3/4-Ton 2wd Rear Spring Replacement: Advice?

[KCKKen]

Hi Everyone!

In order to get Project Calvin back on track I need to replace the rear springs on my 78 3/4-ton -- one has the main leaf broken just aft of the U-bolts. I have everything on-hand to replace (including shocks while I'm at it), the only part I have to re-use is the plate the U-bolts attach to. I figure to just cut everything to get it out of the way, and reassemble with new parts since the spring looks _this_ bad I can only imagine the headaches of trying to take out bolts and re-use them.

Has anyone done this lately, and is there any advice on what to look out for? Definitely doing one side at a time so I can see how it's put together on one side in case I forget

I appreciate any and all who will take the time to reply, this group has been a resource I don't think I could have tackled these trucks without.

Take Care,
Ken Snyder
In KCK

 

[75gmck25]

I haven’t replaced my springs, but I’ve installed new poly bushings. Jacked up the truck by the body until the wheels were clear of the ground, and then put a bottle jack under the axle so I could move it up and down independently. If you do one side at a time the axle should stay lined up.

Bolts for the spring eyes were tight, but all it took was a long breaker bar. However, they are also stuck in the rubber bushings so I just used a electric impact to turn them until the rubber broke up around them and they could be pulled/hammered out.

With new springs you probably get new bolts, sleeves and bushings that are correct. When doing the old springs you have to know exactly which combo you need, since GM changed them slightly over the years. For example the sleeves that came with one set of new poly bushings was too small to fit the original shackle bolt through the middle. To reuse the old sleeves I had to clean them up completely, lube them, and then press them into the new bushings.

 

[Rustisbest]

The bolts may be frozen/rusted in the bushing sleeves. I would start spraying them with penetrating oil a week or 2 beforehand.

 

[Catbox]

Make sure you have new high quality U bolts for it.
We did our 1995 Sub a bit ago and this is what came out of it...

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We have a spring builder near by so we had new custom ones made on the spot for it.
While we were having the rearend rebuilt, we put some new to us 3/4 ton springs under the 1/2 ton Sub.
Before that happened we hit everything with a wire wheel and then wiped it all down.
Here is a dirty stock 200K 1/2 ton spring next to a freshly painted stock 3/4 ton spring with 390k on it.

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The 3/4 springs came out of a junkyard sub, so we cleaned them and painted them to be purdy.

While you are down there dinking with things, just cleaning it all and painting it will look fresh for years to come.
I used the cheapest paint that Home Depot had at $1.58 a can.
I used 3 cans and it looks good even now a few years later.

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[Big Ray]

Love the way my 2wd 3/4 ton burb handled, empty and loaded.
When I do my 1/2 ton 4x4 burb I'm putting 3/4 ton springs out back.

 

[Catbox]

Love the way my 2wd 3/4 ton burb handled, empty and loaded.
When I do my 1/2 ton 4x4 burb I'm putting 3/4 ton springs out back.

It definitely fixed its droopy butt.
The back of the sub is now level with the front and it does not ride overly harsh as the springs are "broken in"...

 

[Juggernaut]

Be prepared to have to cut the front spring hanger bolts. Being you're in the rust belt with me, the bolt likes to rust to the bushing sleeve and is nearly impossible to get out. Sawzall and some good Milwaukee Torch blades do the trick for me. You will probably have to cut the bolt at both sides of the spring bushing to get the spring out

 

[bucket]

Be prepared to have to cut the front spring hanger bolts. Being you're in the rust belt with me, the bolt likes to rust to the bushing sleeve and is nearly impossible to get out. Sawzall and some good Milwaukee Torch blades do the trick for me. You will probably have to cut the bolt at both sides of the spring bushing to get the spring out

Yep, usually frozen solid. Often the shackle bolts too. The Diablo brand Sawzall blades also work very well. The fine tooth type.

If the hangers are to be replaced as well, you can remove them first and then press the spring bolts out in a press.

@Catbox those GMT 400 u-bolts are self-removing in Ohio. I'm amazed you even got the nuts off of them, lol.

And since it was brought up, I 100% believe that ALL squarebody Suburbans should have come with 56" springs for a 1-ton or heavy 3/4 ton. Good capacity and the ride is just as good as 1/2 ton 52's.

