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2005 Chevrolet Tahoe Suspension Fabrication - Rosco P. Drivetrain: Part 2

Posted in Project Vehicles on March 26, 2015
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Last month in the Rosco P. Drivetrain project we introduced you to our former cop car turned family wheeling project rig. We hacked the two-wheel-drive front suspension from our 5.3L 2005 Tahoe's frame and slung a Dodge 3/4-front axle under the front of the SUV. We then attacked the rear of the Tahoe, dumping the wimpy 10-bolt GM rear axle in favor of a late-model GM full-float 14-bolt from our local pick-a-part junkyard. While at the yard we also grabbed a GM NP241 transfer case from a late-model GM 4x4.

This month we take things a bit further. We are fabbing up the basics for our front suspension using custom parts from Rob Bonney Fab, and adding custom links from Rusty's Off-Road Products so we can cycle the front suspension. Out back we tune the ride and height with springs from Skyjacker and spacer pucks from Daystar. We also ran down to State to State Transmission in Phoenix, where our 2WD 4L60E was torn apart so that a 4WD mainshaft and tailhousing could be installed. This will allow us to bolt the GM NP241 behind the 5.3L and 4L60E and will further our transformation of this former cop car into a reliable family wheeling rig.

This month we also tear into the rear sheetmetal to help clear brand-new 37-inch Mickey Thompson Baja Claws TTC Radials on Mickey Thompson wheels from National Tire & Wheel. These tires and wheels hold a secret that will help keep us informed of what's going on with our rig on down the road—and trail.

As we worked on our Tahoe, the arrival of our twins grows closer. Sometimes parts aren't available, projects get delayed, and stories get held, but these babies are going to arrive whether or not their family chariot is finished. We'll keep whittling away at the project in hopes that one day we can all hit the trail, but don't expect an update for a few issues because for the next few months we'll be busy changing diapers instead of suspensions. Forgive us if there is a pause in the project as we welcome two future dirt heads into the world.

1. We pulled the 4L60E transmission from our 2005 Tahoe. Once we started loosening bolts and crawling around under the truck it looked that the transmission had been rebuilt recently. We had planned to have the transmission rebuilt with a 4WD 4L60E mainshaft and our junkyard-fresh 4WD tailhousing, but once it was out we saw it was fresh. We took the transmission down to State to State Transmission, in Phoenix, where Bill Macmaster blew it apart, replaced the mainshaft, and added the 4WD tailhousing within about a day. He also reported that the transmission was in good shape. Great news!

2. The rear suspension of our Tahoe will need some fine tuning when it comes to setting the final ride height. As we said last time, we want the truck to sit as low as possible. Our plan for tuning the ride height involves using Skyjacker 2 1/2-inch-lift Tahoe rear springs and Daystar Polyurethane spacer pucks.

3. We will finalize the ride height with these doughnut-shaped bits of plate steel, which slide over steel tubing welded to the GM full-float 14-bolt rear axle. We had the 1/4-inch plate doughnuts cut at Rob Bonney Fab just down the road in Peoria, Arizona. Bonney, joking with us, threatened to make these parts look like lily pads (that will make a little more sense soon, we think). In the meantime, know that Rob Bonney Fab can custom-cut just about any bracket you need.

4. Another key to keeping the Tahoe as low as possible involves trimming a bit of sheetmetal. We made this simple tool out of a piece of wood, a permanent marker, tape, and a nail. With the tool we can draw a reliable line 1 inch higher than the factory fenderwell opening.

5. With a little well-planned trimming we hope to retain the general shape of the rear wheelwells while opening them up a touch to better house 37-inch Mickey Thompson Baja TTC Claw radials on Mickey Thompson wheels from National Tire & Wheel. We started by cutting the lower lip off the wheelwell with an air saw.

6. We used an air nibbler and a 4 1/2-inch angle grinder with a cut-off wheel to trim just the outer sheetmetal. We cleaned up the cut with a grinder and removed paint and any zinc from the metal to prep for welding.

