Rusty Bowtie
General Category => GM Tech Questions and Answers => Topic started by: themoose on December 18, 2013, 09:06:02 AM
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Jef
I often see the question asked about whether or not running a 700 without the lockup functioning will cause damage. Most would answer a definite Yes but Performance Automotive Transmission Center has a statement on their web site that says the following.
If you have a 1982-83-84 car or truck never drive it with the wires on the side of the transmission unplugged. This will overheat the transmission on a long trip. On a 1985 or later it is O K to have the wires unplugged, because of a design change made in late 1984. The only part of this transmission that is electronic is the torque converter lockup. You will still have all four speeds with the wires unplugged.
Is this a correct statement and if so what changes were made that would eliminate the need for TC lockup?
Moose
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Moose,
This is a good question. If you don't mind I would like to add to the question. Is there a way to check to know if your TC is locking up? I purchased a 700r4 from TCI when I built my '35 and have had a number of issues with it. I purchased a lock up kit with it, but a TCI rep said that it was already installed in the transmission so I returned it. I have also had issues with the shift points. I ended up purchasing a Bowler Tru-Shift kit and it helped, but I think it was heat related. So, I installed a tranny cooler and it helped a bunch. I still am not sure it is working correctly. So, not to high jack Moose's question, but I would like to know if there is a test for this issue. Any information would be helpful!
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From the top of my head, I have a mini 12v LED on my dash, it has constant 12v (fused) via my brake pedal switch (ie foot off pedal LED & Tranny solenoid get power via purple wire).
I tapped into the light blue wire coming from the 700R4 to my ECM, the blue wire supplies the ground to the trans via the ECM (lock up) and -now- my LED.
Driving without brake pedal depressed both the tranny & LED have 12v (purple wire), the ECM determines lockup by sending ground to the tranny solenoid (& my LED) via the blue wire.
Stepping on the brake pedal opens the power circuit and cuts power (un-lock)to the tranny and LED.
That's using an ECM to lock up the tranny...don't know what lock-up system you are using.
I suspect that Jef will jump in and talk about proper TV cable adjustment..which is critical.
BTW: Some trans builder send out the 700R4 with the lock-up feature disabled and without lock-up torque converter....but for the lock-up solenoid to work it needs 12v power.
Ed
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Ed,
Thanks for the reply, but unfortunately I am not running an ECM. I am starting to regret this decision. I am running a crate 350 HO with a demon carb. So I am locking up off of vacuum. I do have a power and ground going to the solenoid, but I think it is actived by vacuum. I have checked and I am getting good vacuum, but I haven't checked it while driving. The only other thing I have considered is putting in Bowler's lock up kit. This does away with the vacuum and uses a timed delay to lock up the TC. I really don't want to keep dumping money into this tranny, but I want to get it right also. Hopefully, Jeff can offer some insight. Okay, I am done high jacking your thread moose!
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Senior31
Hate to keep jumping myself...but one way to determine if it's locking up is to over-ride that vacuum switch (toggle) and drive the car...if you feel it stalling as you stop, like forgetting to push in the clutch on a manual car...you know the torque converter is locked??
To see if the vacuum switch is working why not wire in a small inline LED.
Ed
Sorry Moose...but would still like Jef clear up your original question...I know tranny shops offer the 700R4 without the lockup option (my buddy bought one last year).
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Wow! Talk about a lot to talk about.
First, TV cable adjustment is easy, it's TV installation that must be right. The cable must be perpendicular to the throw of the throttle arm pickup point, and it must swing in the proper arc. So if you use late model Quadrajet that was used with a 700R4 or a 200R4 you're ok. If you run a Holley or an AFB (Edelbrock) style carb you will have to purchase and install a cable corrector bracket. Once you get the cable happy just set it so that it is tight a wide open throttle and adjust it back and forth a click at a time until you get the shift points where you want them. If you have to go more than a few clicks then it I time to start modifying the governor springs, or changing the governor itself to a Corvette style and changing springs on that. I can give you more if you need it. If you run an E transmission, such as a 4L60E then you don't have these issues.
More on this later if you need further explanation.
