Rear Spring Questions....Any Answers?

[westofb]

I have a 3/4 ton 75 model truck that is going to be a half ton truck and static dropped no matter how much it wants to fight me. I have the 1/2 ton rear and bought a set of 3" spring perches to weld to it to flip the axle over the springs...also bought a c notch kit. I was planning on using the 3/4 ton springs (it has 8 leaves and one overload per side) and removing the overloads and at least 4 of the leaves, but after getting it a part, I notice that the 3/4 ton springs have much less arch to them than 1/2 ton springs. If I were to use these springs, the rear axle would almost contact the the frame with the c notch installed, there is no way it would even go in without the c notch installed. I guess my real question is, will 1/2 ton 2 wheel drive springs fight the 3/4 ton spring mounts? Also, was wondering if anyone knows the amount arch the different model trucks have...ie 4x4 vs 2 wheel drive, balzer, suburban, short or long bed? I don't know how they specify the amount or arch a spring has, I guess you could take a straight line between the eyelets and measure down to the top of the spring where the locator pin is....ok, ok, I am kind of rambling on, just trying to figure out what I need to get a hold of to make this half ton flip work. Any and all comments and suggestions are appreciated...thanks all!

[Kalashnikov46]

Measure the width - [1 1/2", 1 3/4", 2", 2 1/2", 3", Other]
[D] Total pad thickeness at centerbolts (all leaves)
[C] Measure the free arch. hold a straight edge through the centerline of the spring and measure from this line to the top of the main leaf next to the centerbolt
[A, B] Measure the 'A' and 'B' lenght of the main leaf spring (longest)
Identify the end type of your spring (standars, berlin, reversed, square cut, square cut w/ point, or tapered)

where i borrowed this from

[westofb]

thanks for the diagram. was kind of interested to know if anyone new the differences in the amount of arch the different trucks have and if 1/2 ton springs will physically bolt onto 3/4 ton spring mounts....I reread my starter, I even confused myself and I knew what I meant!

[xrcr]

I put 1/2 spring on a 3/4 chassis using the 1/2 ton hangers. I had to reposition the front mounting holes but the perch in the axle housing was a non issue. I had the same 9 springs(3/4) to 5 springs on the 1/2

[staggerd86c-10]

just flip it with the springs it has. Why do you want to put 1/2 spring in it?

[westofb]

Originally Posted by staggerd86c-10

just flip it with the springs it has. Why do you want to put 1/2 spring in it?

because the 3/4 ton spring has much less arch to it, the isn't enough room between the top of the spring and the bottom of the frame for the axle tube to fit. Even with the c notches installed, there would be no room for suspension travel.

Okay, today my parts truck was delivered and I began striping it down to get the much needed suspension parts to complete the swap. The donor truck is a plain Jane 80 1/2 ton short stepper. After getting the bed and front clip off (I need the upper and lower control arms and the leaf springs from this truck), I did some measuring of the leaf springs. The 1/2 ton springs are approximately 4" shorter eyelet to eyelet than the 3/4 ton, but from the front eyelet to the axle center measure the same. So, I guess I will remove the rear spring hanger and move it forward on the 3/4 ton frame. Hopefully everything will come off the donor truck without too much trouble, I will post some pics of the modifications necessay to complete the swap. Thanks for the input guys!

[USSkoval]

Most 3/4 trucks got 56 inch springs, like you have found on yours. They must be very worn out because the total arch is generally similar between all models. The difference in height between 2wheel and 4wheel comes from the spring hangers. The holes should already be in the frame to move your rear hangers forward.

[westofb]

Yes the 3/4's are 56" long while the 1/2's are about 52" long. I don't think the 3/4's are worn, the truck in it's current condition sits with a slight rake and all components look to be in good working order. I guess I should have mentioned this truck is a rust free California truck with 454/ 400 and only 63k actual miles. If the truck was not in such good shape, I would have found a 1/2 truck to build!

Thanks for the heads up on the bolt holes USSkoval, I sure hope you're right, was dreading having to drill additional holes in the frame. Plus was worried about getting my measurements correct!

[westofb]

Hey guys, one more question. I am going to sale the 3/4 ton rear, what's a 3/4 ton positrac with 4.10 gears worth? Thanks.

[westofb]

Hey guys, one more question. I am going to sale the 3/4 ton rear, what's a 3/4 ton positrac with 4.10 gears worth? Thanks.

[USSkoval]

$100-$150, they are pretty common.

[westofb]

Originally Posted by USSkoval

$100-$150, they are pretty common.

Okay, that what I was thinking, thanks!

[grinch4om]

if I had to do it over, I would buy the hanger drop kit and remove the overload spring and maybe 1 or 2 more leafs...instead of the flip kit

[westofb]

Originally Posted by USSkoval

The holes should already be in the frame to move your rear hangers forward.

Just my luck the holes are not in the frame for the rear hangers!

[USSkoval]

Originally Posted by westofb

Just my luck the holes are not in the frame for the rear hangers!

Well that stinks! Oh well, it's just holes... of course, I'm not the one that has to drill them, lol.

[westofb]

Thanks for the encouragement, just eight more holes to drill. I do have the bed off so it won't be too bad, going to start on the front suspension drop tomorrow if everything goes right, figured I better get it done first so when I do the rear drop I can get my pinion angle set at ride height.

Yesterday I completed removing the suspension componets from the donor truck and today I got the rest if the front clip painted (hood and the front valance), so all that is left to do is to get it lowered and then body and paint work on the bed. Then I have to decide whether to flame or not flame the truck....LOL.