Lowering a '72 GMC ???'s

[ablack]

I'm sure this has been asked a few times before around here, but I can't seem to find the answer I am looking for, so I figured I'd ask again. I'm working on a rebuild of my '72 GMC and I'm ready to do the rear suspension, and I want to lower the truck and am looking to see what the options are. I'm sure I can get some springs that do it, and I've seen mention of a "lowering block" (although this makes no sense as I also have a Toyota 4x4 and my only experience with blocks is to put them in to GAIN height). Any information/opinions on my choices would be gratefully received.

Thanks guys!

Alan
Elk Grove, CA
'72 GMC

[Project1970]

For the front, go with spindles for a 2.5" drop...add springs to that if you want to go lower.

For the rear...lowering blocks work if your axle rests on the suspension, rather than hanging from it...i.e. if you flipped the axle so it rides on top of the leaf springs (assuming a leaf spring truck, and that's about a 4" drop on it's own from what I hear), if you added a block between the axle and the spring, it would lower the truck.

I don't know if lowering blocks work on coil trucks, I don't have a good enough mental picture of the trailing arm setup to know whether the axle hangs from or rests on the arms.

Either way, I think you'd be better off with some drop springs; 4" is a good number to go with 2.5" up front, IMO. It's only what my '70 GMC has, after all.

[crazy longhorn]

Lowering blocks work on a coil rear setup, as the axle is bolted to the top side of the trailing arms. I agree with Project 70, a 2 1/2 4 drop is about the right amount for a driver/hauler. If you go much more than 4" in back, you will need to notch the frame for axle clearance. Flipping the axle on a leaf truck should net you 5-6" of drop(depending on the thickness of the spring stack). I have done my longhorn this way,& figured a little over 6 " of drop after the flat helper & a couple short leafs were tossed. I then relocated the spring hangers down on the frame approx 1 1/4" to raise it back up a bit(5" drop, with 2 3/4" of clearance tween the frame & axle......no bumpstops). i dont have any problems with bottoming, but those old Longhorn springs were pretty stiff to start with. A spindle, or spindle /spring combo would probably be the best no hassel way to do the front. One thing to keep in mind on front spring drops is that the original springs can verywell be sagged 3/4 to 1" ........so a 2" spring may only drop you 1"from where the truck stands. Good luck.....crazy AL

[ablack]

ok..... so now the blocks make sense to me, and I do have a leaf sprung truck. I was pretty much thinking about a 2.5/4 drop, but I've been trying to see if I can find pictures of the drops to see what it will look like when it's done. Do you know of anywhere I can find shots, or do you guys have any shots of yours you'd be willling to share?

Thanks again guys.

Alan

[Project1970]

2.5" spindles / 245/60-15 tires / 6-lug disc front, 4" ECE leaves / 275-60/15 tires rear

[Project1970]

A corner shot

[chevykid04]

not to hijack the thread or anything, but just a quick Q for project 70, did you have any clearance issues with those tires??? i have 245/60 15s in the back and they rub ever so slightly on my inner fender wall, and one other question i guess, gmc/chevys have diff size wheel wells?? or did they use diff sizes, cus my friend with a 70 chevy thinks his look wider than mine?

[Project1970]

Originally posted by chevykid04
not to hijack the thread or anything, but just a quick Q for project 70, did you have any clearance issues with those tires??? i have 245/60 15s in the back and they rub ever so slightly on my inner fender wall, and one other question i guess, gmc/chevys have diff size wheel wells?? or did they use diff sizes, cus my friend with a 70 chevy thinks his look wider than mine?

No, no clearance issues at all...sounds like backspacing issues. I'm running '80s 'Burb rims. I'm pretty sure every '67-'72 had the same wheelwells from the factory...who tubs what from the factory, well, that's a different matter.

[cjwilson99]

I have a 71 Chevy SWB with coil rear. I need to replace all 4 springs. They are worn out bad. I want to do a 2/4 drop.

My question is: If i get 2 inch drop spindles for the front, do I get stock springs? Or do I still get 2 inch drop springs? Would both the drop spindles and springs lower the front 4 inches. I want to do it right and not have any oversteering problems.

My plan for the rear was 4 inch drop springs in the back and then get an adjustable Panhard bar, and then get 2 inch drop spindles and stock springs for the front. Will this work?

[69c10stepside]

If you get two inch drop spindles, you will need to retain stock type coil springs in the front to get the desired two inch drop, you are right when you thought that the two together give four inch drop in the front, your plan should work just fine frank

[imaindianoutlaw]

thanks project I am going to go with the same set up as you in the future!

[GMC Jim]

I plan to use extra length rear spring shackles to achieve a @" drop for a 'level' look..... seems like this might bre the easiest and cheapest way go !!... Any comments .. positive or negative on lowering by using longer spring shackles ????/..............Jim

[crazy longhorn]

The shackles should work for you GMC Jim. You may need to notch one of the box support rails for clearance, & it wouldnt be a bad idea to check the pinion angle after installation. You can pick up angled shims at your local spring shop to correct the pinion angle if needed. Good luck.....crazyL