F-250 Highboy - Weak Power Assist Steering, Is This Normal?

[Bfloeck]

Hi -

This is my first time posting, although I’ve been reading the forum for a while - there’s a wealth of information about these old trucks here! I wasn’t able to find an answer to this question through searching - apologies if this has been answered already.

I have a ‘71 F-250 crew cab F26 4x4 with a Dana 44 HD closed-knuckle front axle, and a Garrison power-assist steering system that has been transplanted in by a previous owner. I’ve gone through the system, and it now functions and doesn’t leak, but the assist is rather weak. I’m trying to understand if I have an issue with the pump and/or control valve, or if this is just how the system operates. The power steering pump and ram cylinder are both new. The steering gear is in good working order with bearing preload and mesh load right where they should be. The control valve is a Garrison unit with new o-rings installed. With the truck on, I still need two hands to turn the wheel. The assist doesn’t change with engine rpm. For comparison, I have a ‘67 mustang with a similar power-assist setup (much lighter car obviously) and I can turn the wheel with one finger even when parked.


I took the measurements below of steering effort at the steering wheel while trying to troubleshoot. This is on 235/85R16 tires

Steering effort, truck parked, engine on: 120 in-lb (10 ft-lb)
Steering effort, truck parked, engine off: ~40 ft-lb
Steering effort, front wheels off the ground, engine on: 50 in-lbs (4.2 ft-lb)
Steering effort, front wheels off the ground, engine off: 80 in-lb (6.7 ft-lb)

For comparison, my ‘67 mustang with a similar power-assist setup with engine on, car parked: 20 in-lb (1.7 ft-lb).

Is this normal? I know these power-assist setups are pretty notorious for being problematic, I’m just trying to understand how much assist I should expect. Even with the wheels off the ground and the engine on, it takes several times more force to turn than my mustang does with the wheels on the ground - this makes me think there’s something wrong.

Thanks for the help!