As in Scoobie's rebuild thread, I have resorted to separating the diff and front pendulum
from the rear tie + inner fulcrum + wishbone combination.

The inner fulcrum shaft remains frozen in the wishbone.

First, in normal operation, is the wishbone supposed to rotate freely
around the fulcrum, bare metal to bare metal? It would seem that
way because no mention is made of an inteference fit requiring
any hammering or pressing during assembly. This is distinct from
the bushings in the front pendulum and rear tie themselves.

Are there any hints out there on how to remove the shaft without
damage?

The plan that I have in mind is:

a) scrape rust off from the shaft in the middle section exposed
by the window in the wishbone

b) stretch some aircraft cable from wishbone arm to wishbone arm

c) use hydraulic jack between rear tie and aircraft cable to jack
the wishbone arms away from rear tie and fulcrum shafts

d) finally remove fulcrum shafts from rear tie

To anyone coming along behind, it might be a good idea to keep
the portion of the shaft reachable through that open window in
the wishbone lubricated with a creeping oil to keep it from accumulating
rust scale.

 

Hi plums,

I've had similar problems with rust-siezed fulcrum bolts but have always managed to get them out with a combination of penetrating oil, an air impact wrench, a bronze hammer, and in the worst case, a little heat carefully applied. Your idea of scraping away the rust on the section of bolt in the gap is good - and you can also work penetrating oil into the wishbone bores from the gap as well as the outer ends.

I thread the fulcrum bolt nut till it is flush with the end of the bolt so I can tap on the end with a bronze or brass hammer with little risk of damaging the threads. Alternate taps on that end with attempts to twist the head of the bolt with the impact wrench. If no luck, then try tapping and twisting at the same time if you can reach, or have an assistant. If several repetitions just won't budge the bolt, you may need to apply heat to the wishbone with a torch to expand it a little if possible. The wishbone may be heat-treated, so you don't want to get it so hot its temper is weakened, but that is unlikely with typical home torches. Penetrating oil and heat can be "exciting," so it may be wise to wipe up as much of the oil as you can before you use the torch.

Hope one of these ideas works, or that someone else has even better ideas.

Cheers,

Don

 

Yep, I have a feeling it's going to be one of those stubborn ones.

I've been applying ATF liberally every time I go to the storage facility.

It is likely that the majority of the rust scale is on the exposed parts,
so it is reachable. The back part can be reached either by bending the
wishbone or using strips of emery paper like a shoe shine cloth.

I figure it is better to invest the effort in rust cleaning upfront before jamming
the rust further along the job.

In the end, is the shaft supposed to spin free on reassembly? Saving of course
the friction caused by tightening the nut again.

++

 

On our XJ40s the the wishbones rotate freely on the fulcrum bolts I think I recall that the wishbones have solid metal bushings (bronze?) press fit into the bores to interface with the fulcrum bolt, which itself is hardened steel. I use plenty of copper grease on the bolt when I reassemble (except on the threads) to reduce the recurrence of the corrosion.

Have you found ATF to be as effective as a low-viscosity penetrating oil? I've never tried it for busting rust.

 

Well, I had it mixed with Liquid Wrench as an experiment.

Ran out of LW and kept going with vintage ATF, mid 90's bottle I couldn't even give away.

Works as well as any, and I trust it more around rubber.
Of course, I've been drowning everything in it on every visit
on the theory that time is your friend in these things.

I think busting fasteners loose is 90 percent technique and 10 percent luck.

That mention of the bronze bushing is interesting. I wouldn't think steel would
bond to bronze. I do realise though that the joint has to be a precision fit.
Otherwise, lots of mysterious wandering out back would result. That's
why I am being careful about not damaging anything. Even if it was
steel to steel, I wouldn't want to wallow out the bore.

No one has ever mentioned needing to recondition the bore itself.
I wonder if it is just getting ignored during rebuilds.

The original inboard brake versions seem to have had rolller bearings
at that interface. Some places are selling bronze bushings for that
application as an upgrade.

++

 

Plums- as to steel bonding to copper alloys, I am rebuilding MGTF hinges for a friend. The hinges are brass and I have had to drill out two of the steel pins. Maybe the tin or silicon vs. zinc as alloy makes a difference, but I think it's just the increase in diameter due to rust and the softness of the bushing that results in mechanical lockup, not bonding.

 

Mechanical wedging seems to be a reasonable hypothesis.

In your case, what could have worked to leach the rust would have been a
citric acid bath at 10 percent concentration. It actually dissolves rust.

The problem is that the solution does not cut through oil.

Another one that works, but takes longer is water. And apparently, older steam fitters
like industrial vinegar for corroded boiler fittings.

 

It seems that it is most likely the wishbone does rotate about
the fulcrum shaft at the time it leaves the factory.

The biggest clue is the earlier design. That design incorporates
not one, but two needle bearings at each point where the wishbone
mounts to the fulcrum. In addition,there is a grease fitting between
the two bearings of each set. That pretty much points to a desire
that they rotate freely. The X40/X300/X308 did not receive the
benefits of this design.

Then there is the thought that even Jaguar could not guarantee
a specific built in rate of rusting or a specific amount of rust as
a X300/X308 left the factory. Not one of them would be the same
by the time it reached a customer.

In order to achieve the same degree of freedom in that joint as
it left the factory, it is necessary that the joint in question is
not rusted solid ... as many of them are by this point.

I have finally noticed that there is a small "ear" at the rear of
the wishbone where it meets the wishbone tie. This might serve
to anchor a loop of aircraft cable so that the cable can be jacked
against the wishbone tie. This will apply pressure while the wishbone
is receives healthy belts from a hammer to loosen everything up.

Once they are apart, I think a grease fitting is in order.

We'll see ....

++

 

Hey Plums, did you ever get to the bottom of this?

 

Well it is still sitting in storage.

But, every time I go there, I douse it in more ATF.

Brushing the ATF soaked exposed part of the shaft in the window
between the two bushes with a brass brush removed a lot of loose
rust. Almost as if the ATF was dissolving it.

The ATF treatment seems to have loosened it such that there
was some small movement of the shaft. Only a few mm but
very encouraging. This led to more dousing in ATF.

This has been going on for some months and not everyone
has the luxury of waiting that long.