Jaguar Repair: 1984 XJ6 setting rear output shaft bearing preload, caliper brackets, flange bolts

Question
Howard,

  I'm replacing the oil seals in the rear caliper brackets which requires the bearings to be set up.  The Haynes manual says to use a torque wrench or 'spring balance' to record the torque required to start the shaft moving when the nut is finger tight.  Then tighten the nut until the torque to turn the shaft is 1 - 5 lbf in more than the previous figure.  How do you connect a torque wrench to the shaft or hub ?  Make a bracket to span 2 of the caliper bolts and connect the torque wrench mid way ?  Or connect it somehow to the other end - the splined shaft ?  Or use a spring balance whatever that is ?  (Fish scale ?)  Also does 'lbf in' refer to inch-pounds ?

  Thanks,

  Steve.

Answer
Hi Steve,

Jaguar has some special tools to do the job but probably too expensive to buy just for one car job. There are a couple of ways to do the job at home.

First, the end objective is to have the nut tightened to a point that it requires 8 inch lbs to start rotation of the shaft in the hub. If you exceed that figure the crush sleeve must be replaced. (12 inch lbs = 1 ft lb) so you can't use a ft lb torque wrench.

Here are two ways to achieve this.

Make a plate to go across the center of the flange mount for the brake rotor with a bolt in the center to put an inch lb torque wrench on so that that bolt is dead center of the shaft.
Then clamp the hub assembly in a vice so it will not move. Use a flat bar as leverage at the flange bolts the hold the brake rotor to hold the shaft from rotating and snug up the large nut just by hand at first. Then remove your flat bar and put your inch lb torque wrench on the centered bolt and see what it takes to rotate the shaft. (It will probably be between 4 inch lb and 8 inch lb)(You can't use a ft lb torque wrench because 12 inch lbs = 1 ft lb.) Now, tighten the nut only so that a point of the nut only moves 3/16 inch and check the torque required to start turning the shaft. Repeat this process until you see 8 inch lbs to start turning the shaft and bend the lock tab over to lock nut in place and you are finished. If you exceed 8 in lbs, you can't just back off on the nut as you have destroyed the crush sleeve and now need a new one.

The other method would be to clamp the flange of the stub axle that supports the disk in a vice so that the stub axle is level with the ground. Now, make a short strap of metal that can be bolted to the caliper mount or other bolt hole. The strap must extend straight out from the center of the stub axle and you need to drill a hole EXACTLY 8 inches from the center of the AXLE. This gives you a 8 inch torque arm from rotational center. Then hang an exactly one lb weight on a wire placed in that hole that is exactly 8 inches from center of the stub axle while the torque arm is exactly horizontal to the ground.

Howard