Building a GD427 Cobra Replica

With a new inner oil seal delivered, completing one of the rear hubs was indeed a quick job. Pressing in the oil seal, but now making sure it was straight!

This completes one rear hub. To complete the other one I’m waiting on the (extra thick) spacer and another inner oil seal.

Got one inner oil seal delivered today out of the two ordered, so decided to quickly press that in the rear hub waiting for it. Too quickly it turned out; I pressed it in while it was not lining up exactly with the opening apparently because it bent.

So, out it came again and I’ll have to order a new one. No progress made today

With all parts galvanized, a next step can be taken in building up the rear hubs. I can’t complete the rear hubs completely because a spacer thickness needs to be determined to get the necessary endfloat in the hubs. Starting by putting the rear hub in a vice…

…and greasing up the bearing.

After placing the housing on top of the bearing and filling the cavity with lots of grease, the inner bearing can be driven in, but not completely. Formally, a jaguar specific tool (J15 or something like that) should be used to put pressure on the bearing. This tools contains a machined edge with a specific height (0.152″ I think) which makes sure the bearing is not driven in completely. By leaving a little bit of room a (large) endfloat can be measured and from there the necessary spacer thickness can be calculated. Not having this tool I ordered the thickest spacer (0.148″) for an alternative procedure.

With this spacer on top of the inner bearing the whole hub was put under the press to drive in the bearing. When the spacer is flat with the bearing the endfloat can be measured.

In my case the endfloat was 0.016″ The target endfloat is between 0.002″ and 0.006″, aiming at the average 0.004″. So, instead of the 0.148″ spacer I would need a 0.148″ – 0.012″ = 0.136″ which is exactly the size I took out of the donor part, so I can reuse that one.

This result was expected for one hub only though. One of the hubs had to be replaced because of a crack. It is likely that this hub has different dimensions and another size spacer will be needed. Doing the same procedure for the other hub revealed that the 0.148″ spacer would lead to an endfloat of near zero ?!?

Hmm…

So, I would need a spacer with a minimum thickness of 0.150″ (leading to the minimal endfloat of 0.002″) This spacer used to exist, but apparently not anymore. Need to sleep on this one what to do here.

Fitting the water throwers turned out to be more labour intensive than I thought. A little bit of research on jag-lovers.org gave me some experience tales of other people and some insight on what to expect. Heating the thrower and quickly fitting it around the machined edge on the hub seemed the way to go.

There are a couple of hurdles to overcome. First, when the thing gets hot gloves are mandatory which makes handling the piece more cumbersome and handling the thrower quickly but steadily over the hub proved to be quite a dexterity challenge.

Next, to much heat will ruin the passivation layer on the zinc, so I do not want to heat them up to the point where that happens.

And third, the heating will expand the part, but we’re talking parts of millimetres here; I figured about .5 mm difference between the cold and heated part. This means we’ll have to make sure the cold part is brought within that range. There’s also not much room for error.

So, first thing was to do a trial run to get some feel for the procedure and the measurements. The cold part inner diameter was about .8mm smaller than the diameter of the edge. Heating did not make it possible to fit the part but clearly showed a difference in size. I had the hub in the freezer overnight which may have helped a bit too, size-wise.

So, the only thing I could think of was putting the ring in a reference position (cold) and marking how far the circumference would go over the edge by pushing sort of in the same manner I would be able to do while handling the hot part. Marking the arc on the ring and then carefully sanding the complete inner diameter of the thrower to enlarge it a little, fitting the piece regularly.

After quite some sanding and trial fitting and two ‘hot sessions’it dropped on!

You can see the reference mark and some burn traces in the bottom part of the picture. I’m not sure if you can make it out on the picture below, but the hard work paid off. Nice fit I think.

Fitting the seating ring and bearing is easy with a press. There is a little bit of room between the bearing and the seating ring. I’m not sure if that is supposed to be there, but I do not want to push too hard with the press on the bearing.