8hp70 heater bypass

hawsk99gt said:

yeah I still have my active shudders. But wouldn't it be consistently getting hot every time I drive? My other temps are fine. It drove a good 50 miles one way and then parked for an hour in a concrete garage, then the problem began. I'll check the A/C condenser regardless, thanks for the suggestion.

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The shutters are easy to pop in and out,you might want to try popping the middle ones out,as it doesn't cost you anything to pop them out,and if you decide you don't like them out,you can pop them back in. If cleaning the condensor and removing the shutters doesn't cure your issues,then you'll have to start digging deeper.But whatever you do,"do not" flush the transmission,just do a pan drop and filter service job on it,but i'd personally start with the cheap fixes first,and work from there

There are a few cases I’ve seen pop up on Facebook of slipping torque converters causing high heat in the trans under load and higher speeds are heavier load. They haven’t been proven yet but it’s a theory. Not saying that’s the case but may need to find a way to log trans input speed and compare that to engine rpm to see if the tc is slipping more than it should at higher rpm or if the tc isn’t fully locking up.

crazykid1994 said:

There are a few cases I’ve seen pop up on Facebook of slipping torque converters causing high heat in the trans under load and higher speeds are heavier load. They haven’t been proven yet but it’s a theory. Not saying that’s the case but may need to find a way to log trans input speed and compare that to engine rpm to see if the tc is slipping more than it should at higher rpm or if the tc isn’t fully locking up.

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the only stress I have ever put on this truck is twice I have put a load of rock in it for a short distance. This truck does not toe anything other than me and some light lumber from Home Depot once in a while. Otherwise I baby it. I haven't felt any slippage. But thanks for the input.

hawsk99gt said:

the only stress I have ever put on this truck is twice I have put a load of rock in it for a short distance. This truck does not toe anything other than me and some light lumber from Home Depot once in a while. Otherwise I baby it. I haven't felt any slippage. But thanks for the input.

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I don’t mean load necessarily as in hauling. Just something that puts stress on the transmission. But like I said it hasn’t been proven yet but that’s the theory I’ve been reading. Most of the guys having the issue I’m seeing are not heavy hauling or anything. And it appears completely random

crazykid1994 said:

I don’t mean load necessarily as in hauling. Just something that puts stress on the transmission. But like I said it hasn’t been proven yet but that’s the theory I’ve been reading. Most of the guys having the issue I’m seeing are not heavy hauling or anything. And it appears completely random

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random is definitely the case. I did read some cases online that you mentioned but not really towards the RAM so much. It is pretty scary, since if I am on a long trip I could get stranded. Did I mention that this is not the original transmission. I'm at 92K miles now and it got replaced at 63K.

hawsk99gt said:

random is definitely the case. I did read some cases online that you mentioned but not really towards the RAM so much. It is pretty scary, since if I am on a long trip I could get stranded. Did I mention that this is not the original transmission. I'm at 92K miles now and it got replaced at 63K.

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Do you know if the TC was replaced with the trans? What was the issue with the original trans? Overheating? If so I’m wondering if it is the TC either not locking up or slipping during lockup causing the exaggerated temps. I honestly wouldn’t be surprised if that’s the case. Is your truck tuned? I think hp tuners gives some better options at system monitoring if you can do that.

crazykid1994 said:

Do you know if the TC was replaced with the trans? What was the issue with the original trans? Overheating? If so I’m wondering if it is the TC either not locking up or slipping during lockup causing the exaggerated temps. I honestly wouldn’t be surprised if that’s the case. Is your truck tuned? I think hp tuners gives some better options at system monitoring if you can do that.

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No it had nothing to do with heat as far as I know. The main problem started with the bump from the back feeling when i came to stop and then from there the truck would like skip in second gear, then eventually threw a code which the dealer finally said I get a new transmission. That was the Readers Digest version. I know, I just dated myself. I'm old. And no it is not tuned.

