Question about 700R4 w/lockup T/C
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Pro
Joined: Oct 2007
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From: Overland Park Kansas
Question about 700R4 w/lockup T/C
The 79 vette I recently purchased has a 700R4 that was built to racing specs (clutches, servos, etc). It also has a 2800 stall lock-up converter on the car. I've only owned standards in the past really, so my question is about the gearing with the lockup. As far as I can tell, the 700R4 has 4 gears. I thought (when getting on the highway for instance) that I should feel/see 4 RPM drops from the tranny, and then when the T/C locks another. So it should seem to look like 5 gears in the car, correct?
If this is indeed true then I'm wondering why I only seem to see 3 drops. It looks like the T/C is never locking up. How is this controlled and is there a good way to see if it's actually working?
Thanks!
-Josh
If this is indeed true then I'm wondering why I only seem to see 3 drops. It looks like the T/C is never locking up. How is this controlled and is there a good way to see if it's actually working?
Thanks!
-Josh
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Decent to strong possibility you have a non locking converter there, in which case extended freeway operation without a significant cooler in there will cause premature tranny failure.....
especially with a racing converter 2800 is a pretty high stall for the street....doo able with the lockup feature,.....
now you could also have a failure or maybe the lockup is purposely disconnected electrically, everything seems normal, but just the 4 speeds, and no bump to lockup.....it's also possible the lockup takes place so fast in 4th gear, you think it's part of the shift....best possible scenario.....in 4th and cruising say 70 mph.....hit the gas and lift quickly, does the engine rev/slack about 3-500 rpm's if so, it's not locked, if it seems to be tight like a stickshift would be, no slop in RPM with that throttle blip....it's locked....
especially with a racing converter 2800 is a pretty high stall for the street....doo able with the lockup feature,.....
now you could also have a failure or maybe the lockup is purposely disconnected electrically, everything seems normal, but just the 4 speeds, and no bump to lockup.....it's also possible the lockup takes place so fast in 4th gear, you think it's part of the shift....best possible scenario.....in 4th and cruising say 70 mph.....hit the gas and lift quickly, does the engine rev/slack about 3-500 rpm's if so, it's not locked, if it seems to be tight like a stickshift would be, no slop in RPM with that throttle blip....it's locked....
Thread Starter
Pro
Joined: Oct 2007
Posts: 587
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From: Overland Park Kansas
Ok, so I got out today and tested it. I got up to 80 and blipped the throttle and it's still not locking.
Soooo...... what can cause it to not lock? I know next to nothing about these systems, someone told me the TV cable, I've read electrical, but I really have no idea...
Any suggestions?
Thanks
-Josh
Soooo...... what can cause it to not lock? I know next to nothing about these systems, someone told me the TV cable, I've read electrical, but I really have no idea...
Any suggestions?
Thanks
-Josh
Racer
Joined: Oct 2001
Posts: 420
Likes: 11
From: tuttle ok
I have installed a 700 in a 77 and a 200 in a 79. So when you take off you should feel 2nd then 3rd then 4th and depending on how your TV cable is rigged and also how your tranny is wired you should see a drop in rpm somewhere after shifting into 4th gear. (the drop is the solenoid locking up the torque converter) This drop will depend on again on how the TV cable is rigged. My tranny is wired so that the power going to the lockup solenoid goes through a pressure switch in the 4th gear circuit of the valve body. So the tranny will not lockup unless it is in 4th gear. Hope this helps.
Thread Starter
Pro
Joined: Oct 2007
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From: Overland Park Kansas
So the lockup is controlled by the TV cable? How do I adjust it to get the TC to lock? I only tested it cruising up to 85 but there is no RPM drop in 4th.
Last edited by neuroclast; Oct 31, 2007 at 08:02 PM.
Safety Car
Joined: Aug 2001
Posts: 3,688
Likes: 202
From: Waterford Mi
Most lock up convertors lock as soon as it goes into 4th so you would not see it. The way to check to see if the convertor is locked is to drive on the highway and when you know it is in 4th, lightly touch the brake pedel enough to kick on the brake lights. The switch shoud unlock the convertor and you will feel the rpm's change about 200-300 rpm's.
Drifting
Joined: Oct 2002
Posts: 1,818
Likes: 13
From: ar
The kit I have used on a couple 700Rs looks like a small switch mounted on the firewall with 2 wires running to it plus a vacuum hose. It should be connected inside the transmission to tell it to lock up after shifting into 4th gear. Then it unlocks when you hit the throttle and the vacuum drops or when you hit the brake pedal.
Jeff
Jeff
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Safety Car
Joined: Oct 2004
Posts: 3,725
Likes: 5
From: Minnesota
Yes. The stock switch should have been replaced with one where the contacts open for the lockup and close for the brake lights when the pedal is pushed. There should be a wire going from the tranny to the brake light switch. You need this to deactivate the lockup when you hit the brakes. I also installed a vacuum actuated cutoff inline with the brake switch that will deactivate the lockup under moderate load in 4th gear so the tranny essentially has 5 gears.
