Lowering a C20-CS Longbed

[HYPR]

Ok, I know most want to lift these 3/4 tons but that's just not me.
Looking at two vendors for Drop spindles
Performanceonline DS7187 2.5" $449.99
Gmcpauls 19722647 (Fits 71-72 C20-BO until May) 2.5” $410.00
Both claim to be American made.

Now comes the rear leaf springs which are spring over axle so using lowering blocks is out. Since I will not be towing my thoughts are to remove the two helper springs which gives me about 1". I can dial in some dampening using a set of QA1 double adjustable shocks for ride. So far all the 2.5" Lowering shackles are either made for C10s '73 or newer and POL makes the RHK7391 which offers a 3-4" drop but only made for the 73-91 C30 which according to my research is the same width spring so I am not sure why this wouldn't fit and just toss the mounting bracket. I can't seem to find anything for the '72 C20 (2.5" wide leaf spring) so I am looking for recommendations before I resort to having my son fabricate some (Fabricator) by welding up a set. I really don't wan't to go through the expense and experimentation of de-arching the springs. So any assistance would be appreciated.
Bob

[Astro-Balls]

it would be Cheaper and Easier to get Lifts for your Shoes...

[HYPR]

Originally Posted by Astro-Balls

it would be Cheaper and Easier to get Lifts for your Shoes...

Well ok, but how is that going to make my truck look cooler and easier to load my Harley in the bed? LOL!
Actually Sky from GMCPauls replied to an inquiry I posted:Hi, Bob
I'm sorry we do not have a manufacturer for these. Options we know of are remove leafs to lower loosing some load carrying capabilities, use 1/2 ton shackles by drilling them out to accept the larger diameter bolt used on the 3/4 ton shackles. This leads me to think that the only difference may be the mounting bolts and bushing diameter. If that is the case than the set for the C30 might use and even larger bolt that the C20 which would only require the use of the appropriate bushing and possibly drill the hole in the mount larger. That would be really cool. So if someone with a C30 could please give me the diameter of the spring bushings and bolts I would be grateful.
Bob

[HYPR]

Doing some more research based on GmcPaul's response I decided to see what spring bushing a '72 C20 uses and what a '73 C30 uses. According to SDtrucksprings.com all 2.5 wide springs use a 3" wide shackle and the variance is the bolt size. The C30 uses a 9/16" bolt. The C20 also does. In addition they both call for the same bushing part number and same OEM style shackle on their website: Crossover Part Numbers
330-148A, SE-434

Vehicle Applications
Years: 1969, 1970, 1971, 1972
Models: C&P 20/30 2wd, K10/20 4wd
Years: 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982
So unless I am missing something the drop shackle for the C30 should work just not using the Shackle hanger and stick with the one on the C20. Worst case is needing to remove the C20 Hanger by grinding off the rivets and installing the one from the kit.

[Mike C]

I'm not a fan of pulling leaves from a spring pack other than the overload. Early Classics and DJM both offer 2 1/4" leaf spring drop shackle.

On my old C2500 I ran a drop shackle in the rear and stock height front. I pulled heavy and needed the overload.

On my '69 short step I'm running a DJM flip kit but that results in a 7" drop, which is awesome on my little truck but too much without C-notching a C2500. You can get 4" drop springs for the rear and except for the cost that is the way I would drop a C2500 if you still wanted to load it up. They would be the same springs as for a C1500 but you could add overload air bags which would be slick.

[1971 for fun]

I used djm sh1012c2 drop shackles and they fit great.

[CG]

There are a lot of dropped 3/4 tons on this site. They will chime in as they see your post or you could do a search.

[HYPR]

Originally Posted by Mike C

I'm not a fan of pulling leaves from a spring pack other than the overload. Early Classics and DJM both offer 2 1/4" leaf spring drop shackle.

On my old C2500 I ran a drop shackle in the rear and stock height front. I pulled heavy and needed the overload.

