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| [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356376] |
Fri, 03 July 2020 10:30  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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In our latest 78 Royale. That we got in 2015. I've rebuilt, replaced, or updated everything that can be rebuilt, replaced, or updated. I've even cleaned/painted the bottom side. Replaced a nice awning with a new one. Then widened the entry door by 7 inches. The only things that I haven't done is Ken Hendersons electric wipers. ( Thinking about it) And going to 6-wheel disc brakes. So. Now what should I do?
Back in 2005. I got some rear disc brakes off of a Tornado. And a Eldorado complete. Drilled the holes that needed to be done. Blasted/painted, Then put them on the shelf. About 3 years ago. A friend had an extra set of Lee Harris disc. I bought them. Not thinking that I had 2 sets at home on that shelf. (Not bright on my part.)
Now what do I do since I have the parts? The original 4 drums were fine. If you manually adjust them every year. And about no one does that. The ONLY reason that I had ANY interest in rear disc. Is that my GVW ( Gross Vehicle Weight ) runs between 17,000 LBS to 24,000 LBS all the time. And what would happen if my trailer brakes failed. This put me past my Comfort Zone. ( I just don't ever do that)
So, what to do with the extra disc brake set up? I have 80mm front. 78?mm on the mid axle. Drums rear, And a stock master cylinder up front. With the brake lines switched. I have reservations. As to what I'm really gaining. Other than not having to adjust the rear drums ever year. And getting parts off that shelf.
This topic has been batted around for DECADES. So, what's the latest thoughts. Doing nothing sounds nice. ( GRIN)
Bob Dunahugh
78 Royale since 2003
r
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356378 is a reply to message #356376] |
Fri, 03 July 2020 11:31  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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BOB,
i am in the camp that believe that having brakes on ALL is most desirable.
When we go for just 4 there are times it can not be advantageous.
It is a debatable issue.
I prefer the all 6 disc system utilising the Reaction Arm System.
Reaction Arm system is great., but expensive as there is lot of machining
and special parts and few people that will order them.
On Fri, Jul 3, 2020 at 8:30 AM Bob Dunahugh via Gmclist <
gmclist@list.gmcnet.org> wrote:
> In our latest 78 Royale. That we got in 2015. I've rebuilt,
> replaced, or updated everything that can be rebuilt, replaced, or updated.
> I've even cleaned/painted the bottom side. Replaced a nice awning with a
> new one. Then widened the entry door by 7 inches. The only things that I
> haven't done is Ken Hendersons electric wipers. ( Thinking about it) And
> going to 6-wheel disc brakes. So. Now what should I do?
> Back in 2005. I got some rear disc brakes off of a Tornado. And a
> Eldorado complete. Drilled the holes that needed to be done.
> Blasted/painted, Then put them on the shelf. About 3 years ago. A friend
> had an extra set of Lee Harris disc. I bought them. Not thinking that I had
> 2 sets at home on that shelf. (Not bright on my part.)
> Now what do I do since I have the parts? The original 4 drums were
> fine. If you manually adjust them every year. And about no one does that.
> The ONLY reason that I had ANY interest in rear disc. Is that my GVW (
> Gross Vehicle Weight ) runs between 17,000 LBS to 24,000 LBS all the time.
> And what would happen if my trailer brakes failed. This put me past my
> Comfort Zone. ( I just don't ever do that)
> So, what to do with the extra disc brake set up? I have 80mm front.
> 78?mm on the mid axle. Drums rear, And a stock master cylinder up front.
> With the brake lines switched. I have reservations. As to what I'm really
> gaining. Other than not having to adjust the rear drums ever year. And
> getting parts off that shelf.
> This topic has been batted around for DECADES. So, what's the latest
> thoughts. Doing nothing sounds nice. ( GRIN)
> Bob Dunahugh
> 78 Royale since 2003
>
>
>
>
> r
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356379 is a reply to message #356376] |
Fri, 03 July 2020 12:04 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Senior Member |
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Sell them to me 
BobDunahugh wrote on Fri, 03 July 2020 11:30 In our latest 78 Royale. That we got in 2015. I've rebuilt, replaced, or updated everything that can be rebuilt, replaced, or updated. I've even cleaned/painted the bottom side. Replaced a nice awning with a new one. Then widened the entry door by 7 inches. The only things that I haven't done is Ken Hendersons electric wipers. ( Thinking about it) And going to 6-wheel disc brakes. So. Now what should I do?
Back in 2005. I got some rear disc brakes off of a Tornado. And a Eldorado complete. Drilled the holes that needed to be done. Blasted/painted, Then put them on the shelf. About 3 years ago. A friend had an extra set of Lee Harris disc. I bought them. Not thinking that I had 2 sets at home on that shelf. (Not bright on my part.)
