8hp70 heater bypass

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hawsk99gt

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You got a link to that thread. I'm starting to think that my jerking problem when slowing to a stop.
I went thru that and the dealer flashed my computer a couple of times before eventually and finally a code appeared and they said "you get a new transmission & you get a new transmission!" Yep, I got a new transmission. Then my overheating transmission came to life. I was wondering if that was the problem all along. Didn't know my transmission was overheating till I took my first road trip to Orlando, FL and I got the warning that I needed to slow down or pull over at 285* temp while doing 80mph.
 

hawsk99gt

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So after reading @hawsk99gt 's report of the persistant overheating problem even after installing one of @caulk04 's bypass plugs, it occurred to me that if there IS an internal problem with my transmission, installing the bypass plug would only mask it by substantially lowering the temperatures, and I might not ever know there was an internal problem, and thus internal WEAR, until much later once much more damage may be done.

So, I decided I wanted to know if it was indeed a faulty thermostat, bit the bullet, and purchased a new one, and unfortunately it comes with an entire thermal exchange unit attached to it.

View attachment 492420
View attachment 492421

Now, I own a cheapie pair of retaining ring pliers with adjustable jaws for various angles, but the jaws have a lot of play and for the life of me I can't get enough of a grip on the snap ring to pull it out. I heard someone mention a "good" pair of pliers must be used. Does anyone recall what brand/style those were? I may be looking for a good pair myself. If I can't get this thing undone on my work bench with ease, I don't stand much of a chance wedged up in the underbelly of my truck.
Dang...that must have been a $400+ purchase for that whole unit. I haven't had any issues yet and I have been purposely doing some fast highway runs in the 80* degree weather we have been having and so far the highest at 80mph has only been 165* degree. But mostly it's around 140ish. Hope you find some kind of result.
 

Shawn Burns

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I installed one of Caulk's bypass'. This is a pic of the before temps while pulling a trailer about an hour.


20220422_130118.jpg


This is a pic of the temps after install, again after towing about an hour. That's nearly 60 degree difference, folks. I am very pleased.

20220430_064037.jpg
 

hawsk99gt

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wow, all your temps are much better than mine without doing anything stressful on my truck. I was driving around for well over an hour yesterday and with 82* degree weather my trans temps were around 174*. But even my oil & coolant temps are higher than yours with Caulk's bypass installed. My trans temps are still way better than what it use to produce, so I am not complaining. It still helped. I am thinking of putting my heat shield wrap back on the cross member part of my exhaust that runs under the pan. I think that helped last summer some. Took it off during the winter since I wanted some heat during the freezing months.
 

Wild one

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wow, all your temps are much better than mine without doing anything stressful on my truck. I was driving around for well over an hour yesterday and with 82* degree weather my trans temps were around 174*. But even my oil & coolant temps are higher than yours with Caulk's bypass installed. My trans temps are still way better than what it use to produce, so I am not complaining. It still helped. I am thinking of putting my heat shield wrap back on the cross member part of my exhaust that runs under the pan. I think that helped last summer some. Took it off during the winter since I wanted some heat during the freezing months.
It's also 31F if you look at his evic,that'll make a differance on his other temps
 

BlownGP

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I went thru that and the dealer flashed my computer a couple of times before eventually and finally a code appeared and they said "you get a new transmission & you get a new transmission!" Yep, I got a new transmission. Then my overheating transmission came to life. I was wondering if that was the problem all along. Didn't know my transmission was overheating till I took my first road trip to Orlando, FL and I got the warning that I needed to slow down or pull over at 285* temp while doing 80mph.

God I hope not. They already replaced the driveshaft and it seemed fine for about 3-4 months then it started it again.
I just haven't had time to bring it too them again since I need my truck just about everyday. lol

It almost feels like the torque converter is still moving when I come to a stop. Then when I let off the brake to move. It stops and the truck jerks.
It will either do it when I almost come to stop or once I've stopped. I let go of the brake and it will do it.

My trans stays cool with Caulk's bypass but I guess if it starts getting hotter than normal then it might be time to bring it by the dealer.
 

hawsk99gt

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God I hope not. They already replaced the driveshaft and it seemed fine for about 3-4 months then it started it again.
I just haven't had time to bring it too them again since I need my truck just about everyday. lol

It almost feels like the torque converter is still moving when I come to a stop. Then when I let off the brake to move. It stops and the truck jerks.
It will either do it when I almost come to stop or once I've stopped. I let go of the brake and it will do it.

