Subject: [TR] J vs D Type Overdrives

From: Joao Simoes <[email-masked]>
Date: Sun, 8 May 2016 16:27:13 -0400

Hello, all.

As mentioned before, I am building a Spitfire bodied GT6, using a 73 GT6 chassis and running gear.

I have 2 questions:

1- The GT6 has a 3 rail trans that can be mated to a D type overdrive. I was told the J- type overdrive is stronger and was used on 74 and later Spitfires with the new, single rail, 'Marina' gearbox.
I happen to have both transmissions and was curious if I could adapt a J type overdrive to go on the 3 rail trans, or use the single rail on the GT6. Any tips?

2- I mentioned before I am also building the 2.0 liter inline 6 to be 'warmer', hoping for say 130 hp. Any recommendations on a cam and if I would need head work, better con rods, induction or exhaust improvements? 

Thanks for any wisdom you can impart. And also does anyone live near the Ann Arbor area?

Take care,

Joao

** [email-masked] **

Archive: http://www.team.net/archive

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From: Barry Schwartz <[email-masked]>
Date: Mon, 09 May 2016 05:20:11 -0700

yes, not a problem, I have one on my 70 GT6.  The J type was used on the
three rail for a 1974 Spitfire so all you need is an adapter from that
year,  The problem is finding one.  It would appear that Victoria British
has one for about $170 which is a bit pricey but...  You could modify a
later adapter by cutting off the section of the adapter that encompasses
the single rail section so that it fits under the selector rail housing.  I
believe I have just such a modified adapter laying about somewhere (was
thinking of using it on my wife's, before I went with the later single
three rail tranny).  You can't use a single rail transmission on a GT6
however as the input shafts on GT6 and Spitfires are different lengths
(among other things).  I suppose you could make an adapter, but I don't
know if it would be worth it since ratios would be all wrong unless you
could get racing ratios etc...
-----------------

*************************************************************
>1- The GT6 has a 3 rail trans that can be mated to a D type overdrive. I
was told the J- type overdrive is stronger and was used on 74 and later
Spitfires with the new, single rail, 'Marina' gearbox.
>I happen to have both transmissions and was curious if I could adapt a J
type overdrive to go on the 3 rail trans, or use the single rail on the
GT6. Any tips?
>
>2- I mentioned before I am also building the 2.0 liter inline 6 to be
'warmer', hoping for say 130 hp. Any recommendations on a cam and if I
would need head work, better con rods, induction or exhaust improvements?

---

From: "[email-masked]" <[email-masked]>
Date: Mon, 9 May 2016 11:28:13 -0400

I don't think that I would worry too much about the differences in the
types as far as strength is concerned.  For a GT6, even modified, they are
plenty strong.  The tranny will fail long before the overdrive does.  The
D-type is 40s/50s technology, while the J type is 70's and should have
improvements over the older models.  They use a slightly beefed-up version
of the J-type in motor homes and Hot rods from a company here in El Cajon
that still makes and modifies the J types.  If they can stand the 500+Hp of
a rat rod, and the drive-line loads of a motor home, they should be fine in
any TR. The other concern is that the J type will probably have a larger
supply of parts and is, I believe, a little more compact than the earlier
ones.  I used the J-Type simply because my GT6 didn't originally come with
an overdrive, and I found a really nice J-type spitfire tranny in a U-pull
it junk yard around here (many years ago)for $75.  The overdrive from it
has been in my GT since then.  The real problem is finding an original type
shift lever for the GT6 single rail overdrive tranny.  It's not quite the
same as the Spitfire (its slightly shorter and stubbier and I ended up
making one myself).  Even one for a Spitfire is not all that easy to find
but will work.

Yeah, I know, I'm supposed to have a stalk mounted switch, but I really
don't care for the look and operation of the old stalk mounted switches,
and prefer the more "James bond" type switch in the shift lever!

Original email:
-----------------
From: [email-masked] [email-masked]
Date: Mon, 9 May 2016 13:37:43 GMT
To: [email-masked]
Subject: Re: [TR] J vs D Type Overdrives

    Thanks, os it woryh it? Is the j type that much stronger?I know i can
get a d tupe from spitbits but how about a j type?
😉Joao
ake care,>>Joao>

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From: [email-masked]
Date: Mon, 09 May 2016 11:08:58 -0500 (CDT)

