3/4" vs 5/8" water pump shafts


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By 63 Red Stake Bed - 16 Years Ago
Is there a difference in the repop alum. water pumps shafts?  I don't recall & need a new (reman) pump.  I was quoted 200+ for the 3/4", & 56 for the 5/8".

Is there a misquote going on or is it worth my while to just get the new alum. one?

By crenwelge - 16 Years Ago
I use plain old rebuilt water pumps. They have been working for me for 50 years. As long as I have a good radiator and not too much buildup in the engine, cooling has never been a problem for me. If I were going to spend money on cooling, I would put on a radiator shroud. We used to build them for our old trucks and it made a world of difference.
By pegleg - 16 Years Ago
Cren,  the larger diameter shaft was for the trucks. All of the other applications will use the 5/8" shaft. Your pulley will also be different between the two sizes.
By Doug T - 16 Years Ago
Here is a pic of the two pumps.The large shaft water pump was used on heavy duty trucks.  The bigger shaft allows for use of bigger bearings which are necessary because the HD trucks often have two belts which are also bigger than the pass cars. This puts vastly increased loads on the bearings. The HD pump has extra gussetts cast on the snout to carry the bigger loads and the snout itself is bigger.  There is likely to be more pumping difference between the various designs of impellers than the HD and standard pump as originally delivered by FoMoCo.

Because the casting is different between std and HD it is unlikely that ReBop has built aluminum HD pumps but Frank can confirm.

By pegleg - 16 Years Ago
Right,

       the Rebop pumps were small diameter shaft, standard pass castings. I did try to improve the impeller design some, wasn't happy with many of the aftermarket variations.

By crenwelge - 16 Years Ago
Reman pumps are very available and somewhere around $50. I have always known that water pumps for truck application looked different than passenger water pumps, but I didn't know that the shaft size was different. A truck application pump might be expensive because there isn't near the demand as for passenger water pumps.
By 63 Red Stake Bed - 16 Years Ago
Do they make a rebuild kit for the 3/4"?

Has anyone ever tried doing a rebuid themselves?

By crenwelge - 16 Years Ago
I have put kits in passenger pumps but I never had occasion to rebuild a truck pump, but I would think the principle would be the same. Try these guys. http://www.kanter.com/truck/trwp.html