On my '69 short step I'm running a DJM flip kit but that results in a 7" drop, which is awesome on my little truck but too much without C-notching a C2500. You can get 4" drop springs for the rear and except for the cost that is the way I would drop a C2500 if you still wanted to load it up. They would be the same springs as for a C1500 but you could add overload air bags which would be slick.

Ok, I thought I missed something but after checking both sites, yep same as all the others, Nothing specific for the 1972 C20. The springs, like the C30 are 2.5" with 1.5" eyelet bushings and 9/16" bolts which is why, unless I am missing something like the drop distance position of the Hanger anything for the '73 C30 should fit.
I'm used to having to mod parts since I have a '56 210.
Isn't Hot Rodding fun?

[rjs53]

I may have missed it but why not do an axle flip, and put the springs on the bottom of the axle? You'll more than likely have to C notch it.

[PepperTreeGarage]

2.5 drop spindles, 3 in drop springs, and shorter shocks.

[PepperTreeGarage]

On the rear I used a flipkit, c-notch, shorter shocks, and pulled one leaf, the one next to the overload. Then added air bag helpers for loads and towing. Good Luck with your build.

[PepperTreeGarage]

And I also beefed up the CPP c-notch kit. Made extra 1/4 in. thick outside plates and 3/8 in. thick inside plates.

[HYPR]

Originally Posted by rjs53

I may have missed it but why not do an axle flip, and put the springs on the bottom of the axle? You'll more than likely have to C notch it.

That certainly has been a consideration. Over all it is not a difficult process especially considering I have a lift and all I would need it a differential jack which are available use cheap.
However I do want to consider all my options first. So far the only thing I have passed on is to convert it to a Trailing arm and coil suspension.
I have looked at a 4 link since my son is a fabricator and has the skills and ability to make all the needed components.
Since this truck is basically going to used to haul items in the bed for small construction projects and as a Harley hauler (hence the desire for a long bed over a short bed) I was looking at the most cost efficient process.
My main Hot Rod is a '56 Chevy DelRey 210 sedan with a Supercharged 383 stroker (your basic 719HP grocery econobox). Suspension sits 5" in the rear and 4.125 in the front. At one time it was one inch lower.

[HYPR]

Originally Posted by PepperTreeGarage

And I also beefed up the CPP c-notch kit. Made extra 1/4 in. thick outside plates and 3/8 in. thick inside plates.

Originally Posted by PepperTreeGarage

On the rear I used a flipkit, c-notch, shorter shocks, and pulled one leaf, the one next to the overload. Then added air bag helpers for loads and towing. Good Luck with your build.

Originally Posted by PepperTreeGarage

2.5 drop spindles, 3 in drop springs, and shorter shocks.

Thanks for the excellent reply. Looks like we have the same truck!
Excellent Build man!
Your suspension build is exactly what my son and I were considering as a good option (although his number one choice is to bag it and number two is a four link). As a metal fabricator he has a CNC plasma table, a fixture table several Mig and Tig welders, plus all the other necessary equipment and skills to actually build most of what is needed to do the C notch and flip. We would only purchase the spring perches since they are so inexpensive. He has done flip kits going both directions as well as Axle housing beefups including girdles for off road and towing rigs.
I actually used those Firestone Air Springs before on my '56 at one time when it was really slammed. I have also installed about a dozen of the bag Ride Right systems for towing rigs.
As mentioned in the previous reply above one of the uses will be as a Harley Hauler in which my son is going to build a auto ramp lift that will auto load the bike up into the bed and off load it so we would like it to be as low as practical but not slammed.
Your final ride height is fairly close to where I am planning although yours is a little lower.
Whose front drop spindles did you end up using and are you happy with them and the quality?
Thank you again for taking the time.
Bob

[PepperTreeGarage]

Spindles are from POL. They seem to be nice and no issues with the install. Yes, Bag and four link would be ideal. Trying to keep this build at about $25,000. We've rebuilt the Dana 60 and added a Yukon posi with 3.73 gears. The Dana 60's take a good bite out of the budget, as parts are costly. The other high ticket items will be the 383 from Chevrolet Performance, might be adding injection, and backed by a 4l80e with controller. I've done a complete rebuild on the front end. The rest is all labor equity. I did read on this thread.....http://67-72chevytrucks.com/vboard/s...d.php?t=783230 …..that drop spindles for C20's are not to be found, but should be available sometime in May. Good Luck.

