Chevrolet, GMC - Poor Man's Airbags 1970 C10
This is to help anyone with a coil spring C10 who is considering installing an Airlift 1000 Universal kit in their rear coils.
I just did this on my 1970 Longbed C10 and decided to go with these instead of the Timbren Kit because they are cheaper and it didn't look to me that the geometry of the bump stop riveting (loaded in shear) could handle the loads as well as just the original mounting points of the coils.
My truck has the Moog CC603 type (910 lb load rated) of progressive rear coils - they are 5.5" inside diameter and have about 11" clearance of height on the inside of the springs.
Took me quite a while to decide on the right part number at Airlift - I chose the 4.9" diameter bags that are 10" tall - part number 60921 and $103 delivered from Summit. (see attached page from the Airlift owner's manual - part specs in red box)
Pretty sure mine are the original 47 year old springs - so probably they are clapped out but the ride is good and I was worried if I put new and heavier rear springs in the ride would be too harsh when unloaded.
I decided to sand down the old coils to bare metal and repaint them first so all that grit and grime wouldn't be grinding into the air bags. It didn't take as long as I thought - maybe 40 minutes each sanding with 220 grit; then a coat of ospho; rattle can primer and satin black - I think the whole thing was probably less trouble than taking them somewhere for powder coating
Had to cut six threads off of the lower coil mounting bolt so the bolt wouldn't stick into the bottom of the bags (photo)
A whole lotta crap came out of that lower coil mounting bolt hole in the trailing arms (photo 04).
Instructions call for drilling a hole through the upper coil mount and chassis rail for the air line- it looked to me on my coils that there was plenty of clearance (1-1/4" even if the coils bottomed out to just run the 1/4" od air line out between the top two coils. I'm not saying anyone should do this it is just what I did. I cut a circle of 1/2" polyethylene with a slot for the airline to exit out the side (white layer in photo 16).
The air line is 3/16" ID and 1/4" OD and barbed fittings in the tops of each bag that are moulded into the bag.
My original hardware (1/2"-13 threads per inch) was still good - it was all grade five and a little wire brushing and ospho, primer/paint was all it needed - though I ran a tap and die on each one to make them easier to work with.
I haven't tried loading anything heavy yet and driving around - so I'll report back once I've given this a road test..
Hope that helps someone.