850RE Transmission heat exchanger delete

[roaniecowpony]

I swapped mine and have been fine since. I believe OP abandoned that plugging/delete route and has such done the same

We'll see soon enough if I need the clearance. I'm dropping my JLUR at a friend's shop Monday for a MetalCloak 3.5" Gamechanger, 37s, skids, gears, etc, which requires a driveshaft change. If I do need more clearance, I'll machine an aluminum plate with cross drilled passage and O-ring seals to retain the original flow path.

I don't like the idea of the heater, since I live in an arid climate where most of my use is in hot weather as high as triple digits.

Meanwhile, I've been monitoring trans fluid temps. Seems to run around 200F just driving normally in 85F weather (with the OE 2018 thermostat/heater assy).

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[Upsidwn]

Yeah when I swapped to the bigger driveshafts and tons I ended up busting mine to pieces lol. Mine doesn’t really see any road use, just trail, so I wasn’t too concerned with the heater function, I mainly wanted to un-complicate it if I was down there working on it anyway.
I was going to buy another oem one, chop it up and weld some AN fittings and whatnot on to make it work, but was pushed for time to make a big trip so just put the oem back on and had the driveshaft reworked.
Hopefully the tcase holds together until I get an atlas so I don’t have a loose driveshaft tearing it back apart

 

[roaniecowpony]

Yeah when I swapped to the bigger driveshafts and tons I ended up busting mine to pieces lol. Mine doesn’t really see any road use, just trail, so I wasn’t too concerned with the heater function, I mainly wanted to un-complicate it if I was down there working on it anyway.
I was going to buy another oem one, chop it up and weld some AN fittings and whatnot on to make it work, but was pushed for time to make a big trip so just put the oem back on and had the driveshaft reworked.
Hopefully the tcase holds together until I get an atlas so I don’t have a loose driveshaft tearing it back apart

So, I got the new one a week or so ago and just now disassembled it. It's completely different. You can't just tap those round ports out and put in AN fittings for a bypass. Note that the ports on the heat exchanger are at the ends and oval. But there is a small bypass valve and port in case the heater gets plugged. The actual openings on the valve body face are irregularly shaped. So an old heater assembly with the thermostat would be the one you'd want to do a screw-in fitting mod to.

I'm thinking I'll machine an aluminum plate about an inch or so thick and cross drill it , then mill a couple ports open that fall within the crazy shaped O-rings, pipe plug the cross drill end , drill the hole pattern to fit and just bolt it on.

 

[roaniecowpony]

So, here's my mod plate to eliminate the heater and still have a normal flow path as designed by FCA/ZF.

I took a remnant piece of 6061 T6, squared it up and cut it to approximate size, drilled the hole pattern, crossdrilled the port connection and tapped the end for a plug, transfered the port location and shape with some of my wife's art tracing paper, milled the ports open, then a friend CNC profiled the outer surface just for giggles and some weight reduction. Pix below.

 

[roaniecowpony]

 

[roaniecowpony]

@mgroeger
...

Engineering quote of the day - "Clearance is clearance."

Aviation quote of the day - "Give me the clearance, Clarence"

 

[roaniecowpony]

I just ran across the thread on the Mishimoto trans cooler.

My thoughts on adding the Mishimotor or any other enhanced cooler;

The OE thermostat equipped valve body/heater won't allow temps to drop below the thermostat set point, regardless of the enhancement of the cooler efficiency. Changing to the new valve/heater assembly which doesn't have a thermostat, will allow the existing OE or an enhanced cooler to perform properly.


The heat exchanger (heater) uses the engine coolant, either on the OE or new superseded valve/heater assembly, will heat the fluid, so the front mounted cooler will have to overcome the heat input from that heater. Eliminating the heater will give you a better chance of lowering trans temps below the engine coolant temps. If you live in a cold climate, retaining the heater may be a better decision. In the hot climates eliminating the heater may give you cooler temperatures.

 

[grimmjeeper]

Aviation quote of the day - "Give me the clearance, Clarence"

"Roger Rodger. What's our vector Victor?"

 

[roaniecowpony]

"Roger Rodger. What's our vector Victor?"

"Vector heading 380, rock your wings for radar identification."

 

[oldcjguy]

I just ran across the thread on the Mishimoto trans cooler.