7. After making relief cuts with the air saw, we used a body hammer and these super-wide locking pliers to bend the inner lip of metal up to meet the new edge of the wheelwell. This bent lip won't cut the tire should it ever get flexed far enough to touch the body, or if we happen to run larger tires than 37s, but the goal is to limit the uptravel so that doesn't happen.

8. Once the sheetmetal was trimmed and bent, we tack-welded the inner and outer pieces of metal back together. With a little grinding and maybe some light Bondo work and paint, the new lip of the rear fenders will be smooth and rounded, yielding a factory look. Now we can bolt the wheel and tire in place and check for tire clearance. This allows us to keep the truck low and retain uptravel.

9. These sexy tires and wheels from Mickey Thompson hold a secret that we alluded to earlier. We ordered the tires and wheels from National Tire & Wheel, and they arrived all mounted and balanced with four GM tire pressure sensors in place, so all we had to do was just bolt them on and go. The sensors will communicate with the truck's computer and keep those annoying flashing dash lights to a minimum.

10. Switching gears back to the front suspension, we've built this suspension in our minds about 15 ways and finally decided to go with a four-link with track bar. Initially we thought of duplicating Dodge 3/4- or 1-ton front short-arm links. Later we contemplated grafting on a long-arm kit designed for Dodge 3/4- and 1-tons, but the forward Chevy body mount would need major reengineering. We then flirted with the idea of a three-link or just running radius arms, but decided that the three-link would require too much engineering and that radius-arm front suspensions, while simple to fabricate, are prone to binding when the axle articulates. After playing with some four-link calculators and talking to experienced fabricators, we decided that just copying the stock Dodge suspension design would be the best option. We started building bits and pieces to mock things up using stock-length 2012 3/4-ton Dodge upper control arms but with longer lower control arms.

11. We cut and lengthened factory Dodge lower control arms to be 30 inches long with a little scrap tubing we had sitting around. The plan is to keep both the upper and lower arms as close to parallel as possible with the frame at ride height. This should help keep caster (and pinion angle) changes to a minimum as the suspension cycles.

12. We then tacked some temporary brackets in place on the Tahoe frame and cycled the front suspension. Cycling the suspension with one side compressed and the other at full droop with brackets that are tack-welded in place allows us to be sure that nothing will bind up when the suspension is done. If something binds, a tack-weld will pop. This also allows us time to design more permanent brackets and have control arms made.

13. Fast-forward a bit, and a set of adjustable control arms from Rusty's Off-Road Products has arrived. Rusty's can make custom arms for your project and just about any application. We requested adjustable arms so we could fine-tune caster, pinion angles, and axle placement under the Chevy. These are the upper control arms that are the same dimensions as the factory 2012 Dodge arms shown below. These arms use flex joints on the frame end and polyurethane bushings on the axle end to absorb vibration.

14. The upper arms will use the factory Dodge axle-end mounts and will be tucked into the Chevy's frame just forward of the body mount. We had these 1/4-inch plates cut by Rob Bonney Fab; they will be used to form a box that holds the frame-end of the upper arm in double-shear.

15. Our lower control arms will parallel the frame and will be held in double-shear using these funny-looking 1/4-inch plate brackets again from Rob Bonney Fab. The outer plates kind of look like a frog's head, don't you think? Hence the lily pads mentioned earlier...maybe Bonney was making fun of us? If you're having a hard time envisioning how the frog heads—er, brackets—are going to work, you'll have to wait until the next installment of Rosco P. Drivetrain, and it looks like that might take a while. The wife is calling. It seems urgent. Maybe the twins will be here sooner rather than later. Wish us luck!

Sources

Skyjacker Suspensions
West Monroe, LA 71294
318-338-0816
www.skyjacker.com
Daystar
Phoenix, AZ 85043
800-595-7659
www.daystarweb.com
National Tire & Wheel
Wheeling, WV
800-847-3287
www.ntwonline.com
Rusty's Off Road
256-442-0607
http://www.rustysoffroad.com
Mickey Thompson Performance Tires & Wheels
Stow, OH 44224
www.mickeythompsontires.com
Rob Bonney Fabrication
602-370-7955
facebook.com/pages/Rob-Bonney-Fabrication/193559750764429

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