[Mike C]

Originally Posted by HYPR

Ok, I thought I missed something but after checking both sites, yep same as all the others, Nothing specific for the 1972 C20. The springs, like the C30 are 2.5" with 1.5" eyelet bushings and 9/16" bolts which is why, unless I am missing something like the drop distance position of the Hanger anything for the '73 C30 should fit.
I'm used to having to mod parts since I have a '56 210.
Isn't Hot Rodding fun?

The springs on your C20 should be 2.25” wide. If you have springs that are 2.5” wide, something else is going on with your truck. The 69-72 4x4 trucks and Longhorns had 2.5” wide springs, but the C10/C20 trucks use a 2.25” wide spring.

[HYPR]

Originally Posted by Mike C

The springs on your C20 should be 2.25” wide. If you have springs that are 2.5” wide, something else is going on with your truck. The 69-72 4x4 trucks and Longhorns had 2.5” wide springs, but the C10/C20 trucks use a 2.25” wide spring.

Hi Mike,
Yep, from my research Longhorns and Camper Specials all have 2.5" wide springs just like the C30s.
Wouldn't you know it mine is a fully featured C20 CS complete with BB and a DNE2 OD.
Seems I am a glutton for punishment because I always seem to buy the odd balls! Let's see now (just staying with the 4 wheel vehicles because the 2 wheel ones would take too long ), I've owned a '67 Cortina Lotus, a '69 Formula S Cuda, a '96 Z28 (note not the later model LS1 LOL!), a '06 GMC 2500HD with an LMZ Duramax and my '56 210 DelRey. Each of these had something unique (aka just close your mouth and open your wallet) making building them or making slight mods, well something a little bit different.
Bob

[HYPR]

Originally Posted by PepperTreeGarage

Spindles are from POL. They seem to be nice and no issues with the install. Yes, Bag and four link would be ideal. Trying to keep this build at about $25,000. We've rebuilt the Dana 60 and added a Yukon posi with 3.73 gears. The Dana 60's take a good bite out of the budget, as parts are costly. The other high ticket items will be the 383 from Chevrolet Performance, might be adding injection, and backed by a 4l80e with controller. I've done a complete rebuild on the front end. The rest is all labor equity. I did read on this thread.....http://67-72chevytrucks.com/vboard/s...d.php?t=783230 …..that drop spindles for C20's are not to be found, but should be available sometime in May. Good Luck.

Yep, I know about the BO. Apparently some manufacturing issues do to changes every vendor wanted are causing the delay but for me no problem. I know it but the Dana 60s are bullet proof. I had one in a GMC that we towed an 18K pound 5th wheel. Ran over 270,000 miles with only one problem caused by the weight of the 5th wheel directly over the axle breaking the gears. Solution was installing a 5th Airbourne hitch, having my son welding the axle tubes to the housing and Fabricating a girdle over the top of the rear with plates connecting to the tubes. The truck went over 250,000 mile after with zero issues.
I am running a Supercharged completely forged 383 in my '56 with a built TH400.
Have you given any thoughts to going with an LS based motor and 4L80e.
The LS motor besides having more potential is bullet proof and buying virtually any combo with under 100K is fairly cheap to rebuild because the bottom ends are so strong. Basically hone, rings, crank polish and bearings (plus perhaps a stronger cam).
L96 with 4L80e or even 6L80 (six speeds) can be picked up for under $3K including all accessories, computer (reprogram/Tuning and deprogram is about $250) harness and it comes with FI already. Add say $2K-$2500 for rebuild and conversion install items and you are done at about $5K. Stock L96 is 350HP and 380FT and gains of 20-50HP and 20-30FT are easy. Stock Vette LS intakes and TB are plentiful and cheap if you want to go that way. If you want to go with basically a done package I have seen and had buddies pick up L99 Camaro drivetrains with 6L80 combos with 50K-80K od for between $5000-$6000 complete so just add the install items and you have a nice happy bone stock 425HP package. Plus in both cases the MPG will simply be double the 383 set up. Again going with the LS your costs to install and degree of difficulty is about the same. BTW, Resale value with an LS package it a huge benefit to plus no oil leaks typical with the Gen 1 motors.
The L96 package is my choice of what I am doing because I am not building a Hot Rod.
Bob

