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Discussion Starter · #1 ·
I know, I'm beating a dead horse here. but the search function turned up no answers to my trouble.
particulars are 1985 Pontiac Parisienne, 305, 700R4. Gut stock origional. TC locks up at about 5mph, from a dead stop no matter throttle position. TV cable has been adjusted forty eleven times, in all manner of positions, to no avail. Brake switch works just fine, and unlocks as soon as brakes are applied. I currently have a "disable" switch installed, but would like very much to get it to work properly. Several different tranny shops have been baffled by this problem. Car is still fairly new with only about 430,000 miles, and about 200,000 on engine, and about 1000 since tranny OH. Trouble has been evident since tranny was OH'd. There's not been a shop that could fix it, as yet. (been to 4 different ones)
I'm about ready to put a Mercedes running gear in it. o_O
 

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Shorty you got me laughing so hard I cant think the problem through right now.

I suppose “Shorty” means you’re 6’6” or better?

Bogie
 

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1949 Ford Coupe RESURRECTION
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If I read your description correctly, you are TRULY having "lockup" and not "very early shift". Since you said that your brake switch works to disengage, that indicates that it really is locking up..

Lockup is entirely controlled electrically, but is powered through a "4th gear hydraulic switch", which is the only device that is within the transmission to initiate lockup. Assuming there are no other issues, that switch only closes due to pressure on it when it shifts into 4th. If disconnecting power temporarily fixes the lockup, it sounds as if your 4th gear switch has failed in the closed position. But you didn't make it clear if once you take your foot off the brakes, it locks up again...

Attached is a control diagram. But you must have a two pole 4th gear switch.This works to have 3 modes of operation. Stock shifts with lockup only in 4th, lockup in 2,3,and 4, or no lockup in any gear. This is on my website in the "700R4 Chapter 2" gallery...

617676
 

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Discussion Starter · #4 ·
Thanx for the info. If the 4th gear switch were truely stuck in the closed position, would the TC not lock up even sitting still, in gear, as long as power is applied? Thus stalling the engine?
As long as the vehicle is in motion, under power, the TC will lock up when the brake is released, but when sitting still, in gear, will remain unlocked, without brakes applied. (sitting on a slight incline) But start moving and will lock up at about 5-10mph. Tap brakes and will unlock for a second or two, then lockup again. Definately not early shift.
 

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1949 Ford Coupe RESURRECTION
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GEEEZZZ that is weird.. then assuming your 4th gear switch is not deffective, then somehow you're getting 4th gear pressure on the port that it's hooked up to. Unfortunately I have no idea how that could possibly happen. You might try calling Precision transmissions in Amarillo Texas and see if you can talk to the guy that does the videos. However it's very difficult to reach him because he is very very busy and when he is busy they will not put you through.
 

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Thanx for the info. If the 4th gear switch were truely stuck in the closed position, would the TC not lock up even sitting still, in gear, as long as power is applied? Thus stalling the engine?
As long as the vehicle is in motion, under power, the TC will lock up when the brake is released, but when sitting still, in gear, will remain unlocked, without brakes applied. (sitting on a slight incline) But start moving and will lock up at about 5-10mph. Tap brakes and will unlock for a second or two, then lockup again. Definately not early shift.

there is no oil pressure by GM design for converter clutch lockup until the trans is in 2nd gear
 

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You obviously have an early model of the 700R4, it was pretty problematic in its early years going through a major redesign in1987.

Over the years this had some different combinations TCC lock could occur. The earlier models could lock the converter clutch in second, third and fourth; later third and forth while be the end as it became identified as the 4L60 with no E suffix only 4th gear enabled the TCC. In all models of this transmission first gear and reverse locked out the TCC fluid apply path.

If in fact you’re getting a lock up in first rather than an early shift to second or even getting a second gear launch with a lock up sans starting in first. This is something you need to tease out probably comparing starts in Drive 4 compared to Drive 1.

I’m going to have to trace circuits to see if a check ball failure, which is common as these age, could create a sneak circuit allowing the TCC to lock in first. This is pretty much an unheard of failure mode and the published failure paths don’t offer any information.

A further test is to see if you can feel it come out of lockup when a lot of throttle is applied but with downshifts that might be hard to sense same of course with braking touching the brake pedal should unlock the TCC and releasing the brake pedal should restore lock up this you should be able to feel.

A still operating 37 year old 700R4 is quite an accomplishment.

