Double Cardon Joint CV Driveshaft:
Building and Refitting
We’ve
all done it, fitted our nice shiny suspension lift to out rovers, only to drive
down the road and experience mild (or severe!) driveshaft vibrations.
I
won’t go into <why> we get the vibrations, enough has been written about
it on the D90 list, but in short, it is because the 2 CV joints either end of
the shaft are running at too great an angle, or the pinion of the differential
no longer lies on a parallel with the pinion on the transfer box.
So,
enter ‘stage left’…..Double CV driveshaft. This little monster will enable
us to run our vehicles (not just Land Rovers, any vehicle with raised suspension
comes under this title) with lifted suspension. It works by using the ‘double
cardon’ joint, which is in effect 2 CV’s mounted back to back, but with a
spider between them to stop them ‘drooping’ down when hanging between the
axle and transfer box (see diagram 1)
Figure
1
What
I managed to do was buy a brand new front driveshaft from a Land Rover 110 that
was fitted with the Salisbury HD axle. These vehicles came with the double CV
driveshaft as standard (due to the extra length of the Salisbury casing,
therefore shorter shaft length, and therefore greater angles between the UJ’s).
If you manage to come across one of these shafts (or one off of a series 3
109” stage 1 V8) then grab it with both hands. They’re rare and horrendously
expensive!
LR
part numbers for the shafts are:
FRC
7697 or FRC 9762
The
series 3 stage 1 V8 prop is: FRC 2175
For
the front of 90/110’s you can directly install the front shaft off of the
Discovery series2, as this is also a double CV shaft, but the joint is non-greasable
so will have a limited lifespan. Part # for this is: TVB 000100 and you’ll
need the replacement front drive flange for the LT230 transfer box, part # STC
4379.
Anyway…back
to the tech description of how to build your own CV shaft.
First
off, you’ll need a double cardon UJ unit, a decent spare driveshaft and
someone (or access to) who can do a bit of metal turning on a lathe and milling
machine. A CNC shop like I used was ideal for the ‘1 off’ job I required.
Here
is the driveshaft adaptor that I had made up; it fits between the handbrake drum
and the rear drive shaft. I had mine made out of stainless steel (just so it
always looked shiny!) but you could have it done from mild steel. I considered
aluminium, but it wasn’t strong enough for the allowable thickness.
This
converts the stuff pattern of the transfer box (standard rover driveshaft) to
the bigger (3” x 3” PCD) of the double CV shaft, most of the ones I have
seen seem to use this sort of size.
So
I had to take my new-ish rear shaft, and cut off the CV joint from one end (the
opposite end to the sliding joint), if you take a 4” angle grinder, and gently
cut through the weld at the end of the shaft, you can easily remove the joint.
Like
this!
The
same was done to the double CV joint off of its respective drive shaft. Then the
new tube had to be cut shorter, by the length of the new double CV unit, plus
the extra thickness of the adaptor (which in this case, was 32mm)
This
is the double CV joint just ‘tack welded’ onto the shaft.
Once
the shaft is roughly assembled like this, then it’s time to fit the driveshaft
adaptor to the rear of the transfer box. First
of all however, the handbrake drum needs to be removed so that the rear drive
flange can be removed and longer bolts fitted. This is because the stock bolts
are only long enough to pass through the thickness of the handbrake drum and the
end of the stock drive flange, but we need them to be an extra 30mm long so they
can fit through the adaptor.
So
here’s how to get the handbrake drum off; remove the rear driveshaft (4x 9/16
nuts) and remove the small cross head screw that locates the drum.
Once
this screw has been removed, you can pull/wiggle the drum off of the propshaft
studs, but make sure that the handbrake is fully ‘off’ otherwise the drum
won’t move at all!