700r swap
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Heel & Toe
Joined: Jul 2009
Posts: 23
Likes: 0
700r swap
I have found a 700r4 tranny to drop into my 78 and know that the driveshaft will have to be shortened but does anyone know what else, I beleive that the new tranny has an electric plug? It is out of an 88 chevy pickup truck that had a 350 in it.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
The plug is the lockup convertor. Several ways to hook it up- Feed 12v to a toggle switch and then to the correct pin on the plug.
Don't run without the lockup-- it'll burn the trans up pretty fast- it relies on the added flow from the the lockup for cooling.
Don't run without the lockup-- it'll burn the trans up pretty fast- it relies on the added flow from the the lockup for cooling.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Do a search and read up so you don't burn up the trans. You must have and adjust the TV cable, you have to modify the crossmember mount, you may have to move the E-brake wheel on the crossmember, you have to modify the shifter detent to get 1st gear, you have to deal with lockup, etc...
Do a search on 700R4 swap and you should find a wealth of information.
Do a search on 700R4 swap and you should find a wealth of information.
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
You should have the unit rebuilt and provide the specs, weight of car diff gears. I have been told by tranny guys that the tranny should be rebuilt for the car specs to shift at the right points, many variable settings with the 700. Bowtie is one place that has the parts you need for lockup and crossmember.
http://www.bowtieoverdrives.com/index.shtml
http://www.bowtieoverdrives.com/index.shtml
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I put a 700R4 in my 79. Its a great swap. Went from 16 mpg. to 25. You can get all the parts to do the swap from the Corvette suppliers as GM put the 700 in the 82's. There are several different tailshaft lengths. Try to get the right one. It makes things much easier. You will have to relocate the park brake pulley on the crossmember. Have the trans modified by your trans shop to only have the lockup convertor lock up in 3rd and 4th. You have to run power to it. Don't remember esactly how I did it, but there is a vacuum switch in the hookup. Hardest part of the swap is getting the exhaust to clear the trans. where it goes through the crossmember. I modified the crossmember to move the exhaust hole outboard a couple of inches.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You can also buy a lockup module to manage the lockup engagement. I think lectriclimited.com has them. There may be other sources as well. Personally, I wouldn't want to operate with just a toggle switch. That will work fine for normal driving. But what happens in the instance of a panic stop or avoidance maneuver? Will you hit the toggle to drop lockup, or will it just kill the engine or cause tranny damage because it remains engaged?
Intermediate
Joined: Nov 2009
Posts: 26
Likes: 1
From: Acworth GA
Anything after a 86 700R4 is good. The last year 1991 would be better.
A crossmember from Bowtie would be awesome. Then shorten the drive 3" and your ready to go. 1600 to 2000 stall would make it right. Don't worry about the elec. hookup. YOUR READY TO GO!!!!!
A crossmember from Bowtie would be awesome. Then shorten the drive 3" and your ready to go. 1600 to 2000 stall would make it right. Don't worry about the elec. hookup. YOUR READY TO GO!!!!!
Last edited by dbt1959; Dec 12, 2009 at 11:51 PM.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
You can also buy a lockup module to manage the lockup engagement. I think lectriclimited.com has them. There may be other sources as well. Personally, I wouldn't want to operate with just a toggle switch. That will work fine for normal driving. But what happens in the instance of a panic stop or avoidance maneuver? Will you hit the toggle to drop lockup, or will it just kill the engine or cause tranny damage because it remains engaged?
I did a 72 Chevelle with a 700 some years ago- used a vacuum switch from an 80-81 pickup, thru the brake light switch and into the trans- I had put a 4th gear pressure switch in the valve body so it had to be in 4th gear too. IIRC, I found a switch that needed 40-45 PSI to close. Worked out that 40-45 PSI is right about the same in MPH.
I used a Trans-Go kit in the trans- bigger servo, and TV/Reverse Boost valves. You can also get a Corvette specific TV valve so it'll hold 4th gear at WOT. No other GM application had that installed from the factory.
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Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Using a momentary-closed switch [instead of a toggle] for the "Lockup ON" function and a normally-closed switch at the brake pedal for the "Lockup Drop" function would solve most of the safety concerns presented when installing an 'electronic' transmission in a 'non-electronic' vehicle. The only other major risks are 1) letting the car "coast" down with the lockup ON and experiencing a downshift during lockup when the tranny governor demands it {that would probably kill the engine}; and 2) having the tranny downshift (on its own) going up a steep hill when in lockup mode. Those 'unusual' shift conditions, and others, are properly managed by the computer in cars built with electronic trannies. Considering someone just spent around $1000 to install a 700R4 tranny in their car, spending another $100 to get it to work correctly sounds like a smart idea...IMO. Spending $5 on a toggle switch...doesn't. 
Drifting
Joined: Jul 2004
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From: Kissimmee fl
Finalist 2021 C3 of the Year - Modified
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St. Jude Donor '07
The 700R4 that is in my car is set up to only go into lock up when it is in 4th gear. I have a brake switch used for cruise control in the power loop. One side operates the brake lights as normal and the other opens when you hit the breaks to dis-engage the TC. I also have a toggle switch in line to prevent the TC from locking up if I choose to turn it off.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
That would accomplish the 'minimum requirements' I described above. But a full-function controller would still be more beneficial, IMO. Sounds like you thought it out pretty well, though.
Drifting
Joined: Sep 2007
Posts: 1,572
Likes: 51
From: Wichita Kansas
I have a cousin who builds street rods and he has used 700R's many times. I asked him how he controls the TC and he stated that he purchases a kit that taps a "T" into the trans pressure line with a pressure switch that sends a signal to the TC conection. Said he has never had a problem with this set up.
Advanced
Joined: Dec 2005
Posts: 70
Likes: 0
From: Martin TN
I put one in an El Camino a few years ago and I wired a floor mounted dimmer switch(the real dimmer is in the column like the Vettes) to the TC lock up. It worked great, and if for some reason I forgot, the car never died at a stop, It just shifted funny. Once you get used to it, you just do it without even thinking about it, sort of like driving a manual trans. To make it fail safe, you could install some sort of indicator light to come on when the lock up is engaged.
Pro
Joined: Jun 2005
Posts: 583
Likes: 61
From: USA
you can get a pressure switch that screws into an existing port in the valve body, for 4th gear, and it closes the circuit when you're in 4th gear. you get lock-up in 4th gear. doesn't have to mess with vacuum or stoplight switch. you provide switched 12V (one wire) to the connector on the trans. very simple, incredibly effective.