Joe _S2013 said:

@pacofortacos, This makes a sense to me after doing some high speed rapid acceleration testing. I just replaced the Transmission Heater Assembly and have an OEM stock thermostat in the Heater Assembly and the stock 203 degree thermostat in the engine. With outside temperature in the 80's, my normal transmission operating temps was (prior to the swap) between 220-230, and 230-250 under heavy acceleration(Northern VA driving).

With the AC on max, I initially had difficulty getting the trans temps w/new unit over 185 degrees, it seemed to get there quick, but wanted to stay. Then with the rapid acceleration I was able to get it into 197 range and I could see the temps gage drop pretty quick back to the 185 range. I then took to the back streets with a lot of stop signs and traffic lights and with more heavy acceleration I was able to get it to 200 degrees, but it then would go fairly quickly (less than 2-3 minutes) back to the 185 range, as I returned to normally acceleration. Without the AC on I could not get the temps over 190 with same driving style and conditions. I believe all of this is coming from the AGS opening, and allowing increased airflow over the radiator (still have mechanical clutch and not electric fans) . The Coolant is showing over 210 and the engine and heater thermostats should be open the whole time.

I have seen many ATF temperature charts, but not sure how they apply to the ZF 8/9 speed Magic Unicorn pea these transmissions have. My truck has 160K has ran hot 200-250 for tens of thousands of miles (way outside the chart parameters above). When I changed the transmission fluid it was as dark as any stout I have drank, smelled God awful, but no chunks in the fluid or pan, and the transmission was running fine (fortunately I found trany temp on the instrument cluster) with a very slight bump when stopping, as other have described, and I believe the bump was due to low fluid. - 4.5 quarts came out and I added 6.5 quarts. I Will go into more detail in a later post that covers all I did and how much it has changed the performance of the transmission.

I have one of @caulk04 eliminator's that I plan to install after more testing to see what my MPG is with the lower transmission temps. I would like to keep my transmission temps below 175, but I have to see the difference in MPG. I saw a 5- 10% increase in MPG in the summer with higher transmission temps. I would like to see the temp chart for the ZF8/9 speed transmission fluid, I am convinced it is magic unicorn P. -Lol. I am sitting her writing this amazed I am not replacing the transmission or at least worried about the one I got.

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Honestly, on my 2016, my trans temps have never gone over 203-204 degrees and that was towing the boat up a large hill at 60+ mph on a very humid high 80's degree day.
Even towing the boat from Pa. to Fl and back, I very seldom see 200 degrees on the trans. Oil temps are usually a bit higher in the 230's maybe but I am towing doing 70+ mph and trailer weighs in the range of 5k or so.

I have since removed a few of the upper rows of the AGS ( I think I only removed 2 rows at most and left the lower rows in place) and now my coolant is pretty steady at 199-206 or so with the stock stat and both stock fans - using a 2018 Ram Sport grille.

The Big Horn (earlier sport models, etc) grille does limit cooling capacity - I have hit it's limits towing on a hot day at highway speed - temp was mid 90's.

The honeycomb grille (my stock Outdoorsman grille) provides the best air flow and cooling capacity.

hawsk99gt said:

It happened again........Went to Atlanta today, doing some hot highway driving, temps here are around 85 degrees. Was fine on the way down from Northern GA tranny temps were at 145 degrees at 80mph. But on the way back it jumped to 235 while my coolant was at 201 and my oil was a little higher around 203 - 209 at 70 mph. This went on for 30 miles till I hit some crawling road construction. So for a couple of miles my average speed was 5 - 15 mph. Once I got thru that temps dropped to 165 degrees and stayed like that all the way home doing between 70 and 80 mph. I already have CAULK04's thermo by pass installed and it works for the most part. Does anyone think that I may need to get my transmission flushed for debris possibly and have new fluid put in there? Any suggestions, please.

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I would never machine flush a trans ( have been told this by several transmission mechanics ) by doing so you loosen up small bits that can clog up fluid veins in your tans, when that happens things tend to go down hill, then you will need to visit the repair shop...