My trans stays cool with Caulk's bypass but I guess if it starts getting hotter than normal then it might be time to bring it by the dealer.
Yeah I know that jerking feeling. It almost feels like someone lightly rear-ends you, when you start coming to stop. Like I said they reset the computer a couple of times and it kind of helped at first, but then returns. Hopefully, you have a warranty still. Mine was covered, but for the over heating issue the dealer agreed that it was too hot but would not do anything till a code flags. So basically I had to wait till it failed before they would do anything. It sucks, even when they recognize that it was getting too hot. Thank God! for Caulk's bypass.
 

BlownGP

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Yeah I know that jerking feeling. It almost feels like someone lightly rear-ends you, when you start coming to stop. Like I said they reset the computer a couple of times and it kind of helped at first, but then returns. Hopefully, you have a warranty still. Mine was covered, but for the over heating issue the dealer agreed that it was too hot but would not do anything till a code flags. So basically I had to wait till it failed before they would do anything. It sucks, even when they recognize that it was getting too hot. Thank God! for Caulk's bypass.

Well mines a 2018, so I'm still under the power train warranty I think for another year.

It just feels like someone bumped me. Sometimes it's bad, sometimes I can barley feel it. Sometimes it's bad.
One dealer told me it's normal and to deal with it. haha I was like, well I'm never coming here again.

So a completely new trans fixed your problem?
 
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HEMIMANN

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Yep - just like destroyed lifters and cams under 100,000 miles is 'normal'. It's one thing if these Dealers were ignorant early during the 1st failures. It's quite another when they lie to your face 20 years later.
 

Shawn Burns

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That day was strange. I was pulling a trailer to a track day in freezing Temps, but drove home in 65. I didn't make much of a difference to my coolant Temps. I will keep an eye on it in July and August.
 

hawsk99gt

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Maybe it has something to do with where the trucks are built. Like on my VIN it starts with a 1 which means it was made here in the USA. It would be interesting to see if it is only happening here in the US or if the Mexico builds which I believe start with a 3 on the VIN are having the same issue. I think Canada is 2 on the VIN. Just a thought.
 

Fritter

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@hawsk99gt I was searching around the internet for insight into our overheating problem, and I found this thread that brought up a potential failure mode I hadn't thought of before:

From Post # 5 on the above thread:

This seems like it could make sense, especially if it's confirmed not to be related to the thermal management unit. Like caulk04 said, it might be internal at this point. I'm afraid my problem might be the same. When that uncontrollable temperature spike hits, it climbs FAST, like 2 degrees every 5-10 seconds. I have to catch it RIGHT when it happens and slow way down, or pull over entirely.

@Wild one , I know you're no stranger to transmission issues. What do you think of a transmission that isn't able to keep the torque converter locked. Would that lead to our overheating issues? Is that an easy fix (programming) or does that need a transmission drop and repair/overhaul? Or is a new transmission best?

Luckily, it only seems to affect me when I'm above 60 mph, so city driving is okay. And the few times it's happened, I've caught the temperature before 230 F. But long trips limited to 60 mph is kind of grueling. I'd want to get this repaired. Are there trustworthy places that work on these transmissions? I can pony up if I know the job will be done right... I've kept good care of the truck since 17,000 miles. She's got a lot of life left in her.
Follow on to post #374
hawsk99gt & Daniel Ortiz, first post I’ve seen that is similar to the operation of my Ram. I have a stock vehicle but I’m awaiting the arrival of caulk04’s modified thermal bypass valve (TBV).

This is not an attempt to reopen all the good work already done to explain the transmission heat issues reported. I am interested in a what-if scenario that installing the modified TBV does not result in lower tranny temperatures. Following Daniel’s though process regarding the modified TBV covering the symptoms but not fixing the root cause.

Here is what I’ve noticed about the operation of my truck:

1st observation: The change in tranny temperatures appears to coincide with the speed of the truck at speeds higher than the upper 50’s mph. NOT rpm dependent. The tranny temperature has hit 262 F on a few occasions, usually at speeds above 75 mph. No codes have been registered nor has the tranny temperature warning light illuminated. Once the speed drops below the upper 50’s then the tranny temperature starts to decrease. Outside air temperature (OAT) does not affect the max tranny temperature, only the time to temperature since the delta T is different.

2nd observation: The engine coolant and oil temperatures rise above the engine thermostat opening temperature until the tranny temperature is higher than approximately 222 F. This is a crossover point where the tranny temperature continues to increase and the oil and coolant temperatures decrease. The oil and coolant temperatures then stabilize at what could be considered more normal values (oil T between 212 – 217 F; coolant T between 197 – 203 F).

3rd observation: The tranny temperature fall rate is faster than the rise rate when speed drops off.

