Rear Axle Reassembly - Part 5 - Rear Wishbones

 With the hubs done and ready to be installed, I turned my attention back to the chassis and the installation of the rear wishbones.

The rear wishbones are new items supplied by AK.  I bought new inner pivot bolts from SNG Barratt as I ended up "slightly" damaging the original ones whilst stripping down the donor axle/rear sub-frame.

The AK setup also requires the use of a spacer tube; these didn't come with my X300 axle but I managed to source a spare pair from Ben at Simply Performance.

Looking at the AK Build Manual, the installation of the wishbones is fairly straightforward.  The (new) outer pivot bolt is passed through the rear of the new wishbone, through two washers, through the rear differential tie bar, through the spacer tube, through the front wishbone mount, through two more washers, and finally, through the differential pendulum mount before being secured with a final washer and bolt.  The pivot bolts were given a liberal coating of copper grease prior to installation.

Simple.

Wishbone, new pivot bolt, washers and spacer tube

Well, it was simple, apart from a couple of small issues.

First, the AK Build Manual calls for the use of 1 1/2" by 7/8" washers.  But for some annoying reason, they don't supply these washers.  This is a complete pain because despite exhaustive internet searching I could not find this size washer outside of the US of A.  Fortunately I was prepared.  Having read Richard Chippendale's blog and his solution of using M22 washers instead, I had already pre-ordered a pack of suitable replacement size washers.

Close-up of wishbone mounting configuration...

...and view of installed wishbone.

The second issue is that the AK Build Manual suggests the use of an M12 is needed for the end of the inner pivot shaft.  This is incorrect.  Had I read/remembered Richard's blog better, I would have already known this.  But I was not prepared for this eventuality, and so there was a short break in the proceedings for another order with SNG Barratt.

(I couldn't actually find the original fulcrum nuts from my donor axle.  But even if I had, they were so rusty from when I removed them, that I wouldn't have wanted to re-use them in any case.)

The nuts are actually I believe an M14 thread.  However, the proper Jag nuts have a bit of a skirt on them.  This helps spread the load more evenly onto the washer on the end of the fulcrum bolt; this washer bears onto the metal sleeve in the bushing in the pendulum mount and a "normal" size bolt might cause some distortion of the washer when tightening.

Nice flange...

Once these arrived it was a simple job to pop them onto the end of the fulcrum bolt, along with an M14 washer and fasten up hand tight for the moment.  I will torque these up fully to around 70-75lb-ft / 90-102Nm once the wheels are on and the suspension is partially loaded.

Next step is to get the drive shafts reassembled before I can refit the hub carriers.

Rear Axle Reassembly - Part 7 - Pig Pen, this here's Rubber Duck...

Before the rear hubs can be reinstalled into the carriers the brake backplates, which hold the handbrake mechanism in place, need to be fixed to the hub carriers.

In my view, there is a distinct flaw in the Jaguar design for this set-up.  The hub carriers are aluminium and the brake backplates are steel.  Fixing the two dissimilar metals together results in a chemical reaction, known as galvanic corrosion.  This accelerates the breakdown of the natural coating of the aluminium and produces aluminium oxide (remember all that white crusty crud under the backplates when the hubs were stripped down).

This process is exacerbated by moisture and salt (like er...road salt) and so to ensure that the conditions for this galvanic corrosion are fully optimised, the Jaguar engineers decided to leave the aluminium mating face of the hub in a rough cast form to really allow the ingress of water, dirt and salt to take place, and then to ensure that it remains trapped in place to do its evil deed. 

A haven for dirt, debris and road crud!

A number of solutions have been proposed on the various build blogs that I have perused; including just bolting it all back together, a liberal application of copper grease, or the use of the dreaded RTV silicone sealant.

I decided to try an alternative solution and go with a rubber gasket.  This should keep the two metal components separated to reduce the opportunity for galvanic corrosion and also, hopefully, keep water and crud out of various nooks and crannies resulting from the rough cast face of the aluminium hub.

I made up an initial paper template. The centre hole was sized by placing the backplate on a sheet of paper and simply running a pencil around the edge of the hole.  This was cut out using a sharp knife and placed onto the hub.  Using a suitably greasy finger, I rubbed over the paper to trace the shape of the edge of the hub and the screw mounting holes.  The template was then completed by trimming the outer edge and screw holes.

Why you shouldn't wash your hands.....

Final template

I then stuck the paper template down onto a sheet of 1mm thick rubber sheet (purchased from that well-known internet auction site).  I used a scalpel to cut around the edges of the template and create the rubber gasket.  The template was stuck down a second time and the process was repeated to create a second gasket.

