Pinion Angle Correction

IT'S ONE OF THOSE LITTLE THINGS THAT JUST HAS TO BE DONE FIND OUT THE GRITTY DETAILS OF SETTING YOUR PINION ANGLE!

Pinion angle is one of the most important considerations on a lifted vehicle, but sadly it is often overlooked. The wrong angles can lead to horrible drive line vibrations, as well as premature failure of U-joints, driveshafts, pinion bearings and even transfer case output bearings. 'Pinion angle' is the difference between the driveshaft angle and the pinion angle on the differential. Driveshaft-related vibrations usually occur at roughly engine speed* in high gear.

Wheel/axle vibrations usually occur at 1/3rd engine speed or driveshaft speed because of the differential gearing. Every U-joint that operates at an angle creates a vibration. This is because the U-joint cross rotates with the shaft in a circular motion while also moving from front to rear. That rocking back and forth motion as it rotates causes the cross in the U-joint to accelerate and decelerate. This creates what is called excitation torque.

Keeping the pinion parallel

with the output of the transfer case will keep the angles the same, avoiding vibrations. A double cardan type constant velocity joint assembly has a centering mechanism that keeps the angle between the two internal U-joints correct, allowing them to completely cancel out the speeding up and slowing down and spin the drive shaft at a constant speed.

On axles with a double cardan style shaft, the pinion and driveshaft should ideally be at a 0-degree operating angle at ride height. It is important to allow the double cardan joint at the transfer case to take up the difference in slope between T-case output and the driveshaft.

Coil sprung live axle vehicles such as Patrols and 'Cruisers often require a change in rear control arm lengths once a lift has been added. The best ways to do this are by replacing the often thin OE rear links with a heavy duty replacement item.

Superior Engineering has a range of heavy duty upper and lower control arms ideal for your 4WD. With the rear control arms being a key component for both smooth handling and putting power to the ground, they are also one of the lowest points and vulnerable to damage when off-road.

Heavy duty control arms

are available for most popular models and have both extended fixed length and adjustable length control arms available to suit any lift height. Solid axle rear vehicles such as Toyota LandCruiser and Prado as well as Nissan Patrols are catered for with fixed / adjustable upper and lower arms available to allow the diff position in the rear wheel arch as well as pinion angle to be corrected.

With touring and towing vehicles in mind we also developed a bent upper control arm to help with clearance on vehicles fitted with a long range tank - these are also available in either fixed or adjustable. Long-arm extra-long competition style arms are also available with pinion correction as a key feature.

On leaf sprung axles, pinion angle can be adjusted by adding tapered shims between the semi-elliptic springs and the mounts on the axle housing. Six degrees is about the most angle you want to run with a wedge.

Beyond that, the spring perches should be cut off and replacement perches re-welded to the correct angle.

In some situations extended shackles may add a small amount of pinion angle adjustment as well as reducing the chance of shackle inversion. Front axles with incorrect pinion angles are often the cause of vibration as well as poor steering and bad handling.

Live front axle vehicles may also suffer incorrect caster angles and the steering problems that go with it such as shimmy or head shake. Although caster plates, drop boxes and drop arms will help the steering geometry, always be sure to check the pinion and driveshaft angles.

In some extreme lift setups, getting a balance between correct pinion angle and caster angle may require having your steering knuckles cut off and re-clocked, to regain acceptable kingpin caster angle.

IFS front vehicles have fixed pinion working angles.

Installing a reasonable size lift may require a diff drop to help CV working angle, always be sure to consider if the diff drop supplied has the correct spacers to allow for adequate pinion and diff rotation to reduce vibrations. When correcting pinion angle in any vehicle always check that the tailshaft open and closed length is within the limits of the shaft, if not the addition of a tailshaft spacer may fix the problem for minimal cost.

Gearbox or transmission spacer kits can also assist in controlling driveline vibration and noise by reducing the operating angles. These spacers are designed to fit neatly between the transmission or mount and the chassis.

Spacers may also help

In adding clearance for the tailshafts at full suspension droop. Please remember, if your axle has been rotated for steeper pinion angles, check for proper fluid levels in the diff housing, as you may need to overfill to ensure that the pinion bearing is not starved for oil.

Whilst there isn't a one-sizefits-all remedy, with proper driveline geometry, there is no reason a lifted rig can't run as smooth as a stock one. As with any suspension components you may need, contact your local 4WD suspension specialist for information on the best parts for your vehicle.

*Engine speed is the 1:1 ratio of engine revolutions to gearbox revolutions

Driveline vibrations related to engine speed are most noticeable at shaft or engine speeds above 1500rpm. Whereas wheel/axle vibrations are related more to road speed rather than driveshaft or engine speed.