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Discussion Starter #1 (Edited by Moderator)
6.5 Year Update 19 Sep 2016: NOT A SINGLE ISSUE HAS EVER COME UP DUE TO THIS BYPASS. That's right folks. From the Mojave Desert, to the Frozen Frigid Tundra of Minot North Dakota, followed up with a 5500 Pound Trailer Tow, (9300 Pound Gross Vehicle Weight), from Minot to SLC. This has only given me confidence. Take it as you will.
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APPLIES TO AUTOMATIC TRANSMISSIONS ONLY ~ "MANUAL TRANSMISSION GUYS THIS DOESN'T APPLY TO YOU"

OK, here's the Executive Summary:

Corrosion in the OEM Radiator causes an internal leak that allows the Coolant to mix with the Automatic Transmission Fluid. The root cause is not known: whether the corrosion is due to the Coolant Chemistry, AT Fluid Chemistry, or a flaw in the Radiator design and manufacture. What is well known is the effects of this failure: A dead Transmission and a high dollar repair. What this modification does is completely eliminate the potential for that failure to occur, and attempts to mitigate the loss cooling provided by the now Bypassed Radiator Transmission Cooler by adding a second Aftermarket Cooler behind the OEM Transmission Cooler. The majority of this thread is dedicated to the merits and potential consequences of this modification.
OK. There is an EASY way to prevent your Radiator from eating your Transmission. Check this out:

Here is your Transmission Cooler framed in Red.


All I did was switch the two Hoses. The Hose indicated by the Red Stripe used to be connected where the Hose indicated by the Green Stripe is connected and vice versa.


That's it!! That's all you need to do to Bypass the Radiator. I took my Bumper and everything else off just for pictures. You could do this by only taking your Radiator Skid off.

STOP HERE IF YOU DO NOT ADD A SECOND COOLER
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Now since I'm in the Mojave Desert, I decided to ADD a Second Trans Cooler. Check this out for easy.

Complete Steps One and Two above. Purchase any Cooler you wish, so long as it fits. I got AutoZone Part Number: 911403 (thats set as my hometown store, make sure to check yours! :) )
I added mine to the Rear of the Stock Cooler:


Trans Fluid comes into the new Cooler on the left (Red), exits on the right (Yellow) and goes into the factory one (Green). No need for any other Hose changes!

As you can see plenty of clearance behind!


Hardly can tell its there!


I have some more out of focus Pictures, if anyone needs more clarification, (no pun intended). Lemme know if this works for you!
 

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I am a little lost of the benefits of this mod?
It prevents your engine coolant from leaking into your transmission. If the cooler fails...it will allow the two fluids to mix...if they mix...your tranny is dead! By bypassing the radiator you no longer have to worry about the fluids coming in contact....pretty self explanatory IMO...

the last thing on earth you want is antifreeze in your tranny....
 

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When doing the bypass is there any loss of trans fluid? Do you need to flush and refill immediately? Also, when refilling I'm assuming you'd need to add less fluid. Do you happen to know how much less?
 

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Do we have any idea how much heat from the transmission was being rejected through the radiator? There is an electric driven fan that draws air through the radiator and the tranny cooler, does it have enough pressure capacity to draw through this extra tranny cooler?

Really like the mod, thinking of doing it as I can't stomach the thought of my tranny going out. Just trying to work through logistics in my head. Not sure if there is a way to find out those spec items.
 

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Do we have any idea how much heat from the transmission was being rejected through the radiator? There is an electric driven fan that draws air through the radiator and the tranny cooler, does it have enough pressure capacity to draw through this extra tranny cooler
this is of no concern there is enough suction for the fan to draw the air through both coolers...and additionally, the fins and pipes are spaced out enough that plenty of air will find it's way through. I would imagine, from looking at the pictures and working in building automation control, this additional cooler would only add about .1 inch of water column to the pressure drop across the tranny cooler assembly..which is of negligable consequence...
 

