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1991 Chevy 3/4 Ton Truck - 4Wheel & Off-Road Magazine

1991 Chevy 3/4 Ton Truck - IFS Exploration

Fred Williams Brand Manager, Petersen’s 4Wheel & Off Road 1991 Chevy Three Quater Ton front View Photo 9230878

We've been wrenching, welding, and improvising on our IFS Chevy and this month we'll show you some of the custom upgrades that we've done to try and make it stay alive for another 30 days or more.

We found that the Tuff Country suspension was holding up just fine, but all the stock components like axle halfshafts, steering, and even the driveshafts can't take the abuse of even moderate off roading.

So this is the point where we left the normal path of upgrades and started working with different folks to find new options. The ultimate plan here is to try and determine if IFS can be built to be as strong as a solid front axle, and just how expensive that goal is.

Some of these parts are available now, and others are prototypes for possible future parts depending on demand. Either way, in an upcoming issue (probably September or October 2006) we will wrap up the IFS episode and let you know if it's worth all the effort to keep it alive or if going to a solid-axle swap makes more sense.

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Every time we took our project Red Sled '91 Chevy 3/4-ton out wheeling we had roughly 30 minutes of fun before one of the front axle halfshafts would explode into bits, so we knew that some upgrade there was a priority. Rough Country is the first company we have found that is offering a better-than-stock halfshaft, with an amazing three-year or 36,000-mile warranty on its heat-treated steel-slip spline shafts and six ball-fixed CV joints. Currently these shafts are designed for use on IFS Chevy lift kits that would normally use a spacer puck between the differential and the axleshaft and thus are made 2 inches longer than stock. However, a modified version could be put into the parts catalog if there is enough demand.

Since our Tuff Country 6-inch suspension does not use spacers, we needed to shorten the Rough Country halfshafts (left). The shafts only have about 2 1/4 inches of spline so we could only afford to cut off 1 inch of the splined shaft and still have enough spline engagement (center). This would be fine on the passenger side of our truck since last month we discovered that side to be nearly 1 inch longer from the differential flange to the knuckle, and thus seemed to overextend the stock shafts (right), causing them to break. Total cost for a set of two shafts from Rough Country is $800, but remember the three-year warranty and the fact that every time we broke our stock halfshafts it would cost between $75 and $100 to replace...and we broke one almost every time out on the easy trails.

As we were installing the new halfshafts we decided to jack up the truck and noticed that the passenger-side unit bearing was very loose and coming apart. This $330 part reminded us to be sure the external halfshaft nut is good and tight (150 to 160 lb-ft).

After installing one of the new Rough Country halfshafts, we headed out for some night wheeling in the mud and rocks. It was a beautiful rainy sleeting night, and our big-block truck was happy as a clam clambering over a small boulder field. Then after our final run through this groomed obstacle course, the truck seemed to bog down, and felt as if the rear brakes were locked while the front kept pulling. Much to our delight we found the rear driveshaft twisted like a pretzel and snaked up along the passenger side of the truck, effectively locking the rear end from turning. Not good.

Lucky for us our rear driveshaft has a carrier bearing a third of the way from the 241 transfer case. So we could drive it home with just the short section still sticking in the slip-yoke style case. What looked like doom was actually a chance for another IFS test-could we drive at highway speeds on just the front end while in 4-Hi? As it turns out, we could and with little to no vibration when the truck was under load climbing hills. Oddly there was some serious shudder while on the downside of the rise where the truck was coasting. We wouldn't recommend driving on just the front end all the time, but our 3/4-ton did fine for the 60-mile cruise home.

Our new driveshaft was assembled by the folks over at Wenco Driveshafts. They replaced the carrier bearing, rear yoke, all the U-joints, and the rear tube with a heavier wall piece for around $350. As we've said before, if you want a cheap hobby, take up Frisbee 'cause wheeling can get spendy.

Another thing we did before our night run was make this skidplate out of a sheet of 1/8-inch plate. We simply heated it up with a torch and bent a 90-degree angle into it, and then drilled and bolted it to the lower subframe. It worked OK, but we plan to add some ribs or dimpled holes to the bottom face to gain rigidity in defense of rock bashing.

After we got the axles upgraded, we focused on the steering. Our stock parts were surviving, but flexed enough to require toe-in adjustment after each trip out. When we looked at the price of a spare set of complete tie rods and ends, only to have more weak stock parts, we decided to upgrade. Our research led us to Blitzkrieg Motorsports. Known for their long-travel two-wheel-drive and solid-axle suspensions, the folks at Blitzkrieg happily accepted our big red bucket into their shop for some beefy steering upgrades.

The Blitzkrieg crew quickly convinced us that our front sway bar was more a hindrance than a help and would be in the way of a new set of chromoly tie rods. In seconds it was cut off and tossed. We haven't missed it since.

They measured for the new TIG-welded 1 1/2 inches over 1 1/4 4130 tie rods with high-misalignment Heim joints. The idea here is that the beefier tie rods and rod ends will take the abuse of larger-than-stock tires, plus will offer sufficient flex for our less than trophy truck. Tie-rod kits are available for '99-to-present GM HD trucks, 1/2-tons, and H3s, while our earlier era '88-'98 variants were prototypes that ran about $500 complete with joints and installation.

Installation isn't too hard, but it does require drilling out the Tuff Country centerlink and stock knuckles to clear a 9/16-inch bolt. It shouldn't be that hard. Of course, when you are lying under the truck with hot shavings falling down your sleeves and a hefty drill twisting your hands into the frame, you can come up with a few other things you'd rather be doing.

The high-misalignment spacers and rod ends are just enough for the 5 to 6 inches of travel we experience. Plus we don't foresee any issue with running the 9/16-inch bolts in single shear, though we've already played with some ideas for a double shear gusset if it becomes a problem.

With the new stronger steering components in place, we decided to look into a ram-assist system to help turn 35-inch or larger tires. We had used the Off Road Unlimited's kit on solid-axle trucks in the past, so we offered them the challenge of building one for an independent front suspension. As this goes to press, the truck is up on the rack at ORU, so we'll have to show you how the ram assist turned out in a future issue, and how all our exploratory upgrades fared after some more aggressive trail abuse.

1991 Chevy 3/4 Ton Truck - 4Wheel & Off-Road Magazine

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