| Torsion Bar Damage: [message #189267] |
Mon, 05 November 2012 18:52  |
noi
Messages: 293
Registered: October 2010
Location: South of Fremont
Karma: 0
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Senior Member |
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Greetings:
While doing a little R&R on my torsion bars, I found the right one had a couple of interesting “nicks” on it after I had scraped off all the (mostly) surface rust – The “nicks” are about 20” from the hex end and too far away to have been caused by the lateral support bar – Plus, examining the lateral support bar did not show any indication of contact/wear - They are also VERY shallow and can hardly be felt when “scratching” at them with a finger nail – If it had not been for a small amount of paint at the bottom of the “nicks”, I would probably have missed them all together.
Other than the “nicks”, the torsion bar was in fairly good condition and pretty straight when rolled on two edge blocks.
Close up:
http://www.gmcmhphotos.com/photos/stuff/p46289-tb-cu.html
Farther back:
http://www.gmcmhphotos.com/photos/stuff/p46290-tb-fo.html
I have some questions that hopefully can be answered….
* Anyone know how our torsion bars were made – Forged or drawn with forged hex ends?
* Is it possible that the “nicks” are some sort of artifact left over from the manufacturing process?
* Any cause for concern? – Is it replacement time?
The left torsion bar was in much better condition with most of the original paint still intact and only some slight surface rust on about 1/3 the bar – Though a close look at the area near the lateral support intersection did show some ever so slight “rubbing” that did little more than take the paint off – A close look at the left lateral support bar seemed to suggest it was caused by a build up of dirt on the top of the bar - As once the dirt was brushed away, there were no signs of any direct contact – The left torsion bar did have a very slight “wobble” though when rolled on the edge blocks.
Thanks in advance for any thoughts you may have on this subject.
Carl P.
76 Birchaven
South of Fremont
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| Re: Torsion Bar Damage: [message #189278 is a reply to message #189267] |
Mon, 05 November 2012 20:12  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| noi wrote on Mon, 05 November 2012 18:52 |
Greetings:
While doing a little R&R on my torsion bars, I found the right one had a couple of interesting “nicks” on it after I had scraped off all the (mostly) surface rust – The “nicks” are about 20” from the hex end and too far away to have been caused by the lateral support bar – Plus, examining the lateral support bar did not show any indication of contact/wear - They are also VERY shallow and can hardly be felt when “scratching” at them with a finger nail – If it had not been for a small amount of paint at the bottom of the “nicks”, I would probably have missed them all together.
Other than the “nicks”, the torsion bar was in fairly good condition and pretty straight when rolled on two edge blocks.
Close up:
http://www.gmcmhphotos.com/photos/stuff/p46289-tb-cu.html
Farther back:
http://www.gmcmhphotos.com/photos/stuff/p46290-tb-fo.html
I have some questions that hopefully can be answered….
* Anyone know how our torsion bars were made – Forged or drawn with forged hex ends?
* Is it possible that the “nicks” are some sort of artifact left over from the manufacturing process?
* Any cause for concern? – Is it replacement time?
Carl P.
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As the "nicks" are lengthwise rather than a cross-ways nick, and they are tapered and have no sharp edges or abrupt changes I would not worry about them. The nicks appear to have no features that would concentrate internal stresses that could lead to a failure. No idea on how the bars are made or if the nicks are a manufacturing artifact.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Torsion Bar Damage: [message #189281 is a reply to message #189267] |
Mon, 05 November 2012 21:28 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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My experience with gmc torsion bars has been that, after many years of use,
they twist, and fatigue. I check them with a digital level on the hex ends,
comparing one end to the other. I often find them out 10 degrees or more.
As they are quite scarce, we use rotated pork chops that Manny T. makes to
allow for twist. RIDE HEIGHT IS THE MOST IMPORTANT ADJUSTMENT ON YOUR
COACH!!! Yes, I am yelling. Get it to ride HEIGHT before you try to align
it. Otherwise you are wasting your money getting it aligned. I see the
marks you describe fairly often and don't worry about them much.
Circumferential ones I worry about if they are caused by interfering parts.
Your experience may vary.