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Not as simple as all that Rook. Need to go back to study some heat transfer in compact heat exchangers:)

Yep, the pressure drop of the air across this additional compact heat exchanger would be negligible, however there is additional pressure drop of the transmission fluid being pumped through the cooler due to the increased flow resistance of this cooler added in series. Whether or not that adversly impacts the overall heat transfer would need to be calculated. (Since heat transfer is a time dependent function, there is more time for the fluid to flow through the heat exchanger to be cooled... however it is also a mass flow rate dependent function, with higher mass flow rates = higher heat transfer... this is an optimization problem)

Its actually a really interesting problem to analyze. On the plus size you've added more surface area for heat transfer to the air. On the minus side you've added flow resistance for the air going through both coolers and the radiator at that location. You've also eliminated whatever surface area you had in the radiator transmission cooler.

Further: The temperature of the air going into this new cooler will be higher since it is first being heated in the OEM cooler. Since both coolers acting together have increased surface area, the temperature of the air leaving the new cooler will be higher than from just the OEM cooler, and that is entering the A/C condensor and radiator at that location with a lower flow velocity, thereby adversly impacting their efficiency. As long as the condensor and radiator aren't fouled, they should have plenty of margin to still provide the required amount of heat transfer though.

Its an interesting mod, and I'm thinking about doing something similar. But I was thinking more along the lines of mounting it on the driver's side of the radiator, where the power steering cooler is. Maybe something with a thermostatically controlled electric fan on it. I do worry about losing the capacity to warm up the tranny more quickly with the heated engine coolant though.
 

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^^ In all fairness I was merely answering his question about the airflow through both of the finned tube coolers in correlation with the fan itself...but yes what you have laid out there is very accurate GPZ..lol nice work!
 

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this is way off topic... but gpzguy... im currently taking thermodynamics and heat transfer. im not blowing my own horn, but i completely understood what you just said. :iconbiggrin:

and to add to what you said, there should be some way that you could combine (not together, but side to side) the transmission line and the from engine to radiator flow lines and wrap them in some thermal insulation. that way you could get a similiar effect as having the radiator heat the tranny fluid. it may be hard to accomplish because of the necessity of running more lines, but if you were able too, i believe that you could accomplish the same task, heating the fluid, while maintaining parallel systems.
 

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Another problem, and I guess part of the reason I'm hesitant to do this, is not knowing how much heat is rejected to which cooler. Liquid to liquid heat transfer has a better thermal coefficient if you want to start using engineering terms. So, are you still getting the same amount of heat rejection now that you are doing it all to ambient air. Air does not have as large of a thermal coefficient, so you need more surface area for air flow to accomplish the same amount of cooling. Of course the part in the radiator is only cooling your tranny fluid to something near the temp of the coolant in the radiator.

The part in the radiator is probably just a tube passing through the coolant (low pressure drop). Won't we also be adding pressure drop through the tranny fluid? Or maybe there is plenty of pressure there to overcome this as well.

I do like that the mod isolates the tranny from the radiator, and the simplicity of the mod. I'm just trying to think what else it might impact, but maybe I'm overthinking it. Right now to me, there seem to be a lot of unknown variables, but I don't like the idea of a craptastic radiator ruining my transmission. I guess I'm holding off for now, but am going to keep my eye on this to see what some of you creative folks do.

I'm taking my truck to the dealer tonight so they can start working on my timing chain whine, so I'm planning to ask them if they've seen any radiator failures ruining the tranny, or any suggested fixes. Not sure what I'll find out from them.
 

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this is way off topic... but gpzguy... im currently taking thermodynamics and heat transfer. im not blowing my own horn, but i completely understood what you just said. :iconbiggrin:
Excellent! Fluid dynamics too? Along with stress analysis, this is the domain of the mechanical engineer. We own it!
 

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Throw in some flight mechanics, orbital mechanics and higher math (along with a few technical electives and a design course or two) and you'll be downright marketable as a systems engineer in the Aerospace and Defense industry ... and pretty much match my curriculum for a BS/MS in AE.
 

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i wondered how you guys knew so much about this stuff :) good to have you engineers around, mighty helpful. i never had the mind for that stuff with the math and all, so i've spent the last 7 years (2 to go) studying medicine, so i'll have a different skill set in the field :)
 

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Another problem, and I guess part of the reason I'm hesitant to do this, is not knowing how much heat is rejected to which cooler. Liquid to liquid heat transfer has a better thermal coefficient if you want to start using engineering terms. So, are you still getting the same amount of heat rejection now that you are doing it all to ambient air. Air does not have as large of a thermal coefficient, so you need more surface area for air flow to accomplish the same amount of cooling. Of course the part in the radiator is only cooling your tranny fluid to something near the temp of the coolant in the radiator.

