Manual Transmission Question?

Now we come to the reason I actually came to this forum - and it was not to
talk about speeding tickets and Cadillac "trucks"

Has anyone here "retrofitted" an older Vette with a modern 6 speed overdrive
tranny?
Yes, I remember form doing the clutch (years ago) that getting the tranny in
and out is a royal PITA but I'm willing to go through it again.

I'm thinking of doing this "refit" to my '68 roadster (a driver painted AMC
"fresh Plum",with no matching numbers anyway) to increase fuel economy, and
of course it can't hurt performance. My syncros are worn (and have been for
years) so it's another excuse to pull it.

I have a friend working at Borg-Warner so he can get me a real good deal on
it.

-W

"Clams Canino" > wrote in message
...
> Now we come to the reason I actually came to this forum - and it was
> not to
> talk about speeding tickets and Cadillac "trucks"
>
> Has anyone here "retrofitted" an older Vette with a modern 6 speed
> overdrive
> tranny?
> Yes, I remember form doing the clutch (years ago) that getting the
> tranny in
> and out is a royal PITA but I'm willing to go through it again.
>
> I'm thinking of doing this "refit" to my '68 roadster (a driver
> painted AMC
> "fresh Plum",with no matching numbers anyway) to increase fuel
> economy, and
> of course it can't hurt performance. My syncros are worn (and have
> been for
> years) so it's another excuse to pull it.
>
> I have a friend working at Borg-Warner so he can get me a real good
> deal on
> it.
>
> -W

Not to difficult but like you said getting it out is difficult. Best
to start off with the engine loose. Many sites on the web that show
step by step instructions for the change. Most are for 5 speed changes
as the 6 speed has a bad shifter location if I remember correctly. GM
in the early 80s had a 4 speed over drive in their pickup that is a
fit for your car. Most are worn out and are expensive to rebuild. Take
a look at
http://www.classicchevy5speed.com/Co...nstall-WU.aspx

If you take a good look at this change there is one small item that
they did not mention. The exhaust pipe is close enough to the
speedometer cable, now made from plastic, then it doesn't take long to
melt it and then twist the cable off.

Even with a 35% reduction in RPMs you won't see that much in gasoline
savings. You will still be running a inefficient V8 of yesteryear that
may save you 15/20% at best. I'm having lunch with a friend that made
this change and an upgrade on his fuel deliver management (injection)
and I'll let you know how his worked out.

"Dad" > wrote in message

> Even with a 35% reduction in RPMs you won't see that much in gasoline
> savings. You will still be running a inefficient V8 of yesteryear that
> may save you 15/20% at best. I'm having lunch with a friend that made
> this change and an upgrade on his fuel deliver management (injection)
> and I'll let you know how his worked out.


Yes, I'm curious.
If I'm gonna do the work, I kind of want a new 6 speed - at least until that
becomes impossible.

Again... this is still "out there" a bit. I plan to "rescue" the car from
long term storage and move it to my SC home next month. Then I'll see where
it's at and what it "needs" - then comes what I "want".

-W

"Clams Canino" > wrote in message
...
>
> "Dad" > wrote in message
>
>> Even with a 35% reduction in RPMs you won't see that much in
>> gasoline
>> savings. You will still be running a inefficient V8 of yesteryear
>> that
>> may save you 15/20% at best. I'm having lunch with a friend that
>> made
>> this change and an upgrade on his fuel deliver management
>> (injection)
>> and I'll let you know how his worked out.
>
>
> Yes, I'm curious.
> If I'm gonna do the work, I kind of want a new 6 speed - at least
> until that
> becomes impossible.
>
> Again... this is still "out there" a bit. I plan to "rescue" the
> car from
> long term storage and move it to my SC home next month. Then I'll
> see where
> it's at and what it "needs" - then comes what I "want".
>
When he installed the 5 speed Tremac it was before they had started
modifying them to fit the Corvette shifter location. Consequently he
had to modify his floor pan. That is my thought on the Borg 6 speed
also, the shifter location is back to far to fit the existing shifter
location. He nor I have any on hands experience with that transmission
so further actual location data would be needed. Just looking at old
data I have of the Tremac top mounted shifter is 19.5 from shifter
center line to mounting face, and 26.4 to bell housing face of the
T56. Be aware that on the T56 that the bell housing is part of the
transmission. In any case you're talking .68:1 versus .62:1 between
the 5 or 6 speed. Also the back (top) of the T56 is higher than the
shifter mount which will require a tunnel alteration. On the other
hand an economical purchase of a 5 speed Tremac, new clutch, engine
removal to install, plus the shortened drive shaft required, new
speedometer cable, and shifter will produce a really neat "cool"
factor.

