Automatic Transmission change over
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Joined: May 2002
Posts: 59
Likes: 0
From: Ocean Springs Ms
Automatic Transmission change over
I have a 78 Corvette with the original 3 speed automatic transmission (no overdrive) . How hard/expensive is it to change over to an overdrive transmission :confused:
Melting Slicks
Joined: Aug 2000
Posts: 2,310
Likes: 1
Re: Automatic Transmission change over (7t8corvette)
Fortunately, there are quite a few members who can provide you with the details of doing this swap.
The most common swap is either the 2004R or the 700R4 transmission.
Here's some info I was sent by Bowtie Overdrives:
Jerry:
The difference between the Th-2004R and the Th-700R4 is first gear. The
Th-700R4 has a very aggressive first gear ratio compared to all other
General Motors automatic transmissions. This makes for fun stop light
action.
The first gear ratio in the Th-700R4 is 3.06:1, 2.74:1 in the Th-2004R
and 2.52:1 in your current Th-350.
The Th-2004R has gearing quite similar to your current Th-350, so if
you're happy with the way your Corvette performs now, the Th-2004R will
end up very much the same in the first three gears. The overdrive will,
of course, drop your cruise rpm dramatically as will the Th-700R4.
So the big question is whether you want the added spunk off the line.
The Th-2004R is easier because it's basically the same length as your
current Th-350 so you don't need to spend the $65.00 to $75.00 to get it
shortened and balanced like you do with a Th-700R4 installation. The
Th-2004R will work with your existing cross member which will save the
$179.00 for the necessary cross member for a Th-700R4.
All is not one sided, the cost of the dip stick and inspection cover is
more with the Th-2004R which is more expensive by about the same as the
cost of the drive shaft work. So the choice boils down to whether you
are willing to spend the extra $179.00 for the cross member because you
want the more aggressive first gear. The rest of the installation is the
same cost and work. Durability has proven the same if both are built,
set up and adjusted correctly.
Hope this is helpful. I tried to call you but no answer.
Sincerely
Steve Holmes
Bow Tie Overdrives
760-947-5240
Here's their website... http://www.700r4.com/trans/
There are other companies out there, but Bowtie sounds like they have their act together too. There's a good chance I'll go with them when I put a 700R4 in mine.
Hope this helps.
The most common swap is either the 2004R or the 700R4 transmission.
Here's some info I was sent by Bowtie Overdrives:
Jerry:
The difference between the Th-2004R and the Th-700R4 is first gear. The
Th-700R4 has a very aggressive first gear ratio compared to all other
General Motors automatic transmissions. This makes for fun stop light
action.
The first gear ratio in the Th-700R4 is 3.06:1, 2.74:1 in the Th-2004R
and 2.52:1 in your current Th-350.
The Th-2004R has gearing quite similar to your current Th-350, so if
you're happy with the way your Corvette performs now, the Th-2004R will
end up very much the same in the first three gears. The overdrive will,
of course, drop your cruise rpm dramatically as will the Th-700R4.
So the big question is whether you want the added spunk off the line.
The Th-2004R is easier because it's basically the same length as your
current Th-350 so you don't need to spend the $65.00 to $75.00 to get it
shortened and balanced like you do with a Th-700R4 installation. The
Th-2004R will work with your existing cross member which will save the
$179.00 for the necessary cross member for a Th-700R4.
All is not one sided, the cost of the dip stick and inspection cover is
more with the Th-2004R which is more expensive by about the same as the
cost of the drive shaft work. So the choice boils down to whether you
are willing to spend the extra $179.00 for the cross member because you
want the more aggressive first gear. The rest of the installation is the
same cost and work. Durability has proven the same if both are built,
set up and adjusted correctly.
Hope this is helpful. I tried to call you but no answer.
Sincerely
Steve Holmes
Bow Tie Overdrives
760-947-5240
Here's their website... http://www.700r4.com/trans/
There are other companies out there, but Bowtie sounds like they have their act together too. There's a good chance I'll go with them when I put a 700R4 in mine.
Hope this helps.
Racer
Joined: Feb 2002
Posts: 272
Likes: 1
From: MOBILE ALA
Re: Automatic Transmission change over (7t8corvette)
Doing one right now on my 75.Going from a Th400 to 200-4r.Got all the parts,wiring,hoses-lines,tv,yoke,u-joint,dust.shift conversion, from bto for less than $600. Found a used trans and installed a tci rebuild kit and the mods bto suggested for around $400. You could do it cheaper but I wanted all the goodies. It looks so far that the only" pita" will be the shifter detent plate.As of now everything has been a simple bolt in. :D
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: Automatic Transmission change over (7t8corvette)
Been there. Done that. Do it! :D
The only thing to really watch is the TV cable. The TV Made EZ system from Bowtie is highly recommended, whether you use a junker transmission or one of theirs.
BTW: My tranny is a Level 2 200-4R from Bowtie. It is a plug-n-play installation. It fits exactly where the TH350 did. No messing with the driveshaft or crossmember!
The only thing to really watch is the TV cable. The TV Made EZ system from Bowtie is highly recommended, whether you use a junker transmission or one of theirs.
BTW: My tranny is a Level 2 200-4R from Bowtie. It is a plug-n-play installation. It fits exactly where the TH350 did. No messing with the driveshaft or crossmember!
