Slant Six stalling when foot on brake & engine warm - transmission issue?

[AlmightyAstro]

Hi folks, I have been reading posts on here for many years as I have been using my 64 Dart GT as a daily driver in summer weather for about 7 years or so. A few years back I rebuilt the engine and then transmission as they were original and tired. This car has a lot of miles on it! It's the 225 slant six and the corresponding torqueflite 904 with pushbutton shift. Posts from many folks here, the slant six forum, and a couple of emails from Pat Blais were all very useful to me during the rebuilds. Last fall my car developed a new issue which I have been unable to figure out. When the engine is warm and I put my foot on the brake, the idle dives way down, and the engine either quits or almost quits, and it sounds like it's fighting a lot of resistance. Now I know that "idle" when in gear with the brake on is often a little lower than in neutral, this is a huge dip, from say 1000RPM to 500RPM, and with "puts" that dive down to 200 it seems. Recently I noticed that it seemed like I had lower than nominal fuel pressure, but I believe I corrected that last night (fuel line around the front seemed partly plugged before I blew it out). I'm now back to my original theory that something in the transmission is not releasing when I apply the brake. It reminds me of when you don't clutch properly when braking on a manual, though a little less dramatic. I can feather the gas to keep it alive as I brake but that probably creates risk of damage somewhere. I'll also note that this issue seems to appear whether I have the idle and/or mixture high or low, and the ignition voltage is normal.

I am thinking the torque converter or a clutch could be hanging up, something like that, or maybe the hydraulic pressure needs adjustment? Do these symptoms sound familiar to anyone? I notice when the engine is cold (choke open or closed) this is far less prevalent and often not noticeable. I have to go for a drive on the highway or up some hills to get into the "quit mode". The converter was pretty full of contaminants before I did the transmission (clutches cooked, then I did the redo). I cleaned out the converter extensively and everything was performing good for a good while after that, until this past fall.

I am going to do some more reading, but I was focused on the engine for a while and now think it's not the engine. This engine got me home running on only 4 cylinders with badly uneven compression before its rebuild.... and now it runs as even as a carbureted slant can.... I'll double check timing & such, but this dramatic drop in RPM and appearance of "load" makes me think transmission problems.

Sorry for the long post but I thought it'd be better to post more info than not enough. I appreciate any thoughts that come to mind. I am getting mighty frustrated with this issue, it's going to remain parked until I have a good feeling about what to do next.

Thanks!
Lou

 

[moparlvr166]

Tell us what tools do you have? It can be various things.
Vacuum gauge, timing light, Dwell meter, feeler gauges.
If you have stock ignition (points) possible just clean and adjust, dirty fuel filter and sediment in carb, valves out of adjustment? I don't think it's in the trans, but I have been wrong before.

 

[AlmightyAstro]

Tell us what tools do you have? It can be various things.
Vacuum gauge, timing light, Dwell meter, feeler gauges.
If you have stock ignition (points) possible just clean and adjust, dirty fuel filter and sediment in carb, valves out of adjustment? I don't think it's in the trans, but I have been wrong before.

Thanks for the tips! I have a recent distributor with a pertonics module, new ballast resistor, new coil, recent plug wires, newly rebuilt alternator, new regulator. I am going to get a new set of plugs too for good measure. Like I say I will check the timing once more as it's been a little while since I last did that. Carb is a carter BBS, I just gave it a thorough cleaning and noticed the float was out of adjustment, so I fixed that. Got the lid to seal up good on that too. The carb is getting tired, I need to swap to something else someday but it seems to be behaving well. I have a decent set of mechanic tools and have access to tools from a street rod builder, so tools themselves shouldn't be an issue. I have a decent amount of experience with engines and with this engine, which is part of why I am so frustrated. Like I say, I have been through this engine and man does the car lurch when I let off the brake when it's warm that made me migrate to thinking transmission, but I can easily be wrong. I'll try to take a video where I make the symptom arise & we can hear the engine & see the tach.

 

[65TerrorCuda]

Power brakes or manual?

 

[AJ/FormS]

I sortof agree with your diagnostics
Here is what you need to know;
Reverse is created by the application of the Hi-drum and the L/R band.
All forward gears go thru the forward clutch, which Chrysler calls the "rear" clutch.
After that,
Third gear adds the Hi-drum, while
Drive-Second disengages the Hi-drum, and engages the "K/D band, and
Drive-low, goes thru the rear sprag while Manual low re-engages the L/R band.
With the factory VB, you cannot get past First gear until the Governor pressure comes up high enough, which makes diagnostics for your case, difficult.
But I'll give it a try.

