Rear 2" Drop Shackles - Please Educate Me!

Sniper · January 4, 2008

Hello everyone!

One of the members here (Darkanion) mentioned to me a few weeks ago that the pic of my truck looked like the rear had been dropped. It hadn't, and I agreed with him about the fact that it looked level in the pic, but really never gave it a second thought. At work Wednesday morning, "the boys" got together in the parking lot and we started talking about different things revolving around our personal vehicles. Well, as you might imagine, the "rake", "low front", "high rear", "disproportionate level from front to back", etc., on my truck was brought up (yeah, the one I never noticed, UNTIL THEN!). By that time, we measured and found a 2" difference. It was at that moment that the height discrepancy became VERY visible (in my head - LOL!) and "the boys" decided that something had to be done. Well, I went home and started researching 2" drop shackles. That's when all the fun started! (NOT)

I've searched the old and recent threads looking for information and now I find myself in the situation that I usually find myself in. After racking my brain and reading for hours, I'm clear on certain things, thanks to the input from various members, but now I'm confused about other things and have many unanswered questions.

Here's what I need your help with...

I've read up on the different manufacturers. Different people recommend different manufacturers, and that's okay, but which one REALLY edges out the rest? Yes, I agree that they're just a couple of dinky pieces of bent metal and they all do what they're supposed to do, but being the overanalytical person that I am, I have to understand everything about them before pulling the trigger.

WHO IS BETTER?

It seems that the most talked-about shackles are made by either DJM, GroundForce or BellTech. Is there another manufacturer that I should be looking at? What about the Velvet Ride two-piece design?

BUSHINGS?

I've read where people have mentioned that the bushings are fixed on some models and moveable on others. Is this true and, if so, does this make a difference?

GREASE FITTINGS?

Some people have mentioned that they should come with grease fittings because they make an annoying squeaking sound? Is the grease fitting something that can be added after the fact? Shouldn't they be greased initially during installation? If there's no grease fitting and if one can't/shouldn't be added after the fact, then how do you grease them up, as per the recommendations of one manufacturer's instructions to "periodically grease the bushings"? Do you have to undo everything and start over?

PINION ANGLE?

I've read where some people drop the rear 2" and don't have a problem with pinion angle/vibration, but then I read somewhere else where a 4 degree shim kit is needed on a 2" drop because of vibration caused by the pinion angle. Which one is it? Can it be both? Assuming a shim kit would be needed, what is the difficulty of installationl?

CLEARANCE ISSUES?

There are reports of having to shave/modify the bolt heads/bolt lengths in order to remove and replace them. There are some that recommend tossing the factory bolts and using different bolts, altogether. There are reports of having to remove the towing hitch assembly for ease of installation, while others say it's not necessary. There are reports of protruding metal panel seams that must be cut/bent in order to allow for proper clearance/installation. There are some that say that the bump stops are in the way and must be cut/removed. There are some people that mention removing the 1" spacer block and some that recommend not touching it. Some even say that you have to remove it in order to drop the whole 2", while some say that this would yield you a 3" drop. What is YOUR personal experience with all of this?

OVERALL RIDE?

Some people say the ride is stiffer. Some say it's the same. Which is it? Is a front-end alignment necessary when dropping the rear or is that only when dropping/lifting the front?

FRONT OR REAR?

I'm assuming that the rear should be dropped to take into account the 2" difference. How about those of you who have purchased those 2" front lift kits? Is that the way to go, instead or is this left to personal preference?

PART NUMBERS?

Not just for shackles, but I wish these companies would update their websites more often!!! Some companies list Chevy, but not GMC. Some list the Sierra, but not the Denali. Some list through 2006 or 2007, but don't list for 2008. I know that this is a personal complaint, but it bugs me when someone lists a part number for my truck that they've personally used (so you know it fits), only to be told by the website that "this part number is not available for your vehicle". UGH!!!

What installation woes, words of wisdom, added advice, reasoning, logic or anything else can you add about purchasing and installing 2" rear drop shackles on an '08 Sierra Denali?

I apologize for writing a book instead of a post, but I'm interested in learning more about this topic.

Thank you all in advance for your replies!

hubbycap · January 4, 2008

Lot of questions man! Here is a recent thread that may check a bunch of those off:

http://www.gm-trucks.com/forums/index.php?...=72045&st=0

Good discussion there.

y2kz71 · January 5, 2008

Yours is only 2" difference?...what are you measuring?

This guy has a 3" kit and stll looks taller in the rear and his is a denali too

http://www.gm-trucks.com/forums/index.php?...c=72446&hl=

DUKE70301 · January 5, 2008

That was my post about the 3"...Mine measures actually 1/2" lower in the rear but looks higer? Wierd but its an illusion because of the white rear fender wells lol. I would go 3" if I were you..If you don't like you can always but the factory block back in a few minutes...Thanks

Darkanion · January 5, 2008

Greeeeat, I don't post much for a couple of days and then things get blamed on me! haha!

