56" springs on a half ton?

[brothers69c-10]

Anyone ever put 56" long springs on the rear of a half ton 4wd? I've been poking around on the internet and have read about some people who want to try it. I am putting 3/4 ton axles under my half ton and want to beaf up the rear springs and all the 3/4 tons that had the 56" springs, even though they had more leaves, always rode better than my half ton with 52" springs. I know where there is a set of 1 ton 56" springs i could get pretty reasonable and they would be perfect since i'm going to put a gooseneck hitch in the bed and yes i'm going to beef up the stress points of the frame. Anyways any and all input is always appreciated.
Thanks
Mathew

[James McClure]

Brothers, you may run into drive shaft length issues with 56" springs. Also the added length, even with extra leaves, is going to affect vehicle control, they are wishy-washey leading to trailer "whip". I've dealt with whipping, and believe me, when that trailer tries to pass you your life will flow past your eyes & you'll leave a skid mark or two in your drawers. Stick with the 52"'s.jim

[Pyrotechnic]

GM did this from the factory. It was referred to as "Heavy Duty Chassis Equipment" on the option sheet. It was marketed as Big 10 (Chevy) or Heavy Galf (GMC).

Amongst many upgrades, one thing it included was the longer 3/4 ton leafs springs. The rear shackle hanger is simply mounted further back on the frame. All half ton frames have both sets of mounting holes, it's just a matter of drilling/grinding out the rivets then bolting the hangers back in the appropriate position.

[87Bob]

Originally Posted by Pyrotechnic

GM did this from the factory. It was referred to as "Heavy Duty Chassis Equipment" on the option sheet. It was marketed as Big 10 (Chevy) or Heavy Galf (GMC).

Amongst many upgrades, one thing it included was the longer 3/4 ton leafs springs. The rear shackle hanger is simply mounted further back on the frame. All half ton frames have both sets of mounting holes, it's just a matter of drilling/grinding out the rivets then bolting the hangers back in the appropriate position.

What about the earlier post about the drive shaft length if you do what you suggest? Also my 85 is listed as having a heavy duty spring could you have a HD spring that wasn't the longer one?

[Pyrotechnic]

Driveshaft length stays the same, wheelbase stays the same.

The short and long springs are identical length ahead of the axle mounting point. The long springs get their extra length behind the axle, and the shackle hanger is moved back to compensate.

[tomtuna1978]

i just did this mod on my 79 gmc short bed 4x4. i did it for the lift and the softer ride, not to tow anything. i got the ord kit and some 56inchers from the local pick a part. i love how the rear rides now and would do it again in a heart beat! and im thinking or buying the kit to put my 52 inchers in the front because the tough country 4 inch lift springs ive got in the front are pretty stiff! i dont know about the towing characteristics when doing this mod, id prolly wait for some more poasts

[brothers69c-10]

Thanks for the reply guys. Considering that one tons came with the56ers and so did most of the 3/4's i think they should tow just fine especially with a 9 pack of leaves. I forgot about the conversions for the front springs. I had thought about putting 49and a 1/2's up front once, but may wait till another day for that one.

[asphaltburner]

Yo! REALLY?!
I was SO worried that the 5560 lb rated axle/spring combo from my donor 3/4t flatbed was gonna ride so rough in my 3/4t P/U (4800lb axle/springs origonally),...and it's so smooth! Sure love my result! Mine was a direct swap though, '73 flatbed to '78 P/U (both 3/4t), so I didn't have to worry about incompatibilities.
Cool, Todd.

[bigblock73]

both my 1/2 tons have the 8 leafs 56'ers from the factory. Buy the springs, move the rear hangers back, install the springs, call it a day. Truck will run/drive just fine, drivesahft won't be an issue. Be sure to get all new grade 8 hardware, and use anti-sieze.

[brothers69c-10]

Grade 8 is a definite and I always forget the anti-seize.
hanks for the input.

[bigblock73]

FYI

The bolts are 9/16", 4.5" long, coarse thread. If you need U-bolts, they are 5/8", 3" inside diameter, 8" long.

Just trying to save you a trip to the HW store in the middle of your project.

[brothers69c-10]

Thanks jeff i will write that down. I already got brand new u bolts. The guy i'm getting the springs from was going to put a 4 inch lift on his brothers truck then opted for a 6 inch. So free bolts equals it's finally time to put the lift kit on!

[brothers69c-10]

Next question, what i have to do is move the the REAR spring mount back 4 inches correct?

[KQQL IT]

The holes should already be there cut the rivets and bolt them down at the new spot.

[2tons of fun]

yes. x2

[brothers69c-10]

There are no holes on my frame. Are you guys referring to 4x4 or 2wd frames? and yes my springs are 52 inches long i double hecked when i couldn"t find any holes.

[lolife99]

Got any pics of the rear frame area?

[bigblock73]

My 2wd has both sets of holes...but am not sure about 4wd frames.

[brothers69c-10]

No pics, but i looked at a 3/4 ton frame and it didn"t have holes for the 52's not that it means anything. I was measuring and if i move the rear spring hangers back 4 inches i may have to grind down the bumper brackets.

[bigblock73]

Originally Posted by brothers69c-10

I was measuring and if i move the rear spring hangers back 4 inches i may have to grind down the bumper brackets.

No you don't. On my 56" 1973 and 1977 C10's, the rear hangers are about 1/8" apart from the bumper brackets. Just slide the hangers back to the bumper brackets, the shackles will take care of any minor difference there may be.

[brothers69c-10]

Ok, I think i can get way with that. I am putting a lift kit on it at the same time so that should help with the play.