If the engine gets dragged down in reverse,
Either the convertor is bad, OR, the Forward clutch is.
If the engine gets dragged down in manual low;
Either the convertor is bad, OR, another clutch pack is engaged, probable it has been locked up by cooking it.
At this point, your only choices are the Hi-drum and the K/D band.
If you could get it up to speed, and you found ONE of those two gears worked perfectly, that would be the locked up one.

At this point it doesn't really matter cuz the trans is PROBABLY gonna have to come down, and inspection should tell the story. BUT,
You could perform an air-test , which involves pressurizing all the servos and bands one atta time and seeing/hearing what happens.
If you can prove that they are all working and the oil does not stink, well then, the TC sorta must be the problem.

If you get to thinking that the TC is the problem, you can get the rear wheels off the ground, start her up and run the speed up, if it now shifts every gear pretty much normally, that points to a failed Convertor. Then, as you brake the wheels to a stop, and that action again brings the rpm to near stall, that proves it.

 

[Darter6]

it sounds like it's fighting a lot of resistance.

THIS IS ONLY FYI. Had a torque converter that had the stater go bad till it finally locked up.
This made the car stall as soon as you dropped into drive (or reverse).
50+ years of Mopars and this only happened once. And on a Slant 6 car.

 

[AlmightyAstro]

Power brakes or manual?

Manual, original. Going to do the dual master conversion at end of season

 

[AlmightyAstro]

I sortof agree with your diagnostics
Here is what you need to know;
Reverse is created by the application of the Hi-drum and the L/R band.
All forward gears go thru the forward clutch, which Chrysler calls the "rear" clutch.
After that,
Third gear adds the Hi-drum, while
Drive-Second disengages the Hi-drum, and engages the "K/D band, and
Drive-low, goes thru the rear sprag while Manual low re-engages the L/R band.
With the factory VB, you cannot get past First gear until the Governor pressure comes up high enough, which makes diagnostics for your case, difficult.
But I'll give it a try.

If the engine gets dragged down in reverse,
Either the convertor is bad, OR, the Forward clutch is.
If the engine gets dragged down in manual low;
Either the convertor is bad, OR, another clutch pack is engaged, probable it has been locked up by cooking it.
At this point, your only choices are the Hi-drum and the K/D band.
If you could get it up to speed, and you found ONE of those two gears worked perfectly, that would be the locked up one.

At this point it doesn't really matter cuz the trans is PROBABLY gonna have to come down, and inspection should tell the story. BUT,
You could perform an air-test , which involves pressurizing all the servos and bands one atta time and seeing/hearing what happens.
If you can prove that they are all working and the oil does not stink, well then, the TC sorta must be the problem.

If you get to thinking that the TC is the problem, you can get the rear wheels off the ground, start her up and run the speed up, if it now shifts every gear pretty much normally, that points to a failed Convertor. Then, as you brake the wheels to a stop, and that action again brings the rpm to near stall, that proves it.

Wow thanks for the detail. This takes me back to all of the reading I did when we did the rebuild and I got it all adjusted back then, a couple years back! I may have forgotten to mention before that the way the car drives and shifts is still normal, the way it always hails before and after the clutch/band job we did. Whether I am putting it into drive from neutral (with foot on brake) or braking going to a stop light/sign its the same darn symptoms, but again only when the engine and transmission are warm. Acts fine after a cold start... until it stops being cold! I can get it off the ground and try stopping while its "driving" in the air as you say too, but on the ground it does what you were saying it might if it was the TC.

Related note: I'm using Valvoline ATF+4, is there a better fluid or an additive that people like better?

Thanks again for the dialog folks!
Lou

 

[slantsixdan]

This happens only when you step on the brake? Or is it actually when you take your foot off the accelerator? If you were to put chocks in front of the wheels, start the car, and shift into Drive without touching the brake, would the problem occur? Or not until you step on the brake? What happens if you're driving along and you shift to Neutral before stepping on the brake to bring the car to a stop? What happens if you step on the brake while the car's in Reverse rather than Drive?

ATF+4 is fine. Dexron-VI is superior in every respect, but not enough so to warrant spending the time, effort, and money to go draining out your ATF+4 and replacing it with Dex-6. These transmissions are highly tolerant of crummy fluids; they'll even last a long time with an archaic, inferior-across-the-board fluid like Type-F, so don't fret about it. If you eventually have occasion to drain the transmission and torque converter, pick a reputable brand of Dex-6 (Mopar will even sell it to you, if you want).

 

[AlmightyAstro]

This happens only when you step on the brake? Or is it actually when you take your foot off the accelerator? If you were to put chocks in front of the wheels, start the car, and shift into Drive without touching the brake, would the problem occur? Or not until you step on the brake? What happens if you're driving along and you shift to Neutral before stepping on the brake to bring the car to a stop? What happens if you step on the brake while the car's in Reverse rather than Drive?