 

[Catbox]

@Catbox those GMT 400 u-bolts are self-removing in Ohio. I'm amazed you even got the nuts off of them, lol.

I bet it would make you mad if I took a photo of the under side of the Sub.
It is still fairly clean and rust free down there, just road grime.

 

[Big Ray]

From another forum. I'm going to crawl under mine and take a look see...Rust never sleeps...

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[KCKKen]

Thanks, everyone!

After removing the springs on the project truck I agree about the bolts being a PITA to get out -- one on each side was frozen solid, so there was a bit of cutting done to finish the job (and wasn't the same one on each side). Since nothing will be saved any and all options will be on the table, including the heat wrench.

Since I have a couple of weekends before I will be free to work on this I think I'll get a couple cans of PBlaster and soak them suckers pretty good until then.

Thanks again for all the advice! I will try to get pictures of the process.

 

[KCKKen]

OK, first day of progress: some good, some not so good.
First of all, I only had the front spring bolt and the lower shock bolt give me much hassle. I had the frame supported under one jack stand (forward of the rear axle) and after removing the tire I put one under the rear axle as close to the back of the backing plate as I could. Finally, started cutting everything out -- the only thing I needed to save was the bracket that sits over the springs and the U-bolts go through.

I was surprised to find that the U-bolts had so much tension on them, but nothing came out of place during the disassembly. To really get good access to the front bolt I eventually "disassembled" the stack (I found it already had _two_ leafs broken, and I swear one half of one leaf was missing (see picture of the aftermath). I also cut what was left of the broken top leaf at the bushing. This gave me as much access as possible, I definitely need to look at better reciprocating saw blades! The lower shock bolt was easier with the new cordless grinder with a thin cutting disc on it.

With everything out of the way, I started to put the spring and shackle in place -- this is where everything fell apart. I put the bolt in the front mount (with plenty of anti-seize) and in the shackle to the rear mount (same), now I can't get the rear spring mount to line up with the shackle, and the locating pin on the rear axle doesn't line up with the spring. I checked the dimensions, and they are correct per the website, but still no joy. They seem shorter than the other side (only took one side apart at a time) but both original springs are totally trashed. It's about 3/4" off on the center pin, and it's correctly positioned front-to-back (back being longer dimension).

Did I miss something? Should there be some tension with new springs? Right now I'm at a loss as to what's needed next.

Take Care,
Ken Snyder
in KCK

 

[KCKKen]

Hi Everyone!

Well, things went from bad to worse for me, and for the truck it got a little better, then went downhill.

First of all, thanks for the recommendations on the reciprocating saw blades! I was able to get things done with one blade that took for of the cheaper ones. Still very happy with the work the cordless cut-off tool, made quick work of the U-bolts.

I was able to lower the rear end and get the spring/shackle bolt in, I just didn't have enough room to start with. Once I started removing the spring on the passenger's side the pin on the spring pack lined up with the axle, so now it's looking better. However, it turns out that the U-bolts from Rock Auto aren't the right size -- they're too narrow, they don't fit around the axle tube. I was able to patch one of the U-bolts back together that I cut off, and I'm guessing that they're 3 & 3/8" wide, does that sound right for a 3/4-ton? The ones from RA are 3 & 1/4" wide (as listed on their tag) and I compared them to the 1/2-ton rear, it appears the ones on the 1/2-ton are 3" wide. LMC shows they're out of stock, any recommendations on another supplier?

For me, I've had knee issues that will start to get addressed in November with a full replacement on one, followed by a full replacement on the other next year. As I was finding out the U-bolts aren't right I suddenly found myself going through severe vertigo -- the preliminary diagnosis is that the Meniere's Disease I addressed in 2001 has returned with a vengeance. Going to go through more tests this week, if it ends up like in 2001 surgery is on the horizon.

Take Care,
Ken Snyder
in KCK

 

[idahovette]

WOW take care of yourself first @KCKKen !!!! Good thoughts going out to you

 

[bucket]

Well dang, I hope all goes well with your surgeries. As for the u-bolts, yeah they should be 3 3/8's. I've usually had local shops make u-bolts. When I've bought them online, I've got them from Offroad Design.