My latest endeavor rebuilding the IRS I picked up a couple of months ago. I got the big bushing out and pressed in the new one, only to discover I may have pressed it in upside down.
How did I do it? I used the new bushing to press out the old bushing. I used a steel plate with 3 spacers between the low spots and the plate on the new bushing then pressed the old bushing out and the new one in at the same time. Safety 3rd right?
there is a pic in the FSM showing orientation of how the bush should be pressed out & in
the lip is quite small, and it may be possible to push the bush out, flattening it
I cant tell from the pics if they are correct
I think once the bushes are in like that, they are in, as they will be either correct, or the lip is flattened out, if they got pushed in the opposite way
there is also the issue of the âcutoutâ orientation in the bush, some say perpendicular, others say parallel, yours are at neither (but I dont think it matters all that much)
I did check the shop manual. This is what is says.
Removing.
Remove radius armâŚ
Use the special tool that I donât have, and press front bush from housing.
Refitting.
Press new bushing into the rear bush housing so that the bush is central in the radius arm
Use the tool I donât have to press new bush into the front bush housing so that holes in bush rubewr are in line with center of radius arm. Press bush into radius arm.
Press the bush into the radius arm until the bush ring is flush with the housing. When pressing, have the small hole in bush core upwards.
Well, CRAP!!
The holes donât line up. and I didnât press the bush with the small hole upwards. A long list of obscenities are what Iâm mumbling right now.
I canât remember if the hole in the radius arm is on one side onlyâŚin which case it should be on the bottom to drain water⌠But from memory I pressed the bush into the arm from the underside with the retaining flange on the topside.
I think you should have the cut outs aligned with the length of the arm âŚbecause the cut outs reduce the stiffness in this direction and this is needed to allow the bush to âflexâ in this direction. The suspension arm moves vertically and the radius arm pivots so something has to âflexâ.
The âeasyâ way to do it is to get a bit of bar stock slightly larger than the outside diameter of the large bush retainer and machine a hollow in it which just fits the outside diameter of the bush retainer. This holds the arm safely in the exact position while you do the pressing. Then machine a further hollow a smidgem larger than the bush diameter and deep enough to contain the bush width. You can then press the bush out of the arm into the hollow in the bar stock . I tried several times to press with steel on the thin rim of the arm but pieces flew everywhere so I went with plan B.
There isnât a picture other than the radius arm being pinched at the big end between two mandrels.
When I re-read the refitting bit. Or actually read it and didnât just skim over it, I noticed the bit about the holes in the rubber. The green bible states should be centerline. Iâm debating on sacrificing this bush in order to get it right. The other came out in bits. From several failed attempts.
The hole lining up will make a difference on the torsional twisting of the radius arm. The way it is now, itâs going to put undue stress on both bushes. Do I care? Right this minute. NO. Will I later? Count on it.
**
The good book says âholes in line with centre line of the radius armâ, Tony - as Mark states. And cryptically mentions a âsmall hole in the bush core upwardsââŚ
The cut-out holes influence the elasticity of the bush - so while misalignment may not be âcrapâ, it should not be wilfully doneâŚ
I did mine a few months ago. The cutouts are supposed to be front to rear to maintain the âJaguarâ ride. Turning them 90 degrees is what Jaguar did for the âsportpacâ upgrade.
Fitting the bush with the âcutoutâ orientation perpendicular to the radius arm center line is how the XJS Sportspack did it, slightly firmer suspension and a bit more âpassive rear steeringâ effect, as the forces will be compressing the rubber instead of flexing it.
Well this is intriguing. holes parallel to the front and rear of the car or perpendicular. I am a spirited driver, and enjoy tossing a car into the corner waiting for a bit of oversteer. Though Itâs been my experience in a Jag, specifically My XJ-S when the oversteer comes into play it happens very quickly and if youâre not on your toes, youâll be facing where you were. Does "passive Rear Steering help negate some of the âBOOM!!! youâre facing the opposite directionâ or intensify it?
That being said, I donât know what you mean by âpassive rear steeringâ.
If you put the holes across the longitudinal axis the mounts will have a bit less compliance fore-aft, so the IRS will move correspondingly less under accelerating/braking.
back to kinda the original question. or atleast one of them. is there a top or a bottom to the Radius arm? or is it strictly based on bush orientation?
Iâve laid the arms side by side, on the floor, and if I turn one upside down from the other, there is about 3/16 of an inch height difference between the two radius arms. though I canât tell if itâs related to the bush orientation or if the arm itself has a slight bend to it.
They didnât design this for dummies like me that would state âTOPâ on one of the sides.
Mark
I just had a look under my XJS. I put it back the way it was assembled. The arm has holes top and bottom so draining water is no issue. Mine is assembled with the retaining lip on the large bush end on the bottom.
The photo in the Haynes manual (Page 263) looks like it is the other way around with the retaining lip on the top.
This sorta makes sense because it means that the arm cannot slide down off the bushâŚbut there is a strap there to retain the whole thing anywayâŚand⌠it took about 10 tonnes to press it into position so nothing is moving anywhere in a hurry!!!
Either way wonât make a scrap of difference to the mechanismâŚ
The bottom suspension link is mounted on bearings attached to the diff. There is no âflexibilityâ in this connection apart from the deflection in the arm itselfâŚso I donât think there is any âpassive steeringâ designed into the mechanism.
The trailing arm is there to help absorb the thrust from accelerating and braking.
But the Jag arrangement has the bottom link taking all these loads so
the outside end of the arm is pushed and pulled by the wheel PLUS it is twisted in both directions by the wheelâŚthis is why it is quite a big thick tube of steel!!!
All these loads are transferred into the diff housing by two bearings which have to absorb the thrust and torsion.
The trailing link is such that it canât help with the torsion loads but can help with the thrust loadsâŚexcept that it is designed to pivot so rigidly connecting it to the back axle âŚwhich moves straight up and downâŚwould bend somethingâŚso there is a large flexible bush there which absorbs the movement.
It looks like there are compromises there to make the system work âŚbut it does work although the complexity makes it quite difficult to maintain the rear suspension and very difficult and time consuming to get it set up correctly!!!
Matt