The part in the radiator is probably just a tube passing through the coolant (low pressure drop). Won't we also be adding pressure drop through the tranny fluid? Or maybe there is plenty of pressure there to overcome this as well.

I do like that the mod isolates the tranny from the radiator, and the simplicity of the mod. I'm just trying to think what else it might impact, but maybe I'm overthinking it. Right now to me, there seem to be a lot of unknown variables, but I don't like the idea of a craptastic radiator ruining my transmission. I guess I'm holding off for now, but am going to keep my eye on this to see what some of you creative folks do.

I'm taking my truck to the dealer tonight so they can start working on my timing chain whine, so I'm planning to ask them if they've seen any radiator failures ruining the tranny, or any suggested fixes. Not sure what I'll find out from them.
And the dealer will of course say "Oh I've never heard of that happening!"

I'm really not sure about the heat exchanger located in the radiator assembly. I'm thinking that it really doesn't have a lot of heat exchange there from the transmission rejected to the coolant. ATF generally should be kept at temps lower than 175 degrees F, whereas I've seen engine coolant regularily run at 185 to 190 degrees in some engines. I'm thinking that its sole function is to heat the ATF quicker. The radiator on my Mercedes has a built in tranny cooler on the bottom 1/4 of it, but there is a visible demarcation between the two and I don't recall reading about any failures of this type with that design.

I'm thinking that I'm due to change my ATF soon, and I want to do this mod at the same time. I could capture the volume of ATF in the radiator, then try and calculate the amount of surface area from that volume and guestimate the flow rate, then use my infrared pyranometer on the goesinta and goesoutta lines to measure the temperatures. From that its a simple Mdot*Cp*DeltaT calc to start with.... (that is the mass flow rate (Mdot) times the specific heat of ATF (Cp) times the difference in temperature between the incoming and outgoing (DeltaT))....

I used to love doing this stuff, like flow balance equations for various heat loads in multiple compartments in a reactor building from the same cooling source... good stuff.

Anyway, I'm going to give this mod some serious thought, as the consequences of failure of the radiator are too high.
 

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Well, I have a my BS in Mechanical Engineer But i work in controls and Green engineering (LEED AP). But I did have my fair share of thermo, heat transfer, and all the fun rediculous math courses that go along with an engineering curriculum...so I know what you are saying...you could also use the specific small heat exchanger equations based on the length of pipe, number of fins surface area ect. to calculate the convective losses from the metal to the air. and from the fluid to the metal. Again you would need inlet and exit temperatures to get the effective heat loss (q) of the exchanger and you would need the convection coefficient of the material used for the piping. If insulation is added to this piping as Xguyforlife suggests it could be...it becomes a much more involved equation and your heat rejection of the system gets divided by a logarithmic ratio of the inner and outer radius of the insulation which is then all divided by the insulation thermal conductivity (k) multiplied by 2*pi* the length of the pipe.

Yeah we could all overanalyze the crap outta this..but in the end I think I'm just going to do the mod...the benefit of not having a effed up trans outweighs the possibility the fluid may not heat up in time. There will be considerable resistance put on the pump...but IMHO not enough to cause an issue.....I'm just going to do the mod...and have a piece of mind...lol..

^good engineering info up there tho guys :geek:
 

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Service guy at the dealer did admit they had two people come in that had the radiator fail. The one guy left and they never heard from him again. The other guy they flushed the tranny and replaced the radiator and everything was fine. Which of course the dealers never think there is a problem with their product.

I guess I was under the impression that the tranny would be at a higher temp than the radiator. Otherwise the radiator doesn't really get up to temperature until the engine has reached operating temperature correct? As your thermostat doesn't open until whatever set point (165 F maybe?). I wonder how long it takes the transmission to get up to temperature if your not going through the radiator. I believe kneebuster said in another thread that he bypassed the radiator and added temperature monitoring. I wonder what he has seen with his transmission since he added that?

Not trying to be a pest with all the comments, just trying to understand how our transmission and cooling system are set up.
 
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