Drive Shaft Care

The secret to trouble-free drive shaft life is regular checking and maintenance, especially after off road use. Regularly check the boots for perishing and tears – look for tell tale signs of grease being flicked out. The boots have to resist high temperatures from the engine and exhaust, high speed rotation and suspension and steering movement. Re-greasing the boots every 70,000 to 100,000 km is a good policy.

Fitting boot protectors provides good protection for off road use. On the older models MY80-84, standard boot protectors were fitted front and rear. It is an easy job to increase the size of the protectors for better protection. For the earlier 1970’s L57 and 88, brackets had to be fitted front and rear. Saddle type brackets could be bolted onto the front steering arms. The best setup for the rear inner joints on lifted models and early L series, MYs and 85-93 L series is to make C-shaped brackets that are welded onto the diff carrier. This moves the boot protector closer to the boot. For the rear outer joints, make L-shaped brackets that are welded onto the suspension swing arms.

Click here to see photos of boot protectors on an L-series rear

From the 85 L series to the current models, fitting useful sized boot protectors is not possible because the sway bar is in the way. From 1997, the front outer boots of the Foresters, Outbacks and Libertys are made from a hardwearing hard plastic compound. From the first Libertys to the current models, the rear outer boots are quite well protected by the base of the struts, whilst the rear inner boots are quite well protected by the diff carrier and suspension assembly.

The front outer joints are called CV (constant velocity) joints because they rotate, move up and down with the suspension, and turn with the steering. The front inner joints and all of the rear joints are called DOJ (double offset joints). They only rotate and move up and down with the suspension.

An easy method of diagnosing front joint noises is:

·         If the clicking noise comes from the front on tight turns, it is a CV joint.

·         On a right hand turn, it will be the LH front CV clicking because most of the car’s weight is transferred to the LH side (and vice versa).

·         If the clicking is heard when accelerating or decelerating, it is an inner front DOJ.

To extend the life of the joints once they start clicking, the complete shaft and the inner and outer joints can be removed and changed from the LH side to the RH side and vice versa. This means that they will now rotate in the opposite direction and will now click only in reverse gear. A good rule of thumb is that if the ball bearings fall out of the cage of an inner DOJ when the joint is apart, then there is a fair bit of wear in the joint. If the inside gear is rotated 180°, then the ball bearings are moved to a new, unworn position.

Another problem that can affect the front inner DOJ is that the cup’s internal welch plug can work loose, allowing grease to leak out. Occasionally, the welch plug can fall out completely. If this occurs, the welch plug becomes mashed up, causing a bad vibration. When a joint is apart, check that the welch plug is seated correctly. If not, tap it into place and then tack weld in using a cut down soft drink can to protect the cup from weld splatter. If required, new welch plugs may be purchased

The four rear DOJs are usually trouble-free if they are maintained regularly. Two common problems can occur:

·         The outer joint may rust onto the wheel’s stub axle spline, or the inner joint may rust onto the diff spline. This can make joint removal very difficult. Always grease all splines thoroughly with bearing grease (however, moly driveshaft greases are not recommended as water and moisture break them down).

·         A chattering sound may emanate from the rear LH side when cruising on bitumen, but the sound disappears when 4WDriving under load. The sound is caused by loose fitting splines on the stub axle due to wear because roads are rougher on the LH edge. First, check if the outer rubber packing washer has been fitted. If it has, fit an extra fibre washer to take up the slack. As with the front assembly, switching the left and right driveshafts will reverse their direction. If the outer rubber packing washers and spring pins appear worn, it is a good idea to replace them. This loose spline problem does not occur in all models. In models since the 89 series 1 Liberty, the rear drive shaft axle and wheel stub axle came as a complete unit, similar to the front drive shaft assemblies; and the spring pins on the inners were replaced with internal circlips.