ATF+4 is fine. Dexron-VI is superior in every respect, but not enough so to warrant spending the time, effort, and money to go draining out your ATF+4 and replacing it with Dex-6. These transmissions are highly tolerant of crummy fluids; they'll even last a long time with an archaic, inferior-across-the-board fluid like Type-F, so don't fret about it. If you eventually have occasion to drain the transmission and torque converter, pick a reputable brand of Dex-6 (Mopar will even sell it to you, if you want).

If i put it in neutral before stopping the engine goes to warm idle and its fine. If I put it in drive or reverse without the brake on it runs and drives forward fine. If the brake is on when I swap to reverse or drive it quits or near quits. I did not try a wheel chock approach yet but I can. I just re-adjusted idle mixture and idle speed to the manuals instructions and it didn't help; bit lower rpm now but same story otherwise. Weather permitting, I'll check timing and do plugs tomorrow.

Did the '64 torque converter have the lock-up feature?

 

[AJ/FormS]

Did the '64 torque converter have the lock-up feature?

No, That came in the late 70s/early 80s IIRC.

 

[slantsixdan]

No, the lockup torque converter didn't come along until '78, and cannot have accidentally been installed in your '64. It would be possible to make a lockup transmission to suit a '64, but it would require a great deal of deliberate and knowledgeable custom modification work.

Maybe there's something the matter with the torque converter, but before suspecting that I'd pay close attention to the band adjustments — both of them. How sure are you they're correctly adjusted and not too tight? The first two things listed in the FSM under "Transmission drags or locks" are "Kickdown band out of adjustment" and "Low-reverse band out of adjustment". The next two are "kickdown and/or low-reverse servo, band, or linkage malfunction", and "front and/or rear clutch faulty" — all possibilities here, as it seems — and then "Planetary gear sets broken or seized" (probably not; sounds like the transmission works fine other than this what you're experiencing) and "Overrunning clutch worn, broken, or seized" (also possible).

 

[AlmightyAstro]

No, the lockup torque converter didn't come along until '78, and cannot have accidentally been installed in your '64. It would be possible to make a lockup transmission to suit a '64, but it would require a great deal of deliberate and knowledgeable custom modification work.

Maybe there's something the matter with the torque converter, but before suspecting that I'd pay close attention to the band adjustments — both of them. How sure are you they're correctly adjusted and not too tight? The first two things listed in the FSM under "Transmission drags or locks" are "Kickdown band out of adjustment" and "Low-reverse band out of adjustment". The next two are "kickdown and/or low-reverse servo, band, or linkage malfunction", and "front and/or rear clutch faulty" — all possibilities here, as it seems — and then "Planetary gear sets broken or seized" (probably not; sounds like the transmission works fine other than this what you're experiencing) and "Overrunning clutch worn, broken, or seized" (also possible).

Yeah I was just reading that section of my book and landed at a similar spot. I think band checks seem like the next logical possibility. I don't remember how much I can see of the overrunning clutch without disassembly but I'll see what I can do. "Drags/locks" seems like an appropriate descriptor. It's just so strange since everything else works fine. Thanks for the thoughts. I'll let folks know what I learn.

 

[MDchanic]

I have a recent distributor with a pertonics module...

How does the timing of the start of this problem relate to the timing of installing the Pertronix?

And is it a Pertronix I or II?

– Eric

 

[slantsixdan]

Real good, lettuce know how you go. I think I'd be tempted to back off the band adjustments more than seems reasonable — maybe one at a time, or maybe both at a time — and see what happens.

Don't stray off into the tall grass chasing your tail with doubts about car parts that aren't causing this problem. Diagnosis, when there's no clear direct line between the problem and a single cause, is a matter of carefully considering the symptoms and crossing off possible causes that would make the car present with a different set of symptoms. The ignition system, carburetion, exhaust, headlamps, radio, and window winders have no way of knowing or caring whether you are applying the brakes. The automatic transmission, on the other hand, while it doesn't know the status of the brakes themselves, it can certainly misbehave in a manner that causes it to transmit drive when it shouldn't be — like when the engine's at idle speed and the car is held still.

I bet this car creeps forward on its own quite a bit more than it should at idle speed.

 

[Charrlie_S]

Every one is talking converter or trans. I say it can't be the trans. Must be converter or engine. Evenn if the input shaft of the trans were totally sized in the trans, the converter would still have slippage, and not pull the rpm down from what the converter is designed for. The only thing that will pull the rpm down is converter problem, or lack of engine input torque. I suggest looking in the factory service manual , and doing the converter test, after making sure the engine is idling correctly.

