Overboosted Power Steering - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DeepPurple · 09-02-2004, 02:07 PM

Hello folks, instead of pitching insane ideas, I have a problem.

I recently replaced the power steering gearbox that was leaking with a new one (supposedly for our years) from LMC (yeah yeah, I know).

Suddenly the power steering has gone from tolerably overboosted to...absolutely insane. I can tap the wheel with my fingers and it'll spin one full revolution. I'm not expecting rack and pinion here, but this is kinda silly.

For background information it's the LMC gearbox, and a "joined" pump (pump and reservoir don't really seperate) off of a mid to late 70's passenger vehicle.

bigvinnie · 09-02-2004, 04:18 PM

is the ps pump pulley same size as stock..??? can't remember whether it's bigger diameter or smaller that will help correct the problem...

bumpster · 09-02-2004, 04:22 PM

Don't know much , but when I set up my 68 with an old sytle pump and new style gearbox I had to switch the fitting on the back of the old style pump with the fitting from a 73 pickup pump for the hoses to fit. When I took the fittings out, springs fell to the ground. With my usual care and precision I put the longer of the two springs in, because it's the one I picked up first. I have been told those springs are what sets the pump pressure. Anyhow,when I finished, you could back a stock trailer using the horn button. Putting the other spring in helped considerably. Good luck.

DeepPurple · 09-02-2004, 05:05 PM

Quote:

Originally Posted by bigvinnie

is the ps pump pulley same size as stock..??? can't remember whether it's bigger diameter or smaller that will help correct the problem...

I'm unsure of that.

See, the pump came with the engine that I swapped in a few years back (engine is no longer with the truck). The truck has manual steering that I updated to power steering (used a junkyard box) and as such the only factory power steering I've seen is in pictures.

Longhorn Man · 09-02-2004, 07:46 PM

Your spring is probably messed up. Pully diameter won't do anything. Once it gets to 'X' PSI, it goes through a bypass valve, and it is at that PSI at an insane low RPM.

bigvinnie · 09-02-2004, 11:03 PM

guess I heard wrong on the pulley, good to know the real scoop...

Longhorn Man · 09-03-2004, 02:47 AM

If you were to disable your ignition, and crank the engine over while turning the wheel, you'd feel the power assist kicking it...at reduced power of course. And a starter only cranks the engine over at about 200 RPM at the most.

DeepPurple · 09-04-2004, 06:25 PM

A question then, now that I have had time to reflect on this, and allowed my cursing to die down to a dull roar.
Are our trucks supposed to handle like they're on ice?

ASSuming the pump is good (I haven't been able to check it yet) what are the differences in pump pressure/volume between the mid-to-late 70's GM truck power steering pumps and ours if any?

Also, anyone here had much experience with the AGR power steering systems?
In particular their variable ratio one?

Frustrating is such a simple sounding word...

09-02-2004, 02:07 PM	#1
DeepPurple Real Deep... Join Date: Jun 2002 Location: St. Louis Posts: 116	Overboosted Power Steering Hello folks, instead of pitching insane ideas, I have a problem. I recently replaced the power steering gearbox that was leaking with a new one (supposedly for our years) from LMC (yeah yeah, I know). Suddenly the power steering has gone from tolerably overboosted to...absolutely insane. I can tap the wheel with my fingers and it'll spin one full revolution. I'm not expecting rack and pinion here, but this is kinda silly. For background information it's the LMC gearbox, and a "joined" pump (pump and reservoir don't really seperate) off of a mid to late 70's passenger vehicle. __________________ 1970 GMC C10 (Deep Purple) 383/700-R4 Mass Modifications 1976 GMC K5 Jimmy (Big Blue) 400/TH350 Coming soon to a drive-in near you... We have done So Much with So Little for So Long.. We are now qualified to do Anything with Nothing.

09-02-2004, 04:18 PM	#2
bigvinnie Registered User Join Date: Aug 2001 Location: escondido, ca 92026 Posts: 1,222	is the ps pump pulley same size as stock..??? can't remember whether it's bigger diameter or smaller that will help correct the problem... __________________ '72 short step, 350, 700R4, tilt, ps, pdb, a/c, lowered coils, etc., other work in progress... San Diego, CA 72 Stepside Project

09-02-2004, 04:22 PM	#3
bumpster Junior Member Join Date: Jan 2004 Location: Stillwater, Oklahoma Posts: 63	Don't know much , but when I set up my 68 with an old sytle pump and new style gearbox I had to switch the fitting on the back of the old style pump with the fitting from a 73 pickup pump for the hoses to fit. When I took the fittings out, springs fell to the ground. With my usual care and precision I put the longer of the two springs in, because it's the one I picked up first. I have been told those springs are what sets the pump pressure. Anyhow,when I finished, you could back a stock trailer using the horn button. Putting the other spring in helped considerably. Good luck. __________________ 72 C10 10 yr.daily driver 68 C10 18 yr.money pit 72 Nova all original 99 H.D. Heritage[sanity check] 71 VW topless bug[summer fun] "When I have the money, I don't have the time ; when I have the time, I don't have the money.

09-02-2004, 11:03 PM	#6
bigvinnie Registered User Join Date: Aug 2001 Location: escondido, ca 92026 Posts: 1,222	guess I heard wrong on the pulley, good to know the real scoop... __________________ '72 short step, 350, 700R4, tilt, ps, pdb, a/c, lowered coils, etc., other work in progress... San Diego, CA 72 Stepside Project

09-04-2004, 06:25 PM	#8
DeepPurple Real Deep... Join Date: Jun 2002 Location: St. Louis Posts: 116	A question then, now that I have had time to reflect on this, and allowed my cursing to die down to a dull roar. Are our trucks supposed to handle like they're on ice? ASSuming the pump is good (I haven't been able to check it yet) what are the differences in pump pressure/volume between the mid-to-late 70's GM truck power steering pumps and ours if any? Also, anyone here had much experience with the AGR power steering systems? In particular their variable ratio one? Frustrating is such a simple sounding word... __________________ 1970 GMC C10 (Deep Purple) 383/700-R4 Mass Modifications 1976 GMC K5 Jimmy (Big Blue) 400/TH350 Coming soon to a drive-in near you... We have done So Much with So Little for So Long.. We are now qualified to do Anything with Nothing.

09-02-2004, 07:46 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Your spring is probably messed up. Pully diameter won't do anything. Once it gets to 'X' PSI, it goes through a bypass valve, and it is at that PSI at an insane low RPM.

09-03-2004, 02:47 AM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	If you were to disable your ignition, and crank the engine over while turning the wheel, you'd feel the power assist kicking it...at reduced power of course. And a starter only cranks the engine over at about 200 RPM at the most.



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