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Killer Chevy Mods

Posted in How To on December 1, 2010
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We've dealt with a lot of Chevys over the years, and we've seen a ton of modifications, a ton of innovation, and a ton of things we don't ever want to see again. But there are a few mods that have come to be Chevy favorites for us, and we try to use/employ them on every applicable Chevrolet we get. Here are a few things that should be on your wish list.

NP205/NP203 Doubler Kit
With around a 2:1 (technically 1.96:1) low range, neither the NP205 nor the NP203 make great choices for slow-going on the trail. Unfortunately, those two T-cases were pretty much the only things available for older Chevys. The 2:1 ratio is more along the lines of something to run in the desert or sand dunes, which is great if you're in one of those spots. Years ago, Offroad Design designed a doubler kit that allows you to put part of an NP203 in front of an NP205 and "double" them together. This does elongate your drivetrain, but it also gives a 1:1, a 2:1, or a 4:1 gear ratio to choose from by multiplying the low range drives together.

6-Lug Semi-Floating 14-Bolt
If you've got a '98-or-older Chevy/GMC 1500 half-ton truck or SUV, you're rolling around with either a 12-Bolt or 10-Bolt rear axle. These axles actually aren't too bad, but with larger tires and lots of off-road abuse, these C-clip axles can break (often it's the factory limited slip that seems to blow up) and leave you stranded. The last time that happened to us, we went looking for a light-duty semi-floating six-lug 14-Bolt rear axle. These axles are sort of rare, and we believe they came out of late '80s and early '90s light-duty 2500 trucks. They bolt directly in place of the original half-ton axle on your 1500, and still allow the fitment of 15-inch six-lug wheels. The drum brakes are quite a bit larger, as are the axleshafts, and 9.5-inch ring gear. It's still a semi-floating axle design, but it's much stronger than a 10-Bolt or 12-Bolt axle.

Beefy Shackles
The front shackles on older straight-axle Chevrolet 4x4s can get a little sloppy after 30 or so years. The bushings wear out, the metal wallows out, and the shackles themselves are a little thin to begin with. You can make yourself some new custom shackles, or you can get an Offroad Design shackle kit that comes with new hardware and front and left shackles. You won't notice much performance difference, but you won't break the ORD shackles and adding these might replace worn-out parts and keep your truck a little tighter and handling better.

Aluminum Heads and Cam
If there's one thing we've found that really wakes up old GM 350ci engines, it's got to be a new set of heads and a camshaft. We've currently got an older Chevy small-block with a set of Dart Pro 1 Platinum cylinder heads on it. The engine has never been rebuilt, with about 132,000 miles on it. It was starting to feel a little dumpy, but after pulling off the heads we found the bottom end to be in pretty good shape. We replaced the timing chain, added a Comp Cam, and bolted on the Dart Pro 1 heads. We've done cam swaps before and we've done head swaps before, and it seems like the two modifications are clearly more effective if done together. Adding a cam might give a little oomph by itself, but without a modified head and some bigger valves, you won't see the biggest performance improvements.

Aftermarket Gauge Additions
If you've got a '73-to'87 GMC or Chevrolet truck, then you have a similar dash bezel as the one pictured. Did you know that, with some time and basic wiring skills, you can remove the instrument cluster and actually fit Auto Meter gauges with a little plastic trimming? The difference is obvious, and gives a fully-custom look and feel to an otherwise stock dash.


Auto Meter
Sycamore, IL 60178
Comp Cams
Memphis, TN 38118
Offroad Design
Dart Machinery
Troy, MI 48084

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