Trying to upgrade my power steering pump to handle my heavy wheels and tires better. The factory iron pump is pretty much garbage. I've gone through two...

My problem is, regardless of the model year I choose, all the ZF pumps are about 1/4 inch too big from pump face to rear mating surface. This spaces the pully too far out. They otherwise bolt up fine.

The two pics show my pully pressed on (I machined the bore diameter of a factory pully) and then fully seated against the housing of the pump, and it's still not enough to get it in line. Tried an 03-08 ZF pump, and also an 08-14 (I believe) pump. They're the same dimensions.

I know it's a common upgrade for cummins machines, am I just SOL with my front cover setup? I'm waiting on one final pully to get in which is an 8 rib, hopefully with the backspacing I need to get it to line up. Otherwise, am I just stuck with these garbage snap ring / iron pumps?

This is pressed on nomially.

This is fully seated against the pump housing.

Edit - yes I know that pully is cracked, it's for mockup

 

Could you machine the mount to space the pump back further??

 

Yes but that would require a complete front engine disassembly to remove the front cover...

 

That seems just a bit extreme......

What was the pump originally from? Would a pump from a diesel be any better?

 

Got a new pully in today. It's a Dorman 300-149. It solves all the issues but makes a new one... this pully is bigger and fits right over the pump housing, lines up great now. Except... now it interferes with my crank pully. ughhh

Looks like I might need a $400 overdrive crank pully that's smaller.

Edit - Science!

So the factory damper is 7 3/16" diameter, the factory power steering pump pully diameter is 5 9/16"

That gives a drive ratio of 1 : 1.29, so the power steering pump in the factory setting turns 1.29 times for every turn of the crank (not accounting for groove depth which reduces the pully diameter...)



If I put a TFS Underdrive crank pully on, that measures 5 1/2 inches in diameter. The new power steering pully is 6 3/8" in diameter, for a final drive ratio on that setup of 1 : 1.16 or 1.16 crank turns for every 1 turn of the power steering pully. That's almost what, 33% slower than factory.



And finally, if I could actually fit the new pump and pully combo on with the factory crank pully, the final drive ratio for the power steering pump would be 1 : 1.13. Slightly better, but still worse.


I'm not sure what to do now. Maybe I'll buy a new (used) front cover for $100 on ebay, have it machined, and just run a stock pully size. It'll be cheaper than an underdrive pully and I'll get better performance too.

 

Success! With just a little bit of clearancing on the casting of the pump, and with a fully seated pully, it lines up perfectly.

I measured the casting in the two areas I clearanced, It's not even close to any internals.



I guess I'll grab a new pully tomorrow and get it properly machined out to .663 for the new diameter of the new pump..

 

I’ve been looking for a thread on this topic. Installing a zf pump next weekend on a 06 1500 4.7l. Have u noticed an improvement after this swap. I’ve been having the same poor experience w the snap ring pumps.