I'm actually curious about a lot of these same things, as I'm thinking about a drop on mine. I've just been doing other things first and waiting around, until I could find the info.

Great post and thanks for asking all these questions. There does seem to be a lot of conflicting info and I'm glad to see I'm not the only one who has noticed it.

Sniper · January 6, 2008

hubby,

I've been following that thread, too. There's still a few "gray area" issues being discussed there, which is why I'm trying to get everything organized into one thread.

y2kz71,

The 2" difference is being calculated by measuring from the floor through the center point of the wheel to the bottom lip edge of the wheel well opening. I get 36 1/2" up front and 38 1/2" at the rear. Looking at the RPO list for my truck, it shows the "Z60 Suspension Package:High Performance". Does this have something to do with it?

Dukester,

This is part of the confusion! Some people mention that you can't use anything over 2" because you're already at your limit. It's something to do with clearance? If that's the case, how can you go down 3"? Also, I just read tonight that the rear blocks are 2". I haven't measured mine, but they look like 1" to me. Maybe different style trucks or different suspension packages are what's causing the discrepancies I'm reading about? Again, the more I read, the more differences I see people citing!

Michael,

This is all YOUR FAULT!!!

Seriously, bud, are you seeing the same things I am or not? Are your measurements similar to mine? Also, does your rear spacer block look like a 1" or 2" block?

I'M CONFUSED!!!

Darkanion · January 6, 2008

Michael,

This is all YOUR FAULT!!!

Seriously, bud, are you seeing the same things I am or not? Are your measurements similar to mine? Also, does your rear spacer block look like a 1" or 2" block?

Ok... When I saw the 2" spacer think, I pretty much figured "well, they meant to say one inch spacer" and left it at that. I've also seen where some people have said the rear-end is 3 inches and-something-eighths higher than the back. Now, I'm reading that there's on 2 inches of difference. I haven't measured mine, so I'm not sure... yet. I may go wash the truck, grab the measuring take, cameras, and go find a park or something, though... (It is a nice day, after all, outside.)

Now for the pictures and what I've seen, but didn't realize I had seen... I went back through my exhaust pictures and I found a couple that may explain the descrepancies in just how big the spacer actually is.

The first one (0339), is a shot fo the exhaust, with the spacer, part of the leaf, etc. in the background. Judging by that, the spacer seems like it could be bigger than one inch. I'm not sure if it's two inches, but it looks like it could be bigger than one, to me.

The second picture (0379), was a shot of something else, all together, but it happened to have the leaf and a semi-shot of the spacer. Judging by this one, it looks to me like the spacer is longer on the ends than in the middle. I'm also guessing that the spacer conforms to the curve of the leaf spring. So, that'd probably make the middle even thinner. So... My guess - and this is a guess - is that by the time you get to the middle of the spacer, between the axle and the leaf, we're at the inch most people have been talking about.

If / when I find out more, I'll pass it along...

hubbycap · January 6, 2008

hubby,

I've been following that thread, too. There's still a few "gray area" issues being discussed there, which is why I'm trying to get everything organized into one thread.

y2kz71,

The 2" difference is being calculated by measuring from the floor through the center point of the wheel to the bottom lip edge of the wheel well opening. I get 36 1/2" up front and 38 1/2" at the rear. Looking at the RPO list for my truck, it shows the "Z60 Suspension Package:High Performance". Does this have something to do with it?

Dukester,

This is part of the confusion! Some people mention that you can't use anything over 2" because you're already at your limit. It's something to do with clearance? If that's the case, how can you go down 3"? Also, I just read tonight that the rear blocks are 2". I haven't measured mine, but they look like 1" to me. Maybe different style trucks or different suspension packages are what's causing the discrepancies I'm reading about? Again, the more I read, the more differences I see people citing!

Michael,

This is all YOUR FAULT!!!

Seriously, bud, are you seeing the same things I am or not? Are your measurements similar to mine? Also, does your rear spacer block look like a 1" or 2" block?

I'M CONFUSED!!!

Well Sniper, I might shed a little light on your response to Dukester anyway: The means by which the bed is lowered or raised is the length of the shackle that supports the leaf spring. In the GMT900 specifically, the TOP of the shackle is attached to the end of the spring and the bottom to the shackle bracket on the frame. Lowering requires a LONGER shackle, about twice as much additional as the desired drop, do to the fact of lever advantage. eg. if you raised one end of say . . a 10' 2x4 above the ground by 2', the measurement of lift at the mid point would only be about 1'. The problem with accomplishing a lowering strictly with a longer shackle length is that there is a limit to how high the end of the spring can be, and the limit is the bottom of the cargo bed.

