Intermittent Steering Issue Under Heavy Load

[Sleeper68]

Hello All,

I have been having an issue with my steering system randomly under heavy load ever since I switched back to recirculating ball from a crappy rack.

During hard slaloms, at some corner entries, and some corner exits a very abrupt and sharp feedback will come through the steering wheel which feels like a bind. This lasts far less than one second. It only happens when trying to turn in or straighten out the steering, under heavy load. I checked the steering output side (linkages, tie rods, steering arms, etc.) and suspension rigorously to look for interference and have found nothing.

Maximum steering wheel input when this issue occurs is 90 deg from center either direction. I have not as of now experienced this issue at all while driving normally on the street, ONLY during autocross or other very hard driving. No discernible odd noises or vibrations, although this is so abrupt and random that it is difficult to completely rule out. The engine is also quite loud so whining may be masked. The box does not appear to be leaking anywhere, nor does the rest of the system. System has been bled well and fluid condition is good, very little aeration, at least at idle.

The car is a 1968 Camaro. Steering specs: TurnOne 12.7:1 670 Delphi box, Saginaw TC iron case pump from Vintage Air w/ Front runner system for gen 1 SBC, -6 JIC pressure line, -10 JIC pump feed line, -6 JIC return lines, remote Allstar Perf reservoir, mocal inline PS cooler, Chassisworks Z/28 7075-T651 aluminum steering arms, factory drag link, Howe quick bump outer tie rods, short pitman and idler arm.

As for now I have two different suspicions but I will wait to reveal them as to not bias any suggestions.

Other than this random issue the steering is great. Good feedback, very linear, proper ratio, less then 0.030" bumpsteer over 4" of travel, etc.

Thank you all in advance for your help.

[Sleeper68]

Bump.

Anyone have any ideas?

[David Pozzi]

If your pump was originally purchased for a rack, it needs more flow (GPM) & a bit more pressure to supply a recirculating ball box.
Many late aluminum body pumps do not use shims on the valve assy to set pressure. The "nut" is screwed part way in and secured with loctite. You can buy a shim kit, measure the gap between valve body and nut head, then figure out the shim stack to fill that gap, and deduct a shim or two to increase pressure.

If your pump is the older style it probably has just the shim stack. The shim kits come with a slice of aluminum tube that is split. It allows you to safely clamp the valve in a vise for disassembly. It's pretty tough to disassemble the valve without this tool.

check that you have enough belt tension and no oil contamination of the belt or pulleys.

Also check your reservoir for fluid aeration after running. Some reservoirs do not handle the fluid very well.

We had a similar problem with a rack system. Loss of boost on corner entry or mid turn. Tried a few things which did not help. Finally the pump went bad and we replaced it and no more problems, so it was an early sign of the pump failing I guess.

[Sleeper68]

If your pump was originally purchased for a rack, it needs more flow (GPM) & a bit more pressure to supply a recirculating ball box.
Many late aluminum body pumps do not use shims on the valve assy to set pressure. The "nut" is screwed part way in and secured with loctite. You can buy a shim kit, measure the gap between valve body and nut head, then figure out the shim stack to fill that gap, and deduct a shim or two to increase pressure.

If your pump is the older style it probably has just the shim stack. The shim kits come with a slice of aluminum tube that is split. It allows you to safely clamp the valve in a vise for disassembly. It's pretty tough to disassemble the valve without this tool.

check that you have enough belt tension and no oil contamination of the belt or pulleys.

Also check your reservoir for fluid aeration after running. Some reservoirs do not handle the fluid very well.

We had a similar problem with a rack system. Loss of boost on corner entry or mid turn. Tried a few things which did not help. Finally the pump went bad and we replaced it and no more problems, so it was an early sign of the pump failing I guess.

David,


I too was following the path of an intermittent loss of assist from the steering box, mainly due to the amount of changes I made from the rack to the box (need for more volume or pressure, remote reservoir, longer feed line, longer pressure line, added fluid cooler in return path, box heat soaked by header, the fact the steering box went through a fire, etc.)


The pump is a cast iron unit and did have a Loctited pressure bypass screw. I removed the screw and used shims to set the "pop-off" pressure to about 1350 psi. Pump is overdriven @17%, which could be an issue at high engine rpm (redline is 7200 crankshaft rpm). I also experimented with different volume restriction orifices. Feed and pressure hose fittings were changed to reduce minor flow losses as much as possible.


I seemingly tried everything with the exception of rebuilding/replacing the pump and box until a particularly prolonged hard feedback came through the wheel while testing. The prolonged nature of the event allowed me to more easily feel what was going on, as it lasted about one second. I could distinctly feel a sliding/grinding feeling like one associated with mechanical interference. During the subsequent search I found that the rag joint was rubbing on the #7 header primary under some dynamic condition. The location of the rub was on the rear side of the tube and cannot be seen from the engine bay. It appears the torque reaction on the block (~450lb-ft) was causing the engine to move about 3/8" towards the rag joint. The only part of the joint that touched was the part that connects to the box input shaft directly, which means that the header would only interfere with the joint in two radial steering wheel locations under heavy throttle and right hand cornering loads.


I moved the column and joint back 5/16" as well as clearanced the joint and it seems the problem has been solved after a few sessions of testing.


Thank you for your help.

[pitts64]

This is the shim kit..

https://www.summitracing.com/parts/brg-899001