Cab Isolators

Jake707

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Mar 30, 2020
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I def didn’t plan on taking them apart. Is there something better I could use to paint them assembled? I only planned to use POR because I still have a quart from a project from a couple years ago.
 

Jake707

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Mar 30, 2020
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Ok pressed out the old bushings today at a friends shop. Also found out that shops don’t sell replacement bushings as Chevy has them labeled as non serviceable. WTF. Even the lady at the parts counter at the Chevy dealer was shocked when it said I’d have to buy whole leaf springs not just bushings.

so I’m looking at them online now and the Dmax store has the Energy ploy bushings kit. will poly make the ride even rougher than some OEM rubber types?

also do these replacement bushings need the outer metal sleeve from the original bushings cut out and removed or do they fit with it in there? I wasn’t sure so I didn’t cut them out.
 

TheBac

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From the looks of it, Rockauto has them. Dayton RB172 (rear) and RB250 (front). Same bushings as 1/2 tons, too. Please doublecheck the dimensions against their listing first, though.
 

fl0w3n

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Jan 8, 2015
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His springs are worn/sagged based upon the measurement of the gap he took from the overload leaf to the rest of the pack. His spring pack is sitting physically lower and doesn't take much movement for them to engage the overload leaf. On a spring pack in good health, there is a much larger gap that allows the spring to flex the much more compliant leafs as opposed to the heavy/very stiff overload.
no one realizes how bad the rear springs get because its a gradual over time occurrence. the leafs on a 01-2020 2500hd are virtually unchanged in their overall design for ride height and overload clearance. 2011 they switched to a higher capacity leaf pack, made the change again in 2020 but the concept of having a linear spring rate as the suspension collapes onto the overload is still there and you MUST have decent clearance above the overload for it to actually work right and ride nice. its all designed together.
Do you guys have a measurement range for what's OK and what's considered worn out?

I'm wondering if a Deaver mini-pack would be a decent band-aid as well, since it would get rid of the overload and sort of help the rest of the spring pack keep its arch? And with the bags, you could retain heavy load compliance with the bags and no overload.
I loved how my mini-pack rode on my LBZ. Ideally you'd get a full pack or have the whole thing re-arched.

as mine are getting older, and rougher and rougher, I find myself thinking about "someday" seeing if I can get a lift spring from Deaver and mounting it under the axle to retain stock height :)
If you call Deaver they should be able to custom make you a pack that's stock ride height.
 

Chevy1925

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It’s from the prothane poly style he installed, not the hydraulic rear ones.

You need to look at your rear springs. More times than not I’m seeing guys with worn out rear leaf packs and the overload is maybe a 1/2” from the main pack. Makes the truck ride rough. You should have 1.75-2” clearance at the very back edge of the overload and the leaf pack. New pack isn’t too expensive or have them re-arched
Do you guys have a measurement range for what's OK and what's considered worn out?

I'm wondering if a Deaver mini-pack would be a decent band-aid as well, since it would get rid of the overload and sort of help the rest of the spring pack keep its arch? And with the bags, you could retain heavy load compliance with the bags and no overload.
I loved how my mini-pack rode on my LBZ. Ideally you'd get a full pack or have the whole thing re-arched.


If you call Deaver they should be able to custom make you a pack that's stock ride height.

Bold above. it wasnt there before, was part of this issue we are having where sections of posts got deleted. ive fixed this thread though.

adding a mini pack is just a badaid. sagging leafs mean preload has fallen off and spring rate has fallen off. the deaver mini pack will put some back in but at the expense of the mini pack not set for the correct spring rate above it and more load placed on the mini pack. it will work, just not as well as it could and will wear out quicker. the idea behind the mini pack is to create a more linear spring rate and not so much a progressive as stock is.
 

fl0w3n

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Bold above. it wasnt there before, was part of this issue we are having where sections of posts got deleted. ive fixed this thread though.

adding a mini pack is just a badaid. sagging leafs mean preload has fallen off and spring rate has fallen off. the deaver mini pack will put some back in but at the expense of the mini pack not set for the correct spring rate above it and more load placed on the mini pack. it will work, just not as well as it could and will wear out quicker. the idea behind the mini pack is to create a more linear spring rate and not so much a progressive as stock is.
Got it, thanks. Hopefully y'all figure it out soon lol, there's some threads where there's just a bunch of one letter posts

Sure, agreed it would be a band-aid, although you mentioned things I didn't consider.

