Poor Man's Airbags 1970 C10

[Gromit]

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.

[Gromit]

More photos

[Gromit]

Few more photos.. the measuring tape shows the relatively critical dimension for choosing an airbag that will fit - the inside height between the two mounting plates of the mounted spring with no weight on the axle. The urethane pads are 1/2" thick and have a hole in the center so those pads fit over the stub of the lower coil mounting bolt.

Other photo is just of the bump stop mount where normally you would install one of those Timbren kits in place of the original rubber stop.. Those kits are more like $150 and as mentioned above I liked the airbag geometry better.

[Andy4639]

Good write up. I did mine about 12 years ago. Didn't do as good of write up but just about the same thing per word.
My kit # is in my signature.

[Gromit]

Update: Okay as promised I did the road test and went today to get a full yard of decomposed granite loaded into the bed to test my $100 dollar airbags. It filled about two thirds of the long bed.

Here is a photo of the airbag with what they said was 3800 lbs (but I kind of doubt it - the stuff was really dry - I would put it closer to 3,000 lbs.).

The truck is siting on a slope in the photo so that might be why the spring looks a little off center.

I only had to drive a couple miles like that and just putted along but definitely the ride is much improved with the airbags. The rear hardly sagged at all.

The Airlift instructions call for 50 psi in each bag if the spring hoops are 1" apart or closer - so that is what is in there. I'll bet that pressure would spike a bit when you go plus 3,000 pounds - so I told the skip loader guy that if he heard a huge bang not to worry it was just the urethane bag and I was testing them out He did look pretty worried though and I noticed he dumped that decomposed granite in very gingerly 1/2 yard at a time.

Even if the bag popped I don't think there would be any metal shrapnel but still wouldn't want to put my head right next to it.