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Eagle Eyes
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Discussion Starter #1
For years I, like everyone else, has hated the drive system designed for our alternators. Looking at the gassers, at least some of the 350’s and 454’s of the 80s had a wider belt. The 6.2 system had a single 10mm belt. This is simply inadequate for our trucks let alone a 6.2 stuck in a motorhome with more then two batteries to charge.

The situation is that with the original belt you are likely to have major slippage of the belt causing squealing or squeaking on high loads- first startup, highbeams, high fan, etc. The GM requested upgraded belt, Gates 5725, fixes the squeal but you still have the issue of not enough belt area/grip to drive the alternator correctly. This special belt is 11mm and apparently, that little extra surface does the trick in most cases.

Many posts on this forum dances around this issue. Some like member “jdemaris” solved the issue by putting on a larger pulley on the trucks of his fleet. This equals more belt surface for grip. However, it also equals lower charging at idle. I did not want to do method because the 5725 belt seemed hard to get on a standard size pulley due to its length let alone a larger pulley. In addition, I was already dealing with a light dimming issue at idle under load. When stopped, engine at idle and highbeams on the headlights would dim. With heater fan on it would be worse. This is either the alternator not putting out enough by design (a possibility) or the belt is slipping causing the alternator to not put out enough (likely knowing the issue).

Others swap everything out to the serpentine setup, but I did not want to change out my waterpump, etc. This swap is needed to correct the pump rotation.

My solution was to dual belt the alternator pulley. This is possible, because thankfully, and proudly, these engines are used in the military HMMWV in both 6.2 and 6.5 flavors. In the 6.2 HMMWV application the crankshaft and waterpump pulleys are 4 groove. Some of the waterpump pulleys had 5 grooves. Later they went serpentine belted. 4 groove pulleys equates to us a dual belt alternator and a dual belt power steering pump, or a single power steering and keeping the AC compressor as well.

This dual belt alternator modification was also available for civilian 6.2 Hummers, specifically to deal with “reduced alternator belt life or belt slippage.” This bulletin is attached bellow the pictures.

The known problem to this modification is that the HMMWV’s use a very different power steering pump and a much different design alternator. Because of this, using the two military pulleys creates an alignment issue. Talking it over with the “Turbonator” guys, who have done this upgrade before, it turns out this is not as big of an issue as it seemed. The way I did it, I did not even have to change out any bolts…all were long enough to allow the spacing out.

What you need:
1- Military four groove crank pulley, part number 5578966D.

1- Military four groove water pump pulley ( there is a 5 groove, I think it may work the same) Part number is 12338781.

XX-a bunch of washers, it took 3 washers on each mount to space out, each accessory is 4 points mounted, the amount of washers you use may differ.

1- Dual groove alternator pulley. I found an original USA made Delco Remy/GMC pulley. They are easily found aftermarket however. There are two options, I believe the one I selected is the correct one. The other has a larger belt spacing of 16mm instead of 14mm. Part number is 1961408, new aftermarket number is 241110.

1- Same height power steering pump pulley. The 6.2 stock one is a single for non AC, or with AC it’s a dual belt but double height pulley. If you keep the double height one I believe the belts will fight each other as the military pulley has no height change. You can keep the double height one, I believe, if you intend on having air conditioning. The pulley I used is the same diameter as the stock one. I believe this will increase the pump rotation slightly but I have not noticed any ill effects. Part number is 354325AC.

Special note: depending on if you want air conditioning or not, you will need matching belts. The alternator needs to having matching belts, if you dual belt your power steering you will need matching belts. If you run air conditioning, you only need matching belts on the alternator. You need matching belts or only one of your two belts on that drive will do the work. The other will just go for a ride, which negates the whole reason of doing this project. Matching belt is done by exact length of the same belt part number. When I first mounted the four belts, one on each drive was clearly slack the other taught. You need to switch them around or try to find correlating numbers, or specifically get matching belts. Not all four need to match, only two sets of two or one set for the alternator with air conditioning.

Note: My Air conditioning is currently broken so I am not belting that up. Instead, I will have true dual belt power steering for the time being.