@hawsk99gt, A bag or lose rag floating around in the grill blocking the condenser at higher speeds then blowing off when you slow down. What gear was it in when it jumped to 235. On mine it is easy to manually shift to a lower gear when seting the cruise and once you slow the shifting returns to automatic shifting from manual. If there is something wrong with the transmission it stays in a lower gear and causing temps to go up. Also did you notice what your tac was reading for RPM when it jumped, it would also be a good indication the transmission was slipping.

Joe _S2013 said:

@hawsk99gt, A bag or lose rag floating around in the grill blocking the condenser at higher speeds then blowing off when you slow down. What gear was it in when it jumped to 235. On mine it is easy to manually shift to a lower gear when seting the cruise and once you slow the shifting returns to automatic shifting from manual. If there is something wrong with the transmission it stays in a lower gear and causing temps to go up. Also did you notice what your tac was reading for RPM when it jumped, it would also be a good indication the transmission was slipping.

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I honestly did not check what gear I was in, but it was not revving high at all, it was actually driving normal if it wasn't for my trans temp gauge I wouldn't had noticed anything was wrong. Again this happens from time to time, not consistent at all. Seems to only happen when doing long highway travel and even then it is on the return trip when it happens. I am going to look at it this weekend as far the grill is concerned and make sure there isn't anything blocking. Not really crazy about removing any shutters from the front. Oil and coolant are running at their spec temps so that's why I guess I never expected the problem could be in the front. Is there a way to tell what gear I am in or do I have to be in manual mode only in order to see what gear i am in? ("What gear was it in when it jumped to 235") Don't remember off the top of my head. For the most part my truck shifts very smooth. Even in reverse, you don't feel it shift. This truck is garage kept so it is very clean and not abused at all. For a 2016 it is in very good condition both inside and out and I would love to keep it for as long as I can. Just kills me that I don't trust it for long trips. The service department at the dealer is useless. They won't touch it unless it throws a code or if I want to pay for it out of pocket for them to just sit on it. Very frustrating.

06 Dodge said:

I would never machine flush a trans ( have been told this by several transmission mechanics ) by doing so you loosen up small bits that can clog up fluid veins in your tans, when that happens things tend to go down hill, then you will need to visit the repair shop...

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I agree, after hearing from other folks here and looking online, I will not being doing a flush.

@hawsk99gt, is the transmission still inder warranty? Are you doing the work on your transmission or is the shop? Did you install @caulk04 eliminator or did the shop? Have you checked the fluid level yourself? I had a stuck fill plug, but used the hammer and punch method and came right off. Youtube has a few different videos depending how bad you damage the plug.

How i checked my fluid: I have a sloped drive way so 1.Early in the morning with temps in the low 70's, I backed my truck up the drive way until it was level. -I used a torpedoe level I got from HF and checked it at multiple locations on both sides of the transmission. 2. I put bricks behind and right up against the back tires and used my kids chalk to make sure i knew the exact spot. 3. I made sure the fill plug was only hand tight, but not lose enough to vibrate out, the transmission fluid temp was in the 80's, i think mine was 81. I then took the truck down the street making sure to get in all the gears for about 5 seconds, including reverse, another reason to do this early, so you dont have to worry about the neighbors getting upset about racing through the neighborhood. 4. Backed it up into my driveway using the bricks and chalk marks, my temps were now around 95 and climbing, left the truck running and applied the emergency break. I quickly put on my insulated welders gloves, also from HF, and grabbed my level, ATF fill device (modified garden sprayer) presurized and loaded with the ZF8/9 magic oil. Climbed under the truck checked that the transmission was level, unscrewed the fill plug with the gloved hand, i dont know how people are doing this with the egine running and nothing but a rubber glove on, and filled until full( trans fluid temp was about 115) I got almost another quart in it (it shifts like butter and no more of that little bump). This seemed a lot simpler, safer, and quicker than trying to get it up on four jack stands in my driveway and I know the transmission was under load and shifted into all gears, so filled with fluid. After checking for debris in the grill and on the condenser this would be my second check. At least one person has mentioned their transmission was over filled at the shop.