Jim Hupy
Salem, Or
78 Royale 403
On Nov 5, 2012 4:52 PM, "noi" <v76_Birchaven@yahoo.com> wrote:
>
>
> Greetings:
>
> While doing a little R&R on my torsion bars, I found the right one had a
> couple of interesting “nicks” on it after I had scraped off all the
> (mostly) surface rust – The “nicks” are about 20” from the hex end and too
> far away to have been caused by the lateral support bar – Plus, examining
> the lateral support bar did not show any indication of contact/wear - They
> are also VERY shallow and can hardly be felt when “scratching” at them with
> a finger nail – If it had not been for a small amount of paint at the
> bottom of the “nicks”, I would probably have missed them all together.
>
> Other than the “nicks”, the torsion bar was in fairly good condition and
> pretty straight when rolled on two edge blocks.
>
> Close up:
>
> http://www.gmcmhphotos.com/photos/stuff/p46289-tb-cu.html
>
> Farther back:
>
> http://www.gmcmhphotos.com/photos/stuff/p46290-tb-fo.html
>
> I have some questions that hopefully can be answered….
>
> * Anyone know how our torsion bars were made – Forged or drawn with forged
> hex ends?
>
> * Is it possible that the “nicks” are some sort of artifact left over from
> the manufacturing process?
>
> * Any cause for concern? – Is it replacement time?
>
> The left torsion bar was in much better condition with most of the
> original paint still intact and only some slight surface rust on about 1/3
> the bar – Though a close look at the area near the lateral support
> intersection did show some ever so slight “rubbing” that did little more
> than take the paint off – A close look at the left lateral support bar
> seemed to suggest it was caused by a build up of dirt on the top of the bar
> - As once the dirt was brushed away, there were no signs of any direct
> contact – The left torsion bar did have a very slight “wobble” though when
> rolled on the edge blocks.
>
> Thanks in advance for any thoughts you may have on this subject.
>
> Carl P.
> 76 Birchaven
> South of Fremont
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: Torsion Bar Damage: [message #189302 is a reply to message #189267] |
Tue, 06 November 2012 06:11 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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Senior Member |
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Looks like the marks on mine after I had to put a pipe wrench on it to back it up after it spun in the a arm socket. So far no issues though.
Skip Hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: Torsion Bar Damage: [message #189358 is a reply to message #189267] |
Tue, 06 November 2012 17:52 |
noi
Messages: 293
Registered: October 2010
Location: South of Fremont
Karma: 0
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Senior Member |
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Greetings:
Skip….
After bringing my torsion bars to work and vigorously buffing the nicks with a wire wheel, followed up with inspection with a 10x loop, I tend to concur with your observation…. Pipe wrench marks!
Jim….
As I had my torsion bars at work to wire wheel them, I followed your suggestions to check twist.
As we have a very nice and large granite surface table here, I V-blocked them up and checked the twist with a digital angle gauge – Results as follows:
Left Bar (525L) = 1.6* of twist
Right Bar (524R) = 4.5* of twist
The odd part (and easy to see and hard to explain) though was as I rotated the torsion bars on the table from one flat to the next, the left bar (least twist) was more out of round – At the “low” point the center part of the bar was touching the table, then rotating to a high arch.
The right bar, with more twist, never touched the table nor did it arch that much.
As I said, hard to explain and can take/post pictures if needed or anyone is interested.
And yes…. I have “lurked” on this forum long enough to understand the importance of getting ride height set RIGHT first…. BEFORE doing anything else!!!! LoL 
Seeing as the wire wheel treatment “buffed” the nicks out a bit more and added to Steve, Jim, and Skip’s group thought…. Will not worry about them for now.
Thanks for everyone’s thought.
Carl P.
76 Birchaven
South of Fremont
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| Re: Torsion Bar Damage: [message #189359 is a reply to message #189267] |
Tue, 06 November 2012 18:01 |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
Karma: 0
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Would some rust inhibiting paint be a good idea to help prevent surface rusting? I think that Porsche coats their torsion bars with something (except at the splined ends), so it may be of benefit.
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: Torsion Bar Damage: [message #189397 is a reply to message #189359] |
Tue, 06 November 2012 23:10 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| GeorgeRud wrote on Tue, 06 November 2012 18:01 |
Would some rust inhibiting paint be a good idea to help prevent surface rusting? I think that Porsche coats their torsion bars with something (except at the splined ends), so it may be of benefit.
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My bars had a coating that appeared to be greenish, sorta like zinc chromate.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Torsion Bar Damage: [message #189404 is a reply to message #189397] |
Tue, 06 November 2012 23:55 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Me too!
Regards,
Rob M.
-----Original Message-----
From: Steve Southworth
My bars had a coating that appeared to be greenish, sorta like zinc chromate.
--
Steve
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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