I also changed off my harmonic balancer and front oil seal, and put on a Fluidampr. Therefore, you will notice that in the pictures.

Procedure:

I wanted to keep the stock fan and clutch. For this to be possible, you need to cut off the military fan hub on that pulley. I used my metal bandsaw to do it accurately, then a sander to clean it up. Check the pulley face is square with the belt face. Member “67 C30” milled out the face of the pulley so that the fan hub sits into the pulley.

You can leave the fan guard on. I completed all the work without having to take it off.

Take off the fan, WP pulley, WP studs.

Take off power steering pulley. I used autozone/OEM Tools tool number 27031 which allows you to take off and install that pulley. You can rent it from them.

I had to remove my alternator. This helps gain access to the mounting points and modification of the two top brackets (easy). Also, it is very helpful in removing the stock pulley and installing the dual belt pulley. To install I used a deep impact socket, put vice grips on it and put the Allen key through the top. I put an extension with socket that slipped over the Allen key for good leverage.

The power steering pump, with the pulley off, should be unbolted at the bracket points to the engine. Once the pump is separated and hanging there, you can place 3 washers at each of the 4 points, then remount. The one stud, the lower left to the timing chain cover will thread on about 75%, the rest will be solid.

The alternator brackets have to be pulled off as well. This includes the top adjustment bracket as well as the bracket that holds the CDR valve. These two brackets need to be modified slightly to allow for adjustment of the alternator towards the front. The adjustment bracket rear ear to the intake stud needs to be cut out. The CDR mounting bracket has three bolts up top in the front. I simply cut out the front two ones and used a file to oval out the rear one. This turned out to be plenty for me and still looks okay. Once that is done you can mount everything back up with 3 washers at each point- the one where the long bolt goes to the block, two for the double Y bracket, and one above that. I also put one washer in between the adjustment bracket to intake stud and the CDR bracket to help it catch better. So, that is, at the intake stud, bracket you modified, washer, CDR bracket, nut. Reinstall alternator.

The crankshaft pulley mounts up as the OEM one does, 4 bolts to the harmonic dampener. I couldn’t find the torque specs for it in the GM service manual so I used a metric torque chart. I think its 20 lb-ft.

The water pump studs have to be longer for the pulley to mount. The originals have shoulders that bottom out against the hub face. I purchased the longest M8 1.25 pitch bolts that were fully threaded. I used blue locktight on them to the pump shaft to secure them. The fan nuts will fully thread on with about one thread extra, if you put the studs fully into the hub as I did. The originals did not go in fully before the shoulder made contact. Note: you will find about 4” of clearance between the fan and AC cooler lines with this setup. Member “67 C30” used bolts instead of making studs to secure the fan hub to the pulley. So that is another option.

You will find that the waterpump centering stud does not come through the face of the pulley. Member “67 C30” fixed this problem by milling out the face of the pulley to mount the fan better. I found that the fan hub has about 1” of depth to it, the pulley is about 3/16.” I cut down a 3/4” bolt and used the shank to increase the centering point. I antiseezed it and it slides right in for a firm fit on both ends. This allows the fan to both fully seat against the pulley face and to accurately center the fan to the pump.

Once the main pulleys are mounted, and with the power steering pump mounted, you can begin to install the dual PS pump pulley using the tool. I had my fan off at the time to do so but it is possible to do it with the fan on. I got the pulley on close to wear it needs to go then slowly installed it until alignment. I checked alignment with eye, with a level, with a belt installed, and with a laser. With it installed, mine will not fully go onto the pump hub, but is about 95-98% on the shaft I would guess. It is only slightly off. If you want it fully on you will have to do a spacing of 4-5 washers instead of three, and you will have to change out some of your bolts and studs to do so.

I have found that with this setup I can keep using the upgraded 5725 Gates belts on the alternator for a dual setup. This is because both alternator, crank, and water pump pulley diameters are the same between the OEM and military pulleys. I also found that the original PS belt will no longer fit, however, the 5725 belts will. This is because the diameter of the water and crank pulley is larger on the military then the OEM. The 5725 belt is longer then the OEM power steering belt, so it fits with about 1/2” left on the tension brackets. Nevertheless, with two 5725 belts driving the PS pump you do not need to have them very tight I am finding. It seems even one 5725 belt on the power steering, due to the 11mm belt face, is gripping the pulley better then the 10mm. With one and another to the compressor I doubt slippage will occur.