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<div style=3D"FONT-FAMILY: Arial; COLOR: rgb(0,0,0); FONT-SIZE: 12px"><div>=
you can still purchase j-type mainshafts for the GT6 box. <br />...obviousl=
y this means a total rebuild since you have to restack the gears on the new=
 shaft.<br />the d and j type adapters (mount the o/d to&nbsp; the box) als=
o must be swapped.... and a single rail adapter moded to fit under the shif=
t lever...so hunt down an earlier ('74?) 3 rail j-type adapter (spit versio=
n is fine) <br /><br />current calculations says FIS6 is still around 136hp=
.&nbsp; mild head work and a cam,,,BUT fuel injected.&nbsp; FI does NOT add=
 HP.&nbsp; It only makes the rest of the system more efficient. BUT breathi=
ng losses are less (doesn't have to 'suck' as hard to get fuel mixutres int=
o the cyls...so it HAS to add HP?... much less induction loses involved)<br=
 /></div><div>&nbsp;</div><span>Paul Tegler<br />[email-masked]<br />w=
ww.teglerizer.com</span><div>&nbsp;</div><div style=3D"border-top:1px solid=
 #bcbcbc;margin:5px 0px;"></div><span style=3D"font-size:12;font-family:ari=
al;color:#000000;">On 05/09/16, <span>Joao Simoes<jmbs46@<span class=3D"mis=
spelled">comcast.net&gt;</jmbs46@<span></span> wrote:</span><div>&nbsp;</di=
v><div style=3D"font-size:12;font-family:arial;color:#000000;">Hello, all.<=
br /><br />As mentioned before, I am building a Spitfire bodied GT6, using =
a 73 GT6 chassis and running gear.<br /><br />I have 2 questions:<br /><br =
/>1- The GT6 has a 3 rail trans that can be mated to a D type overdrive. I =
was told the J- type overdrive is stronger and was used on 74 and later Spi=
tfires with the new, single rail, 'Marina' gearbox.<br />I happen to have b=
oth transmissions and was curious if I could adapt a J type overdrive to go=
 on the 3 rail trans, or use the single rail on the GT6. Any tips?<br /><br=
 />2- I mentioned before I am also building the 2.0 liter inline 6 to be 'w=
armer', hoping for say 130 hp. Any recommendations on a cam and if I would =
need head work, better con rods, induction or exhaust improvements? <br /><=
br />Thanks for any wisdom you can impart. And also does anyone live near t=
he Ann Arbor area?<br /><br />Take care,<br /><br />Joao<br /><br />** <a c=
lass=3D"parsedEmail" href=3D"mailto:[email-masked]" target=3D"_bla=
nk">[email-masked]</a> **<br /><br />Donate: <a class=3D"parsedLin=
k" href=3D"http://www.team.net/donate.html" target=3D"_blank">http://www.te=
am.net/donate.html</a><br />Archive: <a class=3D"parsedLink" href=3D"http:/=
/www.team.net/archive" target=3D"_blank">http://www.team.net/archive</a><br=
 />Forums: <a class=3D"parsedLink" href=3D"http://www.team.net/forums" targ=
et=3D"_blank">http://www.team.net/forums</a><br />Unsubscribe/Manage: <a cl=
ass=3D"parsedLink" href=3D"http://autox.team.net/mailman/options/triumphs/p=
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/triumphs/[email-masked]</a><br /></div></div>

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From: tr3driver <[email-masked]>
Date: Mon, 9 May 2016 21:45:34 -0400 (EDT)

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I dunno.  Herman once showed me a pile of  D type mainshafts all broken in the same place. 
Sure seems like there must be a weak spot there. The equivalent place on a J type looks at least twice as strong.

YMMV

- Randall

On 9 May 2016 11:28, [email-masked] <[email-masked]> wrote:
  I don't think that I would worry too much about the differences in the
  types as far as strength is concerned. For a GT6, even modified, they are
  plenty strong. 
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<p>I dunno.  Herman once showed me a pile of  D type mainshafts all broken in the same place. <br>Sure seems like there must be a weak spot there. The equivalent place on a J type looks at least twice as strong.<br><br>YMMV<br><br>- Randall<br><br>On 9 May 2016 11:28, [email-masked] &lt;[email-masked]&gt; wrote:
<br>  I don't think that I would worry too much about the differences in the
<br>  types as far as strength is concerned. For a GT6, even modified, they are
<br>  plenty strong. </p>
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From: "[email-masked]" <[email-masked]>
Date: Tue, 10 May 2016 08:06:22 -0400

There you go, I have not seen such a pile but would seem an obvious weak
point and a reason to go with a J type-

Original email:
-----------------

I dunno.  Herman once showed me a pile of  D type mainshafts all broken in
the same place. 
Sure seems like there must be a weak spot there. The equivalent place on a
J type looks at least twice as strong.

YMMV

- Randall

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