With a properly arched main pack, no overload, and a mini-pack - you're saying this is a fully linear setup? I thought there was still some linear rate to the main pack without the overload. Obviously the spring rate drastically increases when it gets to the overload, but without it and instead air bags in place and properly inflated, wouldn't that keep the ride smoother even with a heavy load over the axle VS having an overload?
 

Chevy1925

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Got it, thanks. Hopefully y'all figure it out soon lol, there's some threads where there's just a bunch of one letter posts

Sure, agreed it would be a band-aid, although you mentioned things I didn't consider.

With a properly arched main pack, no overload, and a mini-pack - you're saying this is a fully linear setup? I thought there was still some linear rate to the main pack without the overload. Obviously the spring rate drastically increases when it gets to the overload, but without it and instead air bags in place and properly inflated, wouldn't that keep the ride smoother even with a heavy load over the axle VS having an overload?

no, no leaf spring will be 100% linear like a coil-over spring (even coil-over springs are not perfect but as close as you can get). it will be much closer to a linear rate spring setup (less progressive). the stock leaf pack is all progressive, the overload creates this because the leafs are laying on top of the overload as suspension compresses. this starts to spike spring rate till they are completely on top of it and then the whole overload as to flex, in which case it goes back to semi linear rate.

air bags are a whole nother issue within them selves. they are progressive rate and on small helper bags, its very hard to make them not sky rocket the spring rate up as suspension compresses. sadly, without knowing the rate of each individual spring, its hard to say how many leafs would work with a helper bag in place to get you load capacity and not make it ride like a brick loaded or unloaded. I personally HATE helper bags, loaded or not. They just limit your ride comfort and suspension travel.
 

fl0w3n

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no, no leaf spring will be 100% linear like a coil-over spring (even coil-over springs are not perfect but as close as you can get). it will be much closer to a linear rate spring setup (less progressive). the stock leaf pack is all progressive, the overload creates this because the leafs are laying on top of the overload as suspension compresses. this starts to spike spring rate till they are completely on top of it and then the whole overload as to flex, in which case it goes back to semi linear rate.

air bags are a whole nother issue within them selves. they are progressive rate and on small helper bags, its very hard to make them not sky rocket the spring rate up as suspension compresses. sadly, without knowing the rate of each individual spring, its hard to say how many leafs would work with a helper bag in place to get you load capacity and not make it ride like a brick loaded or unloaded. I personally HATE helper bags, loaded or not. They just limit your ride comfort and suspension travel.
right the bolded part is what I thought but just wanted to confirm because I thought you were saying without overload it’s linear.

I’ve never really messed with bags, had some Firestone’s for my LBZ with that deaver mini pack but never wound up mounting them. But I’ve heard they are tough to get setup right like you said.

a little more on topic, are the isolators being talked about in the thread the ones from the GMT900 trucks? I seem to recall doing a swap to some newer OEM isolators on the back of my LBZ ext cab and it helped the ride smooth out.
 

Jake707

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Mar 30, 2020
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I ended up buying the OEM style from rock auto as I was afraid the poly type would be harsher and/or louder and since I don’t haul anything heavier than my boat I should be fine

questions now are which side do these press in from? They have a lip like the factory bushings but just on one side. So would I press them in from the back side And the lip would be on the frame rail side or the outside and the lip would be on the wheel well side? Should I grease them up before installing and what grease? Does it matter what Leaf spring is on what side? Also do I take the truck off the stands and on the ground before tightening up the leaf spring eye bolts?
 

Chevy1925

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I ended up buying the OEM style from rock auto as I was afraid the poly type would be harsher and/or louder and since I don’t haul anything heavier than my boat I should be fine

questions now are which side do these press in from? Doesnt matter They have a lip like the factory bushings but just on one side. So would I press them in from the back side And the lip would be on the frame rail side or the outside and the lip would be on the wheel well side? again, doesnt matter Should I grease them up before installing and what grease? no need Does it matter what Leaf spring is on what side? If they have been re-arched, it wont matter Also do I take the truck off the stands and on the ground before tightening up the leaf spring eye bolts? Yes for ALL the spring pivot bolts (front spring to hanger bolt, rear spring to shackle bolt, shackle to shackle mount bolt. just barely get the nut up to the steel, lower down, torque to spec)

see reply in red
 

Bdsankey

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right the bolded part is what I thought but just wanted to confirm because I thought you were saying without overload it’s linear.

