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The Autoblog project garage - lifting my GMC K2500

When those of us at Autoblog aren't busy writing about cars, we're busy working on them. A few months ago, I mentioned that I had scored a great deal on a set of Hummer H2 take-off wheels and tires. Being approximately 5" taller and 3" wider (they're the metric equivalent of 35x12.50"), fitting them was more than a simple bolt-on affair, and some lift was going to be required.

I'm not a big fan of standard suspension lifts for GM independent front suspension (IFS) setups. They require dropping the front diff to keep the CV joints happy, resulting in no improvement in ground clearance in that critical area. Dropping the pickup points for the upper and lower control arms is accomplish via a set of bolt-on brackets, which is an arrangement that simply does not appeal to me as it seems inherently less robust than the stock setup. And then there's the issue of lifting the entire truck by 4-6" (in addition to the height gained from taller tires), which would have a dramatically negative effect on handling.

Fortunately, my 3/4-ton sits up a bit higher than a half-ton, and has considerably stiffer suspension. That led me to think that a simple 3" body lift would suffice. Up top, there's a picture of my truck in the stock condition. Below the jump, I've got some pics of the installation, and of the final result.

First, some mandatory disclaimers. Working on a project like this is hazardous. Don't ever get underneath a vehicle that isn't supported by jack stands or some other mechanical means, and don't ever trust a hydraulic jack with your life. A lot of "mission critical" components are affected by performing modifications such as this, and if you can't bet your life (and those of others) on your mechanical skills, seek the assistance of professionals. Follow the kit's instructions exactly, and refer to a factory service manual as needed. OK, now on to the fun stuff:

This picture shows the 245/75-16s and the H2's 315/70-17s; there's a substantial difference in size between the two tires.

I pulled the truck into my barn (my secondary choice for a project of this magnitude, but my garage was already occupied with an immobilized vehicle and a woodworking project). In the absence of a better plan, I started by, um, actually following the instructions for my Performance Accessories 3" body lift kit. First, I first installed the steering shaft extension:

In the meantime, my wife removed the grille and bumper trim:

All that stuff has to be removed for the sole purpose of accessing the bumper bolts. The front bumper is then removed, along with the stock brackets. Once that's done, the seat must be removed from the interior, and the floor covering pulled back to expose the shifter cable. No, really - there's no way around it. A small clip has to be removed from the cable so that an inch or so can be pulled through the grommet (don't worry - there's about two feet of extra cable coiled up under the seat). I somehow didn't get a picture of this process (probably had something to do with the fact that it was about 20 degrees outside at this point, and my Coleman propane heater wasn't winning the war against thermodynamics). I did, however, get this shot of all the crud that had accumulated under the rocker panel trim:

Clearly, I need to remove that trim and clean this out once a year or so, because all that debris will trap moisture and encourage corrosion (and 10-year-old trucks in Michigan need no further encouragement in that regard).

After unclipping the fuel lines and wiring harness from the left framerail, under the cab, it's time to remove the six bolts retaining the body and get the actual process of lifting the truck underway:

This is done via my floor jack and a chunk of 4x4 lumber, placed behind the rocker panel (note that the cab is being lifted by the floorpan, and not the rocker sheetmetal!).

Yes, the lighting in these pictures sucks. Sorry, my full-time photographer was.. well, actually, that's me, and I was occupied with fending off frostbite. Once the cab has been lifted, the nylon lift blocks are slipped into place:

This is a good time to remind everyone that a thousand pounds or so of cab is being suspended by a solitary hydraulic lifting device. In other words, don't put your fingers anywhere you wouldn't want them to be if the cab came crashing down without warning.

The bolts on this side are installed a few turns, and then we repeat the process on the other side. Once all the blocks are in place, the bolts are removed one at a time, red Loctite is applied, and then the bolts are reinstalled to the "factory torque specification" (in other words, tighten them as if you never wanted them to come loose).

The process is repeated for the bed:

Yes, that's a scary stack of lumber. That thought was at the front of my mind as I inserted the eight blocks under the bed, which is why I made damn certain to keep my body parts clear of any pinch points. Once again, we do one side, then the other, and the bolts are then treated with an application of threadlocker, and tightened.

There's four blocks that need to be welded to the bed crossmembers that normally contact the frame (you can see one of them just to the upper right corner of my lumber stack). I didn't do that here, since my MIG is in my other garage. It would appear that this is absolutely necessary before any substantial load is put in the bed.