I’ve included 2 charts in this posting that illustrate these observations. The thermal management unit (TMU – also know as the tranny heater) is designed to keep the transmission oil at an operating temperature of 176 F (80 C) according to 2 documents I’ve found online (both were introductory manuals for maintenance personnel).

What I’m trying to determine is if there is some other issue that would cause the symptoms of the cooling system’s inability to manage the transmission heat when at highway speeds. There are sufficient posts to indicate that if all components are working correctly than the tranny temps would be expected to be in the 170 – 180 F range. In my vehicle the heat generated in the transmission is overloading the tranny cooling system without impacting the engine oil and cooling temperatures but ONLY at highway speeds running between 1,700 – 2,000 rpm (3.92 gear ratio with 33in. tires).

The runaway transmission temperatures shown in these charts can be the result of a lack of cooling caused by an open TBV or blocked flow to the transmission cooler. Are there any other potential causes? What is the rationale for the tranny temperature fall rate faster than the rise rate especially since the engine oil and coolant temperatures remain relatively stable during that time?

Some other features that have an impact on this situation are the active grill shutters (AGS) and transmission torque converter (TCC). The TCC appears to be working correctly (typical symptoms for issues not present) but I question this component given the speed relationship. I’m interested in any thoughts on this item. I have yet to test the AGS for both nominal operation and impact if shutters are open at highway speeds.

Any other ideas or inputs? Looking for new insights.
 

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Wild one

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Follow on to post #374
hawsk99gt & Daniel Ortiz, first post I’ve seen that is similar to the operation of my Ram. I have a stock vehicle but I’m awaiting the arrival of caulk04’s modified thermal bypass valve (TBV).

This is not an attempt to reopen all the good work already done to explain the transmission heat issues reported. I am interested in a what-if scenario that installing the modified TBV does not result in lower tranny temperatures. Following Daniel’s though process regarding the modified TBV covering the symptoms but not fixing the root cause.

Here is what I’ve noticed about the operation of my truck:

1st observation: The change in tranny temperatures appears to coincide with the speed of the truck at speeds higher than the upper 50’s mph. NOT rpm dependent. The tranny temperature has hit 262 F on a few occasions, usually at speeds above 75 mph. No codes have been registered nor has the tranny temperature warning light illuminated. Once the speed drops below the upper 50’s then the tranny temperature starts to decrease. Outside air temperature (OAT) does not affect the max tranny temperature, only the time to temperature since the delta T is different.

2nd observation: The engine coolant and oil temperatures rise above the engine thermostat opening temperature until the tranny temperature is higher than approximately 222 F. This is a crossover point where the tranny temperature continues to increase and the oil and coolant temperatures decrease. The oil and coolant temperatures then stabilize at what could be considered more normal values (oil T between 212 – 217 F; coolant T between 197 – 203 F).

3rd observation: The tranny temperature fall rate is faster than the rise rate when speed drops off.

I’ve included 2 charts in this posting that illustrate these observations. The thermal management unit (TMU – also know as the tranny heater) is designed to keep the transmission oil at an operating temperature of 176 F (80 C) according to 2 documents I’ve found online (both were introductory manuals for maintenance personnel).

What I’m trying to determine is if there is some other issue that would cause the symptoms of the cooling system’s inability to manage the transmission heat when at highway speeds. There are sufficient posts to indicate that if all components are working correctly than the tranny temps would be expected to be in the 170 – 180 F range. In my vehicle the heat generated in the transmission is overloading the tranny cooling system without impacting the engine oil and cooling temperatures but ONLY at highway speeds running between 1,700 – 2,000 rpm (3.92 gear ratio with 33in. tires).

The runaway transmission temperatures shown in these charts can be the result of a lack of cooling caused by an open TBV or blocked flow to the transmission cooler. Are there any other potential causes? What is the rationale for the tranny temperature fall rate faster than the rise rate especially since the engine oil and coolant temperatures remain relatively stable during that time?

Some other features that have an impact on this situation are the active grill shutters (AGS) and transmission torque converter (TCC). The TCC appears to be working correctly (typical symptoms for issues not present) but I question this component given the speed relationship. I’m interested in any thoughts on this item. I have yet to test the AGS for both nominal operation and impact if shutters are open at highway speeds.

Any other ideas or inputs? Looking for new insights.
If the thermostat is staying closed ,the fluid in the cooler will be noticably cold,compared to the fluid in the transmission,and once the thermostat does open and start circulating fluid,the transmission should cool off rapidly,if the cooler fluid is cool.The only way to know is to install Jesse's bypass,and see what happens. Have you gave any thought to dropping the pan and doing a transmission service,that would also let you check the pan for clutch material and shiny aluminium particles,which would give you an idea on how healthy the transmission is.
 
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