Underdrive pulley experience - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 10-30-2005
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Underdrive pulley experience

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I got Jacob's (TheForce02) underdrive pulley and belts in a deal I made with him and I put it on today. Quite an experience. It started with taking off the skid plate, then...

1. I have not got a bladed fan to use as a place to immobilize the belt/pulleys to get the bolts loose. And I was by myself. So, it turns out the hole in the power steering pump shaft used to press on the pulley is the same thread/size as the bolts which hold the crank pulley on. I used one of the new bolts and put a socket wrench on it, pointing down and to the drivers side and up against the battery tray. That held the belt train pretty well.

2. BUT: it still twisted with a long breaker bar (1/2" drive) with a 1/2-3/8 adaptor and a 13 mm deep socket. I found that "hammering" the breaker bar with a mallet broke the bolts loose without turning the pulley -- like an impact wrench more or less. I got all 4 bolts loose, then removed the belt like the how-to on here explains -- but that was how I could do it alone without a belt driven fan.

3. Put the new pulley on and used the original bolts which have enough thread to work fine. You can snug them down without a belt on, but not torque them.

4. I used the 87.2 inch belt. Jacob gave me a an 87.2 and and 86.5 and said the 87.2 was too short for his truck -- but for some reason it worked fine in mine.

5. With the belt on, I could find no way to immobilize the belt train without a wrench on the nut in the center of the alternator. I couldn't do that and the bolts underneath -- but my neighbor chose that moment to come home...(:Hey, Chris, I need you for a minute -- can you give me a hand?...")

6. With Chris holding the alternator pulley, I was able to put the 45 Ft-lbs of torque on the crank pulley bolts.

Testing

First, just drove it. No difference in how the power steering felt. With the lights off, charging was at 14.2 volts -- perfect.

Drove it around and if there is any difference, I didn't feel it much but I don't really expect to. I thought I felt a difference (good) -- but you know how that is. I'll do some gas mileage checks -- it might show up there.

Turned on the lights at idle -- oh oh. Charging dropped immediately to 13.0 volts, then down, down, until it bottomed out at 12.6 in a minute or two. This is simply not adequate. Using a 60 amp aftermarket replacement alternator. May be different with the stock one. I have a 130 amp one coming soon and perhaps that will charge adequately with the lower RPM.

Worse when the electric fan kicked on -- 12.2 volts, dropping...stable at 12.0 volts. This is battery kill zone. Turned on the high beams which activates my offroad lights -- 11.2 volts. No good. I'm normally at 13.0 with all this stuff on.

So, hoping the other alternator works. I don't know who has actually measured their charging voltage under heavy load at idle with a pulley, but it seems to me, at least with this alternator, that it could be a problem if you offroad and use low RPM's with your lights on. I had to get to nearly 1500 RPM to get back up to 14+ volts. A little over a 1000 RPM to get up to 13 volts.

That's it. Looking forward to the different alternator for sure. I'll keep the pulley if it solves the problem -- if not, it's off and for sale.
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Old 10-30-2005
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Well that sucks man! Hope it works out for you.
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Old 10-30-2005
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Ah, it's okay, thanks. I anticipated it. If I wasn't getting the higher amp alternator, I wouldn't even have tried it, lol.

I know enough about alternators to believe it could be a problem on any stock vehicle. But for the most part, I don't think it would bite many street drivers unless they idle for long periods with their lights on.

But that's something that can happen in night offroading, especially in winter. At least when I do it, lol.
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Old 10-30-2005
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Well you gots to leave it running for the heater!
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Old 10-30-2005
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Exactimundo!
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Old 10-30-2005
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What's with the 60 amp alternator, or is that a miss-type? The data I have shows Rangers either had a 90 amp or a 130 amp from the factory. This is from a wrecking yards computer system which shows the interchange from different vehicles.
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Old 10-30-2005
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I trashed my alternator offroading one day, and it's the only one I could get on a Sunday, lol. No choice in the matter if I wanted to stay mobile! It fit mechanically/electrically, but is of low capacity.

Hey, Wayne, thanks for your how-to on changing out the pulleys without removing the shroud (which I used to mount my electric fan) or radiator. Although I had to improvise, the part about what wrench combo to use was very helpful!
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Old 10-30-2005
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Thanks griggs. I actually need to modify it. The last two I put on I started by cleaning the engine bay. Because of that, the belt would slip using any accessory to keep it from spinning (simple green used to clean it). I ended up by myself and used one socket on the 4 bolts and another socket on the main crank bolt. It worked fine. If you have a manual it is much easier with no transcooler lines getting in the way.

Please give more feedback on this testing as you move forward, or I'll go do some testing on my 3.0's and report back. Your lower than Ford intended amped alternator is probably skewing the numbers. I can test a manual and an automatic. One has the stock 90 and one has the stock 130 amp if I am not mistaken. I can even hook a permacool or black magic fan I have laying around to the battery to duplicate your tests.

