8hp70 heater bypass

tfeni52355 said:

I should have mentioned I left the existing eletric and clutch fans in place. Hemi just seems a lot happier at 185 deg and I'm not cooking that expensive Redline I am running!

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Red Line ain't gonna cook. It has the highest oxidation life of any oil. Unless you wanna run it out to 20k miles or something.

I had a weird situation while making a run from North Ga to Central Fla a few weeks a go. It was actually upon my return trip I had THE PROBLEM. I to have installed Jesse's heater by pass plug several month's a go. And so far has been working perfect. As I was saying about the recent trip I took. The return back I had a different experience with my transmission temps. My temps went from the standard (154 degrees) but then went from 154* to 225*, air temp outside was 50ish. I noticed the vibration sound thru the radio was coming through like before I did the swap. This was while cruising around 80 mph with traffic. So I dropped it down to 65-70 mph, jumping into the slow lane and it dropped about 5 - 10 degrees. It fluctuated for the next 150 - 200 miles like that, but still unusually hot. I even stopped a couple of times to see if letting it cool and settle if it would go back to normal. That didn't work. Finally, by the time I got into the Atlanta area and got stuck in their stop and go traffic hell, I noticed, while I was cruising at about 20 mph for like 30 minutes the temperature magically dropped back to normal. Actually dropped to 130* and then traffic started easing off and I decided to be a baller and jump into the Fast Pass lane, getting up to 80mph. Everything was fine again. Next 60 miles back home it drove solid at 145*.
Anyone got an idea why my truck would give me ghosts of Christmas past again?
I'm having a real hard time having faith in her doing these really long hauls.

hawsk99gt said:

I had a weird situation while making a run from North Ga to Central Fla a few weeks a go. It was actually upon my return trip I had THE PROBLEM. I to have installed Jesse's heater by pass plug several month's a go. And so far has been working perfect. As I was saying about the recent trip I took. The return back I had a different experience with my transmission temps. My temps went from the standard (154 degrees) but then went from 154* to 225*, air temp outside was 50ish. I noticed the vibration sound thru the radio was coming through like before I did the swap. This was while cruising around 80 mph with traffic. So I dropped it down to 65-70 mph, jumping into the slow lane and it dropped about 5 - 10 degrees. It fluctuated for the next 150 - 200 miles like that, but still unusually hot. I even stopped a couple of times to see if letting it cool and settle if it would go back to normal. That didn't work. Finally, by the time I got into the Atlanta area and got stuck in their stop and go traffic hell, I noticed, while I was cruising at about 20 mph for like 30 minutes the temperature magically dropped back to normal. Actually dropped to 130* and then traffic started easing off and I decided to be a baller and jump into the Fast Pass lane, getting up to 80mph. Everything was fine again. Next 60 miles back home it drove solid at 145*.
Anyone got an idea why my truck would give me ghosts of Christmas past again?
I'm having a real hard time having faith in her doing these really long hauls.

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My guess would be Either a clog in the line somehow or something wasn’t happy in the trans. What vibration sound? And has it done this before?

It happened before when my temps would go up into the 250+ range. When I accelerated a drone sound comes through the stereo as you push on the gas. I'm no mechanic, but does the coolant from the radiator have anything to do with the cooling of the transmission. This whole thing for me all started last spring when I decided to have my radiator flushed just before going on a road trip to Florida. My truck had never had one so I thought it was way over due for one. Ever since then I had issues with trans heat. But I did the replacement with the by pass plug and everything was good since, the dealer would not touch it unless it threw a code. I have been toying with the idea of replacing my thermostat with a 180 or 190. Not sure if it is going to help my situation or not.

The engine coolant is what heats the trans fluid, it flows through the heat exchanger on one side and trans fluid in the other side. This is still present and mounted on your trans, but with my part trans fluid bypasses it.

That's an interesting circumstance and I don't see any mechanical reason for it. No idea.

