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Chevy and GMC Truck Buildup Tech Tips - Weak Links, Strong Fixes

Posted in How To on June 26, 2006 Comment (0)
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Chevy and GMC Truck Buildup Tech Tips - Weak Links, Strong Fixes
Photographers: Courtesy the Manufacturers
129 0405 01 z+gm truck buildup tips+lead shot

You can call 'em weak links, design flaws, or whatever you wish. The fact is, there isn't a vehicle made that doesn't suffer to some degree from model-specific quirks. Some of these quirks rear their ugly heads after normal use, while others are the result of accumulated stress brought on by years of 'wheeling.

In this initial installment of Weak Links, Strong Fixes, we take a look at fullsize GM trucks and SUVs. Keep in mind that Chevrolet and GMC vehicles are almost identical, so many of these items apply not only to pickup trucks, but also to the Blazers, Jimmys and Suburbans. To help generate this list, we asked aftermarket GM experts at Missouri Off Road Outfitters and Off Road Design as well as some of the readers of ColoradoK5.com to share their experiences. The following reflect some of the more common problems that owners of GM trucks say they face. Without a doubt, there could be many more items included in this installment, but due to space constraints, we whittled them down to a reasonably sized list that includes the most important and compelling items.

We've tried to include information about which models the problem directly affects, what exactly happens when the component or part fails, and of course we would be remiss if we didn't include info on what you need to fix the problem and where you can get it.

129 0405 02 z+gm truck buildup tips+cracked frame

ALL CRACKED UP
Weak link: Frame cracks around steering box
Models affected: Every straight-axle GM truck and SUV, though pre-'73 trucks don't seem to exhibit the problem as frequently as those built after 1973.
What happens: By today's standards, the GM frames of this era are fairly weak. This is one of the contributing factors to the notorious frame cracking around the steering box (shown).
Sturdy fix: Off Road Design offers a steering-box brace that can help avoid this problem. If cracking has already occurred, Off Road Design offers a weld-on repair kit.
Contact: Off Road Design.

129 0405 05 z+gm truck buildup tips+differential carnage

WEAK AXLE
Weak link: The Corporate 10- and 12-bolt rear axle
Models affected: Late '60s-'91 1/2-ton
What happens: The pros say that these axles seem to handle a 33-inch-diameter tire with no problem, but depending on your driving style and equipment, 35-inchers and up require modifications. Common parts failure when running large tires on the trail include the factory limited-slip differentials, axles, axle bearings and the housing itself.
Sturdy fix: Install a quality locker, quality axleshafts like those available from Off Road Design, Green wide-repair axle bearings and a Missouri Off Road Outfitters Over The Top axle truss.
Contact: Missouri Off Road Outfitters, Off Road Design.

129 0405 06 z+gm truck buildup tips+solid front axle

WEAK AXLE, 2
Weak link: The Corporate 10-bolt and Dana 44 solid front axles
Models affected: Dana 44 '78-and-older, 10-bolt '79-and-newer
What happens: With 35-inch or larger-diameter tires, expect to break a stock axleshaft, especially if using a limited-slip or locker. If you have a lot of weight on the front of your truck, like a snowplow, or if your vehicle sees hard off-highway use, the axletubes can bend. Most of the time the driver-side tube will bend where it enters the centersection. The earlier 3/4-ton Dana 44s had external-spline locking hubs, which are prone to working loose and breaking the bolts.
Sturdy fix: For use off-highway, the pros say that depending on driving style and equipment, the front 10-bolt and '44 can withstand a fair amount of abuse, if they're upgraded. Try installing a pair of chrome-moly or heavy-duty axleshafts and solid Spicer U-joints, and, if you're using a true locker, Warn fusible hub links. Missouri Off Road Outfitters offers a bolt-on under-the-axle truss for both the 10-bolt and the '44 housings, and the company offers its Rock Bruiser diff covers to guard against diff-cover damage (all shown in photo). To solve the hub-bolt breakage problem on 3/4-ton Dana 44s, either carry a wrench and check the bolts often, or swap the entire spindle-out assembly for a later internal-spline 3/4-ton setup.
Contact: Missouri Off Road Outfitters, Off Road Design, Warn Industries.