Can I run without the converter clutch locked. The answer is a definitive YES if your trans is a 1985 or later, and if your hotrod is light weight and you aren't into delivering Abrahm's tanks the the early ones are ok, too. The only time you can run into trouble because of not locking the converter is if you have a heavy vehicle, under a constant heavy load, with a marginal cooler. Again, you should run trans temp gauge if you red worried about overheating the transmission. If you run n E trans it incorporates a thermistor in the internal switch plate which can be read through the controller or scan tool. The post 1984 transmissions routed more cooler oil through the radiator when then TCC is engaged.
The wiring for the TCC is something you have to know from the builder. I wire all of the transmissions I sell with the grounding switch in the fourth gear circuit of the valve body providing ground. I don't need or want the TCC on until fourth. If you look at 700 wiring schematics you won't believe how many different schemes the factory had over the years. To operate the clutch you should need to provide B+ to I the correct terminal on the trans! I always use the right front terminal, interrupted by the brake switch, and I some cases a vacuum switch. But the vacuum switch needs to be adjustable because every car is different and every driver want something different. For those reasons I tend to not use the vacuum switch. You can have a TCC circuit that works electrically and hydraulically that doesn't seem to work which could be for a worn out clutch disc a failed converter, or maybe just the little I seal on the turbine (input) shaft. You can check to see if the circuit is working by connecting a pressure gage into a cooler line and watching for about a 25 psi pressure drop when I the TCC is commanded on.
These explanations are going to raise a bunch of questions, and that's good. And my typing isn't all that good on this iPad, so I am going to use the computer for now on!!
If you are going to build your own transmission I recommend Transgo kits. They have the TV circuit down to science and when you re done it works perfectly. If you want to keep from getting covered with trans fluid from modifying governors the consider an E transmission.
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Jef
Sure am glad you decided to participate in our forum. I'll probably be bugging you with 700R4 and 4L60E questions. I have been hoarding post 1988 700R4's and 4L60E trannys..have a nice collection in my barn - some work - some for parts.
Didn't realize I could get a Transgo rebuild kit "with torque converter" for about $350 delivered. They sell the Corvette servos for about $13 delivered.
Thanks again
Ed
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Hey Ed,
Any of you that need parts can get them from Dean Transmission in Agawam, MA . Extension 118 will get you Debbie, she's my salesperson.
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I also collect as may 700's as I can find. It is only part of what I do here, but I still sold over 30 last year. I had a bone stock on in my truck with good clutches and a B&M kit and I raced it and drove it for 30,000 miles, now it's in my friends '34 with a very healthy 406 and is still working perfectly. But no one is going to sell you a 700 or a 2004R that is going to shift just the way you want it, you have to play with tad cable and the governor to get it just right. If you're mot fussy then it makes it a lot easier. Because I race my truck I used to shift it manually, but with an E transmission I just program it to shift at 7200 and leave it in drive.
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If you are interested in performance you can't pick a carburetor without knowing rear fear, converter stall speed, and all that stuff. I'll put something together for that soon. I'll discuss the difference between racing converters, street converters (flash converters) and stock. And why you can run a high stall converter with a 2.73 rear gear.
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Jef
Thanks for the contact info...won't be needing any parts until Summer. The 700R4 in my 33 Chevy has a B&M rebuild kit in it, behind a 350 TPI engine, flat top pistons, 58cc heads, Crane cam and 3.08 gears with tall tires in the rear. The engine is out of a Corvette and using the vette pedal setup for trans lock/release. The engine is from a 79 vette and the fuel injection from a 1991 vette. Really don't plan on beating the car at all....just hoping to get some decent fuel mileage.
Ed
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With 3.08 gears you will have to run a stock converter.
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10-4...the converter is stock.
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I missed answering your question. I simplify things by using a manual switch mounted in a convenient spot on the dash, through which I run B+ to the trans. Inside the trans I run the ground wire from the solenoid to the fourth gear switch, the other lead from the solenoid to the B+ from the switch. Let's face it, using the TCC is for economy, you are only going to use it in 4th gear, and only when cruising on the highway. So if you like the idea and don't know where the fourth gear switch is located on the valve body let me know, I'll send a picture. You may want to wire the B+ for the switch so it is interrupted by the brake pedal. Up to you. Vacuum with a modified engine is sketchy.
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If you get on line and go to Bowtie overdrive you will find a lot of good info. about using the 700r4 trans.
They also have adapters to hook your TV cable in the proper location on the Carb.
Good luck
Bernie