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1991 IFS Chevy Truck - The 30-Minute WheelerIFS (Inferior Front Suspension) And What Goes Wrong From the June, 2006 issue of 4Wheel & Off-Road By Fred Williams Photography by Fred Williams, Leah Light
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A month ago we set the stage to test some independent front suspension rumors and theories, and since then we've found some problems with our '91 IFS Chevy truck. The plan was to take it outon some gnarly trails, beat the poop out of it, and see what broke. The problems arose when we thought we were being easy on the truck and it just wouldn't hold together. In fact, two of our three off-road runs resulted in less than a half hour of wheeling before we were broke, and the repairs required took up to an hour to do (we're getting faster) and at least $50 in parts. Needless to say, we're not very excited about the performance so far. You may wonder why we only got three runs on the truck, and that's partly due to a non-IFS problem, the transmission. Even though the truck received a new fuel-injected 454 long-block and Tuff Country 6-inch suspension lift, it is still a 15-year-old brute, and it's been showing its age in the rest of the drivetrain. So where does this leave our testing? We are quickly attacking little gremlins (especially in the wiring), and have both upgrades and more dirt bashing scheduled for it. As this goes to print we have about a month before it is time to head for the Easter Safari in Moab, and we are wondering if the truck will still be running the inferior front suspension for that trip, or if something more solid will find its way under there. Wait and see.  Here is where we actually...  Here is where we actually liked the IFS-ground clearance is better than a comparable solid front axle. The problem is that when you are driving a truck this big you sometimes need to drive by Braille, and the aluminum front diff is just waiting for some terminal abuse. We looked into the front skidplate offered by Tuff Country, but it only replaces the stock unit and doesn't add any protection to the differential. So now it's time to bust out some 3/16-inch plate steel and make one or else suffer the consequences.  Our first trip out to the...  Our first trip out to the dirt was at the OHV area near Gorman, California. We raced up there as the sun was setting to test our truck shod with some 315/75 R16 (35-inch) Dick Cepek radial Fun Country II tires and a Tuff Country 6-inch lift that cleared them. It was really a shakedown run more than anything else since it requires an hour drive from our shop and has some easy entry-level wheeling. Our first test was a speed run over some easy ruts. The truck could take an impressive amount of bashing, and though the front suspension has limited travel, it felt like the Tuff Country shocks were keeping it under control for anything but suicidal runs over the whoops.  With the truck loosened up,...  With the truck loosened up, we let it stretch its legs, and found that it really didn't stretch them very far. Even in the shallow ruts we were lifting a tire, and before we headed home we decided to run the 150+ inches of wheelbase up the concrete steps at Gorman. We realized that not only are the IFS and rear leaves stiff, but the hefty 3/4-ton frame keeps the bed and cab within 1 inch of alignment. The next time we go out we will try disconnecting the front sway bar to see what, if any, affect that has on the flex.  Our second trip out with the...  Our second trip out with the Red Sled (its length and turning radius remind us of a toboggan, thus the name) was at Pismo Beach outside of San Luis Obispo, California. We did some initial loops in the dunes and were feeling confident with the big-block power and aired down Fun Country traction, so the next thing we knew the Sled was getting aired out. It landed with an enormous thud followed by the banging of a busted passenger-side halfshaft.  Removing the busted halfshafts...  Removing the busted halfshafts and replacing them is really quite easy on this year Chevy. All you do is turn the front tires so you can access the shaft from behind. Then remove the shock and the bolts holding the shafts in (ours uses a large 36mm socket on the stub), and everything comes right out. If you do not have a spare halfshaft you will need to reinstall the stub CV portion into the unit bearing in the knuckle. If you do not install the stub, the unit-bearing will not be contained and will come apart as you drive home, allowing the wheel to fall off.  In order to get the halfshaft...  In order to get the halfshaft out of the stub-shaft CV first undo the metal band holding the boot on. Then you need to give the bell a few strong smacks with a big hammer to help the star in the stub CV get past the snap ring that holds it on the shaft. If possible, pry up on the ends of the snap ring to help removal, but definitely get the shaft out if you plan to drive on just the stub CV.  Upon removal we found the...  Upon removal we found the shell of the inner CV was busted, the boot torn loose, and some of the trunion bearings spit out. We stopped by the local auto parts shop and ordered up another spare, but ran into a small glitch. Since the busted CV bell rendered the axleshaft unrepairable, it didn't qualify as a core, and thus the price went from $50 to $100. Luckily we found some rebuildable cores at the local auto salvage yard, but they cost us another $25 each, so we ended up with about a $75 investment in replacing the broken halfshaft.  As we were heading home from...  As we were heading home from Pismo we noticed smoke billowing from under the Red Sled. We veered off the freeway only to find automatic transmission fluid dripping onto our hot exhaust. Thus began a two week intermission in our IFS testing as the truck sat stranded in San Luis Obispo with the tranny pulled out. In the end the crew at B&M Racing helped us out by doing an emergency rebuild along with some updates to the 4L80E, all of which we'll cover in a future story.  With the truck back up and...  With the truck back up and running and time slipping away in our month of testing, we headed to the Los Chi Chis trail in the Los Padre Forest area outside of Atascadero, California. Our testing turned into an impromptu fullsize Chevy run in the rain with five trucks ranging from an early '70s stepside to our '91 Red Sled. We were looking forward to seeing if our IFS barge could keep up with all its elder solid-axle kinfolk, but we quickly found it couldn't. We were barely in the trail 1,000 yards when we started sliding off the track at an off-camber section.  We tried a bit of throttle,...  We tried a bit of throttle, but even with our Fun Countrys aired down to below 20 psi, the truck just didn't want to climb in the slippery terrain. Rather than tear up the trail too much we opted for the hook end of a friend's winch cable. To help our mate's lighter Blazer pull our big pig back onto course, we turned the wheel tight, engaged the ARB Air Locker, and let the big-block do its thing, but the next thing you know we heard the now-recognizable bang of another passenger-side halfshaft detonating. Finally with some throttle action, the front Air Locker affording us three-wheel drive, and various angled winch pulls, we got the truck off the edge and turned around so we could trundle back to the head of the trail to repair and regroup. At this time we were down to our last spare halfshaft, it was half rain, half snowing, and when the locals informed us that we hadn't even made it to the start of the tough stuff, we decided that we weren't prepared for this trail until we made some upgrades to our front end. Luckily there was a local tavern to go get warm and discuss our options over a frosty brew.  With the reoccurring carnage...  With the reoccurring carnage to our passenger side we began discussing with other IFS Chevy owners and mechanics and began to see a trend. Thus it was not surprising when we measured off the knuckle and found that the passenger-side halfshaft was stretched nearly 3/4 inch longer than the driver side. We looked over the mounting brackets for the axlehousing, but none of them are notched to allow movement side to side, so we deduced that we either need a spacer to shorten up the halfshaft, or an aftermarket halfshaft that will allow for more slip, so we're working on both. Plus we are looking into longer shafts to go into the passenger-side halfshaft and stronger CVs that will stand up to more throttle when fully turned.  Finally after getting the...  Finally after getting the truck home, we returned to the alignment shop to test the theory that every time you go off-road in a lifted IFS truck you need to realign it. We found the steering toe-in was off just slightly with the passenger-side toed in a few degrees and the driver side toed out. We had noticed the truck slightly pulling on our drive home, but nothing excessive. However, we are going to get spare Moog Steering components before our next trail run just to be on the safe side. Check back in 30 days to see what else we break, 'cause we're headed back to the dirt.
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