We prefer projects that can be tackled in a long weekend or a week of building. That way our limited attention span holds out and we can enjoy the before and after experience of the project. Oh look! A squirrel! At the same time, some things just can't be rushed—or at least shouldn't be.
A good example of that is the in-depth build on our family truckster known as Rosco P. Drivetrain. Last time we explained how two little bundles of joy were about to arrive in our happy home. Well, the twins are here (Christmas babies! Yay!), and we went from having zero diaper changing experience to being a certified ninja master of pee-pee and poopie. Despite frequent diaper changes and dueling with fussy babies, in recent weeks things have calmed down just enough to allow us some time to head out to the driveway to tinker on the ol' Tahoe.
Last time we started mocking up parts of the front and rear suspension. This time we continue to fine-tune how the new and improved suspension will work. Adding to the mix, a modified steering box also arrived at the house from West Texas Off Road. The box is just what we wanted and all drilled and tapped for a hydraulic assist via a Redneck Ram. With the steering box in hand and mounted we could begin to figure out the rest of the steering and start work on finalizing the frame side mounting point for the front track bar.
Speaking of track bars…With our rear suspension lifted and a larger-than-stock rear differential cover we also had to come up with a new rear track bar. We wanted an adjustable track bar, and we also needed to add a bend so that the bar would clear the axle on compression. With a little advice from our pal Rob Bonney we were able to put together a nice heavy-duty adjustable track bar for the back of the Tahoe.
We also got a bit further along with the front suspension by tack-welding the frame-side control arm brackets we got from Rob Bonney Fab in their new homes. That allowed us to test-fit our beefy custom front lower control arms from Rustys Off-Road, cycle the suspension, and get an idea of how long a coilover we can stuff in there.
That's more than enough blabbering about what we did, let's get down to the pictures of what we've gotten done so far.
With the reversed internal box in place we quickly realized that running a pitman arm with any drop would put the draglink too low down. Luckily the guys at West Texas Off Road told us to look for a pitman arm from a 1990s Chevy Astrovan. We were able to pull an arm for cheap at the local pick-a-part junkyard. We then reamed out the tie-rod end of the pitman arm with a 7.15-degree, or 11⁄2-inch per foot, taper reamer. These tapered reamers are available from several parts houses including Summit Racing Equipment (PN AAF-ALL11170).
With the steering box mounted, the newly reamed pitman arm in place, and the tires aimed straight ahead, we estimated ride height. We were able to mock up the factory Ram track bar onto the Tahoe's driver-side framerail. To prevent bumpsteer, you have to have the slope of the track bar match the slope of the draglink. This isn't always easy to see because both parts have bends in them. We measured the height of the center of the passenger-side track bar mount bolt and the passenger-side pivot point of the tie-rod end on the draglink. The tie-rod end's pivot point is about half an inch higher than the track bar bolt on our Ram axle. If we match this half-inch height difference on the driver-side mounting points, the slopes of the track bar and tie-rod end should match.
Next we moved to tack-welding the frame side mounts for the lower control arms. We started with this plate that we had cut by Rob Bonney Fab. This is the plate we showed you last time that kind of looks like a frog's head. With the plate tacked in place we used cardboard from a beer box to make a template for the inner plate for the lower control arm.
Getting back to the control arms, here they are. We sent our measurements to Rusty's Off-Road, and they supplied us with these beautiful parts. We opted for rubber Clevite bushings on the axle end (just like the OEMs use) and Rusty's Forged Flex ends on the frame side. The greaseable Flex ends use Delrin races and fully threaded adjustable retainers that allow you to fine-tune preload even as the parts wear. Rusty's also uses 2x0.250-wall DOM steel tubing for the body of the control arms. Since our new arms are adjustable we made our own cam bolt elimination kit for the axle end of the arms.
With the front track bar in place and all four control arms tacked to the frame, we could once again cycle the suspension. This again gave us a chance to check for any binding of the control arms (if a tack weld popped during cycling) and gave us an idea of where we had to set the front bumpstops.
We also were able to temporarily bolt a tire or two onto the Tahoe to get a good idea where we would need to trim more front sheetmetal. Cycling the suspension also gave us an idea of how long a front brake line we would need. We think we can get away with using factory brake lines for the Ram front axle, although we may have to move some of the mounting points. This means we can also measure wheel travel for front coilover shocks and begin to think about how to build the coilover shock mounts.
With the basic design of the front suspension pretty well sussed out, we moved to the rear suspension. Initially we hoped we could get away with using the factory rear track bar, but once the 14-bolt rear axle was in place it became clear that that was not going to work. As the axle compressed, the track bar and our 14-bolt's large differential cover wanted to share space. We went over a few ideas but finally decided to follow Bonney's sage advice and build our own adjustable rear track bar. For this we would need two rod ends, jam nuts, tube inserts, and a length of 11⁄2x0.250-wall DOM tubing with a slight bend in it. Luckily Bonney also has the equipment to bend that DOM tubing for us. Here we are trimming the bent heavy-wall tubing to length.
With the tubing trimmed down to length, we dry-fitted all the parts together so we could mount the track bar. We ended up using high misalignment bushings to add to the width of the rod ends and drilling the factory mounting holes out to 5⁄8 inch for matching hardware. We plan on adding rubber bushings to the sides of one or both rod ends to keep the track bar from flopping up and down because of the bend. In hindsight we probably should have built our own axle side track bar mount because the factory mount means our rear track bar is shorter than we would like. The longer the track bar is, the less side-to-side movement the axle makes as it compresses and droops.
With the dry-fit track bar in place we added in the 3-inch-lift rear coils from Skyjacker Suspension. With them in place and the weight of the vehicle on the rear axle we get an idea of ride height and also can set the track bar length to center the axle at ride height.
Last time we noticed that our 14-bolt rear axle was a bit narrower than we had hoped. Luckily National Tire & Wheel, who had sent us the mounted and balanced Mickey Thompson tires and wheels, also sells wheel spacers. After a quick call we had this pair of wheel spacers in hand. With the spacers in place and supplied nuts and thread lock, we have a little more tire clearance as the rear suspension flexes and a slightly wider track width.
The width adds stability and helps match the wide Ram front axle. The rear springs will probably settle a little bit, but this picture gives a good idea of where the rear of our Tahoe will sit when all is said and done. Add twins, dog, gear, diapers, diapers, and more diapers and we may just need a set of airbags?
With the axle centered at ride height we can tack the track bar together, pull the springs, and cycle the rear suspension to measure for shocks, to set bumpstop height, and to check for clearance. The Tahoe will have a little less wheel travel in the rear, and we have to clearance the frame in two places, but all in all we are pretty happy with the way things turned out—for now.
Last but not least, we also tracked down a 4WD transmission crossmember for our Tahoe. It's nice to be able to bolt a few things in place when you're spending lots of time cutting templates, tack-welding, and custom-fabricating suspension components. Next time we will be building front shock hoops, mounting and plumbing the steering ram, and hopefully adding shocks, our NP241 transfer case, driveshafts, brake lines, fluids…maybe regear the axles. The end is near! Yay!
Source: https://www.motortrend.com/how-to/1508-2005-chevrolet-tahoe-suspension-fab-and-steering-upgrade-rosco-p-drivetrain/
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