When installing the XH steering box in place of a stock G box, the power steering pump pressure valve (flow valve-alternate name) needs to be changed to one that was used on a Camaro with that box. The higher effort and faster ratio needs a little boost in maximum pressure, and flow, to help it turn smoothly and quickly under all conditions.
The mod involves changing the spring, pressure fitting (with orifice), and removing all washers (if present) from the flow valve. The spring will actually lower the minimum pressure slightly, which helps reduce assist when driving straight ahead. Removing the washers from the flow valve increases the maximum pressure the pump produces, and is needed when turning the steering wheel rapidly left and right. The fitting also produces slightly more flow than stock, which also helps the pump 'keep up' with the demands from the box.
The following text is by Bob Morris, who originally figured this conundrum out :)
The new spring is shorter than either the original G spring or the F
spring I pull out of the 91 F car. To do this swap I'd only buy the spring
#5688037 @ $4.68 (list), the fitting #26009894 (o-ring included with new
fitting) @ $15.03 (list) and use the old valve. Insert a 1/8'' drill bit into
one of the holes in the side of the valve and hold onto the valve with
channel locks using the bit to keep the valve from turning in the pliers, do
not scratch the machined surfaces of the valve. Wash the valve out and make
sure the screen in the valve is clean, do not reinstall any washers and
Locktite the nut back on the end. The new valve # 7809232, $22.69 (list) is
the same body and internal pieces and orifice sizes for all three valves,
only the shims vary, use the original valve, without the shims.
Drilling out the orifice in the fitting would be tricky as there is a very
small hole drilled in the side of the fitting into this orifice and it may
burr, clogging the hole. A #27 number drill is .144'' and could be used to
drill the G fitting out. But at $15 for the fitting which includes a silicone
o-ring (not rubber), I'd just buy the new F fitting or get one from a donor
at the yard.
Only other parts you'll need is a new 3/8'' O-ring for the P/S high
pressure line and a quart of P/S fluid. The tool list is short, a 16mm open
end for the high pressure line, 1'' socket and a magnet to get the fitting,
valve and spring out of the pump. An 11mm box wrench, 1/8'' drill bit and
channel locks to remove the washer from the valve and Locktite to reassemble
it. This swap is easily done on the car and improved the slow speed assist
and feel considerably, no more lack of assist at low speed and the high speed
feel is about the same as before the changes, a definite improvement."
Pics of the different valves, springs, and fittings. The total cost should be around $25, depending on how good a price the dealer will give you. The 1" socket is necessary to remove and replace the fitting on the back of the pump, a wrench won't fit into the small area there!
This shows the new parts needed, except for the valve, which you can reuse yours after removing the washers (if any are present).
This pic shows the differences in the G pump and the F pump (with original equipment XH box). The replacement spring is actually the only one listed for any GM pump!
All three combos represented here.
This is an easy mod and will make the XH and similiar boxes feel a lot better. The road feel actually improves, and the steering wheel can be moved as fast as you want, with no lagging.
Pictures taken by Bob Morris
Created 11/13/2001 by Jeff Davidson