I hate to disagree with transman because he has always had good sound advice.
I had a 88 Olds that had a lock-up shudder, GM couldn’t fix it and with only 2000 miles on the car I disconnected the TCC. I had the car for 10 years and 130,000 miles and never had a problem with the tranny.
I have also had customers complain about lock-up shudder on GM vehicles, I have disconnected or by-passed the TCC and the customers drove these cars for years without any issues.
Sorry transman but from my personel experience unplugging the TCC hasn’t caused any transmission failures. It doesn’t mean there couldn’t be problems, it’s just that I haven’t experienced any.
Thanks transman! I think we are going to get it fixed. I found out that the cheapest one is owned by someone my oldest son knows, so I feel comfortable going there.
Thanks again to all who replied. I like this message board, I have gotten a lot more responses on it than any other one so far.
I take no offense at all Willey. What I said to the OP was this, from my first post: …“Disconnecting the lockup solenoid will not only cause a loss of MPG but it will cause the transmission to run much hotter and depending on how hot your trans is running normally it can most definitely cause the transmission to overheat.” and I also told him this when he was considering just pulling the plug: " Thats entirely up to you, just as long as you are aware of what can happen by leaving the solenoid disconnected. "
Now you and others had good luck with yours by not having the overheating failure but two things none of you can get away from is the reduced MPG’s and the extra heat from the slipping converter clutch.
Whether it overheats it to the extreme of the converter ballooning and turning blue (Which I see quite a bit of in failed converters) is one thing but its a given that the trans will run hotter and your MPG’s will be reduced. Anyone who understands converters will verify that and to prove my point on that I provided 6 different links to read. You see, unplugging the converter clutch did away with one problem but created two more problems, increased heat, and reduced MPG’s. To unplug a converter clutch and let it go is in the same line as putting a piece of black tape over a check engine light.
Tester, who I consider one of the best techs on the board says this:
“Nope. Won’t harm a thing. You just lose the lock up torque converter function which will reduce fuel mileage.”
“Unplugging the torque converter clutch will not harm the transmission or cause it to overheat.”
Then there’s Ellis, whos not a mechanic, who says this:
“Transman says that if you disconnect the TCC you will cause the transmissin to overheat, due to the constant slipping of the converter. I have never bought that assunption and the gas mileage will not suffer much because the converter doesn’t lock up anyway until you reach cruising speed”
What I’ve said from my very first post in this thread is reduced MPG’s and a hotter transmission and I still stand by it.
“I take no offense at all Willey.” Transman, you seem to take offence when I disagree with you. somewhere on here you mentioned a “slipping converter clutch”. The clutch will not slip if turned off and the only slippage in a converter is fluid which has little to none friction.
You obviously have no idea how a converter works and after all those links I provided just for you. Let me help you again. The slippage ocurrs when the converter clutch is UNLOCKED. The slippage is across the converter not across the converter clutch which means the heat is generated when the clutch is UNLOCKED and slipping. Here is a quote from one of the links I provided for you.
" When the converter is in an unlocked (disengaged) state, there is going to be some loss (slip) across the converter during almost all driving situations because of converter slip. The results of this loss or slip is work heat generated into the transmission fluid. How much heat depends on how much loss (slip) is occurring during a specific driving situation. Some of the factors that effect the amount of heat generated, include towing, driving speed, climbing steep mountains or hills, wind effect and weight being carried etc. Overheating is the number on cause of failure in automatic transmissions so controlling this heat is very critical to longevity. As long as the cooling lines are routed to the vehicles radiator, no heat generated inside the torque converter while driving is always better than some heat! Dummy or non locking converters never lock up and are therefore a constant source of heat than must be effectively dealt with."
I just want to thank you Earl. Its people just like you which keep my shop doors open.
I still do not believe any slippage is going on except the fluid coupling in the converter and transmission fluid has very little friction. and FYI I HAVE NEVER HAD A TRANSMISSION IN THE SHOP IN 55 YEARS OF DRIVING AUTOMATICS.
I understand why it could overheat but in the cases I have been involved with I never saw a problem.
Do you think that the transmission cooler was able to dissipate enough heat in these cases to prevent the convertor/transmission from overheating?
In the case of my Olds I changed the transmission fluid every 30,000 miles, I would think regular fluid changes would help in preventing a overheating problem.
Well, you can believe what you want. You have proven from your erratic posts that you do not comprehend this subject at all and I’m finished trying to explain the subject to you. My 27 years tearing down and rebuilding automatics just doesn’t compare to your 55 years of driving them. Thanks once again for helping to keep my doors open and I wish you the best.
Yea, coolers play a big part in it and changing the fluid like you do is definitely a plus. ATF starts breaking down at around 195 degrees so the longer you drive it at higher temps the quicker the fluid breaks down.
transman, no doubt the truck had a heavy duty cooling system by today’s standards. That’s why I offered the caveat regarding marginal designs being more prevalent today than in the past.
There will probably always be situations where the cost to replace the TCC solenoid (for the non-DIYer) or the lack of desire to undertake the work on a beater will result in simply disconnecting the solenoid control cable. If someone does that in a modern car, I’d strongly suggest changing the fluid on a much more frequent basis and keeping an eye on its condition in-between. If you allow the fluid to be compromised, its going to damage the trans. If you keep on top of it, I think you could probably go a long time with the slippage occuring. I could have easily fixed my truck but there’s only so much time in the day and too many demands for time. After awhile it became a challenge to see how far it would go like that.