Like Gene says, if the converter is designed for the lockup but the lockup isn't functioning the tranny will heat up more than it should.
Bowtie overdrives can fix you up with whatever parts you may need and can also answer questions.
http://www.bowtieoverdrives.com/cata...SUBCAT&CATID=O
Like Gene says, if the converter is designed for the lockup but the lockup isn't functioning the tranny will heat up more than it should.
Bowtie overdrives can fix you up with whatever parts you may need and can also answer questions.
http://www.bowtieoverdrives.com/cata...SUBCAT&CATID=O
Safety Car
Joined: Aug 2001
Posts: 3,688
Likes: 202
From: Waterford Mi
Yes. The stock switch should have been replaced with one where the contacts open for the lockup and close for the brake lights when the pedal is pushed. There should be a wire going from the tranny to the brake light switch. You need this to deactivate the lockup when you hit the brakes. I also installed a vacuum actuated cutoff inline with the brake switch that will deactivate the lockup under moderate load in 4th gear so the tranny essentially has 5 gears.
Like Gene says, if the converter is designed for the lockup but the lockup isn't functioning the tranny will heat up more than it should.
Bowtie overdrives can fix you up with whatever parts you may need and can also answer questions.
http://www.bowtieoverdrives.com/cata...SUBCAT&CATID=O
Like Gene says, if the converter is designed for the lockup but the lockup isn't functioning the tranny will heat up more than it should.
Bowtie overdrives can fix you up with whatever parts you may need and can also answer questions.
http://www.bowtieoverdrives.com/cata...SUBCAT&CATID=O
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Ok, so I got out today and tested it. I got up to 80 and blipped the throttle and it's still not locking.
Soooo...... what can cause it to not lock? I know next to nothing about these systems, someone told me the TV cable, I've read electrical, but I really have no idea...
Any suggestions?
Thanks
-Josh
Soooo...... what can cause it to not lock? I know next to nothing about these systems, someone told me the TV cable, I've read electrical, but I really have no idea...
Any suggestions?
Thanks
-Josh
The problem is stock lockup clutches only have about 19 sq inches of holding surface. So if you install a bigger pump, it has more pressure and holding ability. My final TC had a three clutch setup with 54 sq inches of holding surface and I was very careful about only engaging the lockup off throttle.
You can take a 12 volt source and get under the car and remove the Sel wiring plugin jack and you can cause the sel to pick. You can hear it click. If it is cycling - your TC is probably gone. I burned out my 3 clutch setup on my $1140 dollar 9.5 inch 3500 stall and it was $400 to have it reclutched. Or just a little more to get mine upgraded to 5 or 7 clutch model that could take on even more power.
Last edited by gkull; Nov 1, 2007 at 10:23 AM.
Drifting
Joined: Sep 2003
Posts: 1,325
Likes: 6
From: FRANKLIN GA
I agree with George. I have the 5 clutch Vigalanti lock up converter and it's holding up so far. It better for $1400.
I'm not being mean but the problem is defsegx, is I think you don't have a clue about installing a 700.
It's not like bolting in a 350 and going about your way. You have to adjust the TV cable after installing it or you will burn the trans up in a couple of days. DO NOT drive the car again untill you understand how this trans works. Just trying to save you a trans and a few dollars.
Bowtieoverdrives.com has same good articles on how this trans works and how to set up the TV cable. I suggest you read them and adjust the TV cable properly. Then you can worry about the lockup function. Check the bowtie site for a lock up kit while your there.
The lockup function is a whole different beast. If you are installing a 700r4 in a car without a computer (which you are) you must have some kind of a lockup kit wired into the trans. You can build your own from plans on the internet or you can buy a kit from one of the major trans manufactors ie. B&M, Bowtie, etc. I like the vacum switch model as it behaves most like the computer and does everything on it's own automatically.
I'm not being mean but the problem is defsegx, is I think you don't have a clue about installing a 700.
It's not like bolting in a 350 and going about your way. You have to adjust the TV cable after installing it or you will burn the trans up in a couple of days. DO NOT drive the car again untill you understand how this trans works. Just trying to save you a trans and a few dollars.
Bowtieoverdrives.com has same good articles on how this trans works and how to set up the TV cable. I suggest you read them and adjust the TV cable properly. Then you can worry about the lockup function. Check the bowtie site for a lock up kit while your there.
The lockup function is a whole different beast. If you are installing a 700r4 in a car without a computer (which you are) you must have some kind of a lockup kit wired into the trans. You can build your own from plans on the internet or you can buy a kit from one of the major trans manufactors ie. B&M, Bowtie, etc. I like the vacum switch model as it behaves most like the computer and does everything on it's own automatically.
Thread Starter
Pro
Joined: Oct 2007
Posts: 587
Likes: 0
From: Overland Park Kansas
I agree with George. I have the 5 clutch Vigalanti lock up converter and it's holding up so far. It better for $1400.