Now what do I do since I have the parts? The original 4 drums were fine. If you manually adjust them every year. And about no one does that. The ONLY reason that I had ANY interest in rear disc. Is that my GVW ( Gross Vehicle Weight ) runs between 17,000 LBS to 24,000 LBS all the time. And what would happen if my trailer brakes failed. This put me past my Comfort Zone. ( I just don't ever do that)
So, what to do with the extra disc brake set up? I have 80mm front. 78?mm on the mid axle. Drums rear, And a stock master cylinder up front. With the brake lines switched. I have reservations. As to what I'm really gaining. Other than not having to adjust the rear drums ever year. And getting parts off that shelf.
This topic has been batted around for DECADES. So, what's the latest thoughts. Doing nothing sounds nice. ( GRIN)
Bob Dunahugh
78 Royale since 2003
r
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Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356380 is a reply to message #356376] |
Fri, 03 July 2020 12:22 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Bob,
As you know, balance is important. But disks on the rear doesn’t increase
stopping power—at least at the limit of adhesion—drums are pretty good in
that regard. But drums are non-linear, and the balance front to rear thus
changes with speed and braking force. Advantage—rear disks, which maintain
front to rear linearity.
But calipers use up more fluid for a given braking force, and that consumes
master cylinder hydraulic capacity. I used the stock master, too, and pedal
travel is about a mile and a half. I would not mind high pedal effort to
move more fluid quicker to take up runout slack. I don’t think I could lock
the wheels before running out of pedal, though it does decelerate quite
rapidly when I stand on it. One thing that helps is to do whatever it takes
to minimize runout. Good luck with that. But I really am thinking about a
master cylinder with a larger piston. I still have good leg strength, so
pedal effort is not a problem for me.
(There is also reservoir capacity, and the stock master cylinder doesn’t
have enough to accommodate dusk pad wear. I know to keep up with fluid
level checks.)
Disks are also less prone to fade, which seems useful for descending hills
in a way that keeps Manny happy. That’s also nice to have with heavier
loads.
Back to balance. I threw the balance off when I installed the one-ton front
end, which I know is not something you want to do. Those larger-diameter
brakes do have more stopping power for a given hydraulic pressure. It seems
to me that rear disks might restore that balance, at least for light to
medium brake applications, where the drums are on the weak side of their
nonlinearity. I’m probably overthinking that. But I have a light coach, so
my balance will be different anyway.
Of course, disks are easier to maintain and visually monitor.
All in all, a good case can be made either way. I had to redo all that
anyway, and definitely wanted reaction rods. The kit I used required the
disk conversion, and it was the most affordable route.
Rick “needing to run the coach around the neighborhood to clean off disk
rust” Denney
On Fri, Jul 3, 2020 at 11:30 AM Bob Dunahugh via Gmclist <
gmclist@list.gmcnet.org> wrote:
> In our latest 78 Royale. That we got in 2015. I've rebuilt,
> replaced, or updated everything that can be rebuilt, replaced, or updated.
> I've even cleaned/painted the bottom side. Replaced a nice awning with a
> new one. Then widened the entry door by 7 inches. The only things that I
> haven't done is Ken Hendersons electric wipers. ( Thinking about it) And
> going to 6-wheel disc brakes. So. Now what should I do?
> Back in 2005. I got some rear disc brakes off of a Tornado. And a
> Eldorado complete. Drilled the holes that needed to be done.
> Blasted/painted, Then put them on the shelf. About 3 years ago. A friend
> had an extra set of Lee Harris disc. I bought them. Not thinking that I had
> 2 sets at home on that shelf. (Not bright on my part.)
> Now what do I do since I have the parts? The original 4 drums were
> fine. If you manually adjust them every year. And about no one does that.
> The ONLY reason that I had ANY interest in rear disc. Is that my GVW (
> Gross Vehicle Weight ) runs between 17,000 LBS to 24,000 LBS all the time.
> And what would happen if my trailer brakes failed. This put me past my
> Comfort Zone. ( I just don't ever do that)
> So, what to do with the extra disc brake set up? I have 80mm front.
> 78?mm on the mid axle. Drums rear, And a stock master cylinder up front.
> With the brake lines switched. I have reservations. As to what I'm really
> gaining. Other than not having to adjust the rear drums ever year. And
> getting parts off that shelf.