Joe _S2013 said:

@hawsk99gt, is the transmission still inder warranty? Are you doing the work on your transmission or is the shop? Did you install @caulk04 eliminator or did the shop? Have you checked the fluid level yourself? I had a stuck fill plug, but used the hammer and punch method and came right off. Youtube has a few different videos depending how bad you damage the plug.

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Is the transmission under warranty? Well... maybe. I have a 100K drive train warranty, in which they had to replace the transmission a year and a half ago. But I am not sure if it is still under warranty cause my truck is over 5years old with 92K miles on it. So I would have to ask the dealership that replaced it if it is still covered. Which it doesn't matter cause they will not touch it for free unless it throws a code. Currently I am not doing the work on my transmission, I usually like to tinker with my truck oil changes, mostly all fluid changes, differentials etc; Plugs, breaks, shocks and struts. Usually if I can unscrew it I'll do it. But the transmission fluid change is an area I have not ventured into and I'm a little apprehensive on doing myself. Even though there a videos out there, I'll pay someone to do it. Though I did do caulk04 eliminator myself and it seems to do the job for the most part. I have not checked the fluid level yet since I did the eliminator but I only lost a shot glass of fluid. I will look into your method of checking the level or I may play lazy and just go to the dealer service dept and have them check the level.

If you can do the eliminator the fluid is easy. Again, the videos and most of the writeup make it sound a lot more involved. Because of the temp range limits it only takes about 5-10 minutes if you prep it. The biggest problem for me was the fill plug was so tight it strpped, also the exhaust crossover makes almost impossible to get at the fill plug without burning your hand wihile the engine is running. The welders glove was a must and pretty cheap at Harbor Freight, i had no issues with touching the exhaust just felt a little warm through the glove, and made getting the plug in and out no problem.

Many on here and elsewhere swear by some other brand ATF vice the ZF8/9 speed specific, but I am convinced the ZF8/9, is the best. It is expensive, but after what I have experienced with this transmission, 159K, temps in 220-250 for at least 30k miles( only because that is when i found the temp readings in the dash settings), I also believe it lost at least a qua over the years. - I drained about 4.5 quarts when i changed the filter, but ended up adding about 6 quarts.

I bought a case of the ZF 8/9 speed ATF from Amazon, so i had just enough. I also replaced my transmission heater assembly, because of the high temps. I wanted to make sure i could get the truck temps back to what i believe was baseline, before i start to change things and only mask a problem. I am not one to remove or mod something unless i know it is an improvement over normal operations, not a fix to a unknown problem. Once i am convinced this fixed my high temp problems; the bump problem, and also had some minor jumping / stuttering going into higher gears, I am going to install the @faulk04 eliminator. I really want my trans fluid temps below 175, and it seems the normal is about 185-195, and it looks like i am there, so the eliminator sems it would be to improve not fix, and i am good with that.

I would only remove AGS slats if I knew the temps were going up because of load and hills, but not just to fix a random problem I dont know what is causing it, I would fear I am only masking a larger problem and not fixing it, and those fixes tend to catchup with you when you least expect it.

I am not sure how to check the gear without being in the manual mode. I watch my RPM a lot so I would know what RPM is compared to Speed for the road conditions, so if i see RPM higher than usual that woukd be my way of telling. The one thing i really like about this truck is all the data available on the dash and that you can customize it so it is infront of you as you are driving, and dont need to have a laptop next to you to see it from the ODBII. The HP and torque are nice too. Lol

yep I hear you. I really do love this truck and it sucks that I can't rely on a well rounded mechanic to help me figure this stuff out. My faith in the dealership mechanics is very limited. Pretty much the reason why I do my own servicing because I have had too many issues with them either not tightening an oil filter or losing lug nuts off my wheels. Hell, after getting tires rotated I bring my own torque wrench to make sure its torqued properly. I am thankful to have this forum for all its wisdom. This community has set me on the right path many a day.
If i do my own fluid filter change I will surely use the advise given. Probably should check the fluid level at least, just to make sure these guys put in the proper amount when they replaced the transmission.