 

[AlmightyAstro]

Every one is talking converter or trans. I say it can't be the trans. Must be converter or engine. Evenn if the input shaft of the trans were totally sized in the trans, the converter would still have slippage, and not pull the rpm down from what the converter is designed for. The only thing that will pull the rpm down is converter problem, or lack of engine input torque. I suggest looking in the factory service manual , and doing the converter test, after making sure the engine is idling correctly.

Thanks for the thoughts! I will re-read the converter testing part of the book and check that out. Converter is still a strong impression to me so far and honestly its an easier fix than many other potential issues now that I feel good about the engine. I'll check converter test then depending on how that goes, move to band checks. I think one band is adjustable externally and the other internally if I remember right, as long as it doesn't get too loose and drop the link.

 

[MDchanic]

... this is a huge dip, from say 1000RPM to 500RPM, and with "pu[t]ts" that dive down to 200 it seems.

Without giving hypothetical numbers ("say 1000RPM"), can you tell us exactly what engine speed it runs fine at and what engine speed it begins to drop at, and what engine speed it is actually going when it drops?

We know that this doesn't directly involve the brake, as you have manual brakes with no connection to the engine.

SO, can you duplicate this failure mode without the brake, such as by adjusting the idle speed downward?

Is the transmission exhibiting any other signs of misbehavior?

The brake holding the transmission back may provide some back force against the engine through the converter, but we do not know whether the problem is that, or whether it is just the resulting drop in RPMs.

– Eric

 

[moparlvr166]

Just for testing purposes, will need another body to help, check voltage at alt and battery pos & neg when acting up and look for any spikes due to loose connection in ign, brake light circuits?
try disconnecting brake switch for a test. Possible loose/dirty body or battery ground connection.

 

[RustyRatRod]

Get the factory service manual and make sure the engine is in good, specified tune. You will need a vacuum gauge, timing light, dwell meter or feeler gauges for points and also to adjust the valves. Get the engine tuned right FIRST and them move on if it's not that.

 

[Darter6]

You will need a vacuum gauge,

This got me thinking. Is the vacuum advance connected to full manifold vacuum ?
Instead of ported vacuum. May retard when vacuum drops if timing was set with full manifold vacuum.
Just spit ballin' thoughts.

 

[RustyRatRod]

This got me thinking. Is the vacuum advance connected to full manifold vacuum ?
Instead of ported vacuum. May retard when vacuum drops if timing was set with full manifold vacuum.
Just spit ballin' thoughts.

If he gets a factory service manual, all that will be answered for him.

 

[slantsixdan]

Evenn if the input shaft of the trans were totally sized in the trans, the converter would still have slippage, and not pull the rpm down from what the converter is designed for.

Good diagnostic point! OP, do what CS suggests.

 

[AlmightyAstro]

Without giving hypothetical numbers ("say 1000RPM"), can you tell us exactly what engine speed it runs fine at and what engine speed it begins to drop at, and what engine speed it is actually going when it drops?

We know that this doesn't directly involve the brake, as you have manual brakes with no connection to the engine.

SO, can you duplicate this failure mode without the brake, such as by adjusting the idle speed downward?

Is the transmission exhibiting any other signs of misbehavior?

The brake holding the transmission back may provide some back force against the engine through the converter, but we do not know whether the problem is that, or whether it is just the resulting drop in RPMs.

– Eric

I see no other signs of misbehavior, it drives and shifts normal on city streets and highway otherwise. Regardless of the engine idle speed I use I have the issue. I reset the idle mixture and speed from high to normal factory spec last night and same thing happens. It only happens when I'm stopping, or when I put it in gear while holding the brake. If I don't hold the brake and put it in gear the car drives

Good diagnostic point! OP, do what CS suggests.

Thanks all. I appreciate all of the advice and opinions here, especially in just 24 hours! As a bit of a recap of where I have been with this, the engine was tuned into all specs per the service book post rebuild a couple years ago. The trans was tuned in per the book post its rebuild and year or 2 after that, which was maybe 2 years ago. Engine electrical system works fine and has been fully rehabbed. Sadly an ignition wire bare spot from abrasion burned up the ignition system last year so that's new. Alternator is new as of a month ago. Idle speed and mixture dialed in per the manual as of yesterday. Again the issue is only when engine, TC, and trans have been driven to warm them up and going into gear with brake on, or applying brake to a stop. I'm receiving a lot of advice here to check for band issues and TC issues. I don't see a TC test in my FSM but I'll keep looking.

Thanks all!

 

[65TerrorCuda]

If it's really tuned to those old specs, that may be your problem. Needs more initial timing for starters. Spec is what, 5 degrees BTDC? I'd put it 12 degrees and see if that fixes it.
Recurved dizzy and welded slots would be high on my list of upgrades.