I am now a day or two away from having answer on whether an overdrive alternator pulley can be made. IF there are problems with the stock alternator this will resolve it. It should be cheaper than having someone go out and purchase a higher amp alternator.
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Old 10-30-2005
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It's probably having to do with the alternator. 60 amps isn't much at all. Once the higher output alternator is on that problem shouldnt' be a problem.
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Old 10-30-2005
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I am expecting that with stock amperage it won't be a problem. We'll know soon enough.
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Old 10-30-2005
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well since you bought it from me...

to tighten the bolts without the pulley turning i bought a strap wrench that i used to hold the pulley.
in regards to power i didn't notice the diffrence when i put it on, a slight MPG diff. maybe and "maybe" some power, but when i took it off i notcied a MAJOR diffrence. i honestly miss it, but i am using the money to get an 8.8 with 4.10s and LS

good luck john, i need to upgrade my alt. anyways, but with a stock one i didn't have any problems. i did notice the lights get a little brighter when i brought the revs over idle though, but isn't that normal
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Old 10-31-2005
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Yes, it is, Jacob. But I suspect even the stock alternator has more voltage change from idle to rev up with the underdrive than without -- but this is entirely normal. To expect NO change is unrealistic. What we're looking for is a change we can either tolerate or design around.

I was pleased that the power steering was still working fine. Really too cold now to test the A/C well -- but I'll do that at some point. I don't anticipate a major problem there either since it always seems to have more capacity than the truck has ever needed for most weather conditions around here.
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Old 10-31-2005
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Could you put a smaller pulley on the alternator to make it spin faster at the lower RPMs?
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Old 10-31-2005
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An overdrive pulley for the alternator is now available. A further underdrive pulley for the water pump is now available. So this issue can be worked around if needed.

I did some testing on an automatic with the stock alternator this morning. Here are the results.

truck off- 12.79 volts
truck idle, nothing on- 14.05
truck idle, high beams on, stock radio full blast, a/c full blast- 12.44
truck at 1,000 rpm, high beams on, stock radio full blast, a/c full blast- 13.85
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Old 10-31-2005
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Quote:
Originally Posted by graniteguy
truck idle, high beams on, stock radio full blast, a/c full blast- 12.44
... i have about a ~750watt stereo system... not much as big systems go, but way more compared with a stock system.... so the above voltage would probably be reduced to < 12v with my stereo turned up and highbeams on, plus i have auxillery 55w driving lights.

i was hoping i'd be able to upgrade my stock battery to an optima redtop, and do "the big 3" to hopefully increase the charging system's efficiency... but now i'm wondering if it would really do enough? the 130amp alternator might be necessary :o(
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Old 10-31-2005
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The Optima would be able to withstand the voltage swings better than a conventional battery, I do believe.

Wayne, as far as putting underdrive pulleys on the alternator and water pump -- it defeats the whole purpose. When you're done, you've basically put yourself back where you were except for the power steering! If that's what's needed, it would be cheaper to get a BIGGER pulley for the power steering pump, and leave the others ALONE.

If the 130 doesn't do it, I'm not changing out other pulleys -- the underdrive is coming off! No big deal -- somebody will want it who doesn't have my needs for the extra electrical load.
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Old 10-31-2005
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Quote:
Originally Posted by n3elz
Wayne, as far as putting underdrive pulleys on the alternator and water pump -- it defeats the whole purpose. When you're done, you've basically put yourself back where you were except for the power steering! If that's what's needed, it would be cheaper to get a BIGGER pulley for the power steering pump, and leave the others ALONE.
You must have miss read what I wrote. OVERDRIVE the alternator and UNDERDRIVE the water pump is what I stated.
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Old 11-01-2005
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I did miss that! Thanks for the correction.
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Old 11-05-2005
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Update on this?

ScottG
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Old 11-05-2005
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No change. Idling long at night I put it in neutral and rev the engine a tad (about 1.5K rpm).

Waiting for the larger alternator to arrive.

I did have the experience of climing a LOONNNGG hill that I usually can't get much over 65 mph on, and topping out over well over 70 the other day. This is an unusually steep and long hill on route 1 between Media and Painter's Crossing in PA. It was still pulling the speed up slowly when I got to the top. Better.
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Old 11-07-2005
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Okay, I put the new alternator in. What a difference!!!

The problem got WORSE...

But, the reason for that was that the pulley on the new alternator is 10 percent BIGGER than the one on the alternator I HAD in there. So it slowed it down even more. I got this from D. who has a 4.0 and maybe the pulley is bigger on a 4.0.

I took the pulley off the 60 amp unit and put it on the 130 amp unit and the results were: same as the 60 amp unit before the swap. Almost the same voltages under the same conditions exactly.

Time for a smaller pulley on the alternator. Since they're so easy to change, It's not a big deal. Easiest with an impact wrench if you have the alternator off. Harder with it on.

With the alternator off, put on gloves, wrap a belt tight around the pulley and hold it with your gloved hand, and use the impact gun with a 24mm socket. Bada-boom, bada-bing, the nut is off and the pulley slides right off the shaft. Reverse it to install but watch for the kick on your gloved hand as it tightens.

You don't need to overtighten it -- the direction of rotation will tend to tighten it and not loosen it over time if the pulley slips somehow.

There's no part number on this aftermarket alternator I got from D., so there's no way to verify it's specs. It's s rebuilt unit and looks good, but who knows?
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