underdrive pulleys

R

rulesR4suckers

New Member

May 1, 2005

72

0

0

Fairview Heights, IL

May 17, 2007

#1

• May 17, 2007

• #1

So, lately I've been hearing this noise coming from my alternator that sounds like the bearings were about to go. Hearing that, I decided to order a set of underdrive pulleys and make project for myself. I took the old alternator off and just as I was about to pull the pulley off of the new alternator, I noticed that the pulley was the same size as the pulley that came in the underdrive kit. Has anyone else run into this? I thought it was weird, but it saved some time though.

 

The Green GT

No 13 year olds are safe around me.

10 Year Member

Jan 8, 2006

1,269

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99

Louisiana

May 17, 2007

#2

• May 17, 2007

• #2

Mine was smaller, but only about 1 MM if that. most of the size difference is in the other two pulleys. Id leave the stock alt pulley so you have less of a chance of charging issues.

 

True 5.0

Member

Sep 22, 2006

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Southeastern Wisconsin

May 17, 2007

#3

• May 17, 2007

• #3

Most underdrive sets have the alternator pulley much LARGER than the stock one. The concept is to slow down the RPM's of the accessories relative to the crank RPM's. My set has a smaller than stock crank pulley and a larger than stock water pump and alternator pulley. All the others do not get replaced and thus are stock diameter. I'm not sure how the alternator pulley can be smaller and still run the stock belt.

 

R

rulesR4suckers

New Member

May 1, 2005

72

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Fairview Heights, IL

May 17, 2007

#4

• May 17, 2007

• #4

The Green GT said:

Mine was smaller, but only about 1 MM if that. most of the size difference is in the other two pulleys. Id leave the stock alt pulley so you have less of a chance of charging issues.

Click to expand...

Yeah, I'm definitely not messing with the alt pulley. Since it's the same diameter I don't see a point in changing. I'll say this, I have noticed a bit of a difference in power. The interior lights dim a bit at night with the headlights and radio on, but I can deal with that.

 

final5-0

Mustang Master

Apr 6, 2003

6,817

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79

DFW Texas

May 17, 2007

#5

• May 17, 2007

• #5

I would tell you to just keep the OEM set if you're not gonna use the
entire set of pulleys.

The whole reason for the mod is to gain power

This mod yields small gains at best
but
Never the less ... its a nice one for the money spent

By not changing the alt pulley ... the gain is gonna be less for sure

You can find a bit more juice at idle with just 1 to 2 hundred more rpm

Now ... If you got a mega watt pulling sound system ..........
You shouldn't even be considering them in the first place ... IMHO

Grady