RE: {Chrysler 300} ps pump psi 57 C

["'Ron Waters' via Chrysler 300 Club International" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>]

John - To be honest, I don't know which one is the Thompson pump. If S&G says it was used on later Mopars, then I would guess that it is. I mainly see references to 'sleeve' vs a 'slipper' pumps, even in the MTSC booklets. And not to make things more confusing, the parts book shows six different power steering pumps used in 57-8. Whew !

Ron

-----Original Message-----
From: John Grady 
Sent: Monday, January 12, 2026 4:09 PM
To: Ron Waters <ronbo97@xxxxxxxxxxx>
Cc: 'Bob Meritt <bob@xxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} ps pump psi 57 C

Hi Ron looks like it might be , or adaptable via that bracket on the side Is that a so called Thompson pump ? 
Steer and  gear recommends changing 300C  to a Thompson pump , not sure what that is but apparently used on later mopar , “ later “ is however not defined  ,  … 
later is higher psi too to my knowledge to use with the later smaller ps box , which  setup might have been  first used on Plymouth and Dodge   , and pump goes with box? not sure …  

> On Jan 12, 2026, at 1:24 PM, Ron Waters <ronbo97@xxxxxxxxxxx> wrote:
> 
> John -
> 
> As a suggestion, have you tried using a slipper type p/s pump that was used on 58 Plymouth and (possibly) all makes in '59 ? I've been told that it's a direct bolt-up. But haven't verified that. See photo.
> 
> Ron
> 
> -----Original Message-----
> From: chrysler-300-club-international@xxxxxxxxxxxxxxxx On Behalf Of 
> John Grady
> Sent: Monday, January 12, 2026 1:14 PM
> To: chrysler 300 club 
> <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
> Subject: {Chrysler 300} ps pump psi 57 C
> 
> hi , as many may know the 57 pump is problematic   , mine ( rebuilt ) burned up in  and  seized  in 15 minutes at first start  . But sure looked purty .
> 
> Dont really trust it
> 
> So looking at designing a mount to hemi for bulletproof saginaw pump , used on most GM for many years and actually Dodge trucks in 70’s , maybe more years .
> found dual vee keyed pulley and there is enough physical space on 300C , so looks doable , initial thought is to weld adaption to the old bracket.  So save hemi ps brackets But somewhere in distant past , I think someone told me the large coaxial box runs on 600 or 800 psi , not the 1000-1200 of later mopar and apparently all GM boxes ( and what saginaw pump delivers)  .
> The pressure is set by a part of the  outlet fitting , regulator unscrews from outside . ( awwright) And several suppliers make a 600 version to use  it   on mustang rack ; this combo is a favorite of hot rod guys  .
> Does anyone know operating psi of our coaxial box ?
> C and  I think D use it maybe earlier ?  might add to repro parts 
> setup thank you , John
> 
> 
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