DOUBLE-CARDAN U-JOINT WEAR PROBLEMS AND REPAIR COSTS

Starting around 1995, the extended cab 2wd V6 trucks with automatic transmissions came with the constant velocity “double-cardan” style U-joints (shown above), to reduce driveline vibrations on extended cab trucks.

The double-cardan U-joints have a high failure rate on S-10 Trucks which have been lowered, or driven heavily loaded, due to extremely bad driveline angles.

The extreme angles cause the grease to be thrown out of the cups that connect the two u-joints together, and this causes the center section of the joint to wear.

Driveshaft repair shops charge up to $300 to repair the double-cardan U-joints -- and if corrective steps are not made, the joints will fail again.

On a stock 2wd extended cab S-10, the mis-alignment between the rear driveshaft and the differential pinion shaft is typically more than 4°. On lowered or heavily loaded trucks. the mis-alignment can exceed 9°.

On extended cab trucks which use conventional u-joints, the poor driveshaft alignment can cause vibration problems. The extended cab driveshaft alignment kit is recommended for all 2wd extended cab S-10 trucks.

Advantages to improved driveline angles are:

• Reduced driveline vibration
• Less wear on driveline parts
• Better power transfer to the rear wheels
• Improved fuel mileage (minimal)
  
  

Transmission Output Shaft Alignment

The truck shown above is a 1998 Extended Cab with 4.3 V6 and automatic transmission. It has the ZQ8 Sport Suspension, which lowers the truck about 2", compared to "normal" trucks.

For proper driveshaft alignment, the transmission output shaft should point at the differential pinion shaft, when the truck is at normal ride height.

To improve driveline angles, the transmission was raised 3/4" with an aluminum spacer. Ideally, the transmission should be raised slightly higher, however, if the transmission were raised any higher, the transmission would contact the floor of the truck and rattle on bumpy roads, unless the floor of the truck is modified (hammered) to improve clearance.

The bolts that attach the transmission mount to the transmission are longer than stock to accommodate the thickness of the spacer, and are included in the driveshaft alignment kit.

Center Support Bearing Alignment

For proper alignment, raising the rear of the transmission, and raising the center support bearing is necessary on 2WD extended cab trucks.

In the above photo, the center support bearing was raised 1" to improve driveline alignment. If the center support bearing were raised any higher, the driveshaft would contact the floor of the cab on bumpy roads.

The bolts that attach the center support bearing are longer than stock to accommodate the thickness of the spacer, and are included in the driveshaft alignment kit.

Pinion Alignment Shims

The Stealth Conversions pinion alignment shims should be installed directly to the leaf spring with socket head cap screws supplied with the alignment kit.

When installing the shim onto the leaf spring pack, hold the spring pack together with a pair of Vise Grips® or C-clamps before removing the original bolt.

If lowering blocks are used, the alignment shim should be installed on top of the lowering block (see lowering block page). Stealth Conversions Lowering blocks are designed to allow bolting alignment shims on top of the lowering blocks.

Pinion Alignment Shim Installation Tips

The stock bolt (shown on top) that holds the leaf-spring pack together is 3/8" diameter by 2" long with a 3/8"-24 thread. It has a head diameter of 9/16", and a head height of 5/16".

When installing axle alignment shims to adjust driveline angles, the original bolt may be too corroded to remove without breaking — or a longer bolt may be necessary.

The 2° and 3° axle alignment shims from Stealth Conversions are about 1/4" thick at the center, and may require changing the original leaf spring bolt with a longer bolt. The Stealth Conversions Alignment shims come with a pair of 2-1/4" long socket head screws and hex nuts.

If the socket head bolt is too long and interferes with the lower shock plate, cut the bolt with a hack saw, or a grinder.

Lowering Blocks and Pinion Alignment Shims

On trucks lowered with lowering blocks, we recommend billet lowering blocks from Stealth Conversions.

The Stealth Conversions lowering blocks are unique in that the top of the block is threaded. This allows the pinion alignment shim to attach to the lowering block, while leaving the full height of the cap screw for the rear-axle locating hole.