Building a GD427 Cobra Replica

Continuing with little jobs to finish the rear end backend. First up was the final assembly of the top bolts on the diff. It’s not exactly clear to what value these should be torqued, but I guess the value of the original Jaguar bolts will come close. The lock-wire went considerably smoother than earlier (on the diff bracket). I only needed 3 attempts this time!

On to the front, there are six bolts on the suspension which need their head drilled for the lock-wire. Mostly a patience job, making sure the bit gets cooled properly and preventing to much pressure on it. 5 bolts went fine, during the sixth the drill-bit broke. As such that isn’t a disaster, you count on the smaller bits to break soon, but the bit got stuck in the bolt! The bolts are jaguar specific and as such a rip-off (around the € 10,- mark I believe). Having no choice, I ordered a new one.

Having the bench drill now is essential, a hole like below just would not be possible by hand. (1.5mm hole, 2.5mm finish)

Back to the back again. The handbrake mechanism comes with two extra helper springs which somehow need to be attached to the chassis. There are two or three locations which would be suitable, but only one of them was reachable with the rivet tool I have. It remains scary to drill holes in the chassis.

At the right bottom you can see the black dot of a more preferable location (it pulls on the spring straight instead of in a slight angle), but unreachable for my tool.

Looking at the last jobs for the rear end I tried replacing the straight grease nipples with 45° variants, but getting them properly positioned to the inside turned out to be quite a challenge. I’ll leave it on the backburner for now.

I double checked the torque on the drive shaft nu and got a helpful email from Terry about it too. Torqued it to 136Nm and put in the cotter pin.

The overview Terry sent me had torque numbers for the diff cover nuts as well, so out came the nord-lock washers again and the torque wrench. Probably not that important, but alas, looks nice at least.

Last job was deciding wether to fit the flimsy covers for the drive shafts. General consensus on the fora was a big no-no, so that made the decision a bit easier.

So, rear end done! All that’s left now is to fit it to the chassis. (Likely I’ll come up with new jobs for it soon, but my list is empty for now)

Having the rear-end in ‘concept’ I started the final assembly using all new nuts and using the appropriate torque required. Where applicable I’m using the nord-lock washers instead of, or in addition to normal washers.

I’ve got a bit of a routine by now for the final assembly of a part of the car. Roughly it goes like:

1. clean all the parts;
2. put on the appropriate (nord-lock) washer;
3. put some copper grease on the threads;
4. hand-tighten the nuts;
5. get out the torque-wrench;
6. get back into the office to look up the torque requirements (optional step in theory, I always forget what the torque was);
7. torque em-up;
8. mark with nail-polish that it’s done.

(and take some pictures in between all that)

So, what’s left for the rear end?

• I want to replace the straight grease nipples on the Upper Joints with bended ones, as the straight ones seem unreachable, at least with my grease gun;
• need to double check the torque on the big castellated nuts at the end of the drive-shafts keeping the hub in place, 75 Nm seems a bit low;
• the original jag had some protective covers for the drive shafts, should I fit these? They seem a bit flimsy to me;
• mount the whole thing to the chassis obviously.

I think that is about it.

Having both the hubs completed, I wanted to do a quick measurement of rear toe-in (or, let’s hope not, toe-out). So, clamped the laser to both hubs and marked the two projections on the garage-door.

Result: a bit more than 5mm overall toe-in over 4 meters. It’s on the good side of the scale at least! (If it had not been I would not have known how to correct it BTW). The value seems a bit on the low end of the acceptable range, but once the rear-end is in the chassis, I’ll do some more detailed measurements.

Rest of the day was filled with entertaining some friends coming over and a couple of minor jobs, one of which was to paint the upper ball joints as they started to show some rust. We can’t have that, obviously!

Did some research on the allowed backlash and the general consensus seems that a 2/3″ to 1″ backlash measured on the outer rim of the brake disc is acceptable. (which seems very large to me actually)

I should have photographed a measuring tape next to the marks, but it’s way less than an inch, so I guess I’m in the clear.