I'm not being mean but the problem is defsegx, is I think you don't have a clue about installing a 700.
It's not like bolting in a 350 and going about your way. You have to adjust the TV cable after installing it or you will burn the trans up in a couple of days. DO NOT drive the car again untill you understand how this trans works. Just trying to save you a trans and a few dollars.
Bowtieoverdrives.com has same good articles on how this trans works and how to set up the TV cable. I suggest you read them and adjust the TV cable properly. Then you can worry about the lockup function. Check the bowtie site for a lock up kit while your there.
The lockup function is a whole different beast. If you are installing a 700r4 in a car without a computer (which you are) you must have some kind of a lockup kit wired into the trans. You can build your own from plans on the internet or you can buy a kit from one of the major trans manufactors ie. B&M, Bowtie, etc. I like the vacum switch model as it behaves most like the computer and does everything on it's own automatically.
I'm not being mean but the problem is defsegx, is I think you don't have a clue about installing a 700.
It's not like bolting in a 350 and going about your way. You have to adjust the TV cable after installing it or you will burn the trans up in a couple of days. DO NOT drive the car again untill you understand how this trans works. Just trying to save you a trans and a few dollars.
Bowtieoverdrives.com has same good articles on how this trans works and how to set up the TV cable. I suggest you read them and adjust the TV cable properly. Then you can worry about the lockup function. Check the bowtie site for a lock up kit while your there.
The lockup function is a whole different beast. If you are installing a 700r4 in a car without a computer (which you are) you must have some kind of a lockup kit wired into the trans. You can build your own from plans on the internet or you can buy a kit from one of the major trans manufactors ie. B&M, Bowtie, etc. I like the vacum switch model as it behaves most like the computer and does everything on it's own automatically.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
For the record I didn't do anything with the transmission. The 700R4 has been in this car since it was built a few years ago, I just recently purchased the car from that owner. AFAIK the TV cable is set properly by the transmission guy who installed it. But you're right, I know nothing about them. That's why I'm trying to learn.
Thread Starter
Pro
Joined: Oct 2007
Posts: 587
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From: Overland Park Kansas
Well I looked at the brake pedal and the only thing there is the brake light switch. I guess I'll try to pick the car up and look for the TCC by the tranny. The person who sold it to me seems to think it's caused by the TV cable being light, but it shifts hard and on time so I don't know.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I did my 700R4 before any fancy kits came out. I'm kind of a simple person. So I bought a 700R4 modded to be able to not have any kick down. so you could run wide open throttle in 4 gear OD. The tranny also had lockup in 4th gear only.
Then i installed a 50 amp lighted toggle switch on my dash to lock 4th gear.
Most kits and shop these days often cheap out and cut out the whole lockup clutch idea. It saves money and people don't bring it back when it quits. So there is the real possibility that you don't even have a lockup TC
Then i installed a 50 amp lighted toggle switch on my dash to lock 4th gear.
Most kits and shop these days often cheap out and cut out the whole lockup clutch idea. It saves money and people don't bring it back when it quits. So there is the real possibility that you don't even have a lockup TC
Thread Starter
Pro
Joined: Oct 2007
Posts: 587
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From: Overland Park Kansas
I did my 700R4 before any fancy kits came out. I'm kind of a simple person. So I bought a 700R4 modded to be able to not have any kick down. so you could run wide open throttle in 4 gear OD. The tranny also had lockup in 4th gear only.
Then i installed a 50 amp lighted toggle switch on my dash to lock 4th gear.
Most kits and shop these days often cheap out and cut out the whole lockup clutch idea. It saves money and people don't bring it back when it quits. So there is the real possibility that you don't even have a lockup TC
Then i installed a 50 amp lighted toggle switch on my dash to lock 4th gear.
Most kits and shop these days often cheap out and cut out the whole lockup clutch idea. It saves money and people don't bring it back when it quits. So there is the real possibility that you don't even have a lockup TC
This one has the modification that makes it lock up hydraulically without the electrical connection. It was working ok the day we drove it. If you remember when we got it on the highway we were cruising about 60mph and it was locked up under 2k rpm. Anyway, the lockup on that particular TC was always light. The one I had before (the 2400) felt like a gear shifted when it locked up.
If you tighten the cable, it shifts harder and is delayed. If you loosen the cable it shifts softer and tends to short-shift. You don't want either of those, so you sort of tweak it until it seems right. You may want to start by loosening it a notch or two and see what happens. You're not going to hurt it unless you go too far and leave it that way.
If you tighten the cable, it shifts harder and is delayed. If you loosen the cable it shifts softer and tends to short-shift. You don't want either of those, so you sort of tweak it until it seems right. You may want to start by loosening it a notch or two and see what happens. You're not going to hurt it unless you go too far and leave it that way.
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Joined: Oct 2007
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From: Overland Park Kansas