Technical 700R4 OD question

I just installed a (shop) rebuilt 700r4. I used a 2000 stall convertor with a lock-up.
The trani works fine when in 1-2-3, but when I put it in overdrive, the engine seems to always want to return to idle when I take my foot off the gas. I took my car to the shop. They set the pressure. They said it works like it's supposed to. I don't think this should be happening. Any thoughts?

 

If you take your foot of the gas that is what it does goes to idle?

 

this is correct. only in 4th.

 

Tell us about the wiring for the lockup converter?

 

I am using the B&M 70244 Lock-up controller.
I was reviewing the schematic. I do not have a brake switch at the pedal. I have a pressure switch in the brake line. I don't think I wired this thru that switch. Normally open vs normally closed, right? I need to re-evaluate that detail. That may be it.
Thanks.

 

The 700 R4 is a 4-speed transmission 4th gear is actually Overdrive. Lockup gives you an equivalent of a fifth gear. When you are in lockup you can easily tell that it's in lock up because when you let off the gas you can feel the engine braking. If your engine returns to idle when you let off the gas you are not locking up.

Click this link and scroll all the way to the end for a wiring diagram. You don't need anybody's kit to install this.
https://49fordcoupe.smugmug.com/The-700R4-Chapter-2/

Also to see how it is supposed to feel and how it works click this link. The first of the series of videos shows that. Turn up your sound.
https://49fordcoupe.smugmug.com/Driving-around-the-neighborhood-/

Bottom line is your transmission still is not right.

 

A 700R4 has a set of overrun clutches in the input drum, along with a input one way sprag. When in the OD-forth position, the overrun clutches are not applied, therefore the trans will not have engine braking when letting off the gas.
This also makes for smoother coasting downshifts when coming to a stop.
In the 3rd position, the clutches are applied and will have engine braking and harder coasting downshifts.
Also when GM designed the TCC system, the converter clutch is supposed to release when letting off the gas.
What you are describing sounds normal.

Bill

 

attached is the schematic.
I'm currently suspecting the connection to the brake light switch??
I have a pressure switch in the brake system. There is power to the switch, then powers the brake lights when the brake is depressed.

Using this to power the A terminal (yellow wire) on the TCC doesn't work correctly. Do I need a relay from the brake switch signal for a normally closed circuit, then opens when the brake is depressed.

Your help is appreciated. Thanks.

 

Bill, you think when its in overdrive, I should be able to accelerate, but when I release the accelerator, the engine should reduce to an idle at 70mph?

 

Yes you need a normally closed switch for the TCC. Opposite a normally open switch for brake lights.

Bill

 

In OD range, you should be able to accelerate normally. Being that the overrun clutches are not applied, the trans just basically freewheels when deaccelerating. Therefore the engine RPM will drop.
In 3rd, if you deaccelerate the engine RPM stays up longer due to the rear end speed basically powering the trans, loading the engine. "Engine Braking" The overrun clutches are applied.

You should also feel softer coasting downshifts in OD range and harder coasting downshift in 3rd
What's the rear end ratio? We have the RPM at 70?

Bill

 

The rear end gear is 3.91

 

My OT 89 C1500 has a 700r4- driveline is bone stock GM and the transmission works as described- engine goes to an idle when in OD and coasting to a stop.

 

It's easy to test whether your TCC is working or not. Drive on an uphill grade and keep your right foot on the throttle. Lightly depress the brake pedal with your left foot and either listen carefully or observe your tach. If engine rpm's increase, it's working. If not, it's not. Go from there.

 

This afternoon, I am going to install a relay from the brake switch so I can get the normally closed circuit for the lock-up control. I'll use your suggestion when I go out for the next test drive.

Thanks for this. If you don't mind me rephrasing this.....You can be driving down the highway at 70 mph, let off the gas pedal, you feel absolutely no engine/trani engagement and the engine rpm will immediately go to idle as you coast down the highway at 70-mph? (I'm not talking about getting off the exit ramp and coating to a stop.) You then have to accelerate in a completely disengaged state until the engine catches up to the trani? It's just like having your shifter in N during this time. It doesn't seem like this can be right. I thought the Lock-up Controller would keep the converter engaged until you applied the brake. Not?

I guess I have gotten over my head on this one. I can't stop now. Trudge onward, with help. Thanks.

