Radius arms. which side is up - IRS First Time Rebuild

(tony) #21

I am trying not to get confused, so I went and looked at my spare parts pile

the way way the Radius Arm is made and pictured shows clearly their is a top and bottom
for a MKX

there is another rad arm in the pile…it is even sided in appearance, and I believe from an XJ

there appears to be only one distinguishing feature, which is the ridge in the big end bore, no wings pointing down, no bolt flange at the small end

it appears they could be mounted either way, but it also seems that there is an intended orientation

I would suggest the lip should be at the top, as their is a retaining strap at base,
could be wrong of course

(Mark Lee (Pay Pal Patron)) #22

Status update.
I got the F’d up bush out with little to no drama. now I see what everyone’s on about with respect to the ridge.

Here’s the Rad arm that I pushed the bush over the top of FFS.


According the Green Bible; it reads (paraphrasing) to use the mandrel (that I don’t have) and press new bush into front housing so the hols in the bush rubber are in line with centre line of Rad arm. Press bush ring into rad arm until flush with bush housing When pressing bush have the small hole in bush core upwards. Ok, I didn’t paraphrase.

So here’s the next question. is there a right and left Rad Arm? I didn’t mark them. the non Jag bits next to the rad arms are what I used to push the bushes out. the top one looks bent to me :face_with_monocle: I truly hope that’s not the case. also at the big end. there is what looks like an L scribed under what’s left of the paint. the bent flange was there before I monkey’ with it.

Now onto hub removal to replace the u-joints, bearings (maybe - I haven’t decided yet); I want to free up the brakes so I can get a better idea of the condition of this unit.

Oh, yes; that is a 1988 Chev Cavalier Z/24 convertible peering through the big hole. My mum bought the car new. Drove it for 6 months and she hated every minute of it. Not because it’s a shit car but the road noise due to the soft top and no lining.

(Andrew Waugh) #23

Here’s a picture of the arms from an S Type:

AFAIK the trailing arms were a “U” profile up until the XJ, with the correct orientation having the “U” inverted.

On cars with a rear ARB the tabs for that at the small end must point up, notice also that the hole for the small bush is offset down from the C/L of the arm.

The lip in the hole for the large bush is at the top of the hole - it’s function is not to stop the bush falling out, but rather to locate the bush. If the bush weren’t pushed in far enough then the arm might contact the body at full compression, or if pushed in too far then it might contact the safety strap at full droop.

The XJ parts list shows the same part number for both arms, so I would say “no”, otherwise the large bushes would need to be installed opposite to each other w.r.t. the datum lip, and that isn’t the way Jaguar did things. (It would be mentioned in the manual if the large bushes were installed differently in the left and right arms.)

(tony) #24

good to see ur well on the way to getting it sorted.

I put a straight edge on the XJ arm…up & down is slightly different…didnt check handedness

was gratified to see “XJ LB” scratched into the old arm !

when I did my 420G IFS rebuild, I dot-stamped most parts with a punch L or R

I found this surprisingly helpful in assembly, avoids dumb mistakes, and is a permanent bespoke evidence of workmanship

(Frank Andersen) #25

Definitely not, Matt - the intent of the inner and outer pivots is to only allow vertical suspension movement. No fore and aft movement is intended as it will affect rear wheel toe - which should be parallel +/- 0,08 mm. Any rear toe changes will ‘wag the tail’ - which will cause unintended oversteering, imprecise handling…

xj6 85 Sov urope UK/NZ)

(Mark Lee (Pay Pal Patron)) #26

So what you’re saying is to put the new bush (the big one) with the holes parallel to the radius arm (center line) as the book reads, and not 90 degrees from the radius arm (center line) as the “Sportpac” upgrade?

(Mark Lee (Pay Pal Patron)) #27

Well I got the hub and carrier off.

Well I got the hub and carrier off; I did take both nuts off the outer fulcrum shaft - I hope that isn’t going to be a problem later on. Ugh.

What prompted this is I thought the brakes were brakes had rusted themselves to the rotor. Apparently that’s not the case. The hub is frozen cock stiff. Is this common?

so it looks like I will be doing bearings. Also there was only 1 masticated shim on the outer fulcrum shaft.