In summary:
With two belts driving the alternator you will no longer need to over tighten these belts anymore, which led to eventual stretching and breakage.

So, as you can see you will have all four belts in the 5725 flavor. If you have AC, you will have three then the 4th will be the longer belt. I am unsure if the original AC belt will fit at this time but it looks like a strong chance it will as the AC had good length adjustment brackets. If not, its easily to take that belt down a size or two. You will have to space out the compressor brackets as well, but I imagine 3 washers will space that compressor into line with the pulleys. 3-4 washers will easily fit on those without needing to get new bolts and studs.

"Turbonator" guys reported they have been running two belts for two years without any issue. The most I have to do is find a better set of matching belts, or rearrange mine to match better. Other then that, its working.

Advantages:
With this setup we will see longer belt life, and greatly reduced chances of belt breakage due to over tightening the belt constantly. Using the wider 5725 belts in a dual design will allow for maximum pulley grip leading to full design output of the alternator. In fact, with the slippage problem gone, we can increase the amperage (within reason) without fear of slippage or squealing. 94 amps is the largest 12SI alternator they make, this dual belt system should easily manage that. I know some members have gone with larger alternators with higher amperage. I doubt full advantage of those alternators are occurring without first dual belting that drive.

In addition, with more grip on the power steering pulley, that too will stop squealing- I imagine even with a depleted battery.

As a side benefit, dual belt design allows for longer bearing life due to proper tension as well as a redundancy in number of belts. Plus, having all four belts being the same simplifies the need for keeping extras as spares. However, with it being a matched system, belts will need to be swapped out at the same time for each drive.

Oh- and I found a four leaf clover on one of my brackets...apparently the luck of the Irish is with us on this modification.

References:

http://www.dieselplace.com/forum/63-gm-diesel-engines/20-6-2l-diesel-engine/464073-dulal-v-belt-drive-alternator.html

http://www.dieselplace.com/forum/63-gm-diesel-engines/20-6-2l-diesel-engine/366781-hummer-pulley-mod.html

http://www.dieselplace.com/forum/63-gm-diesel-engines/20-6-2l-diesel-engine/456959-6-2-water-pump-vs-hmmwv-6-2-water-pump.html
 

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Eagle Eyes
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Discussion Starter #2

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R.I.P. Sam
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32,078 Posts
Very well illustrated :thumb:

Glad you got the bugs worked and shared it with others.

Adding this into the FAQ's now. I should probably throw it into DIY, it's kinda bare :hehe:
 

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respect the DB4 5722....
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12,490 Posts
great post, excellent as a matter of fact....:thumb:.... we have been running our 140 amp alternator since the spring, no trouble with squealing, but we are also running a modified alternator upper bracket with a threaded bolt and nut to tighten it, there are pics here somewhere, later i will make an effort to find them and post it here if you dont mind, also when we re-drill the upper pulley to take a fan clutch, and also be able to use the hydraulic, i could post them as well.... once again, great post... thanks for getting it in the FAQ's as well rich.....:thumb:
and as a side note, i like that the dieselplace logo is in every pic, shows where the info originated....:clap:
 

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Ex- 6BT Square Body Man
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R.I.P. Sam
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32,078 Posts
thanks for getting it in the FAQ's as well rich.....:thumb:
and as a side note, i like that the dieselplace logo is in every pic, shows where the info originated....:clap:
Thanks for swelling my head some more. :thumb: Made me notice the DIY link is too a silly thread, I have to fix it when I get a chance.
 

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Eagle Eyes
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1,334 Posts
Discussion Starter #7
and as a side note, i like that the dieselplace logo is in every pic, shows where the info originated....:clap:
Thanks for liking this modification...hopefully it will encourage and help others through it.

