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    Lowering Blocks

This article is now being maintained on HowTune.com: Installing Lowering Blocks on GMC Syclone and other S-Series Trucks

Matt Cramer's truck all Jacked up in my garage


       This is fairly strait forward.  The idea is to lower the stance of the rear in order to get a more level appearance.  It also helps lower the center of gravity, helping with body roll around tight bends.

    There are two methods to lower the back end our trucks.  Lowering Blocks, and Lowering Springs.   If the money is available, the springs would be considered the better way to go.   Sometimes blocks have been known to cause problems with the steel springs on our trucks.  Possibly do to improper installation.  Almost all people who use blocks haven't run into any problems.

    The blocks actually change where the axle sits in relation to the rear springs.  It moves the axle up, brining the wheels closer to the bed, and keeping the shocks at the same travel distance because the springs and shock mounting plate actually stay in the same place that they would be in stock form.  This brings the rear differential higher in relation to the transfer case.  Theoretically, this should decrease the angle that the driveshaft has to operate at.  The result would be less wear on the driveshaft's joints.

2 inch Drop kit  ( 2 blocks,4 Ubolts, nuts, washers)


1 - lift/lowering kit (1" to 2")
       {consists of 2 blocks, 4 U-bolts, 8 nuts, 8 washers
        {available at average auto parts store
        {    ~$19 - $25

3 - 6 inch long 3/4 hex head bolts, nuts, washers, and lock washers (1 per bolt)
       {these keep the spring pack together, don't go cheap
        {available at Home Depot or similar
        {    ~$0.50 - $1.00 each

1 - Spray bottle of WD-40
       {your not gonna need a lot, just make sure you have some
        {if you don't know where to find this, go buy a Honda
        {    ~$2 - $5


1 - Jack
2 - Jack Stands
2 - Wheel Chalks (safety children!)
1 - Long torque wrench (up to 100 lb-ft)
1 - Deep 3/4 Deep socket
1 - Drill
1 - ???? size Drill bit
1 - Pair of Vice Gripps
1 - big cut off/grinding wheel (2" - 4" diameter)
1 - Dremel or similar  (unless you got a pair of "Mr. T's Bolt Cutters")
1 - 4" - 6" C clamp
1 - Powered wrench (your arms will thank you later)

Down & Dirty:

    Just so you know what you're getting into, Here' pictures of my stock rear height syclone versus, Matt Cramer's 2" block drop.

stockStock Height2 Inch Dropdrop
The pictures were taken at night, and at differing angles so I drew in a light dotted
line corresponding to the cladding joint for the wheel arch piece.  You can see
a LARGE difference in just the 2 inch drop blocks (look at where the rim is, not the tire).
It actually brings down the top of the tailgate a good 4-5 inches
(due to the change in pitch of the whole truck)

Step 1: JACKIN'

  Jack Placement Its time to start.   Get your truck on a fairly flat surface to jack er' up.  Put the truck in Park.  Don't bother engaging the parking break, It's not gonna hold anything still.   Stick the wheel chalks on the front tires to keep things from going anywhere.   Now, go to the back of the truck, and start jacking up the rear end by placing the jack under the rear differential just like in this picture to the left.  Make sure to jack it up on the flat surface under the dif, and not on the cover's lip.  Jack it up enough until you think you have enough room to get your tools, and self under the truck.   You may want to go up just enough to stick the jack stands under the truck, then jack it up to a workable height, and readjust the jackstands to prevent any mishaps.  Place the jackstands anywhere on the frame ahead of the leaf springs.  We put them right in front of the part that holds the front of the springs onto the truck.  Leave the jack under the differential.




WD-40 on the bolts (right rear)

    Here you can see the spring pack, U-Bolt ends, and the Shock/Achor plate.  Spray some WD-40 on the 4 nuts on the U-Bolts that protrude from the bottom of the anchor plate.  The WD-40 will help you break these things lose.  Take your 50 foot long torque wrench out for these.   Grab the appropriate size socket (3/4) and get those pesky things off.  Don't be too concerned about destroying them Mr. T, You wont need em again.