Template stuck down onto rubber sheet...

...and trimmed to create gasket.

A perfect fit!

Now I have sorted this issue I can press on with reassembly...

Update - Project Snake is still alive (again....)

So in May 2021 I put up a post of hope - hope that I would get some serious work done on the Cobra.  It didn't happen...

I did a few bits here and there (some belated posts to follow) but I had a major distraction with the decision to remove some existing timber decking in my garden and replace it with some stone paving.  As always, the project spiraled and took about 10 times longer to complete than planned (actually at the time of writing it is still not technically complete as the lawn still needs to be relaid...).  Still, my wife is now very happy so maybe, with what is left of this year, I will be able to crack on with the Cobra!

Update photo - the eagle-eyed will spot that it looks almost exactly the same as the update from last year - just wearing slightly more dust!

Rear Axle Reassembly - Part 6 - Drive Shafts

 With the rear wishbones installed, the last thing needed before the rear hub carriers can be installed and the rear axle set-up completed, is to assemble the drive shafts.

AK provide shortened driveshafts as part of the kit.  These need to be mated to the donor splined axle shaft and differential connection plate using new universal joints to complete the drive shaft assembly.

Shortened Drive Shaft - spot the join!

I ordered the replacement universal joints from SNG as per the part numbers below.  The end bearing cups need to be removed from the spider for installation, with care taken not to disturb the needle roller bearings in the cups.  Prior to assembling anything I put a generous smear of copper grease on all the openings in the various components.

Replacement UJ Kit Contents

Bearing Cup Removed - take care not to disturb the needle rollers

My hydraulic press was buried behind several boxes of Cobra parts so I was originally intending to be a bit lazy and follow the AK method of using a vice to assemble the UJs.  However, the initial attempt to wind the first bearing cap into one side of the diff connection plate using the vice resulted in the cap getting slightly misaligned and jammed; I wasn't happy with hammering on the vice lever to force the cap into place so I resorted to clearing the garage up to give access to my press.

I also found that the AK method of pressing one bearing cap into place first, and then inserting the spider didn't work.  Maybe I pushed the cap in slightly too far but there seemed insufficient space to work the spider into the partially inserted bearing cap and the other side of the connection plate.  The solution was to hold the spider in place while the first bearing cap was pressed into place, turn the plate over and press the other side bearing cap fully into place (i.e. so that the circlip groove was visible) and the first circlip could be inserted.  Then the piece was turned over again, and the initial bearing cap pressed in sufficiently to allow the second circlip to be inserted.

Holding spider in place...

...first bearing cap is pressed into place.

Bearing cap pressed in flush with outside of diff plate

Other side bearing cap pressed in fully and circlip installed

TOP TIP - make sure that when you install the spider, that, having installed the grease nipple, it is facing towards the half shaft.  This makes access for greasing of the nipple once it is installed far easier.  Once again you may ask me how I know this (although its not a disaster if the nipples end up facing the other way).

New grease nipple installed and facing towards driveshaft...

This process is then repeated to connect the diff plate to the new shortened AK half shaft; the diff plate / spider assembly is held in place while the first bearing cup is pressed into the half shaft until flush.  Then the assembly is turned over and the second bearing cup pressed fully into place in the half shaft and circlip installed.  Then the first cup is pressed fully in and its circlip installed.

The whole process was then repeated to attach the splined axle shaft to the half shaft.

First bearing cup pressed in to connect diff plate to half shaft

Rinse and repeat for the splined axle end...

...and one completed drive shaft!

I have no intention of having to disassemble the drive shafts ever again, but should that need ever arise, I put a smear of copper grease around all the circlips to give them a bit of added protection against the elements and possibly give a fighting chance of easy removal at some point in the (distant) future.

I also greased up the universal joints with a grease gun filled with a lithium based bearing grease, pumping the grease in until it was just starting to seep out of all the rubber seals of the UJ bearing cups.

And with that, reassembly of the drive shafts is complete!

Rear Axle Reassembly - Part 4 - Grease is the Word..!

So with all the bearing races installed into the rear hubs, the hub pre-load checked, and the correct spacers ordered, now I can crack on with greasing the bearings and finally re-building the hubs, yes?

Actually, yes I can!

Installing the hub bearings is very straightforward and exactly as per the AK Build Manual.

A generous smear of grease applied to the outer race

Grease vigorously massaged into the outer race

Even more grease smeared onto front face of bearing

The outer oil seal was then tapped into place

It's pretty much the same for the inner bearing, remembering to include the fixed spacer and the correctly sized 3.02mm adjustable spacer.

3.02mm Spacer freshly delivered from SNG Barratt

Inner bearing packed with grease and inserted in place with extra grease!