Anyone who says they do not generate heat lacks all credibility IMO. Heat from high stall converters always plagued me in my hot rods. So I built a custom trans that is essentially two TH400s in series. The front trans has the pump, converter and forward gears. The tailshaft has been modified to provide an input shaft to the second trans which has the bell housing chopped off and a custom interface plate to accept the front trans output shaft. The pump and converter are obviously deleted. The rear trans has the full complement of gearing in it. The front trans has a deep pan that feeds through a 3" tube to sump to the shorter rear pan. The fluid pickup is in the rear pan and the tube feeds through the inside of the 3" tube to get to the pump inlet in the front trans. Both valve bodies are set up as reverse ordered, manual. The trans freewheels in all gears except the final gear. I run high pressure (~240) for very positive shifts. Each trans is controlled by a ratcheting shifter. I have 5 forward gears, 3 reverse. I can run a stock converter! I can drive the car to the track rather than trailering it. I’m running around 650 HP through it and lost a few stock hubs so I switched over to better quality parts and no worries since. Not many people can appreciate it beyond- why do you have two shifters? Thought it might be interesting to a trans guy…
I’m jealous man…I wish I had some track toys like that to play with on the weekends. Do you have any pics?? What kind of temps are you running in the 400’s?? Maybe once my daughter gets a little older (She’s 3) she demands a lot of my time right now. That, along with my city/county contracts and the normal customers just keep my shop overwhelmed. I am usually running 4-5 days behind at any given time and I take in work 6 days a week. I would love to put something together like you have and do some track time.
Yeah, I have some pics I’ll try to get uploaded so you can see the beast. I have it installed in a '71 Chevelle but like you, I have had very little time available for it in the last couple of years. I’ve actually started thinking about selling the car because too many of these projects/toys are sitting around wasting away and it kills me to have that happen. I invested a lot of time, money, blood, sweat and tears building this car exactly like I wanted it so it will be tough to part with. 2 months after I finished the car, I hit a deer with it driving to the storage place. Talk about demoralizing! It sat for 2 years after that, I couldn’t bear to work on it again so soon.
High stall torque converters are employed widely these days. The lock up has allowed this to be done to compensate for lower power engines at lower speeds. The lockup allows this advantage without the liability at higher speeds. My 2.5 SE jeep Wrangler (3300lb chassis) with a 30rh (904 =basically) does not change rpm from leaving a light @ 2000-2200 rpm until the lock up occurs in in 3rd gear. The engine never sees it the converter is so loose.
Auxiliary cooling would manage it.
“Slipping fluid” does generate heat. The converter is the number one heat generating component in the whole trans. ATF is a coolant and power transmission fluid that has minor lubrication properties. It fatigues on a Time Weighted Average (TWA) based on the heat it sees. That typically works out to a very long time for most usage.
I don’t necessarily agree with transman’s temp reference. 200F ATF will last a long time. The bouts above 200F will shorten its life on an advancing curve. Again, you’re in a dynamic view with cooler IN:OUT temps. Bulk temps (the pan) tend to give you an “insult reserve” indicator. The less time the fluid sees higher temps, the longer it lasts. 150F-175F would be a nice non-stressed bulk temp.
You’re exactly right. Like I said earlier ATF STARTS breaking down in the 195-200 degree range and the higher the temp the quicker the fluid breaks down. Running at constant high temps requires more frequent servicing. Yes, if kept in the 200 degree range it would take some time to actually wear the fluid down. I build many heavy duty units which are used in towing and racing applications. One of the things I stress to these customers is that its best to keep the ATF temp under 200 degrees as a rule of thumb. Aux coolers with electric fans can be purchased for under $200 which is perfect in HD towing applications. I usually recommend external coolers and even trans temp gauges installed to monitor these critical temps. I have found in following up with my HD towing customers that with a good external cooler they can actually run 170-180 degree temps while towing.
You know, this should be really easy for you to prove or disprove. Try this: go out to your car and remove the cover for the torque convertor.Start the car and set the emergency brake, then put the transmission in drive. Hold your foot firmly on the service brake and hold the throttle wide open for 20 or 30 minutes. Read a book if you’d like.
After this shut the engine off and go put your hand on the uncovered torque convertor. Based on your theory that “Slipping oil doesn’t generate much heat.” it shouldn’t be hot.
Oh, by the way, if you really do this, take your car to transman618’s shop to get the (now destroyed) transmission rebuilt. He’ll get quite a laugh out of it.
If you really want to heat up a torque converter fast just do a stall test or a good brake stand (Powerbraking). Any tech who has ever done a stall test knows that you NEVER stall test for more than 10 seconds at a time. Why? Because that slipping oil can overheat a transmission in no time flat. It is recommended that when doing a stall test you never go over 10 seconds and you let the engine idle at least 30 seconds to cool the converter down before stall testing again. I cant tell you how many times I’ve had trannys on my bench after a good powerbraking session by some young kids.
I still do not believe any slippage is going on except the fluid coupling in the converter
You would be 100% correct in that belief. That is, outside of normal co-engagements that give “velvety smooth shifts” that the auto manufacturers insist that consumers DEMANDED. They’re the chief wear factor outside of heat fatigue and just plain lousy parts. The complexity adds to it in contemporary trannies …but hey, the clowns aren’t going to tell the head of design “Well, you can lay us off! We’ve built the best trans and any other stuff we pull out of our behinds is just going to cost reliability and longevity!” …so we have what we have.
transmission fluid has very little friction.
Well, you really need to read up on a few properties of fluids. It’s more physics than I’ve taken, but just learn about laminar flow and shearing. It’s not even the turbulent environment of the converter with fluid bounce and the other dynamic workings within.
It’s as simple as realizing the power applied and the motion realized. That converter is the shear point in the whole thing. Hundreds of hp applied …and not even one getting to the ground if the load it too high (or brakes applied - towing a freight car - whatever).