Well, Transman, how about driving in town below the speed at which the converter looks up? Will this cause too much heat and destroy the transmission.
Ok… Like I said, torque converters generate heat, regardless. This is due to slippage. Torque converters are designed to dissapate heat so it can handle the heat of in town stop and go driving. Highway driving (Above 40 mph) will cause excess heat due to the excess slippage. This will superheat the converter. The converter is not designed to dissapate that much heat which in turn will cook both the converter AND the transmission. This is why you have lockup at 40 mph, to physically couple the transmission pump to the converter and reduce the slippage. Less slippage = a cooler transmission. I have seen converters get so hot they actually turn blue.
I had a link saved in my computer before it crashed last month of torque converters. It was a great link, I lost it though in the crash. I’ll try to find it and post it for you to look at. It will answer any question you have on torque converters.
How about the transmissiions that did or do not have lockup converters? Were they destined to self destruct if you drove ofer 40? I am not trying to be smart with you, I have never overhauled an auto transmission.
Here you go… http://en.wikipedia.org/wiki/Torque_converter
I couldnt find that other link but I saw this today. This will tell you anything you want to know about torque converters, theory and all…
“This is why you have lockup at 40 mph, to physically couple the transmission pump to the converter and reduce the slippage. Less slippage = a cooler transmission. I have seen converters get so hot they actually turn blue.” Yes with less slippage you would get less heat, BUT the real purpose of the lockup is to increase milage, both gas milage and longer life milage.
That was the intent of the lockup clutch, to improve fuel economy. If you read this link you will also see and understand what I have been saying this entire post that the pump to turbine coupling (Lockup) is so important because it keeps that destructive heat from cooking the trans and the converter. This is why you must NOT drive the vehicle with the lockup unplugged.
OK, let me try this again. Does this vehicle possibly have a mechanical downshift connection?? Probably not, but I had a new '93 Caravan which did and the connection had to be adjusted to cause the Lockup converter to realease at a higher speed. The engine would get down into low RPM and was still locked up, thus would shudder some.
Cool link. The “How Stuff Works” link (at the bottom of the Wikipedia link) is a goo done too.
Transman, This has been an interesting and informative discussion. I will try Lube Gard, but I need a little more information so I know what to tell prospective buyers. The shudder occurs only when I am going up a slight grade. If I ease off the accelerator or step harder on it, the shudder does not happen. Am I okay if I just avoid the shudder? I never feel it at highway speeds. Or is it slipping out of lockup and therefore running too hot above 35 mph or so? Thanks again.
PJ I think these guys are missing the point. Is the car shuddering because the rpm are too low at the time? Like a manual would in 4th or 5th gear and you needed to shift down a gear? Please let me know.
From what you have explained, all the symptoms point to a faulty converter, a slipping converter clutch. This is why it stops when you let up on the gas or accelerate heavy which is when the converter clutch unlocks. There are several reasons for this. A leaking regulator valve in the transmission reducing line pressure and causing the slippage of the converter clutch or even the clutch material worn out and slipping. Also, a faulty TPS (Throttle Position Sensor) since line pressure is controlled by TPS position.
I though of saying this at the outset and probably should have: In order conserve gas, a non-renewable natural resource, I routinely try to keep the car from down saifting when I go up a hill. That means gradually pressing down on the accelerator to maintain my original speed, but without the car downshifting. Doing this may have caused the problem or conributed to it?
If I understand Transman, in a situation like this the converter is locked up but then slips and unlocks, causing the shudder and excessive heat.
If I ease up, the converted says locked and no excessive heat is produced.
If I accelerate, the converter locks up and also does not shudder.
What I think that means, but am not sure of, is that excessive heat is not being produced below 33 mph or so, or at 55 mph or faster. If I can avoid the shudder going up hills by easing up or accelerating, there should not be a heat problem then either. The problem is when the converter is not locked up AND the car is going more than 35 mph.
I will get some Lube gard put in to see if that helps.
But I have a Ph.D. in theology and have never done more than change “points,” plugs and spark plug wires, oil, filters, and – one time in an Army auto shop – brakes, so what do I know?