> This topic has been batted around for DECADES. So, what's the latest
> thoughts. Doing nothing sounds nice. ( GRIN)
> Bob Dunahugh
> 78 Royale since 2003
>
>
>
>
> r
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356382 is a reply to message #356376] |
Fri, 03 July 2020 13:46 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Anyone who has stopped a coach quickly with and without 'reaction arms' will opt for them long before rear disks. Just sayin'.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356397 is a reply to message #356382] |
Sat, 04 July 2020 09:05 |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
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Senior Member |
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Not having experienced a 6 disc coach and it’s stopping ability, I can’t praise it’s merits. What I do see as a few very minor advantages with a 6 disc system are the ability to do roadside repairs with ease, and no need to fiddle with adjusters. Changing a caliper or pads requires little effort compared to pulling a drum to repair leaky cylinders or a broken spring. Of course, if you do your detailed annual maintenance correctly, none of the roadside repairs should occur.
I still think a 6 disc reaction arm system is the way to go simply due to the increased performance at the extremes.
Les Burt
Montreal
'75 Eleganza 26'
> On Jul 3, 2020, at 2:47 PM, Johnny Bridges via Gmclist wrote:
>
> Anyone who has stopped a coach quickly with and without 'reaction arms' will opt for them long before rear disks. Just sayin'.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356399 is a reply to message #356397] |
Sat, 04 July 2020 09:51 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I have a true story that I have personal experience with. I had a GMC
customer that ordered the "whole meal deal". One ton front end,
Quadra-Bags, 6 wheel disc brakes with Buick Rivera Calipers for parking
brakes, Reaction arms with/ cross frame torsion bars. I had a couple of
issues with rotor runout and corrected those. At this time, a P-30 master
cylinder and new distribution valve, complete with stainless steel brake
lines from the master and the valve.
Before all the linings and rotors were fully broken in, I was kinda
disappointed in the overall performance of the system. Imprecise pedal
feedback feel was prevalent, and quite different from the stock system.
Early pedal travel was also a concern. So, I measured the operating rod
between the new sensitized booster and the P-30 master cylinder. It was
about 3/8" too short, and allowed the early pedal travel. A longer rod
cured that issue. The "spongy" feel was somewhat more difficult to address.
Good break-in helped a good deal with that, but did not eliminate it
totally.
Customer came and got the coach, and after a few days, called and
voiced his concerns about the pedal feel. The coach came back, and I wound
up replacing the P-30 with a new OEM master cylinder. That helped a whole
bunch. But the pedal travel was a bit different than OEM brakes after
everything I did.
One Sunday morning, the customer was taking his coach for a drive, and
he was driving down canyon boulevard near the Portland Zoo, a very curvy
and steep downhill grade. An idiot driving a Honda cut in front of him
suddenly, overcorrected for his maneuver, pranged the center divider,
bounced back into both lanes and came to a screeching halt directly in
front of the GMC. The customer jumped on the whoa pedal, and the coach came
to a controlled panic stop just a couple feet short of the Honda.
After changing his underwear, the customer called me. Bragging about
his brakes.
The end result, REACTION ARM DISC BRAKES WORK, VERY WELL.
Jim Hupy
Salem, Oregon
On Sat, Jul 4, 2020, 7:05 AM Les Burt via Gmclist
wrote:
> Not having experienced a 6 disc coach and it’s stopping ability, I can’t
> praise it’s merits. What I do see as a few very minor advantages with a 6
> disc system are the ability to do roadside repairs with ease, and no need
> to fiddle with adjusters. Changing a caliper or pads requires little effort
> compared to pulling a drum to repair leaky cylinders or a broken spring.
> Of course, if you do your detailed annual maintenance correctly, none of
> the roadside repairs should occur.
>
> I still think a 6 disc reaction arm system is the way to go simply due to
> the increased performance at the extremes.
>
> Les Burt
> Montreal
> '75 Eleganza 26'
>
>
>> On Jul 3, 2020, at 2:47 PM, Johnny Bridges via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> Anyone who has stopped a coach quickly with and without 'reaction arms'
> will opt for them long before rear disks. Just sayin'.
>>
>> --johnny
>> --
>> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
>> Braselton, Ga.
>> I forgive them all, save those who hurt the dogs. They must answer to
> me in hell
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356403 is a reply to message #356399] |
Sat, 04 July 2020 13:28 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Our reaction Arm System that was developed from Chuck Auglur's design is
the most tested system.
Chuck came up to our facility and used our large parking lot to do testing
for three weekends having Rick Flanagan coordinating the tests along with
Chuck.
We found out a few things that helped us to realize what happens on a panic
stop at 60mph .
I know that a 4 wheel brake can be ok, but in a panic stop at higher speed
the Rear with massive brakes can skid and create problems.