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ENGINE SUPPORT
Weak link: Engine crossmember
Models affected: '73-'84 trucks and SUVs
What happens: Snowplowing or hard trail use flexes the frame enough to completely break or crack the engine crossmember.
Sturdy fix: There are several options. You can build a new crossmember, weld the broken one, or replace it with an '85-and-up crossmember, which is a better design and less prone to cracking. The challenge, though, is that it is almost impossible to remove the crossmember from a donor vehicle unless the engine is already out of the vehicle. Missouri Off Road Outfitters offers a bolt-in replacement crossmember for vehicles lifted more than 4 inches (shown), and as a bonus it also facilitates the use of a straight drag link in crossover-steering conversions.
Contact: Missouri Off Road Outfitters.

SAGGY DOORS
Weak link: Door hinges
Models affected: '88-and-up trucks and SUVs
What happens: The door hinges on pre-'88 models wore out fast, but the '88-and-up hinges wear even faster. When they wear, they cause door misalignment. This problem is even more prevalent on lifted trucks where the door is used as a grab handle for passengers to enter the vehicle.
Sturdy fix: Replace the hinge pins and bushings.
Contact: Your GM part supplier or your local body shop.

WEAK IDLER ARM
Weak link: Steering system two-bolt idler arm
Models affected: '88-'92 trucks and SUVs
What happens: The two-bolt idler arm is not very stout, and it wears quickly.
Sturdy fix: Replace the two-bolt idler arm with a later model three-bolt idler arm. The swap requires drilling a new hole at the point where it mounts to the frame, but it uses the same end at the steering system, so it is a retrofit. The three-bolt idler arm is much stouter and heavier than the two-bolt idler arm.
Contact: Your local GM dealer to order the three-bolt idler arm.

129 0405 10 z+gm truck buildup tips+drive sleeve

DRIVE SLEEVE
Weak link: Drive sleeve connecting either the Turbo 350 or SM465 transmissions to the NP205 transfer case
Models affected: '84-and-older
What happens: In normal off-highway use they don't usually break, but once they start to wear they tend to break quickly. When the internal drive-sleeve splines strip, the transmission is effectively disconnected from the transfer case. In this photo you can see a worn drive sleeve (left) compared to a new drive sleeve.
Sturdy fix: Replace with a new drive sleeve, available from Off Road Design.
Contact: Off Road Design.

STEERING WOBBLE
Weak link: Steering column tilt assembly
Models affected: '73-'91 vehicles equipped with tilt steering.
What happens: As these trucks age, the tilt assembly comes loose and wobbles. Most people believe that the column is worn out, but this is not the case. For some reason, GM did not use thread-lock on the four screws on the tilt assembly so they loosen, causing the wobble. This is especially found on lifted trucks where the steering column is used as a grab handle during entry.
Sturdy fix: Disassemble the steering column and reinstall the four screws using thread-lock compound. This will permanently solve the problem.
Contact: Do-it-yourself fix.

129 0405 09 z+gm truck buildup tips+4x4 posi lock

4WD FAILURE
Weak link: Thermal Linear Actuator
Models affected: '88-'98 trucks and SUVs
What happens: An overly complex device called the Thermal Linear Actuator (TLA) fails, and four-wheel drive won't engage. See, when you engage the transfer case, the left-front axle begins to turn, and the TLA is engaged. The TLA creates an electrical current that heats an inert gas, causing it to expand and move a plunger. The left axle and intermediate shaft are connected by spider gears in the differential, and the thermal actuator, once heated enough, extends approximately 1 inch to slide the shift collar and fork over the intermediate shaft to connect it to the right-front axle. Other drawbacks to the TLA include the fact that four-wheel-drive engagement can slow considerably in cold weather and it can disengage if submerged in water.
Sturdy fix: Sure, you can replace the TLA with a new unit, but the hot ticket is to eliminate this horrible idea altogether and install the 4x4 Posi-Lok (shown). It allows the driver to engage the shift collar and fork from inside the cab with simply a 1-inch pull on the 4x4 Posi-Lok cable. As a bonus, it allows you to disengage the front axle when in low-range, thus allowing two-wheel-drive low-range operation.
Contact: 4x4 Posi-Lok.

