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700 R4 hydraulic lockup system for 1981 Corvette

Feltman

Well-known member
Joined
Jul 18, 2003
Messages
97
Location
Indianapolis
Corvette
1981 Dark Blue Coup
Ok people.....the 17 month restoration is going smoothly.......waiting for the engine to come back....will be going from 190 HP to about 300 HP..changing the reae end gear ratio to a 3.55 (overdrive warrants the change). I am getting ready to purchase a 700R4........I know Bowtie and others make this conversion. The question I have is the hydraulic lockup function. My TH360 has a harness that goes to the transmission (not sure if it is for lockup or not). One shop is suggesting the hydraulic lockup system (no wiring) while the other is suggesting a wiring kit to control the lock up function......I am stuck in which way I should go.....I have reviewed most all the post in regards to the conversion....drive shaft, shift changes...just not much on the lockup......any help would be greatly appreciated....in the mean time..back to installing my steeroids rack and pinion.....
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Hello Feltman,

I'm sorry I can't give you any real life feedback only what I did till so far. A few months ago I was searching for the same thing, will a (standard!) 700R4 lockup work with the 81 lockup wiringharness and ecm.
To explain the whole thing.. You begin with a + wire that always has current on it (when ignition is on) first the brake switch to unlock while braking, wire goes into the normal TH350 through a switch and solenoid. Back out the transmission again (second wire) to your ecm. The ecm will ground the wire if everything is correct (steady throttle etc) so the lockup will engage.

Now for the 700R4, it has exactly the same wiring for lockup in second and 3th gear! But it also has an extra wire. This third wire comes from the ecm to the 700R4, inside past a switch and grounds in the transmission itself. If the ecm knows your in 4th and everything is again oke, it will put current on the third wire so the 4th gear lockup will activate.

Now the tricky part. The 81 lockup wiring harness has also 3 wires (our th350 only uses 2) so the third wire is already there. BUT it doesn't lead to one connection in the ecm terminal connectors, instead it is grounded somewhere so the wire is useless. Also if the 700R4 has the standard wiring harness inside our ecm will not lockup in 4th.

Then again. If you order the automatic lockup wiring harness from bowtie you can change the wiring harness inside the 700R4. The bowtie harness grounds inside the transmission 4th gear and maybe 3rd (don't know for sure). With this you can put back in the normal TCC connector from the 81 wiring harness. Then it will lockup right away when you put it in 4th (maybe even in 3rd?). If you want to change it back to let the lockup be controlled by the ecm you need to change your the solenoid of the new bowtie harness with your old harness. The solenoid from bowtie grounds right away and the original solenoid has a ground wire that goes to the ecm, which then controls lockup. I think this could be it :)

If you only want lockup in 4th just buy the bowtie wiring harness change it inside the transmission (easy job). Then to be on the safe side check the wiring diagram if you need to cut the negative wiring on your 81 TCC wiring harness and just plug it in. Then it will lockup in 4th :)

Also ask Sensei, he also changed to a 700R4 and is driving as we speak :)

Groeten Peter.
 

wishuwerehere82

Well-known member
Joined
Sep 6, 2003
Messages
2,314
Location
Rochester, NY
Corvette
Red '82 Coupe,Sebring Silver '98 Coupe
I got a B&M lockout kit for my 82.
It has a module that runs off the speedo cable that reads the speed and a harness that plugs into the lockup control. There is a slider Pot inside the car that allows you to control the speed that you want the lockup to occur. Below that speed, the converter is locked out.
 

Feltman

Well-known member
Joined
Jul 18, 2003
Messages
97
Location
Indianapolis
Corvette
1981 Dark Blue Coup
700R4

If I go with the hydraulic lockup system (according to Maddog), no wiring is needed..so can I simply leave my TCC connector off........


Hello Feltman,

I'm sorry I can't give you any real life feedback only what I did till so far. A few months ago I was searching for the same thing, will a (standard!) 700R4 lockup work with the 81 lockup wiringharness and ecm.
To explain the whole thing.. You begin with a + wire that always has current on it (when ignition is on) first the brake switch to unlock while braking, wire goes into the normal TH350 through a switch and solenoid. Back out the transmission again (second wire) to your ecm. The ecm will ground the wire if everything is correct (steady throttle etc) so the lockup will engage.

Now for the 700R4, it has exactly the same wiring for lockup in second and 3th gear! But it also has an extra wire. This third wire comes from the ecm to the 700R4, inside past a switch and grounds in the transmission itself. If the ecm knows your in 4th and everything is again oke, it will put current on the third wire so the 4th gear lockup will activate.

Now the tricky part. The 81 lockup wiring harness has also 3 wires (our th350 only uses 2) so the third wire is already there. BUT it doesn't lead to one connection in the ecm terminal connectors, instead it is grounded somewhere so the wire is useless. Also if the 700R4 has the standard wiring harness inside our ecm will not lockup in 4th.

