Jag IRS Rear Wheel Bearings

[Excaliber]

I recently switched to the Goodyear BIG letter bias ply tires. Right away I noticed I had more road "feel" and suspension "feedback" than I had before. I WAS running radial tires before.

Within a few days I noticed what I felt was a "rear steer" condition. While acclellerating the car would "veer" slightly to the left, when I released the throttle it would "veer" back to the right. Subtle, at first but growing worse with every mile driven.

So I jacked it up to check for loose components etc. in the rear (and front).

What I found:
ERA154 has "play" (is "loose") when I hold the tire at the top and the bottom and "tilt" in at the top and out on the bottom, or vice versa.

This appears to be a result of loose (worn) rear hub carrier wheel bearings. I plan to change the bearings myself (yes I know how to do it and will use the correct "spacer" to adjust end play of the bearings). This is a STOCK Jaguar IRS XJ-6 rear end setup. Everything else is good!

Question:
Would the loose rear wheel bearings be enough to cause a rear steer condition? The LEFT side is much more "loose" than the right side (which is also loose). I will replace both sides.

Ernie

[coyled]

Ernie, I broke 2 rear hubs because the bearings were likely never adjusted properly. You might have broken hubs. They generally won't loosen up to the point where you can feel the kind of play you are taliking about. Once you have the correct spacer, you tighten the nut to 140 foot pounds. Any looseness will cause radical toe changes and yes its scary. Good luck, Scott.

[rdorman]

No Jag hub expert but I would think that you are definiatly going to want to know what caused the looseness in the rear before putting it back together. If it is obvious like a bad bearing or ground up spacer, then fine. I know when my time comes I am going to take them to a realiable machine shop and have them checked for cracks before I put them back together. Just a bit of precaution.
Rick

[wilf leek]

Oinie - the play could be in the bearings, but check as well the bottom hub pivot bearings.

Also, if the diff output shaft bearings are on their way, this also can feel like wheel bearings.

Rarely seen a jag rear end without some play in it.

Don't forget the loctite on the splines when you are done.

Youv'e done these things before anyway, haven't you?

[strictlypersonl]

Wilf's comments are very good. The other thing to check is the condition of the U-joints.

Also see the Jag rear suspension service and adjustment section of the update page.

[Excaliber]

Thanks for the caution guys! Sometime I dive in to deep and then go OOPS!

I did check the u-joints (nice and tight) and the bottom pivot bolt (nice and tight). I took one side apart all ready and checked for cracks etc. Nothing I could see. With no OTHER loose parts I'm left with "play in the bearings" due to "worn condition"?

I was surprised that the axle was well greased and pratically fell out of the hub. Certainly NOT put in there with any kind of loctite. Which of course then had me wondering, WHY should I use locktite on the axle?

Now about that end play on the newly installed bearings (when I get around to it). .002 to .003 recommended, but how much can I get away with "really"? .005? More?

I better follow up on the link for the ERA site! Thanks!

Ernie

[PatBuckley]

Ernie-

There are brass/bronze spacers that come in various sizes that may help your condition.

Pat

[Excaliber]

Indeed I'm thinking shims/spacers maybe the solution Pat. Heres the hypothesis.

Car was built around 1986, only has 9,000 miles on it. The pumpkin is shiny black, "like new paint". The pivot points, u-joints etc tight. The shocks are brand new. I talked to Stuart the former owner I suspect he replaced the shocks "chasing" this problem. He was NOT aware nor did his mechanic find the "play" in the bearings.

The grease on the axle is a clue, NO locktite used. I'm wondering if when the bearings were installed they were NEVER shimmed correctly? Perhaps the bearings ARE good and need only the spacer/shim adjustment? I'll take this thing apart all the way, take pictures, measure twice and get to the bottom of this.

But the BIG question still remains:

Would loose rear wheel bearings result in a "rear steer" condition under accelleration?

Ernie

[wilf leek]

Ernie - I am not sure there is actually a definitive answer to your question.

More than one thing could lead to your rear steer condition:

1/ play in the rear end somewhere

2/ incorrect alignment of rear end

3/ tyre pressures

4/ road camber

and so on.

Probably you are best to track down and eliminate the free play you have found, get the alignment (including thrust angle) checked out, and see what happens. As I said before, I don't think I have ever come across a Jag rear end where you cannot feel some play somewhere. My own included.


BTW - the spines on the outboard ends of the driveshafts are meant to be loctited into position. Not doing so can lead to fretting and wear under torque reversals. Metallurgy and engineering tolerances available when that rear end was first designed and manufactured are the reason.
Usually last thing done after setting up the rear end completely, as once it is done, you will need a press to dismantle again.

[PatBuckley]

#2 above is a winner in my opnion - if your thrust angle is off you will get a rear steer condition on acceleration.

I had some pretty significant play in my ERA without any adverse effects.....

[wilf leek]

Originally posted by PatBuckley


[BI had some pretty significant play in my ERA without any adverse effects..... [/b]

What was her name?

[PatBuckley]

I married her....

[wilf leek]

I thought you said there were no adverse effects?

[coyled]

Ernie, get the correct shims first. I am not sure on an ERA, but on the originals or my hi-tech, there is a bunch of bump steer which leads to toe out on acceleration. Check your bump steer. We had to make a large castor change in the rear to eliminate the bump steer issue. We basically had to move the top of the upright toward the rear of the car. You might also want to run 3/16 toe in at the rear and see if that helps the stability. First things first, make sure there are no loose parts. Good luck. Scott

[wilf leek]

Scott, not sure of what you are saying there. I don't know how to adjust castor on a Jag IRS. Camber, toe, and thrust angle, yes, but castor is essentially fixed so far as I know.

Am I missing something?

[Excaliber]

Camber with the shims behind the drive shafts. Sounds like the castor adjustment would require extensive "re-work" to reposition things! No "easy" way for sure.

What is "thrust angle" and how is IT adjusted?

[wilf leek]

Ernie - it is essentially making sure that the rear axle drive line is exactly at 90 degrees to the car fore and aft centreline.

Can be difficult to set up - easily confused with toe measurements. Adjusted by adding shims in front of the forward inner wishbone pivot bearing caps, where they tie into the chassis. Have to slack off the four bolts holding the diff in at the top as well. Don't forget to safety wire everything on that rear end. Wishbone pivot carrier bolts, caliper bolts, top diff bolts - all need to be safety wired.

[Excaliber]

OH,,,so THATS what thrust angle is.

,,,you know thats not all how Pat explained it.

[wilf leek]

How come I ended up as "Jag IRS know-it-all of the week"????

[Excaliber]

I never had to deal with a Jag IRS in anything except a Jaguar! So you being the English arse, are supposed to be the expert!