Hello again.

I see that the dealer asks for the ESN number when buying a VP44 pump. As they only fit from 98.5 to 2002 (I think i`m right) is there a difference in the pumps if so what is it?
Thanks for being here...Pepper

 

The only difference I am aware of is between the SO and HO models. The HO pump puts out higher pressure.

Chris

 

The two have different cam rings, heads, and programed different on the test stand.
The so pump has bigger plungers in the head thand the ho pump. The pumps cam rings have enough difference on the tpming that you cannot just put a so pump on the ho engine or reverse.
Hopes that helps.

 

Which year truck uses an HO pump and which one uses a SO?

 

The 99 was only available as an SO model.

 

5 Spd is so
6 Spd is ho
Or you can look on the engine data plate on driver side

 

2001-2002 6 speeds were HO's.
1998.5-2002 5 speeds and Autos were SO's.

Also note that there is some 99 and 00 6 speeds floating around out there that are SO's.

 

can we put a HO in the 1998.5 to 2002 autos and five speeds. most of the places where these are ordered from don`t seem to make an exception for this.

 

Im running a 2001 so pump on my 2002 ho engine . it runs alright but alot less power. with comp on level 4 feels about the same as stock.

 

Can we use a HO pump on a 1998.5 and if so will it boost the power or what???