Back to the hub. so if it’s frozen that means there isn’t any grease or the grease has solidified. Which Im thinking this is definitely the case, I’ve been picking off hard green boogers off the carrier around the weep hole. I think the boogers was green grease in a previous life.

Oh goodie, something else to press - the hub from the carrier. another mandrel that I don’t have. This is getting old.

I’m open to suggestions on how others have popped out the hub and bearings. It’s 1:35am where I am at I’m going to call it a night.

Cheers and thank you for your help.

Also I’m open to suggestions on how to get the hub and fulcrum bearings, seals, spacers out.

(Andrew Waugh) #28

There should be a bit of a notch in the carrier where you can get a drift onto the edge of the outer race for the yoke bearings.

The outer fulcrum outer races stick out far enough from the castings, so all you need is a long, thin punch.

Consider changing the seals on the outer fulcrum from the original felt to a modern lip seal (no mods to the carrier necessary). National 471652, Timken: (CR) 11123 ID:1-1/8 OD: 1-5/8 L:1/4

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #29

Be that as it may, the Jaguar IRS does feature toe changes with suspension travel. As the trailing arm swings to near full suspension compression, that wheel is pulled forward. The inner fulcrums don’t flex, but the entire subframe moves on its soft mounts. That means the rear wheels remain aligned with one another, but both of them move together in response to cornering forces.

If you want to design a suspension that doesn’t do this, you relocate the forward end of the trailing arm inboard. If it’s in line with the inner fulcrum, there is no steering effect at all. You can look over the designs of various IRS’s on different cars and see how the designers addressed this issue.

There is a mod for the Jaguar IRS that works like this: A T-shaped plate is fashioned from aluminum that rigidly bolts to the bottom center of the rear subframe in place of the rectangular plate there. This T-shaped plate extends forward and then out to the sides where it mounts to the bosses for the forward ends of the trailing arms using the OEM soft mounts. The OEM trailing arms are omitted; this plate holds the diff aligned and therefore the entire suspension hanging off it. The IRS is still isolated with rubber to minimize noise and vibration. All steering effects on toe are eliminated. You can add diagonal trailing arms from the inner corners of that T-shaped plate (and therefore in line with the inner fulcrums) out to the uprights using Heim joints at both ends (no flex needed, you’ve got flex in the subframe mounts but some argue that the Jag swingarms are so beefy it’s not really necessary.

(Mark Lee (Pay Pal Patron)) #30

Well I haven’t made much progress today, and I’m not too happy about that. Trying to figure out how to get the hub out of the carrier. it’s too wide for my press; and I’ don’t think I’ll be drifting this hub out.

the spacer has all of the indications that it was spinning.

This carrier is a wonderful geological study. the hard glass like substance that I believe at on time was grease, has hardened to the point it chips off the parts. like tar as a solid.

That is the grease. that has hardened

Here’s what’s under the grease seal.

That shit is hard! At first I thought it was another seal or something that once was solid and properly shaped; that had dissolved and solidified in the grease. Nope. just what was once grease. now on its way to returning to it’s natural state rock.

Initially the hub wouldn’t budge in the carrier. but after a half a can of WD40 rust penetrant, & trusty Ol’ Brakekleen, the hub spins freely. By the Way, did you know that you can get brakekleen by the gallon containers? Happy Days!! yes, in gallons as well as a 55 gallon drum. The world is now a better place. Check it out -> [Amazon.com] (https://www.amazon.com/CRC-05090-Brakleen-1Gal/dp/B000CIPUU0)

I’ve been using this water based “solvent” that does work if you let the parts sit in it over night. I wouldn’t recommend putting alkaline or non-furous metals in it over night, the solvent dissolves the oxidation layer. Does it work? to be fair yes it works. Quickly? Not even!.

Brakekleen dissolve grease and oil, and does it very quickly? WD40 rust penetrate is another good one for cutting through grease and grime and smells nice too. So does brakekleen. but I can’t afford to lose anymore brain cells. Sorry side tracked.

Back on track.
Before I went to bed last night I hit it with a bit of WD40 rust release penetrating oil. To come to find the spacers had fallen out. Both of which have all the signs of spinning. Initially I though the input shaft coming off the u-joint was discolored from old grease. I’m not so sure anymore I think it’s tempered from heat. you can also see where the spacers were spinning too. I can’t catch a finger nail on it.

I’m concerned that I’ll have to replace the input shaft as well as the carrier because the shims just fell out on the table.

