers (C213w shock and 225 lb 12" spring), and use the upper mounts from the kit to piggy-back on the engineering that has already been done. This should work well with the NLE low roll panhard I have, and offer excellent control of the rear end.
Starting Goal:
Simplify and add lightness to gain performance
What I decided on:
So this is the old Lotus mantra, but it holds true. If you want to make something handle, but don't have technology (Camaro ZL-1 can handle and it is neither simple or light), make it lighter and work the best that it can.
Here is the list of lightness mods:
- Flow forged 18" wheels (24lbs) and 275/35/18 (~25lbs) tires Should save at least 30lbs of rotating and unsprung weight.
- Coilover mounted "upside down" to reduce unsprung weight
- Removal of excess brackets and installation of 3/8" - 24 bolts through empty rivet holes
- Changing from HO72 to lightweight (relatively) Currie 9" - I don't have a scale to weigh them, but I would guess over 100lbs difference
- Removal of the original coil springs - plan to add Firestone F9000 airbags to increase bed capacity
- No rear sway bar