Bogie
 

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Discussion Starter · #8 ·
Took it for a drive yesterday. Found that as Crosley said, it only locks after shift to 2nd from 1st. But, as soon as shift to 2nd it's locked, which causes engine to bog severely. I tried various speeds while manually shifting from 1st to 2nd, lockup comes in no matter speed, when it takes 2nd. tap brake, it will unlock, release brake, and it locks immediately. I'm about to believe what 46 Ford coupe says that it is an internal switch stuck closed.
Mabe the shops that I've been to just don't want to fool with it. But, the shop that did the OH had better fix it, they've known about it since day one. And should have fixed it then, but they didn't want to fool with it I suppose.
I doubt I can get a factory new from GM, but mabe a re-man, for a few $$k. (more than the car is worth) So, I suppose I'll just stick with the switch on the dash, and only use lockup on the interstate.
 

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Took it for a drive yesterday. Found that as Crosley said, it only locks after shift to 2nd from 1st. But, as soon as shift to 2nd it's locked, which causes engine to bog severely. I tried various speeds while manually shifting from 1st to 2nd, lockup comes in no matter speed, when it takes 2nd. tap brake, it will unlock, release brake, and it locks immediately. I'm about to believe what 46 Ford coupe says that it is an internal switch stuck closed.
Mabe the shops that I've been to just don't want to fool with it. But, the shop that did the OH had better fix it, they've known about it since day one. And should have fixed it then, but they didn't want to fool with it I suppose.
I doubt I can get a factory new from GM, but mabe a re-man, for a few $$k. (more than the car is worth) So, I suppose I'll just stick with the switch on the dash, and only use lockup on the interstate.
If it unlocks when electric power is cut. that points to ppossible pressure switch malfunction that has been mentioned. I will say the only switches i've had good consistent function is a Delco brand switch, silver in color of the metal, single wire post. There are import over seas brands that I have failed on my bench when I test them or they failed on the trans dyno during run in

If the converter did not unlock with electric power cut... the solenoid for the TCC could have a check ball in the end of the snout.. Budget builders did that for lockup of the TCC with out electric to the transmission. It makes the trans shift up and down very harsh
 

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1949 Ford Coupe RESURRECTION
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But if you want full control of shifter modes, you must use a two pole 4th pressure switch as I pointed out in my previous post
 

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The typical way hotrodders wire 4th is as 49 Ford Coupe put it.

You wire the solenoid so the last switch is a pressure switch screwed on the 4th gear pressure apply port which is on the plugged passage on passenger side of the trans main case just behind the second gear band apply piston. So if the trans is not in 4th there is no TCC lockup.

There is no need for lockup in second or third gear the fact that it is there was done as a means for the manufactures to game the emissions and mileage testing rules in force at that time as a means of improving emissions and mileage on the in city portion of the test which was done on a dyno not really driving around Detroit rush hour traffic. So this early lock up in the real world serves no useful purpose. Pretty much nobody cruses around town in second gear, Third maybe but generally if in town there is no need for lockup traffic light to traffic light. On the highway at or above legal speeds is really the only place where slowing the engine down has benefits to lowering emissions and increasing mileage. Even that has limitations as the TCC clutch is not all that strong so if your pulling a steep grade and stripping into the throttle the vacuum switch will shut off the TCC once the manifold vacuum drops down so as to unload the TCC clutch. essentially with a 4th gear pressure switch you get similar protective coverage as if the load causes the trans to shift to 3rd or 2nd as soon as 4th gear is dropped then so is TCC lock up.

For my 350 powered S15 with a 700R4 I don't have any of the factory TCC control system. I have a master panel switch that allows TCC inhibit manually or automatically if I wish one or the other and a 4th gear pressure switch. No brake or vacuum switch nor temperature switch. If the arming switch is ON and the trans is in 4th it can apply the TCC, otherwise not. If the arming switch is OFF then no TCC apply period. I use a safety cover on the switch as a visual for position and with one quick swipe it can be shut to OFF. For heavy loads on steep grades if the trans can’t make the up shift to 4th then no TCC lock as there is no practical reason under that load condition for it. If I take it racing, I just hit the OFF position of the master switch to disallow lock up, though most racing never sees fourth gear anyway.

Bogie
 

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Oh, and it does not come out of lockup when you floor it, to downshift.
A vacuum switch is used to unlock it when stomping on the go pedal.
 
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