Ok took a little trip this morning, about 44miles round trip. Put it in manual gear mode and it drove perfectly normal. Top speed was 60mph off and on. RPM's cruising was anywhere between 1500 & 1800. RPM's only increased if I was accelerating from a dead stop from a light. Trans temps were up to 143 going up and on the return 148 - 153 which I am fine with. But other than that today it ran perfect. Oil temps did get a little hot around 223 on the way back while coolant was in the low 200's like 203 for example.

Might just keep an eye on it and if it happens again you know the general RPMs and verify the gears.

In the past was the AC on in both directions or just one? I have notice my temps will run hotter by about 10 degrees with max AC and a lot of heavy acceleration, but that is at hoghway speed and in stop and go. Any present or past issues with the AC? It has been awhlie since I have worked on an AC system but a ac problem can cause the freon to not transfer heat properly and cause the temps in the systems to get very hot. One of the checks on an AC system is to take temps on each side of the condenser and compressor to see if it is transferring heat properly. I am not familiar with the RAM AC system.to know if it is the same. I only bring this up because it is my understanding the top of the condenser is the cooler for the transmission fluid. This is just a guess, based on that. The odd part about your problem is that yours cools off at slower speeds in construction traffic after running hot. I would expect to see the opposite, temps going up especially when it is hot out.

Have you tried hitting up caulk04 to see if he has seen or heard of this with the elimonator installed. If it happens again and RPM and gear are not it, I would check the fluid level and pull the elimonator to see what comes out. Maybe the dealer didn't flush the system as well as they should have. I am not sure if they replaced the heater assembly when they replaced your transmission. Also might try to run it without the eliminator to see what happens. I say this but if you have miles or years to go on the warranty you have probably voided it with the eliminator.

My 2014 rig is way out of warranty and I bought it used with some problems thinking i was going to add HP, tire size and lift, however gas was only $2.50. I am now just fixing, might still add a lift, but nothing to reduce the gas milage 16MPG is bad enough. Lol.

Joe _S2013 said:

Might just keep an eye on it and if it happens again you know the general RPMs and verify the gears.

In the past was the AC on in both directions or just one? I have notice my temps will run hotter by about 10 degrees with max AC and a lot of heavy acceleration, but that is at hoghway speed and in stop and go. Any present or past issues with the AC? It has been awhlie since I have worked on an AC system but a ac problem can cause the freon to not transfer heat properly and cause the temps in the systems to get very hot. One of the checks on an AC system is to take temps on each side of the condenser and compressor to see if it is transferring heat properly. I am not familiar with the RAM AC system.to know if it is the same. I only bring this up because it is my understanding the top of the condenser is the cooler for the transmission fluid. This is just a guess, based on that. The odd part about your problem is that yours cools off at slower speeds in construction traffic after running hot. I would expect to see the opposite, temps going up especially when it is hot out.

Have you tried hitting up caulk04 to see if he has seen or heard of this with the elimonator installed. If it happens again and RPM and gear are not it, I would check the fluid level and pull the elimonator to see what comes out. Maybe the dealer didn't flush the system as well as they should have. I am not sure if they replaced the heater assembly when they replaced your transmission. Also might try to run it without the eliminator to see what happens. I say this but if you have miles or years to go on the warranty you have probably voided it with the eliminator.

My 2014 rig is way out of warranty and I bought it used with some problems thinking i was going to add HP, tire size and lift, however gas was only $2.50. I am now just fixing, might still add a lift, but nothing to reduce the gas milage 16MPG is bad enough. Lol.

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The thermal heat exchanger isn't included with a new transmission,so odds are if the dealer replaced the transmission,they re-used his old thermal unit again,and that's where the transmission thermostat is located.So if it was originally causing his issues,there's a good chance it might still be causing issues with a new transmission.

Wild one said:

The thermal heat exchanger isn't included with a new transmission,so odds are if the dealer replaced the transmission,they re-used his old thermal unit again,and that's where the transmission thermostat is located.So if it was originally causing his issues,there's a good chance it might still be causing issues with a new transmission.

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you know I kept asking the service guy that too. Did they reuse the heat exchanger and he didn't know. I bet that is the problem. But I wonder what would be triggering it go off if CAULK04's by-pass was installed?