The easiest way to change boots on front drive shafts, either at home or on trips, without using any special tools is to remove the complete drive shaft, still connected to the wheel hub. By doing this, the wheel bearings and seals are not disturbed. Although boots can be changed on the car, it is much easier changing them off the car (unless you have access to a hoist). On all models, the easiest way to remove front drive shafts is:

1.        hit out the inner DOJ spring pin,

2.       remove the steering rack end ball joint,

3.       remove the bottom suspension arm ball joint,

4.       remove the sway bar mounts,

5.       remove the bottom strut leg bolts (on all models from the Liberty on, make sure these bolts are replaced to the same spot so that the wheel alignment is not affected),

6.       for later models fitted with ABS, unbolt the wheel sensor,

7.       unbolt the brake caliper and position it out of the way with wire, and finally

8.       carefully slide out the complete shaft.

If the outer CV boot needs replacing, the inner DOJ must first be pulled apart in order to gain access to the CV joint. To remove the inner boot, loosen the clips, pull back the boot, remove the cup’s big circlip and pull off the cup to expose the ball bearing cage and inner gear. Then remove the inner retaining circlip, which allows the unit to slide off the axle. The boot can now be removed, allowing access to the outer CV boot. The outer CV is held together by an internal circlip. This circlip may be pulled apart using the correct tool, however the shaft must first be removed from the hub.

DOJ Cage

DOJ Race

For re-greasing, clean the joint with petrol or a similar solvent and dry. If you are only re-greasing, wipe away the old grease and repack. For the outer CV’s push in as much grease as possible until it starts to ooze out, then build up around the joint, ensuring that all surfaces that the boot seals on are clean and free of grease. Then fit the inner DOJ boot, followed by the inner bearing cage and its circlip, making sure that the recess is facing the outer end of the shaft. Pack grease in and around the bearing cage, again until it starts to ooze out. Then fill the outer cup to about ½ to ¾ full of grease, refit the cup over the inner bearing cage and put the cup’s big circlip back in place, ensuring that the circlip’s ends meet on a raised ridge and not on the bearing grooves. Most aftermarket boot kits supply a measured tube of grease.

The best (and easiest to use) boot clips or bands are the original factory fitted over-centre type. If undamaged, they can be re-used. Even if they break at the pivot point, they can still be re-used by bending a small 90° angle at the break to make a new pivot point. This, however, shortens the clip and makes it a tighter fit. Genuine supplied and after market clips are always the pull through types. They are more difficult to fit but work well if tightened properly. There is a special tool available for the job. If you do not have the tool, use a flat bladed screwdriver at the sleeve as a stopper and pull the band through with pliers, then bend the band back and over, fold down the holding tabs, tap down the tabs with a hammer and cut off the excess band. Always tighten the big clip first, and then “burp” the boot by pushing the air out before tightening the small clip. The clips should all line up with their cut ends pointing away from the direction of rotation. Another good idea is to change both boots when the shaft is apart as it can save a lot of work at a later date. Cable ties are not recommended for use as replacement clips because they are susceptible to heat distortion, but they are make a good temporary clip in an emergency.

All later model Subarus fitted with the new plastic boots on the front outer CVs have a different type of clip with three retaining hooks and a raised section that adjusts the tension. Because the plastic material is harder to seal, these clips must be tightened to 50 ft lb of torque using a special tool. By all reports, these boots are very durable.

It is a good idea to keep an emergency boot repair kit comprising a front outer CV boot, a front inner DOJ boot, a rear DOJ boot, grease and clips to suit the boots. For a quick repair, carry something to wrap around the boot to stop the grease from flicking out – stockings, rags or plastic bags and duct tape or cable ties to tie the ends. These days, there are many different types of suitable grease other than the tried and proven Castrol LMM grease.  Nowadays companies like Driveline Services (the club’s guest speakers at the May General Meeting) use a specially formulated high temperature grease for the inner front DOJs which resists the heat from the engine and exhaust. Today, only about 5% of Driveline’s business is reconditioning driveshafts because they can supply new complete shafts or single joints at very competitive prices.  Driveline also supply boot kits consisting of the boot, stainless steel clip, inner small circlip and a measured tube of suitable grease.

David Martin SC180