Tapping inner oil seal into place completes the job!

Next up is to install the new fulcrum bearings and new pivot pin sleeves.  On the original Jaguar set up the fulcrum pivot pin has an eccentric head which engages in a machined groove in the rear wishbone and, depending on the rotation of the bolt head, moves the bottom of the rear hub in or out to set the rear toe-in. This arrangement is dispensed with in the AK set-up.  

However there is still a need to install spacers between the fulcrum bearings and the rear wishbone.  The AK Build Manual simply states to reinstall with the original spacers from the donor vehicle. All well and good unless, like me, you somehow threw away / lost some of the original spacers when disassembling the rear axle.

All is not lost as you can buy new spacers easily from SNG Barratt or other Jaguar parts suppliers.  But, like the rear hub spacer, they come in a variety of thicknesses.  Further internet investigation revealed that the rear fulcrum bearings also need to be installed with a certain amount of pre-load.  Except that I could find no explanation for setting this up on the later X300 suspension.

I found a few descriptions on various Jaguar forums on how to set the pre-load, but this only seemed relevant to the earlier type hub carriers, which seem to have a two-piece pivot pin sleeve where the spacers are fitted between the two halves of the sleeve.  So effectively this adjusts the overall length of the pivot sleeve and hence the distance between the two fulcrum bearings to set the pre-load / tolerance.

I couldn't see a way to apply this method to the later style of hub carrier.  The Jaguar X300 Service Manual is not much help either.  While it describes the method for determining the pre-load in the main hub bearings very clearly, for the fulcrum bearings it simply says "install equal sized shims to give 0.003in, (0.0762mm) pre-load".  It doesn't say how or where....

So I dropped Jon at AK Sportscars a message on this matter.  His response was basically not to worry about the preload and just to tighten the outer pivot bolt up enough to pull the ends of the wishbone against the hub carrier.  So with that cleared up, I could press on with installing the new fulcrum bearings.

The fulcrum bearings have an integral oil seal

Bearing given a generous packing with grease

The fulcrum pivot sleeve sits within a void in the hub carrier.  I gave the outside of the sleeve a generous coating with grease to try and delay the onset of any corrosion.  I did see a suggestion on one of the Jag forums where someone had drilled a hole from the bottom of the hub carrier into the void and inserted a grease nipple to allow grease to be pumped into the void and allow the fulcrum bearings to be kept topped up, which seemed like quite a good idea.  Maybe something I might consider doing in the future.

A light smear of grease on the outside of the pivot sleeve..!

Pivot sleeve inserted into place...

...and fulcrum bearing tapped gently into place

The hub carrier was turned over and the second fulcrum bearing greased and tapped into place in a similar fashion. 

Job done!

With bearings reinstalled in both hubs, the next step is to reinstall the drive hub and ABS ring.  But first the handbrake backing plate needs to be installed. 

Rear Axle Reassembly Part 3 - Getting Spaced Out...

So with all the bearing races installed into the rear hubs, now I can crack on with greasing the bearings and finally re-building the hubs, yes?

Well not quite.....

While at this point, the AK Build Manual would have you packing the bearings and installing them and the seals back in the hub carriers, the build manual appears to be silent on the subject of checking the pre-load on the bearings.  

Maybe the AK logic (and that it seems of many builders) is that if you have kept all the parts from the donor hubs together as you strip them apart, and make sure you put all the same parts back into the same hubs, then everything will be OK.  

Maybe...although that does presume that everything was actually OK when the hubs were taken apart.  And in any case, the Jaguar X300 Service Manual includes tolerance specifications for rear hub bearing pre-load and requires the preload to be checked when replacing the bearings; so it would seem that this is something that is important to check.

Basically it is necessary to "dry" assemble the hub with the bearings and the largest available adjustable spacer, measure the end float of the hub and use that measurement to calculate the required thickness of adjustable spacer needed to achieve the necessary level of float/pre-load within the required tolerances.

(Note that the largest thickness of adjustable spacer that Jaguar make is 3.47mm.  I purchased a 3.42mm spacer in error but, assuming that my required spacer thickness is less than this, then I should still be able to use it to calculate the required thickness)

The outer bearing is installed on the hub without the oil seal

Hub inserted into carrier and fixed spacer installed (chamfer facing towards inner bearing)

3.42mm Spacer is then installed...

...followed by Inner Bearing (again without oil seal)

ABS Ring placed onto the end of hub shaft and pressed into place

The hub assembly then needs to be put into compression to tighten up the bearings to the spacers.  The Jaguar Service Manual is not exactly clear how to achieve this.  So I installed the stub axle into the hub, installed the original conical spacer and original driveshaft nut and used an air wrench, set to the maximum torque setting, to try and put the whole assembly into a reasonable amount of compression.

