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Re: [Fot] GT6 differential failure follow-up

To: Scott Janzen <sjanzen@me.com>
Subject: Re: [Fot] GT6 differential failure follow-up
From: Jason Ostrowski <jason@multivintage.com>
Date: Mon, 20 Jul 2015 09:38:45 -0500
Cc: "fot@autox.team.net" <fot@autox.team.net>, fubog1 <fubog1@aol.com>
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Delivered-to: fot@autox.team.net
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Wow, I have not seen that happen before. For me, Usually it's ring and pinio=
n, which often destroys the case.=20
In terms of bearings, We have always used good looking and working original s=
tock ones as well. I suspect this one just went as a result of an high revvi=
ng extreme load under the conditions you describe. As knowing your attention=
 to setup details are spot on the factory manual methods. That is our way to=
o (less the welded spider gear). I think it's just a failure more racing rel=
ated which just happens when you are trying to go fast and shows you are doi=
ng a good job of trying to drive harder ( can't be mad about that).=20

I've been told by some of the best that the 4 bolt spring attachment is fine=
 and will be fine. Yet I agree with you completely and feel that the 6 studs=
 are necessary and a proper choice for the GT6.=20
Thanks for the update.
Keep doing what you have been doing with the differential.=20
And maybe it's best to just try to keep it in third for the descent and shif=
t again way later. Just use second (if you must) after a nice blip once you a=
re all slowed down and ready to accelerate again.=20
Jason Ostrowski
Friendly Ghost Racing

Sent from my iPhone

> On Jul 20, 2015, at 7:08 AM, Scott Janzen <sjanzen@me.com> wrote:
>=20
> Bearings are what was in it.  If bearings look good/feel good, I tend not t=
o replace them. Figure old used stock is probably best, but maybe not.  Pre-=
 load, always suspect.  The diff I have "ready" to put in is going to be dis=
assembled and reassembled just to confirm. Shims and spacers at the ready - !=

>=20
> Sent from my mobile device=20
>=20
> On Jul 20, 2015, at 7:58 AM, fubog1 <fubog1@aol.com> wrote:
>=20
> Scott I realize it's after the fact, and that thing is pretty torn up, so I=
'm a little hesitant to speculate... but when you rebuild it make sure NOT t=
o use the crap bearings on the market, Timken only, and make sure the preloa=
d is correct...
> Glen
>=20
>=20
> -----Original Message-----
> From: Scott Janzen <sjanzen@me.com>
> To: 'Friends of Triumph' Triumph <fot@autox.team.net>
> Sent: Sun, Jul 19, 2015 6:54 pm
> Subject: [Fot] GT6 differential failure follow-up
>=20
> Pulled my differential out and apart today - did not find what I expected.=
 =20
> The input/pinion shaft is sheared off just forward of the pinion gear. =20=

> The crown wheel has barely a mark on it, all teeth intact, no signs of dam=
age.
> The inner tapered bearing race on the pinion shaft is just mangled and the=
re are roller bearings all over the place.  However, the outer races for bot=
h pinion bearings look fine - no sign of discoloration or overheating, signi=
ficant damage, etc.
> It did fail when I was decelerating in second gear at high RPMs down the s=
teep downhill on the new course in Pittsburgh, so the engine promptly slowed=
 down - still, amazingly, there is minimal sign of rotational damage to the d=
riveshaft - just a couple of paint scrapes.  It was essentially unsecured at=
 the rear, but perhaps the outer/forward pinion bearing kept it centered.
> Both the shaft and the gear rubbed against each other so much there's no w=
ay to see any fracture marks.
> One of the four bolts securing the spring to the top of the differential h=
ad cracked the housing, and it clearly leaked some oil there, but judging by=
 the lack of oil on the underside of the car, I don't think this contributed=
 to the failure.  I had just topped it up before the weekend, and there was n=
o sign of oil under the car throughout the weekend.  Guess I'll be tapping t=
he next diff for two more bolts, so there are six securing the spring next t=
ime.
>=20
> Photos attached. <FullSizeRender.jpg>
>=20
> <FullSizeRender.jpg>
>=20
> <FullSizeRender.jpg>
> _______________________________________________
> fot@autox.team.net
>=20
> http://www.fot-racing.com
>=20
> Donate:
> http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums:
> http://www.team.net/forums
> Unsubscribe/Manage:
> http://autox.team.net/mailman/options/fot/fubog1@aol.com
>=20
>=20
> _______________________________________________
> fot@autox.team.net
>=20
> http://www.fot-racing.com
>=20
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/jason@multiv=
intage.com
>=20
>=20