So, now the body has been lifted and the easy stuff is done. What? Yep, the tough part of any project like this is addressing the little details. First, the fan shroud had to be clearanced in order to fit around the transmission cooler lines:

Note: an angle grinder with a 6" cutoff disc is the single best cutting tool to have for any automotive project. Ah, and now we've got some room. Note the zinc-plated drop-down bracket that's used to keep the fan shroud at its original height (the radiator was lifted with the body, but the engine fan is still down at chassis height).

Now, it's time to check for any other clearance issues. Note how close this transmission cooler line was to the fan:

A minute or two of careful bending took care of the problem.

Now it's time to fit the front bumper. These new brackets lift the bumper to properly line-up with the body:

There are a total of four brackets and 18 bolts involved in reattaching the front bumper (or six brackets and 22 bolts, if you didn't read the directions properly). I'd recommend getting a second person to help with this task, even though the bumper itself is far lighter than it looks.

With the bumper now cantilevered above the frame instead of sitting directly in front of the rails (see the before-and-after pics below), I think it's fair to raise a concern that perhaps it's not offering a lot of protection to the front of the truck anymore. A couple of weeks after this lift was installed, I hit a 50 lb dog with the truck, and it was enough to tweak one side of the bumper by about an inch. I think it's time to investigate a better bumper setup.

Once the bumper was in place, a test fitment of the wheels and tires showed that some extra clearance would be needed at the lower rear corners. First, I removed this little piece of plastic trim:

And then I attacked the bumper with the aforementioned cutoff wheel and removed a little chunk of material.

Alright, we're almost done. Time to crawl underneath one last time and tidy up the fuel lines. This was the only area of the project where I had to resort to zip ties.

Yes, that bit of corrosion on the brake lines is cause for concern. Now, it's finally time to mount the wheels and tires. I'm a big fan of using antisieze on the lugs, as well as any area where the wheel contacts the brake rotor/drum. GM states that lugs should never be lubricated, but I simply cannot bring myself to put lug nuts on a dry wheel stud because the odds are good I'll have to remove that nut someday.

Torque the lugs as appropriate. If the service manual specifies a torque for dry threads, I drop the torque spec by approximately 35% to account for the effect of lubrication. I have to recommend that one exactly follows the service manual, however, and that any deviation from that is taken at one's own risk. 

So, how does it look? Here's the truck before:


And after:


More importantly, how do the new tires work? Very well. BFG-ATs are not a great mud tire, but they are probably the best compromise between on- and off-road performance. Dry and wet grip on the pavement are exceptional, and even with the extra width, snow traction is far improved over the Radial Rover's performance back when they still had tread. The ride is, well, a bit different. There's a sensation of additional unsprung mass (the new wheels and tires are substantially heavier), but the larger diameter and additional sidewall serve to deaden the effect of Michigan's numerous potholes. The truck doesn't feel any more top-heavy or tipsy than it did before, and the brakes don't seem to have much of a problem handling the larger tire diameter (we'll see what happens once I get a few thousand pounds in the bed).

There's a little bit of rubbing on the rear of the front fender opening, about half-way between straight-ahead and full-lock. I haven't quite decided how to address that yet, but some cutout fender flares seem like the way to go. I need to ditch the H2 center caps, too; the original caps will fit the H2 wheels with a bit of modification, but I haven't yet gotten around to spending the 10-15 minutes on that task.

Inevitably, someone will ask why I didn't crank up the torsion bars. Take a look at this picture of the suspension in full droop:

When the suspension tops-out, the upper control arm hits the solid stop (circled above). There's only about 1.75" of droop available when the truck is sitting at normal ride height (as measure at the center of the hub), which isn't much at all. Cranking up the bars cuts into that precious little downtravel, and contributes to a harsher ride and poor handling. Additionally, the upper ball joint takes a hell of a beating whenever the suspension tops out, and it won't be long before it separates.

If a torsion bar crank is used to lift the front end, a set of ball joint spacers could be used to gain some additional downtravel. Longer shocks will also be required. That addresses the top-out issue (at least as long as the bars aren't cranked any further than the spacer height), but now there's a legitimate concern about the life of the CV joints. Additionally, the front suspension geometry will be altered, with the roll center being raised and the camber gain altered in ways likely to contribute to additional tire wear. Bottom line - simply cranking the bars isn't a great way to lift an IFS Chevy.

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