I'm going to be unable to make any of my parts for some time, so I think I'll be posting my dimensions and parts list soon. If I can remember to grab it at work...

hawsk99gt said:

It happened before when my temps would go up into the 250+ range. When I accelerated a drone sound comes through the stereo as you push on the gas. I'm no mechanic, but does the coolant from the radiator have anything to do with the cooling of the transmission. This whole thing for me all started last spring when I decided to have my radiator flushed just before going on a road trip to Florida. My truck had never had one so I thought it was way over due for one. Ever since then I had issues with trans heat. But I did the replacement with the by pass plug and everything was good since, the dealer would not touch it unless it threw a code. I have been toying with the idea of replacing my thermostat with a 180 or 190. Not sure if it is going to help my situation or not.

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If the trans cooler line is dumping extremely hot coolant into the trans line heater then yes maybe but I don’t see how it could get that hot because your coolant shouldn’t be getting that hot. Do you still have active shutters?

crazykid1994 said:

If the trans cooler line is dumping extremely hot coolant into the trans line heater then yes maybe but I don’t see how it could get that hot because your coolant shouldn’t be getting that hot. Do you still have active shutters?

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Yes I still do and probably will not be modifying them. My coolant wasn't really getting that hot but it did bound into the teens at times ie; 213* - 219* but would go back down to the 190's.

hawsk99gt said:

Yes I still do and probably will not be modifying them. My coolant wasn't really getting that hot but it did bound into the teens at times ie; 213* - 219* but would go back down to the 190's.

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Then it’s not related to the coolant temp. The coolant temp is going that high because of the active shutters. I’d be leaning towards interval transmission at that point. Something blocking oil flow

at this point I'll just keep an eye on it for now. Still thinking about changing the stock thermostat for a cooler one.

Do our trucks still have the stupid check ball in the transmission lines like older chryslers did? I know these could get clogged with debris over time and essentially plug your cooler line up.

joesstripclub said:

Do our trucks still have the stupid check ball in the transmission lines like older chryslers did? I know these could get clogged with debris over time and essentially plug your cooler line up.

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I'd like to know as well. That maybe the culprit for all this over heating issue.

joesstripclub said:

Do our trucks still have the stupid check ball in the transmission lines like older chryslers did? I know these could get clogged with debris over time and essentially plug your cooler line up.

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I don't think they do,as i didn't see anything resembling a check ball when i replaced my 8 speed and blew the cooler and lines out.

hawsk99gt said:

I had a weird situation while making a run from North Ga to Central Fla a few weeks a go. It was actually upon my return trip I had THE PROBLEM. I to have installed Jesse's heater by pass plug several month's a go. And so far has been working perfect. As I was saying about the recent trip I took. The return back I had a different experience with my transmission temps. My temps went from the standard (154 degrees) but then went from 154* to 225*, air temp outside was 50ish. I noticed the vibration sound thru the radio was coming through like before I did the swap. This was while cruising around 80 mph with traffic. So I dropped it down to 65-70 mph, jumping into the slow lane and it dropped about 5 - 10 degrees. It fluctuated for the next 150 - 200 miles like that, but still unusually hot. I even stopped a couple of times to see if letting it cool and settle if it would go back to normal. That didn't work. Finally, by the time I got into the Atlanta area and got stuck in their stop and go traffic hell, I noticed, while I was cruising at about 20 mph for like 30 minutes the temperature magically dropped back to normal. Actually dropped to 130* and then traffic started easing off and I decided to be a baller and jump into the Fast Pass lane, getting up to 80mph. Everything was fine again. Next 60 miles back home it drove solid at 145*.
Anyone got an idea why my truck would give me ghosts of Christmas past again?
I'm having a real hard time having faith in her doing these really long hauls.

Click to expand...