    Once these are removed the whole side should come apart.  The shock/anchor plate will easily swing out of the way.  The spring pack should stay together because there is a bolt going through them.  Pull the U-Bolts out, and put them aside.  Pay attention to the way things are laid out on the spring pack.  Top down: axle, wedge, spring, spring, helper springNotice there is a wedge on the top where the axle sits on the springs.  These keep your rearend at a certain angle that is important to maintain.  Go ahead and remove the other side's U-bolts as well.  When your done the rear end will be pretty much free floating except for its connection to the driveshaft, and the jack that it is sitting on.  You can slowly and carefully swing it forward one side so that you can get to the bolt holding the spring pack together.  Notice that the rear dif can, and will pitch down.   The front end can drop down, and the back end up.  Put the jack forward enough so that this doesn't happen.  It will probably scare you as much as it did Matt and I if it slips out of place.  If it does, don't worry too much, the springs will keep the rearend from dropping on ya.

Getting that bolt off it trickey

    Now you have to get the bolt out from the center of the spring pack.  The top (head) of the bolt is ROUND!  this makes it a pain to take off.  Go ahead and put the C-clamp you have on the entire spring pack just infront of the wedge.  This will help things stay together while you are removing the center bolt.  Spray a little more of that WD-40 on the bottom of the bolt here.  Use a set of vice grips to grip the round headed bolt on the top, while using a socket wrench to remove the nut on the bottom.  We only took apart one side at a time due to the fact that we only had one C-clamp. 




    The blocks in your kit most likely have a solid area in the center.   The top should have a dimple sticking out, and the bottom should have the reverse, a recessed dimple.  For our purpose we need to completely Say good bye to the center of that blockremove the outward sticking dimple, and drill out the center.  Matt used a all-purpose cutting wheel on his imitation Dremel tool to cut off the dimple on the top of the blocks.  Then, with a fairly large drill (the same size as the bolt going through springs) we drilled through the center as shown in the picture.  It's pretty light metal, so it isn't too difficult to cut.  I just held the block between my feet, and drilled out the center.  Make sure the bolts you bought fit through theI have no idea what BM means centers of the block and the spring pack.  Now, on to the bolts.  That hex head on your new bolts has to be grounded down, and round enough to fit into the hole the old round ones fit into on the axle.  In order to aid installation, we rounded them off, and made a flat spot on each side so that there was a surface for the vice grips to hold on to.  Made installation quite a bit easier.




    Ahh, some progressNow, your half way home.  It's time to put all those parts back together.  From top to bottom the whole assembly should look like this.  The wedge on top, with it's thickest part toward the rear of the truck, just like it was before you took everything apart.  Then the lowing block, thin metal plate, and the spring pack, ending with the helper spring on the bottom.   Insert the new rounded bolt down through the top so that the rounded head goes into the recessed area on the axle's feet.  Go ahead and put in a washer, lock washer, and nut on the bottom to keep things in tight.  Before you completely tighten the bolt down, remove the C-clamp, it will be impossible to get off due to the increased tension on the springs if you wait.  Go ahead and tighten everything down.  Be careful with that Home Depot bolt.  We purchased one that had a flaw, and it snapped in half after some torque.  The springs fell apart, and freaked us out (2 ton truck on top of us).   But we brought it back, and they gave us a replacement for free.  The next one held up strong.  Proceed with installing the block on the other side of the truck.   Of course, You'll have a good 2 inches of bolt sticking out the bottom of your springs now, so you need to cut those off.  Use some bolt cutters, or that cut-off wheel (preferred, makes cool sparks).  Leave a little bolt sticking out, but make sure you get enough off to prevent any contact between the bottom of the bolt, and the anchor plate.



    Use your new U-bolts to hold on to the anchor plate (duh!).  Put them up, over the axle, just as the other ones did, making sure not to crimp any lines under them.  (Brakes occasionally become useful).   Here's the part that's a big pain.  Tightening down these bolts.  We used the deepest socket we could find, and still had to tighten, cut, tighten, and cut the bolts down.  Matt brought his trusty impact wrench, which saved us a few days ofMatt Cramer doing his Terminator impression sore arms.  Just hold on tight to the U-bolts (pulling them as close to the springs/block/axle foot as possible) and blast away with your favorite power tool/wrench.   The kit we got advised that each of these bolts has to be tightened down to 90-100 lb.-ft.  So give em' all ya got.  When your finally done, cut the remaining bolt down, leaving approximately 1/2 to 1 inch of bolt protruding (you don't want for these to come completely off on a nice Sunday drive)  I've seen several people put on a second set of nuts to make sure that nothing is going to move.  Note, that the lowering kit instructions say to re-tourqe the bolts after 50-100 miles, and at 1000 after that.  Finally is a picture of  the finally assembly all together.