Are both bearings pressed on to the hub? before and after the splines?
I’ll be posting videos of this endeavor on youtube. soon.

(Frank Andersen) #31

If the subframe moves with the wheels still parallel, Kirbert - there is no toe change, you cannot have both. But you will then have rear wheel steering on bumpy roads - and bump steering doesn’t seem like a desirable built-in feature for a Jaguar…

xj6 85 Sov Europe (UK/NZ)

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #32

While you’re at it, you might consider a modification to that stub axle to radius the root of the threads for that Jesus nut. That entire threaded end snapping off was common enough that GT Jaguar (now defunct) offered a kit for repairing it that involved drilling and tapping a hole and installing a bolt and washer instead of the nut. There’s a sketch of the mod called for in the Book, but really any reputable machine shop should know what to do.

(tony) #33

from memory on your questions, there is cutouts in the carrier housing to allow bearings to be tapped out, hard to spot with all that grease.

at that time you should be able to tell if the bearings have spun

there is a procedure outlined somewhere in some FSM that shows a jig for pressing the hub from carrier etc

I have seen where the spacer is scarred before. I am of the opinion this is caused by improper bearing setup/clearance

(Aristides Balanos) #34

It works, more or less, the same way as a skateboard…
The radius arms are positioned in such a way that as the car rolls on a turn they pull the one swing arm and push the other, thus slightly turning the back wheels.


(Mark Lee (Pay Pal Patron)) #35

Thank you. that I understand. As a kid, the skateboard was my main source of transportation.

(Carl Hutchins, Jr. ) #36

I was a kid before the skate boards of today!

We made our own ! Started with a pair of skates. Devised to clamp and buckle on to street shoes.
A skate key to hang on a lanyard on one’s neck.

A couple of 2 x 4’s and some scrap smaller bards. Nail the two by’s at a 90. Attach a small board as a handle atop the upright. Two boards to brace/gusset the 90…

Attach the skate wi wheels to the other 2 x /.

Voila. One foot on the 2x the other to push off/ Propel or coast as the terrain (sidewalk or street)

Steer by lean, the skate still has some flex.

Carl .

(Mark Lee (Pay Pal Patron)) #37

I made my first skatebord in wood shop when I was in 6th grade. I’d saved up to purchase the brand new urethane wheels. I thought they were so cool because the wheels were translucent. I think I still have them kicking around here someplace.

(Frank Andersen) #38

With cars there is also tyre flexing, Mark - which means that under sideways load, turning, the rear will ‘crab’ sideways, oversteer. This slip angle, centre line deviation from the direction of travel, depends tyre characteristics - including of course tyre pressure.

Tyres are the major cause of oversteer, which is why wider tyres and/or lower profile increase rear end stability - they have lower slip angles. Unlike the front wheels, driver has no direct control of what the rear end of the car is doing. If you want to experience a lively rear end; deflate the rear tyres to say 25 psi - it’s a scary experience…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

(Mark Lee (Pay Pal Patron)) #39

I’m aware of the affects of how tyre sidewall stiffness plays into handling. I was considering installing the radius arm bushes in with the holes at a 90 degree, but now I’m leaning more towards the centerline of the rad arm.

In a nutshell, I don’t know what I don’t know.
if the only mod done for the IRS for the “sport pac” is to install the bushes at 90 degrees from center, then it would be a worth while venture. if there were other performance mods done, then doing just 1 of the mods isn’t a prudent thing to do.

If its the only mod done to the IRS for the sport pac, then I’d truly consider it. Though, it’s the least of my concerns right now. getting the hub out of the carrier after (what appears to be a spun bearing is my main issue.

What I’ve got going on with this IRS is the reason why one should follow the directions, pay attention to end float. the seal retainer and shim show all the evidence of being spun. ugh, I’ll take pictures later on tonight (here).

thank you again Frank

(Mark Lee (Pay Pal Patron)) #40

Status update
I’ve gotten one side completely apart. It appears there was a bearing spinning where it’s not supposed to be spinning.

It would appear that the bearing was spinning against the oil seal? Here’s a picture of the oil seal seating ring which also has all the indications of it spinning as well. There was a shim in there someplace that was pretty much mutilated. I’m guessing this is why the .015 end play is important.

Or am I missing something.