Under drive pulley

[cp2295]

Just wondering if an underdrive pulley would hurt my engine (cooling) or alternator or ps pump? Also what kinda hp or gas mileage gains has anyone noticed? Lastly, I've only seen the jet ud crank pulley on summit racing and it's $150.. Does anyone else know where I can get one for cheaper?

 

[stmitch]

Underdrive pulleys slow down your engine accessories (water pump, alternator, etc), so if you have lots of electronics you may notice the alternator, but on a fairly stock truck, it really shouldn't be noticeable at all as long as it's not more than 10% underdriven.
I had one on my 3.0 and it seemed to rev smoother and accelerate a bit faster, but it wasn't huge. I have no timeslips/dynosheets to verify, but the manufacturer of my crank pulley had dyno sheets claiming 7hp and 11lb-ft. I also did an electric fan conversion at the same time, so that could have contributed to the power gains I felt, and the mileage increases.

 

[Froggmann]

No decrease in charging or cooling capability, if anything the accessories will last longer due to the lower RPM's. Slight, but noticeable power gain and a consistent 1mpg gain.

 

[RonD]

Most of the time an engine is running is spent above idle RPMs, so for regular use there should be no issues.

For 4 wheeling and crawling all day at low RPMs it might not be a good option, but MPG is not really the concern for that enjoyment , gearing and tire size alone would negate any benefit, lol.

 

[cp2295]

Underdrive pulleys slow down your engine accessories (water pump, alternator, etc), so if you have lots of electronics you may notice the alternator, but on a fairly stock truck, it really shouldn't be noticeable at all as long as it's not more than 10% underdriven.
I had one on my 3.0 and it seemed to rev smoother and accelerate a bit faster, but it wasn't huge. I have no timeslips/dynosheets to verify, but the manufacturer of my crank pulley had dyno sheets claiming 7hp and 11lb-ft. I also did an electric fan conversion at the same time, so that could have contributed to the power gains I felt, and the mileage increases.

Who was your manufacture and where did you get it from? Price?

 

[cp2295]

Also with 32x11.5 will it affect my p/s pump? At idle mostly

 

[stmitch]

Who was your manufacture and where did you get it from? Price?

Mine were made by Underdog and sold on his old site stuffforyourranger.com. But, they haven't been made in several years now, and the site was shut down.

I bought a 10% underdrive crank pulley, a stock size (but lighter) water pump pulley, an alternator overdrive pulley and the correct size Gatorback serpentine belt for around $200.

I have no experience running bigger tires, but I've never heard of anyone having problems with an underdrive pulley and pump speed.