129 0405 08 z+gm truck buildup tips+crossover steering system

WEAK STEERING
Weak link: Stock steering for straight-axle trucks
Models affected: All straight-axle trucks and SUVs
What happens: Stephen Watson at Off Road Design says that stock GM steering does not function correctly in twisty off-highway situations when the vehicle is equipped with a suspension lift of more than 4 inches. Further, the stock GM tie rods are very susceptible to trail damage.
Sturdy fix: Install a crossover steering system, like Off Road Design's kit (shown). They offer a kit for the 10-bolt, Dana 44 and Dana 60 axles. If you use a crossover steering system with a straight drag link, remember to use Missouri Off Road's engine crossmember to avoid contact between the drag link and the factory crossmember. Off Road Design offers a couple of different levels of tie rods for stock applications, as well as a high-steer kit to mount the tie rod on top of Dana 60 knuckles, above the leaf springs, to keep it out of harm's way. Missouri Off Road Outfitters offers heavy-duty drag links for crossover steering setups and heavy-wall tie rods for either stock or crossover steering.
Contact: Missouri Off Road Outfitters, Off Road Design.

129 0405 15 z+gm truck buildup tips+14 bolt differential housing

LOW GROUND CLEARANCE
Weak link: Corporate 14-bolt full-float rear-axle ground clearance, thin diff cover and weight
Models affected: All GM 14-bolts
What happens: Overall, everyone is in agreement that the 14-bolt is an excellent rear axle, but they do suffer from minimal ground clearance, paper-thin rear differential covers and they're heavy overall.
Sturdy fix: Shaving and smoothing the bottom of the axlehousing, usually with a Sawzall and grinder, can improve ground clearance. Replacing the differential cover with a Missouri Off Road Rock Bruiser diff cover will eliminate issues with the stock cover (shown, with a Missouri Off Road Over The Top axle truss). Replacing the drum brakes with discs will shave about 100 pounds from the total weight of the axle, and Off Road Design offers a bracket kit for 14-bolt full-float axles that allows the use of General Motors 3/4-ton front rotors and calipers.
Contact: Missouri Off Road Outfitters, Off Road Design.

POOR ARTICULATION
Weak link: The IFS front suspension
Models affected: '88-and-up
What happens: This suspension offers a great ride, but suffers from poor articulation and durability when used for even moderate off-highway travel.
Sturdy fix: For serious off-highway performance, replace the IFS with a solid front axle using a conversion kit like the one offered by Off Road Unlimited. It includes all of the necessary bracketry and hangers. ORU offers all of the components to complete the swap, including leaf springs from 2 to 12 inches in raised height in 2-inch increments, brake lines, front CV driveshaft and yoke, complete Dana 44 or Dana 60 axles and even a crossover steering kit.
Contact: Off Road Unlimited.

129 0405 12 z+gm truck buildup tips+leaf spring shackles

BAD SHACKLES
Weak link: Front leaf-spring shackles and bushings
Models affected: All solid-axle trucksWhat happens: The front shackles on straight-axle vehicles are notoriously weak and the bushings wear out quickly.
Sturdy fix: Off Road Design offers a heavy-duty front-shackle kit (shown) that strengthens this area with a stronger, harder-compound bushing, a swap to 1/2-inch-diameter shackle bolts (stock are 7/16-inch diameter) and 3/8-inch-thick shackle plates (stock are about 1/4-inch thick). They're also greaseable, so you can keep the pivots lubed.
Contact: Off Road Design.

T-CASE INTERNALS
Weak link: NP203 transfer case internals
Models affected: '73-'79, all duty levels
What happens: The NP203 has problems with chain breakage, as well as differential-assembly failure.
Sturdy fix: Rebuild the unit with quality aftermarket components, or swap in a beefier NP205 using adapters available from Off Road Design and others.
Contact: Off Road Design.

WEAK RAG JOINT
Weak link: Steering-shaft rag joint
Models affected: All straight-axle models
What happens:The rag joint that connects the steering shaft to the steering box wears out and breaks, leaving you with no steering control.
Sturdy fix: Either replace with a new rag joint, or better yet, replace the whole steering shaft with a dual U-joint telescopic heavy-duty steering shaft from Borgeson Universal. This kit's design eliminates the rag joint altogether.
Contact: Borgeson Universal.

WIMPY LINKAGE
Weak link: SM465 manual transmission linkage
Models affected: Pre-'85, all duty levelsWhat happens: When the vehicle is twisted up off-highway, the pre-'85 manual clutch linkage tends to bind up.
Sturdy fix: Beginning in '85, GM switched to a hydraulic assembly that cured the binding problem. This hydraulic clutch assembly can be retrofitted to the pre-'85 units.
Contact: Your local salvage yard or GM parts supplier.