[PepperTreeGarage]

Originally Posted by HYPR

Yep, I know about the BO. Apparently some manufacturing issues do to changes every vendor wanted are causing the delay but for me no problem. I know it but the Dana 60s are bullet proof. I had one in a GMC that we towed an 18K pound 5th wheel. Ran over 270,000 miles with only one problem caused by the weight of the 5th wheel directly over the axle breaking the gears. Solution was installing a 5th Airbourne hitch, having my son welding the axle tubes to the housing and Fabricating a girdle over the top of the rear with plates connecting to the tubes. The truck went over 250,000 mile after with zero issues.
I am running a Supercharged completely forged 383 in my '56 with a built TH400.
Have you given any thoughts to going with an LS based motor and 4L80e.
The LS motor besides having more potential is bullet proof and buying virtually any combo with under 100K is fairly cheap to rebuild because the bottom ends are so strong. Basically hone, rings, crank polish and bearings (plus perhaps a stronger cam).
L96 with 4L80e or even 6L80 (six speeds) can be picked up for under $3K including all accessories, computer (reprogram/Tuning and deprogram is about $250) harness and it comes with FI already. Add say $2K-$2500 for rebuild and conversion install items and you are done at about $5K. Stock L96 is 350HP and 380FT and gains of 20-50HP and 20-30FT are easy. Stock Vette LS intakes and TB are plentiful and cheap if you want to go that way. If you want to go with basically a done package I have seen and had buddies pick up L99 Camaro drivetrains with 6L80 combos with 50K-80K od for between $5000-$6000 complete so just add the install items and you have a nice happy bone stock 425HP package. Plus in both cases the MPG will simply be double the 383 set up. Again going with the LS your costs to install and degree of difficulty is about the same. BTW, Resale value with an LS package it a huge benefit to plus no oil leaks typical with the Gen 1 motors.
The L96 package is my choice of what I am doing because I am not building a Hot Rod.
Bob

We are going with the 4l80e, Still thinking about which way we want to go engine wise. Not a big fan of the LS. Leaning towards a traditional old school looking SB 383. Just something about having a traditional looking engine that I remember from my youth.

[HYPR]

Originally Posted by PepperTreeGarage

We are going with the 4l80e, Still thinking about which way we want to go engine wise. Not a big fan of the LS. Leaning towards a traditional old school looking SB 383. Just something about having a traditional looking engine that I remember from my youth.

Yep I get it which is exactly why I have the Supercharged Stroker in the '56
What part of So Cal are you in? I'm in Santa Clarita

[PepperTreeGarage]

Originally Posted by HYPR

Yep I get it which is exactly why I have the Supercharged Stroker in the '56
What part of So Cal are you in? I'm in Santa Clarita

Riverside area.

[HYPR]

Going to have my son fabricate a set of shackles.
Regarding the drop spindles I discovered all the stories regarding QC issues were just that stories. The truth is (from 3 different resellers same story) the foundry closed then another foundry was found however the volume did not meet their budget goals. Several resellers met with the third foundry and presented the growth and demand and they are on board however we are 6 weeks to two months out.
You got lucky.
Bob