 

What diff ratio are you running and is there any way that a 2000 stall convertor could be part of a problem when your O/D kicks in under 2000rpm
I don't know shit about these trannys and had my own issues when I first installed one, but never heard of the problems that you are experiencing...

I hope you can find a solution and don't forget to share it.

 

Hey, Lovinmysedan, you are exactly right, lock up means locked up lock up means locked up. When in lockup whether you wire it so that you go into lock up in second third and fourth, or 4th only it feels as if you're driving a standard shift and have not pushed the clutch in no matter how fast or slow you go. I can't figure out that comment about going uphill and riding the gas and the brake at the same time he'll it's obvious if your transmission works okay.

See my original post above. You don't need anybody's "kit" to make it work correctly. See my wiring diagram.

 

The TCC lockup is disengaged when you apply the brakes in most circuits. So, if the torque converter is locked up and you lightly apply the brake, the brake light switch opens the circuit and kills the power to the TCC solenoid. When that happens, rpm increases. Simple.

 

Regardless of whether " most circuits" work that way or not why would you want to disengage lock up if you're driving down the freeway at 70 and touch the brakes? Then as you lift your foot off the brake it re-engages? Why do that? Please explain the logic of desirability of your theory...

 

I have printed your schematic. I will spend some time looking at it this evening. I'm on the steep side of the learning curve on this subject. Thanks for your advice.

 

The lock converter on my modern trucks will kick out with brakes applied and also when you let off the throttle.

 

So what?

 

I wouldn’t say it immediately goes to idle-it may take a second or two- but it does go to an idle -the truck has a 350TBI engine and trans- all stock so it still all works the way the General designed it to- converter locks and unlocks automatically

 

Can anyone tell me how the terminals on the plug in connector are identified? I see diagrams like those shown here marked A-B-D but nothing showing what the orientation is on the connector? Is the "notch" or "release tab" for the connector the reference mark on the diagram? If so then "A" terminal is to the left of the tab and closest to it? Which would make "D" directly behind it?

 

Here ya go...

 

Thanks. That helps, but brings up another question. Most diagrams I see show 12+ switched power to the "A" terminal, and ground to the "D" terminal. But your diagram shows 12+ to "A" and "manual lock power" to "D"?
I didn't think "D" got power to it? No way to ground and complete the circuit with two power feeds?
I'm using a Shift Technology Superior Solutions hydraulic pressure switch that locks and unlocks 4th gear when pressure closes or opens the switch. It shows one pin as 12+ and the other as 12_, but didn't give me any indication which pin was which in their instructions.

 

Ive used TCI 376600 on 2 cars with 700R4 with the brake pedal switch, both worked very well. Other than pulling the pan, I dont recall the install being a big deal.

B&M 70244 page 2 of instructuons describes how to install thru brake switch or bypass it. Recommends using brake switch.

 

My apologies. Here is the story. The fact is that 700R4 s came with more than one configuation of internal wiring harness. We are going to have to confirm how yours is wired. The internal wiring that shown on my drawing is the most common but there is a possibility yours could be different. I'm sorry I did not look at the last diagram I sent this afternoon closely enough because it shows that there's nothing hooked to b. That would indicate that the solenoid is grounded internally on the transmission. We don't want that. If you put an ohmmeter between A and B you should read about 20 ohms. If you read open circuit then your solenoid may be grounded internally. If you read open circuit between a and b then ohm between a and the transmission case. If you read 20 ohms there then your solenoid is grounded internally. To make it work with my wiring diagram your pressure switch has to be a two terminal type but you can find online or at any transmission parts house. In the scheme that I used the dash switch it's where the grounding occurs through that switch.
If you ohm from d to either other pen you should read open circuit because that 4th gear switch will be open unless you are operating in 4th gear and that's when that switch closes.
For what we are trying to do here that last wiring case connector diagram is flat ass wrong.

I'm not sure I read before but do you have the pan off the transmission? Can you get to the guts of your transmission?

 

I thought I was talking to loving my sedan. Are we switching OP's?

 

That B&M controller is showing that only the solenoid is wired between a and d and it does not show the 4th gear pressure switch. Do the instructions tell you to jumper the 4th gear switch? And apparently the only input is the speedometer transducer so you can set lock up based on speed of the car and not which gear you're in. I can see the logic in that but it's silly to spend the money ($230 at Summit) on that thing when you can do it by simply wiring it correctly.