1982 C30 looking for 4/6 drop. What did you actually get versus what was advertised?

Am working on putting together parts & pieces to do a 4/6 drop on my 1982 crew cab dually. Measuring where the truck sits right now I think that'd be about right.

If you've done the job, have the drop numbers for each component added up or are there other factors that change the result? For example does a 3" drop spindle and a 2" drop spring actually result in a 5" drop or is it actually less?

Found a 4/6 kit on eBay but I'm thinking the numbers don't seem to line up. All the C30 drop spindles I've seen are 3" and a 2" drop spring doesn't add up to 4". On the rear most flip kits I've seen are 8", some have a 2" lift shackle to get back to 6".

4/6 C30 lowering kit Link to eBay.

My truck has those huge travel tanks on it so I don't want to go any lower. They're even with the bottom of the frame but stick down below the rockers. Thought about taking them off but this thing would have pretty incredible range with those in place!

My truck is a C10 but to give you an example. I installed a kit advertised as 4.5/6. The actual result at the rear was 7. The front was 5.5. I was perfectly happy with the rear. In front I ended up using a 5/8" aluminum spring spacer to put the drop where I wanted it. Turned out the aftermarket springs were softer than the factory ones and sagged to where my tires were right up on the top of the inner fender. The spacer raised and stiffened them, so all was well.

So on my C30 crew cab single wheel I did the Switched Suspensions 6/8 drop kit. This consist of a 3" drop spindle and 3" drop spring as well as a rear flip kit and notches. I measured the bottom of the front cross member at 12.5" to the ground with the 16's on. I can't recall off the bat what the rear was I will have to dig thru my pictures when I get off work.

When I got it back on the ground with my 20's I could barely get my fist under the cross member. I have not put a tape to it but based off of that the front was actually dropped 6.75". The overall difference between the tire diameters was only -0.25"

I did have to modify the rear flip kit due to receiving the wrong axel type (stamped vs cast leaf spring mount) by cutting almost 2" of material off of the top so the axle could sit in the cradle like it was supposed to. I also had to slightly modifying the shock extension mounts. They were extremely tight when mounting.

You will also need to be aware of the issue with more than 2" drop spindles needing a wheel larger than 16" due to contacting the lower A arm. You maybe able to get away with a spacer depending on the size and offset. Just something to be aware of. This may also be different with it being a dually.

OK it's AXLE......... @SquareRoot

If you decide to flip the rear, the only notch on the market for a C30 I'd consider if you still plan to tow/ haul is empire fab.