All this is debatable, but I can confirm my data.
On Sat, Jul 4, 2020 at 7:44 AM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I have a true story that I have personal experience with. I had a GMC
> customer that ordered the "whole meal deal". One ton front end,
> Quadra-Bags, 6 wheel disc brakes with Buick Rivera Calipers for parking
> brakes, Reaction arms with/ cross frame torsion bars. I had a couple of
> issues with rotor runout and corrected those. At this time, a P-30 master
> cylinder and new distribution valve, complete with stainless steel brake
> lines from the master and the valve.
> Before all the linings and rotors were fully broken in, I was kinda
> disappointed in the overall performance of the system. Imprecise pedal
> feedback feel was prevalent, and quite different from the stock system.
> Early pedal travel was also a concern. So, I measured the operating rod
> between the new sensitized booster and the P-30 master cylinder. It was
> about 3/8" too short, and allowed the early pedal travel. A longer rod
> cured that issue. The "spongy" feel was somewhat more difficult to address.
> Good break-in helped a good deal with that, but did not eliminate it
> totally.
> Customer came and got the coach, and after a few days, called and
> voiced his concerns about the pedal feel. The coach came back, and I wound
> up replacing the P-30 with a new OEM master cylinder. That helped a whole
> bunch. But the pedal travel was a bit different than OEM brakes after
> everything I did.
> One Sunday morning, the customer was taking his coach for a drive, and
> he was driving down canyon boulevard near the Portland Zoo, a very curvy
> and steep downhill grade. An idiot driving a Honda cut in front of him
> suddenly, overcorrected for his maneuver, pranged the center divider,
> bounced back into both lanes and came to a screeching halt directly in
> front of the GMC. The customer jumped on the whoa pedal, and the coach came
> to a controlled panic stop just a couple feet short of the Honda.
> After changing his underwear, the customer called me. Bragging about
> his brakes.
> The end result, REACTION ARM DISC BRAKES WORK, VERY WELL.
> Jim Hupy
> Salem, Oregon
>
> On Sat, Jul 4, 2020, 7:05 AM Les Burt via Gmclist >
> wrote:
>
>> Not having experienced a 6 disc coach and it’s stopping ability, I can’t
>> praise it’s merits. What I do see as a few very minor advantages with a 6
>> disc system are the ability to do roadside repairs with ease, and no need
>> to fiddle with adjusters. Changing a caliper or pads requires little
> effort
>> compared to pulling a drum to repair leaky cylinders or a broken spring.
>> Of course, if you do your detailed annual maintenance correctly, none of
>> the roadside repairs should occur.
>>
>> I still think a 6 disc reaction arm system is the way to go simply due to
>> the increased performance at the extremes.
>>
>> Les Burt
>> Montreal
>> '75 Eleganza 26'
>>
>>
>>> On Jul 3, 2020, at 2:47 PM, Johnny Bridges via Gmclist > gmclist@list.gmcnet.org> wrote:
>>>
>>> Anyone who has stopped a coach quickly with and without 'reaction
> arms'
>> will opt for them long before rear disks. Just sayin'.
>>>
>>> --johnny
>>> --
>>> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
>>> Braselton, Ga.
>>> I forgive them all, save those who hurt the dogs. They must answer to
>> me in hell
>>>
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] To have 6 wheel disc brakes or be happy with 4? [message #356419 is a reply to message #356418] |
Sat, 04 July 2020 18:30 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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It is weight transfer forward from severe braking that is trying to rotate
the entire coach around the front spindles. That results in lifting the
rear/rear tires from the pavement, the result is sliding the rear tires and
flat spotting those tires. The reaction arms transfer that torque into the
frame of the coach, preventing the lifting and applying it to the bogies
and the rear tires.
They just flat out work, and very well.
Jim Hupy
Salem, Oregon
On Sat, Jul 4, 2020, 4:16 PM Matt Colie via Gmclist
wrote:
> sandy trout wrote on Sat, 04 July 2020 18:26
>> I was told by several people that the quad-bag system acts like reaction
> bars, keeping the rear wheel on the ground during braking.
>> Any truth to this?
>
> Sandy,
>
> In the mathematical models that I did while trying to fix the rear-rear
> issue without using the floating backplate aka reaction arms, I found that
> dividing the rear suspension into two separate systems will only partially
> correct the issue. The problem is that the individual brake reaction still
> will be trying to lift that tire as long as the force is applied to the
> swingarm. It may be a little better because the dig of the leading swingarm
> does not unload it now, but you give up a lot of suspension compliance for
> it. That dig of the leading arm will also be worse now that the anchor
> point cannot be unloaded.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
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