Oversized power steering pulley

Does anyone have some input on what effects I may cross by putting an oversized power steering pulley on my pump? I stuff the last one which was 100 mm diameter, I've been offered a replacement that is 120 mm. I'm thinking it may cause excessive pressure in the system, or will spin the pump too fast which I'm afraid may stress the pump too much. Can I offset any pressure by reducing the viscosity of the pump fluid? Not sure what other problems could be involved.

The unit is going on a 2.8 in a 99, still has the factory steering box, and the patrol is lifted 2" and sitting on 33's. I'm open to having the steering box rebuilt to accommodate the needs of the pump with the bigger pulley. If anyone has the same pulley for sale then I am interested.

Thanks

If the pulley is on the pump, which is being driven, by the belt off the engine, going up in diameter will slow the pump down. It also will change the belt length as the circumference of the pulley is larger. I would source a replacement of the same diameter to keep everything running as designed. I am unsure what effect slowing the pump down would really have, maybe a reduced 'power assist'? Patrol A Part or even a Nissan Wrecker would have a part, just specify the engine and diameter, maybe the pump shaft diameter for sure.

Is there a workshop near you that can machine the pulley to the correct diameter?

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Originally Posted by mudnut

Is there a workshop near you that can machine the pulley to the correct diameter?

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Unless this is an emergency repair, I can only imagine that costing twice the price of the correct pulley.