I’ve never really messed with bags, had some Firestone’s for my LBZ with that deaver mini pack but never wound up mounting them. But I’ve heard they are tough to get setup right like you said.

a little more on topic, are the isolators being talked about in the thread the ones from the GMT900 trucks? I seem to recall doing a swap to some newer OEM isolators on the back of my LBZ ext cab and it helped the ride smooth out.


Correct, the rear mount on extended cabs and crew cabs can be switched over to the GMT900 rear mount. GM did this under a TSB for frame beaming in an attempt to smooth out the ride.
 

fl0w3n

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Correct, the rear mount on extended cabs and crew cabs can be switched over to the GMT900 rear mount. GM did this under a TSB for frame beaming in an attempt to smooth out the ride.
That's what I thought. I couldn't remember the details of what I had done, and I'd like to do it again for my new truck.

If I also remember correctly, on an ext cab you only do the back two mounts, but on a crew you do the back two and middle. The fronts in either case need to stay the GMT800 style?
 

Bdsankey

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That's what I thought. I couldn't remember the details of what I had done, and I'd like to do it again for my new truck.

If I also remember correctly, on an ext cab you only do the back two mounts, but on a crew you do the back two and middle. The fronts in either case need to stay the GMT800 style?

I know for sure the back can be done on extended cab and crew, I don't know about any others. From my understanding the front mount needs to stay GMT800.
 

Jake707

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Mar 30, 2020
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My never ending leaf spring battle!
I brought a set of springs to a local shop to get re sprung. Cost was about $250 with new bushings, not bad.
I swapped them in today which will now be my 2nd swap yet it’s still a PIA. I also took out the air bags, I don’t need them and they seemed to limit the suspension travel when extending compared to the shocks and leafs so that didn’t seem right.
Anyway I lowered it back down and it seems to have squatted quite a bit for being reworked. Does this seem right? How much should they flex on just the trucks weight? This is back down to about where the old springs were

the ride does actually seem smoother now so I’m thinking those bags weren’t helping in that category.

here’s a pic of the gap with no weight, truck on the jack vs on the tires on the ground B851D8F7-BB28-47AE-A9D0-7A9751BE5951.jpeg
1660A62D-FF08-45B9-8471-3E10D0F00D42.jpeg
 

Chevy1925

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It’s from the prothane poly style he installed, not the hydraulic rear ones.

You need to look at your rear springs. More times than not I’m seeing guys with worn out rear leaf packs and the overload is maybe a 1/2” from the main pack. Makes the truck ride rough. You should have 1.75-2” clearance at the very back edge of the overload and the leaf pack. New pack isn’t too expensive or have them re-arched

Literally the 6th post in your own thread
 

Jake707

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Mar 30, 2020
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Well shit haha. It just didn’t seem right to me to sag that much but I guess it is. It does sit an inch higher I noticed too
 

fl0w3n

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Is there any point that a pack reaches where it’s not worth getting re arched? If the steel has just degraded to the point it won’t retain the new arch for very long?

something not frequently talked about (but mentioned in this thread) is torsion bars. What about replacing torsion bars due to sagging? I believe there was different bars even within the same year/model range, let alone different capacity levels. How do you pick the right ones? Or can they easily be re sprung?
 

Jake707

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Mar 30, 2020
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You got me. I thought that might be the case I had here but apparently 2” sag is norm on all springs.
Torsion bars are for the fronts only aren’t they? I know I’d you wind them up too tight for max lift they will be bumpy as hell in the front
 

fl0w3n

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Yes torsion is front only. I figure the same concept must apply, if the leafs can sag over time and start touching the overload at ride height, the torsions must be suffering from the same.
Only difference is you can adjust the torsion like you said, I don’t know if that “fixes” old worn out bars though.