I decided to add our logo on those pics, with knowing this is a widespread issue I'm sure these pics will hit the internet... just want them to know "you saw it here first"

I noticed the pics in our garage have it but not forum pics.
 

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Un-Official Chat Room Admin
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Good job man we need more members like you
 

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Eagle Eyes
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Discussion Starter #9
Here is the information concerning the belts. As referenced in my pictures of the belts installed, you will notice that the belt closest to the block is not as taught as the other. After rotating the belts all four belts are alot closer to matching, but that groove is still more slack then the others.

As the decrease in taughtness increases the belt will do less work. Its important to get as close to matching belts as possible so the load is shared, which is most favorable, or at least increased over a single belt.

After talking to a Gates representative he kindly gave me this information: "...we do not offer matched belts anymore as our manufacturing processes have improved to the point where any two belts rolling off the production floor should be a matched set in theory. That being said, there are going to be instances of minor differences in belt lengths due to manufacturing tolerances, and this will be a problem for drives like yours where two identical non power-banded belts run side by side to drive a component."

The Gates representative advised me to match the belts as close in the same "lot", that is, obtain two from the same date and plant. You do not have to match all four, just find two pairs of two matching belts.

In our discussion we also found that, even though I purchased them new, that the belts I bought are already old. The representative mentioned their belts have a shelf life of six years depending on storage conditions.

I am including my belt information for long term reference. Belts 1-4 are new belts, belt 5 is the old single belt I was driving for another comparison.
1. 317ET – 31st week of 2007. Built in our Elizabethtown, KY plant.
2. 328ET – 32nd week of 2008. Built in our Elizabethtown, KY plant.
3. 4410SS – 44th week of 2010. Built in our Siloam Springs, AR plant.
4. 3808SS – 38th week of 2008. Built in our Siloam Springs, AR plant.
5. 2510SS – 25th week of 2010. Built in our Siloam Springs, AR plant.

Since I had already ran the new 4 belts I couldn't return them. The next time around I will try to match new ones up but I am thinking it will be a troublesome process as the store only carries two at a time, and I'm sure when I request two more none will match. I think I will have to ask them to order in something like 10 belts then pick the best ones.

I did find that with the 4 I have, matching them up by plant ID got me a pair that matched pretty close. The two on the alternator are very close, the one on the power steering is still a bit slack, and less so then my first trial. However, the fact a 11mm belt is on there with a second slack one has made a big difference in grip.

I'm also attaching information concerning belt alignment and belt matching.
 

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Registered
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16 Posts

TFLundyB275, an outstanding write up / posting!


Information;

The 5 groove pulley, for Water Pump,6.2 and 6.5 Liter with V-Belt and A/C is part number 1233782

A Question;

Did they make a 5 groove for the crank?

Thank You

Joseph
 

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Eagle Eyes
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1,334 Posts
Discussion Starter #11
Thanks, glad its a good read and hope it helps. In my search I never came across a 5 groove crank. As you indicated the 5 groove water pump pulley is listed as for AC....I believe its paired with a 4 groove. As far as I know the 5th groove goes right to the special accessory/AC. So in effect, its a single belt from WP to AC. This would work as the 6.2 in the squarebodies for AC is like a 1/2 wrap of belt. In my head the military one would be more like 3/4 wrap with four belts driving the 5th.

A 5th groove WP pulley may work but I forsee 1 possibly 2 problems: clearance from fan to radiator or the AC lines that are also there, and installing fan onto pulley as the shroud will be in the way more.

I just looked at the only pic of a engine with a 5 groove WP pulley on it, a civilian HMMWV. It is somewhat unclear but does seem to show a 5 WP and 4 crank. Will post the pic if you want.

Whats your plans for a 5 groove?

As an update the alternator still charges like a champ. I still have a bit of dimming at idle under load, relooking over the Delco specs seems thats an RPM issue. 66 and 78 Amp alternators put out less at the lower end of the curve, while the 94 Amp puts out more. With the dual belts a 94 Amp would be a non issue. I'll put that one on next whenever this one gives up (its currently a 66), not going to toss a good alternator.

Still running unmatched belts for the PS so its still finicky.
 
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