A 2" drop requires the shackle to be an additional 4" longer because of diminished effect at the midpoint of the spring and that is about all the clearance there is. With a 3" drop shackle kit the manufacturer also relies on the removal of the 1" spacer that is between the axle and its mounting point on the spring PLUS the shackle change. Of course the 1" spacer change could be accomplished without purchasing anything because it is removal of what you already own. The removal of the spacer has the direct effect of its thickness on height because the truck will drop its exact thickness to the axle in its absence.

I'll admit that on this next one I have no personal knowledge, but as to the different heights between the Z60, Z71, Z66, Z82, and Z85 suspension packages it is possible and likely that clearance variations exist. But what really matters is what you want to end up with and the change you need to make on your truck to get to that point.

Sniper · January 6, 2008

Michael,

PLEASE post your findings! I think we're in the same boat here and I'd love to compare differences in the same vehicle, if any exist.

Thanks!!!

Well Sniper, I might shed a little light on your response to Dukester anyway: The means by which the bed is lowered or raised is the length of the shackle that supports the leaf spring. In the GMT900 specifically, the TOP of the shackle is attached to the end of the spring and the bottom to the shackle bracket on the frame. Lowering requires a LONGER shackle, about twice as much additional as the desired drop, do to the fact of lever advantage. eg. if you raised one end of say . . a 10' 2x4 above the ground by 2', the measurement of lift at the mid point would only be about 1'. The problem with accomplishing a lowering strictly with a longer shackle length is that there is a limit to how high the end of the spring can be, and the limit is the bottom of the cargo bed.

A 2" drop requires the shackle to be an additional 4" longer because of diminished effect at the midpoint of the spring and that is about all the clearance there is. With a 3" drop shackle kit the manufacturer also relies on the removal of the 1" spacer that is between the axle and its mounting point on the spring PLUS the shackle change. Of course the 1" spacer change could be accomplished without purchasing anything because it is removal of what you already own. The removal of the spacer has the direct effect of its thickness on height because the truck will drop its exact thickness to the axle in its absence.

I'll admit that on this next one I have no personal knowledge, but as to the different heights between the Z60, Z71, Z66, Z82, and Z85 suspension packages it is possible and likely that clearance variations exist. But what really matters is what you want to end up with and the change you need to make on your truck to get to that point.

hubby,

Your explanation was AWESOME!!! THANK YOU!!! So, assuming the spacer blocks are 2", then simply removing these blocks (since they're on center where the axle sits) would make the rear drop 2". Okay, but then if the spacer block is only 1", then the drop shackle would need to compensate for the extra inch of needed drop, which means the length of the shackle would have to be 2" for it to cause a drop of 1".

Is there any adverse effect to removing this spacer block? If so, then leaving it alone would be my choice and going with a 4" long drop shackle would be my decision, IF IT FITS!!! That's another issue altogether, because if there's no clearance against the bottom of the bed for a 4" shackle, then the block removal needs to be considered, regardless.

Once again, thank you for taking the time to explain this. Your analogy with the 2x4 drove the point home!!! I appreciate that!!!

7LitreC5 · January 6, 2008

I also have the Z60 suspension. I measured mine and there is 2-3/8" difference from front to rear. The front is 37" and the rear is 39-3/8".

The 2" difference is being calculated by measuring from the floor through the center point of the wheel to the bottom lip edge of the wheel well opening. I get 36 1/2" up front and 38 1/2" at the rear. Looking at the RPO list for my truck, it shows the "Z60 Suspension Package:High Performance". Does this have something to do with it?

hubbycap · January 6, 2008

Sniper,

What is called a 2" drop shackle is designed 4" longer by necessity, and will fit with room to spare. The only adverse effect of block removal would be the U-bolt length extending below the axle; could snag some grass of something. With a 2" drop, use the shackles, leave the spacer and all will be fine.

As 7LitreC5 stated his truck has a 2-3/8" higher rear on the same suspension option. You have to go with what you have on your truck.

Darkanion · January 6, 2008

Michael,

PLEASE post your findings! I think we're in the same boat here and I'd love to compare differences in the same vehicle, if any exist.

Thanks!!!

Ok... Here's what I found. With all the temperatures bouncing back & forth between the 30's and 70's, I need to go put some air in my tires. The fronts and backs still have the same amount of pressure, but the fronts look a little low. Even with that, the overall difference between the front and rear fender was about 2 3/4 inches. I snapped a few pictures of the spacer, but I forgot to take pictures of the shackle.

I've attached a couple of pictures. One is the driver's side spacer and the other is the passenger side spacer. I didn't have my tape measure under the truck with me, but these things look thicker than an inch, to me... Regardless, when I get ready to do anything with the back of my truck, I'm planning to leave these things in there and just add the 2" drop shackle. That should still leave the back a little higher, but get it "out of the air." That will also leave a little bit of an energy/shock-absorber between the axle and the spring. I'm not sure if that'll help the right at all, but it "seems" like it could or should.