129 0405 11 z+gm truck buildup tips+broken adapter

WEAK ADAPTER
Weak link: Broken transfer case-to-transmission adapters on NP205-equipped vehicles
Models affected: All models equipped with an NP205 transfer case
What happens: The adapters tend to crack or break (shown) due to standard wear and/or improper length front driveshaft that bottoms out under flex and puts pressure on the transfer case.
Sturdy fix: Make sure you have the proper-length driveshaft. It's also important to make sure that the strut rod from the bellhousing to the side of the transfer case be retained to help keep the transfer case from flexing. Often, this part is removed and discarded by the unknowing when swapping transmissions or transfer cases. Off Road Design offers new or used replacement adapters.
Contact: Off Road Design.

129 0405 04 z+gm truck buildup tips+shock mounts

SHOCK MOUNTS
Weak link: Rear upper shock-absorber mounts that tear from the frame
Models affected: '73-'91 1/2-ton vehicles What happens: This is a common failure, caused by a number of factors. For those who travel off-highway frequently, the problem is more common, as the shocks are the limiting factor in the rear suspension, causing undue stress at the mount.
Sturdy fix: Steve Frisbie at Missouri Off Road Outfitters says he has successfully welded washers to the inside and outside of the frame, effectively rebuilding the mount. He says he used two different outside diameter washers to eliminate the weak spot in the frame. Missouri Off Road Outfitters also offers a rear bolt-in shock crossmember (shown) that angles the shocks towards the center of the frame and allows increased suspension travel and eliminates the need for the stock mounts.
Contact: Missouri Off Road Outfitters.

129 0405 07 z+gm truck buildup tips+front axle king pins

THE KING PIN
Weak link: Dana 60 front axle king pins
Models affected: All vehicles with Dana 60 front axles
What happens: The king pins wear, creating "death wobble," as well as other maladies. They will wear even faster if the vehicle is fitted with larger tires.
Sturdy fix: Off Road Design offers a kingpin rebuild kit (shown) or just new kingpin springs and bushings.
Contact: Off Road Design.

129 0405 13 z+gm truck buildup tips+doubler kit

SHORT DRIVESHAFT
Weak link: Front driveshaft length
Models affected: All duty levels, '73-'91
What happens: Steven Watson at Off Road Design says that the front driveshaft is a bit on the short side and with some lift and transmission combinations you can run out of angulation capability. Watson says that this is most common with the TH350/NP205 or the SM465/NP205 combinations with a 6-inch-or-higher suspension lift.
Sturdy fix: The solution is to have a company like Tom Wood's Custom Driveshafts or High Angle Driveline make a shaft with more angulation capability. Another option, if a bit pricy, is to use the Off Road Design Doubler Kit (shown), which moves the NP205 approximately 6 inches to the rear of the vehicle.
Contact: High Angle Driveline, Off Road Design, Tom Wood's Custom Driveshafts.

STIFF HINGE
Weak link: Hood hinge stiffening
Models affected: '73-'80 trucks and SUVs
What happens: The hood hinges stiffen when not lubed regularly, thus requiring more force to close the hood. This pressure on the hood causes it to buckle.
Sturdy fix: Keep the hinges lubricated to keep them from stiffening. If the hinges are already stiff, replace them. They're relatively inexpensive, and easy to install.
Contact: You local GM dealer.

TRIPPY FUSIBLE LINK
Weak link: Firewall-mounted fusible links
Models affected: '73-'91 all duty-level trucks
What happens: The insulation on the fusible links tends to degrade due to close proximity to the exhaust manifold. This can cause the fusible link to trip.
Sturdy fix: Steve Frisbie of Missouri Off Road Outfitters says that he cured this problem by replacing the links with blade-type fuses and holders.
Contact: Do-it-yourself fix.

Sources

Borgeson Universal
Torrington, CT 06790
860-482-8283
www.borgeson.com
Tom Wood's Custom Driveshafts
Ogden, UT 84404
801-737-0757
www.4xshaft.com
4x4 Posi-Lok
Coldwater, MI 49036
517-279-7177
www.4x4posi-lok.com
High Angle Driveline
Paradise, CA 95969
1-530-877-2875
www.highangledriveline.com
C.A.R.S. Inc.
Rochester, MI
800-CARSInc
www.carsinc.com
Off Road Unlimited
www.offroadunlimited.com
Missouri Off Road Outfitters
Marshall, MO 65340

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