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div>Wow, I have not seen that happen befor=
e. For me, Usually it's ring and pinion, which often destroys the case.&nbsp=
;</div><div>In terms of bearings, We have always used good looking and worki=
ng original stock ones as well. I suspect this one just went as a result of a=
n high revving extreme load under the conditions you describe. As knowing yo=
ur attention to setup details are spot on the factory manual methods. That i=
s our way too (less the welded spider gear). I think it's just a failure mor=
e racing related which just happens when you are trying to go fast and shows=
 you are doing a good job of trying to drive harder ( can't be mad about tha=
t).&nbsp;</div><div><br></div><div>I've been told by some of the best that t=
he 4 bolt spring attachment is fine and will be fine. Yet I agree with you c=
ompletely and feel that the 6 studs are necessary and a proper choice for th=
e GT6.&nbsp;</div><div>Thanks for the update.</div><div>Keep doing what you h=
ave been doing with the differential.&nbsp;</div><div>And maybe it's best to=
 just try to keep it in third for the descent and shift again way later. Jus=
t use second (if you must) after a nice blip once you are all slowed down an=
d ready to accelerate again.&nbsp;</div><div>Jason Ostrowski</div><div>Frien=
dly Ghost Racing</div><div><br>Sent from my iPhone</div><div><br>On Jul 20, 2=
015, at 7:08 AM, Scott Janzen &lt;<a href=3D"mailto:sjanzen@me.com";>sjanzen@=
me.com</a>&gt; wrote:<br><br></div><blockquote type=3D"cite"><div><meta http=
-equiv=3D"content-type" content=3D"text/html; charset=3Dutf-8"><div>Bearings=
 are what was in it. &nbsp;If bearings look good/feel good, I tend not to re=
place them. Figure old used stock is probably best, but maybe not. &nbsp;Pre=
- load, always suspect. &nbsp;The diff I have "ready" to put in is going to b=
e disassembled and reassembled just to confirm. Shims and spacers at the rea=
dy - !<br><br>Sent from my mobile device&nbsp;</div><div><br>On Jul 20, 2015=
, at 7:58 AM, fubog1 &lt;<a href=3D"mailto:fubog1@aol.com";>fubog1@aol.com</a=
>&gt; wrote:<br><br></div><div><font color=3D"black" size=3D"2" face=3D"Aria=
l, Helvetica, sans-serif">

<div> Sc<font size=3D"2">ott I realize it's after the fact, and that thing i=
s pretty torn up,
 so I'm a little hesitant to speculate... but when you rebuild it make=20
sure NOT to use the crap bearings on the market, Timken only, and make=20
sure the preload is correct...<br>
Glen<br>
</font>
</div>



<div> <br>

</div>



<div> <br>

</div>



<div style=3D"font-family:arial,helvetica;font-size:10pt;color:black">-----O=
riginal Message-----<br>

From: Scott Janzen &lt;<a href=3D"mailto:sjanzen@me.com";>sjanzen@me.com</a>&=
gt;<br>

To: 'Friends of Triumph' Triumph &lt;<a href=3D"mailto:fot@autox.team.net";>f=
ot@autox.team.net</a>&gt;<br>

Sent: Sun, Jul 19, 2015 6:54 pm<br>

Subject: [Fot] GT6 differential failure follow-up<br>

<br>




<div id=3D"AOLMsgPart_1.2.1_41be8232-f801-482b-9c6d-63de8cb238ef">


<div style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-=
break: after-white-space; " class=3D"aolReplacedBody">
=20

<div>
Pulled my differential out and apart today - did not find what I expected. &=
nbsp;
 </div>


=20

<div>
The input/pinion shaft is sheared off just forward of the pinion gear. &nbsp=
;
 </div>


=20

<div>
The crown wheel has barely a mark on it, all teeth intact, no signs of damag=
e.
 </div>


=20

<div>
The inner tapered bearing race on the pinion shaft is just mangled and there=
 are roller bearings all over the place. &nbsp;However, the outer races for b=
oth pinion bearings look fine - no sign of discoloration or overheating, sig=
nificant damage, etc.
 </div>


=20

<div>
It did fail when I was decelerating in second gear at high RPMs down the ste=
ep downhill on the new course in Pittsburgh, so the engine promptly slowed d=
own - still, amazingly, there is&nbsp;minimal sign of rotational damage to t=
he driveshaft - just a couple of paint scrapes. &nbsp;It was essentially uns=
ecured at the rear, but perhaps the outer/forward pinion bearing kept it cen=
tered.
 </div>


=20

<div>
Both the shaft and the gear rubbed against each other so much there's no way=
 to see any fracture marks.
 </div>


=20

<div>
One of the four bolts securing the spring to the top of the differential had=
 cracked the housing, and it clearly leaked some oil there, but judging by t=
he lack of oil on the underside of the car, I don't think this contributed t=
o the failure. &nbsp;I had just topped it up before the weekend, and there w=
as no sign of oil under the car throughout the weekend. &nbsp;Guess I'll be t=
apping the next diff for two more bolts, so there are six securing the sprin=
g next time.
 </div>


=20

<div>
  <br>


 </div>


=20

<div>
Photos attached.
  &lt;FullSizeRender.jpg&gt;
 </div>


=20

<div>
  <br>


 </div>


=20

<div>
  &lt;FullSizeRender.jpg&gt;
 </div>


=20

<div>
  <br>


 </div>


=20

<div>
  &lt;FullSizeRender.jpg&gt;
 </div>


</div>


</div>





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