@hawsk99gt , this sounds like the problem I'm having right now with my truck. I've never had issues with the transmission temperature, even after I swapped to the PPE pan at 50,000 miles (about 15,000 miles ago). It used to hold steady at 185 on the highway on long trips, but now it'll creep up into the low 190s, and if I don't slow down, it'll start skyrocketing, up to 230 F the first time I noticed it on a long drive, and the problem has repeated several times since (I pull over and let it cool down now that I watch out for it). That spike only seems to happen when I'm around 70 mph or above. If I cruise at 60 mph, it seems to be able to manage that indefinitely.

I thought it was my transmission heater thermostat acting up, hence my effort to get a bypass, but if you already have Jesse Caulk's part installed, and still experienced THE PROBLEM, I'm wondering if the culprit is something else, and Jesse's part might not actually solve my problem. THIS TRUCK.

I guess I'll install the bypass plug and see if it solves the issue, or if like you, the angel of trans temp spikes continues to torment me going forward. It really does sound like something is loose in the plumbing and during periods of high flow, it clogs some critical cooling path and BOOM. Cook city. But what could it be? Are the fluid flows involving the transmission dependent on engine speed? Perhaps that's why it only happens at 70+ mph, because there are no more gears left and those speeds are only attained by revving the engine higher. HMM.

EDIT
I should point out that I don't have a good idea of how this system works, from an engineering perspective, and it would be a good idea to study some schematics to find out.

@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:

I've been dealing with this exact same issue for a while. I've been through 3 bypass valves (there's no relay involved). One was locked up, I mucked up the 2nd one and just put the 3rd one in last week trying to figure out the problem.

I finally figured out my problem (and it sounds like yours as well) is the torque converter is not locking up at highway speeds. I have a 3200 stall (I'm making 850ish HP) and I know for fact at highway speeds it's not locking up making excess heat.

60-65mph keeps my temps at around 220, 70-75 hits high 230's...around town it never goes over 205.

The good news is, these ZF's can handle the heat better than any other trans I have ever seen. The bypass doesn't even open up to the cooler until 195-205 degrees. They're BUILT to run hotter than any other trans too. The fact that the light doesn't even come on until 260+ amazed me.

I'm actually about to swap over to a lower stall so I can actually drive it on the highway.

If you're not tuned/built and are still running the stock converter, have the dealer check your electric torque converter lock. Doesn't sound like it's working.

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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.

Daniel Ortiz said:

@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.

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The beauty of the 8 speed is the fact you can lock or unlock the convertor via tuning. Check with your tuner and see where your convertor is locking up,it might need some adjustment.

@Wild one , I'll have to learn, as my truck has never been tuned (by me at least). If the previous owner did, it hasn't affected it until recently. Also, if it had, I suspect Car Max will have re-flashed it to factory settings before I bought it. But who knows. I'll look into tuning and torque converter lockup in general. Thanks!

yeah my truck has never been tuned other than the dealership doing computer flashing in the past to resolve my early transmission issues before they replaced my transmission. I haven't had any issues lately, but I haven't gone on any long drives over 50 miles. I was wondering would old differential fluid cause a heat issue? I'm at 90k miles and I am getting ready to do a front and back fluid change.

hawsk99gt said:

yeah my truck has never been tuned other than the dealership doing computer flashing in the past to resolve my early transmission issues before they replaced my transmission. I haven't had any issues lately, but I haven't gone on any long drives over 50 miles. I was wondering would old differential fluid cause a heat issue? I'm at 90k miles and I am getting ready to do a front and back fluid change.

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I highly doubt old diff fluid will cause the transmission to run hot. It's a good idea to change the fluid in the t-case if you're doing front and rear diffs.

Good idea, hadn't thought of that. How often should I be doing that?

My experience 2 weeks after installation of this item. My highest trans temp in up to 85 degree weather outside weather. Is 140 in stop and go traffic. At speed on the freeway at freeway speed, 132. I'm 5.7 RCSB, supercharged, 190 t-stat, e fan and top 3 and bottom 3 slates in ags removed.

This is about a 53 degree drop in stop and goal traffic and 27 degree drop at speed.

I'm very pleased with this outcome.