Thanks to all of you for all your patience and help. My auto service shop manager may have known all of it, or maybe not. It is obviously a somewhat complex subject so she may have just referred me to a transmisssion shop.
“If I understand Transman, in a situation like this the converter is locked up but then slips and unlocks, causing the shudder and excessive heat.” I still do not believe the clutch is slipping. It is staying locked up when it should be released. When you press a little harder it realeases and feels fine. I hope I hear the final ananysis of this problem.
Why are you getting so worked up over this?? First of all you are telling the OP that him unplugging his converter clutch wont harm or overheat his trans, you were wrong about that. Now you are telling him that his lockup clutch is staying locked up when it should be released. Tell us what level of expertise you have that allows you to make such a diagnosis. If you look at my posts both to this OP and others you will see my posts usually start out like this “From the symptoms you describe, it sounds like…” Unless it is painfully obvious, I never tell anyone definately that this is their problem. When I give an opinion such as for this thread, I take into consideration the make of the vehicle, the year and the trans type and what are the most common things I see with the particular transmission. You see Ellis, I have been doing the same thing for the past 25 years. You have never been inside of a transmission before from what you have said in your previous post, you didn’t even know how a torque converter worked until I gave you a link on it. I generally know what kind of quirks different transmissions have. If I put a 4L60E on my bench and prep it for disassembly, I know exactly what parts of that transmission I am going to zero in on when I overhaul it. I gave Skypilot an OPINION, not a diagnosis. You cant give a diagnosis through a computer screen. I gave him an OPINION based on what I commonly see with his transmission. I’m not right all the time and I dont claim to be. If he decides to have his trans overhauled, we might find out what exactly went wrong with it. I have made the mistake before of giving a customer a DIAGNOSIS without tearing it down and I ended up eating some of that overhaul. Its obvious that you are taking this thread way too personal with your attacks on me. Relax man…I’m not taking it personal…
T-man, I’m not going to attempt to make any judgement calls here regarding the opinions given, but I consider you one of the better “voices” on this website. It’s refreshing to see someone hold a discussion that remains on point and at an intelligent level by folks that know what they are talking about. I have been in the auto garage business in the 50’s - 60’s when cars were vastly simpler. So I have a pretty good sense of most aboout what is being discussed and I have a good appreciation of the difficulty of attempting to diagnose a problem. Keep it up.
Sorry Transman, I did know how a torque converter worked before you were born. I never meant that I was positive about the OPs problem, but He is talking about a shudder and you guys are talkin’ about a lockup clutch slipping. You are right about one thing, I have never overhauled an auto transmission, but I know what it feels and sounds like for a converter to stay locked up after it is supposed to be unlocked. I have had that experience. AND just because you sent me a bunch facts or theories, doesn’t mean that I didn’t already know, at least, part of it.
Your last post (above) sounds somewhat personal to me!! I sure hope PJ doesn’t let some trigger-happy mechanic tear into his transmission until they make sure it is just not staying locked up at too low a speed causing the engine to shudder.
I sure hope that whoever looks at it looks at EVERYTHING before tearing it down because what you call “Trigger happy mechanics” give us good techs a bad name. Now to address your last post from last night:
You said: “I never meant that I was positive about the OPs problem”
Re-read your previous posts, you sound pretty sure to me.
You said: He is talking about a shudder and you guys are talkin’ about a lockup clutch slipping.
News flash Ellis, When a lockup clutch slips, it shudders.
You said: but I know what it feels and sounds like for a converter to stay locked up after it is supposed to be unlocked.
Oh thats right, your 93 3 speed Chrysler once had that problem. Sky pilot has a totally different setup and a transmission which encounters totally different problems.
You are certainly entitled to your opinion, thats what this board is all about, for the pros to give their professional opinions and the non pros who might have experienced a particular problem to share their experiences.
I have asked about 3 times on here if the OPs car had a mechanical downshift connection, but no one has answered. Or is there any way to change the speed at which the converter unlocks? How do you know it is the clutch slipping or the engine shuddering because it is running too slow for high gear. Shurely you have experienced that feeling with a manual tranny when you are pulling around 30 mph in 5th gear, going up a slight grade.
Well, I sure would like to know what the outcome of this matter was.