Then again. If you order the automatic lockup wiring harness from bowtie you can change the wiring harness inside the 700R4. The bowtie harness grounds inside the transmission 4th gear and maybe 3rd (don't know for sure). With this you can put back in the normal TCC connector from the 81 wiring harness. Then it will lockup right away when you put it in 4th (maybe even in 3rd?). If you want to change it back to let the lockup be controlled by the ecm you need to change your the solenoid of the new bowtie harness with your old harness. The solenoid from bowtie grounds right away and the original solenoid has a ground wire that goes to the ecm, which then controls lockup. I think this could be it :)

If you only want lockup in 4th just buy the bowtie wiring harness change it inside the transmission (easy job). Then to be on the safe side check the wiring diagram if you need to cut the negative wiring on your 81 TCC wiring harness and just plug it in. Then it will lockup in 4th :)

Also ask Sensei, he also changed to a 700R4 and is driving as we speak :)

Groeten Peter.
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Sorry don't know that one. I've only looked into the electrical stuff.

Groeten Peter.
 

Feltman

Well-known member
Joined
Jul 18, 2003
Messages
97
Location
Indianapolis
Corvette
1981 Dark Blue Coup
700R4 same question different twist

Hyraulic lock-up vs electrical lock-up....which is better
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
You have an '81, this ain't rocket science. Take the electric lock-up plug and kickdown cable from your th350c, hook them to the lock-up and TV connections on the 700r4 respectively and start driving! IT WILL WORK! I drive the proof every day. God bless, Sensei
 

wadebee

New member
Joined
Dec 13, 2010
Messages
1
Location
Florida
Corvette
1981 Coupe
You have an '81, this ain't rocket science. Take the electric lock-up plug and kickdown cable from your th350c, hook them to the lock-up and TV connections on the 700r4 respectively and start driving! IT WILL WORK! I drive the proof every day. God bless, Sensei

Sensei,

I have an 1981 with stock TH350. A buddy gave me his 700R (rebuilt with 15k miles on it) when he put a racing TH400 in his 460hp alcohol-fueled 1982. He also gave me the old driveshaft | yoke, crossmember, dipstick and TV cable.

I called a local corvette specialty shop in the area today to get a quote for the swap. The guy has done several of these swaps before. Here is what he quoted me.

1. $500 for the swap labor. Includes extra labor required to drill new crossmember mounting holes into frame (he said 82 and 81 have different mounting points)
2. $150 for an electronic lock-up in 4th gear. He said this would be wired into the brake to prevent my stock 350 from bogging down when slowing down.
3. $100 for this shifter conversion (SHIFTWORKS - Corvette - 1968-81)
4. $55 for a universal TV cable. He said the TV cable I have from my buddy's 82 won't work since it is cross-fire injection and the intake manifold | carburetor bracket is not the same.

Does this sound reasonable. From your last post it would seem that I might not need #2 above? My buddy also recommended I have new spicer u-joints installed at the same time. I'll also add that my ECM is not working right now so I am in limp mode (entire unit unplugged). Eventually I want to get the stock ECM running. Will this affect the swap now or when I eventually get the ECM running?

Thanks for any feedback.
Wade
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
I did all of the install myself, but it has been a few years...

1. $500 for the swap labor. Includes extra labor required to drill new crossmember mounting holes into frame (he said 82 and 81 have different mounting points).

I used a BTO tubular cross member made for the swap. It seems I remember people talking about an easy modification to the original '81 CROSSMEMBER (not frame) that would make it work. I would research this.

2. $150 for an electronic lock-up in 4th gear. He said this would be wired into the brake to prevent my stock 350 from bogging down when slowing down.

Take the plug from your th350c and plug it into the 700r4, nothing else to do. (You can split the $150 you saved with me if you want:D)

3. $100 for this shifter conversion (SHIFTWORKS - Corvette - 1968-81)

Do you ever shift your car into 1st manually? If not, you don't need to do this. The conversion kit allows the shifter to go back farther to reach where 1st will be. It also gives you the label that has 1,2,D and OD. Basically, this one is up to you.

4. $55 for a universal TV cable. He said the TV cable I have from my buddy's 82 won't work since it is cross-fire injection and the intake manifold | carburetor bracket is not the same

You could probably make the original cable work, but since you are not doing it yourself, $55 sounds reasonable enough.
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
If you have the 82 crossmember it's easy to install, no mods needed!

Greetings Peter
 

eclectic74

Member
Joined
Jun 22, 2012
Messages
8
Location
campbellsburg, ky
Corvette
1980 c3 sold, looking for a 82
easy no mess retrofit 700r4

You can get a kit from TCI. It has factory plug and play harness :D. Just plug into the factory harness no hacking or added controls. The kit is 80 bucks. Summit racing and holley has the brackets for these swaps (20 bucks). You can do the swap yourself and save alot. If you use the tci kit, it plugs in and does not cause any issues or go into limp mode. Plus hacking your harness is always bad news.
I did these swaps back in the day with zero issues. I would assemble parts from factory plugs and stuff back in the day. So it would look factory and work well. And i never had limp mode issues and NEVER hacked the wiring harness.
I have found if you spend a little extra and do the job right the first time it pays off in the end. If the cable is old and worn never hurts to spring for a new one. Preventive maintence is so over looked and the cause of multiple failures old and new cars.
Doing it yourself : 80 for lock up kit, 100 for shifter retrofit, 20 bucks for bracket, 50 for kickdown cable. A weekend and some beers or sodas whichever you choose. Plus the pride knowing you did it yourself, it is done to your standards, and no wiring mess to worry about.
Feel free to contact me for help.
 

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