Stub axle being installed into hub...

...and then tightened up to put bearings and spacer into compression

The next step is then to measure the end float on the hub.  This needs to be done with a dial gauge.  Fortunately, I acquired such an instrument many years ago when I rebuilt the gearbox on my TransAm; I knew I would find a use for it again one day!

I sat the hub carrier on a spare piece of steel sheet on my workbench to make sure it was sat completely flat and stable.  The magnetic base of the dial gauge was mounted onto my vice and the gauge set onto the face of the hub and zeroed.

I then used a screwdriver between the hub and the carrier to gently lever the hub up as far it would go and checked the reading on the gauge. 

Set-up for measuring end float of hub

Gently levering the hub upwards shows an end float of 0.0135in (0.343mm)

I took an average of several readings, rotating both the hub and the carrier on the bench, ending up with an end float of 0.356mm on the offside hub and 0.324mm on the nearside hub.

From the Jaguar X300 Service Manual the actual required end float should be a minimum of 0.025mm and a maximum of 0.080mm.

So by the power of mathematics it is possible to calculate the mimimum and maximum required thickness of spacer that needs to be installed, in place of the 3.42mm spacer, in order to achieve the correct tolerances.  The spacers come in a range of thicknesses from 2.22mm to 3.47mm, in 0.05mm increments, so it is then a case of selecting the available thickness that falls between the upper and lower tolerance calculated thicknesses.

This then required another order from SNG Barratt, and a short wait for delivery, before I could get on with the final reassembly of the hubs.

(The obvious question that I hear all of you asking is of course "Well could you haved re-use your original spacers?".  And the answer is....no. The thickness of my original spacers was 3.12mm on both sides.  Using these in the reassembly would have resulted in the tolerance being at least 0.1mm (over 100%) out.  So my decision to check this appears to have been the right thing to do.)

Gearbox Part 2 - Delivery!

 I ended up ordering a complete installation package for the T56 Magnum transmission from Roadcraft UK.  This included the following items:

• T56 Magnum Transmission (obviously)
• McLeod 168 tooth Steel Billet Flywheel
• Aluminium Bellhousing
• Roller Spigot / Pilot Bearing
• Transmission Mount
• ARP Flywheel mounting bolts
• All bolts for attachment of bellhousing and transmission

I also opted for the following additional items / upgrades

• Gearbox yoke
• McLeod RST Twin Disc Clutch
• Hydraulic Clutch throwout Bearing

I went for the twin 10.5" disc clutch upgrade since it can handle 800hp with ease and still gives a relatively soft pedal engagement and remains streetable.  The soft pedal element was the key for me.  I still have the nightmare memories of trying to drive my Pontiac TransAm in traffic; the clutch was immensely heavy (although to be fair it was cable operated not hydraulic) and I used to frequently experience the shakes in my left leg trying to ride the clutch in stationary / slow moving traffic.  

After a short delay in delivery (due to the container with all the transmissions going temporarily AWOL) I got a message from Brian confirming my delivery date for end of April 2021.

On delivery day, I received a neatly wrapped pallet containing all the transmission components. 

One shiny new transmission!

Rear Yoke

A well wrapped Bellhousing

Next out of the box were the flywheel and twin-disc clutch.  There's a fair amount of rotating mass with these two components; the flywheel weighs 13.6kg (or 30lbs in old money) and the twin-disc clutch weighs 10.2kg (22.5lbs).  That's a hefty 23.8kg (52.5lbs) in total!

Steel Billet Flywheel

RST Twin-disc Clutch - looks too nice to hide!

Next off the pallet was the hydraulic throw-out bearing.  This is fixed on the end of the transmission over the input shaft and pushes directly on the release 'fingers" on the clutch.  It does away with the normal clutch lever and external slave cylinder arrangement.  This is a standard GM item and comes with the factory style bleed screw arrangement, which requires a special tool to be able to access through the bell housing when everything is bolted together.  First job will be to remove that and replace it with an extended hose and bleeder to make bleeding the clutch a tad easier!

Hydraulic Throw-out Bearing - factory fittings will need to be replaced

And last but not least were the transmission mount, the roller spigot / pilot bearing and a selection of bolts to secure everything together.

Miscellaneous items....and some lube!

Having checked everything out, I put all the components back in their box and put them in the corner of the garage until its time to install the engine.  I need to finish assembling the rear axle first.  Hopefully the presence of a large box of goodies in the corner will give me the motivation to pull my finger out!!!