He is still in the process of updating that Corvette and is going to a
3.08:1 differential to get better mileage. His mileage savings was in
the 3 to 5 miles per gallon range which included TPI injection. That
may give you a .03¢ per mile savings for a $2,500 transmission swap,
or an 84,000 mile payback. I've looked at this a number of times for
my '64 but always come back to the old 4 speed and keep my foot out of
it, yeah, right. ;-)

On the other hand if you can find an early '80 MY6 GM 4 speed over
drive they fit right in, 1st 3.09, 2nd 1.67, 3rd 1 to 1, and 4th .73.
The later models changed the mounting pattern so choose the year
wisely.

Good Luck.

"Dad" > wrote in message news:YKOdnfueWe-

> When he installed the 5 speed Tremac it was before they had started
> modifying them to fit the Corvette shifter location. Consequently he
> had to modify his floor pan. That is my thought on the Borg 6 speed
> also, the shifter location is back to far to fit the existing shifter
> location. He nor I have any on hands experience with that transmission
> so further actual location data would be needed. Just looking at old
> data I have of the Tremac top mounted shifter is 19.5 from shifter
> center line to mounting face, and 26.4 to bell housing face of the
> T56. Be aware that on the T56 that the bell housing is part of the
> transmission. In any case you're talking .68:1 versus .62:1 between
> the 5 or 6 speed. Also the back (top) of the T56 is higher than the
> shifter mount which will require a tunnel alteration. On the other
> hand an economical purchase of a 5 speed Tremac, new clutch, engine
> removal to install, plus the shortened drive shaft required, new
> speedometer cable, and shifter will produce a really neat "cool"
> factor.
>
> He is still in the process of updating that Corvette and is going to a
> 3.08:1 differential to get better mileage. His mileage savings was in
> the 3 to 5 miles per gallon range which included TPI injection. That
> may give you a .03¢ per mile savings for a $2,500 transmission swap,
> or an 84,000 mile payback. I've looked at this a number of times for
> my '64 but always come back to the old 4 speed and keep my foot out of
> it, yeah, right. ;-)
>
> On the other hand if you can find an early '80 MY6 GM 4 speed over
> drive they fit right in, 1st 3.09, 2nd 1.67, 3rd 1 to 1, and 4th .73.
> The later models changed the mounting pattern so choose the year
> wisely.

You have given me much to think about.
I now know "what I don't know" - the crucial 1st step in any plan

-W

"Clams Canino" > wrote in message
m...
Snip
> You have given me much to think about.
> I now know "what I don't know" - the crucial 1st step in any plan
>
As long as we got your head working take a look at this.....

http://www.riversidegear.com/categor...oduct-166.html

They are quoting $1795, less ship/taxes on a new unit with this set of
gears. I'm only 60 miles from them and if I can make an unmodified
swap I might just do that. Not a big ratio change but I have had a
bearing singing in third gear for the last 2 years. Failure will
happen when I least need it, so I thought I'd give this outfit a try.
Also comparing their price to the Tremac 5 speed at a bit higher price
and a lot more parts to change. Haven't heard from them yet but
expect it will be close to $2800.

What was your connection to South Carolina? My son lives down there,
just got back from hog hunting with my sons down by Estell.

"Dad" > wrote in message
.. .
> As long as we got your head working take a look at this.....
>
>
http://www.riversidegear.com/categor...ts/product-166.
html
>
> They are quoting $1795, less ship/taxes on a new unit with this set of
> gears. I'm only 60 miles from them and if I can make an unmodified
> swap I might just do that. Not a big ratio change but I have had a
> bearing singing in third gear for the last 2 years. Failure will
> happen when I least need it, so I thought I'd give this outfit a try.
> Also comparing their price to the Tremac 5 speed at a bit higher price
> and a lot more parts to change. Haven't heard from them yet but
> expect it will be close to $2800.
>
> What was your connection to South Carolina? My son lives down there,
> just got back from hog hunting with my sons down by Estell.


Sorry for the long delay. I was up in NH, amongst other things checking out
the Vette for rescue. I moved to SC, 5 years ago - but the car got left
behind in storage.

I plan to get it down here in 2-6 weeks and start taking stuff apart. It
needs a LOT of work now to get healthy. This before any modifications etc.
Started right up though!

-W

"Clams Canino" > wrote in message

> I plan to get it down here in 2-6 weeks and start taking stuff apart. It
> needs a LOT of work now to get healthy. This before any modifications etc.
> Started right up though!

Update... Corvette rescue mission departs 6/13.

-W