My thoughts on adding the Mishimotor or any other enhanced cooler;

The OE thermostat equipped valve body/heater won't allow temps to drop below the thermostat set point, regardless of the enhancement of the cooler efficiency. Changing to the new valve/heater assembly which doesn't have a thermostat, will allow the existing OE or an enhanced cooler to perform properly.


The heat exchanger (heater) uses the engine coolant, either on the OE or new superseded valve/heater assembly, will heat the fluid, so the front mounted cooler will have to overcome the heat input from that heater. Eliminating the heater will give you a better chance of lowering trans temps below the engine coolant temps. If you live in a cold climate, retaining the heater may be a better decision. In the hot climates eliminating the heater may give you cooler temperatures.

Be careful with this one. The ZF transmissions by design like heat to perform efficiently and correctly. They like the coolant temp to be up around 200. Having a more efficient cooler is good in hot climates and offroad if your trans temps are running high. But, running the trans at cooler temps than it was designed for all the time might not be a good idea.

 

[Old Jeeper]

(Update: JE Reel has been great to work with. Was a honest mistake and we learned how to delete the transmission heater which is prone to failure and creates more space.)

Took my 2021 JLUR 3.6e out in the trail for the first time today after having a new JE Reel front driveshaft installed.

The double cardon is hitting the transmission heater. It’s leaking transmission and coolant now.

Has anyone else had this issue and what did you do to fix it?

Good ole J E Reel, he does make a helluva of a good driveshaft I bought from him about 15 years ago and he is a good guy, enjoyed meeting him. Clarify for me your statement: THere is a Transmission HEATER on the auto??? Does this apply to all of them? Kinda crazy if you live in AZ, NM, Texas, FL????

WOW, reading thru this thread and I should have ordered my 2023 JLR with a STICK trans and I let my wife talk me out of, First Jeep out 22 with an auto...DAMN!

 

[roaniecowpony]

Be careful with this one. The ZF transmissions by design like heat to perform efficiently and correctly. They like the coolant temp to be up around 200. Having a more efficient cooler is good in hot climates and offroad if your trans temps are running high. But, running the trans at cooler temps than it was designed for all the time might not be a good idea.

I'm not worried about too cool. I am worried about too hot. Every 8sp JL out there drives around with fluid temperatures well below the low 200F area every time they start up cold and drive off. Especially so in the cold climates where they may never see above 200F when used in short trips.

When wheeling in the rocks and sand, with little forward speed, the collective coolers and radiators for the drivetrain are in their least efficient operating condition, while the engine and transmission are putting out higher than normal heat. This is especially true in the desert southwest where I live and wheel. Heat input from the engine coolant is not only not needed to keep the transmission fluid in a reasonable temperature range, it puts additional heat into the transmission fluid when it's least needed. Remember, FCA has deleted the thermostat in the latest revision of this valve assembly.

 

[oldcjguy]

I'm not worried about too cool. I am worried about too hot. Every 8sp JL out there drives around with fluid temperatures well below the low 200F area every time they start up cold and drive off. Especially so in the cold climates where they may never see above 200F when used in short trips.

When wheeling in the rocks and sand, with little forward speed, the collective coolers and radiators for the drivetrain are in their least efficient operating condition, while the engine and transmission are putting out higher than normal heat. This is especially true in the desert southwest where I live and wheel. Heat input from the engine coolant is not only not needed to keep the transmission fluid in a reasonable temperature range, it puts additional heat into the transmission fluid when it's least needed. Remember, FCA has deleted the thermostat in the latest revision of this valve assembly.

They deleted the thermostat, but not the heater. Yes, plenty of jeeps start up and drive off with cool/cold temps. The same can be said about coolant temps and engine oil temps, but you wouldn't want to run your engine too cool. Engine coolant and engine oil heat up to a controlled set temp. Keeping a modern engine at 140 or 160 is not good either. The same is true for the transmissions now.

And while I understand what you're saying about not wanting the temps to get too hot wheeling, I wouldn't want my temps staying too cool for normal on road driving. Just something to keep in mind. A lot of people still think cooler is better like the old days when an auto trans wasn't computer controlled with a bunch of servos controlling pressure and flow. Out on hot rocks and in the desert where you are running too cold is probably not an issue LOL. But, plenty of others might think they need to purchase or perform a full bypass because it's available. The ZF transmissions are designed to work properly and efficiently with heat in them, more heat than in the past. If you know what you're doing and why it's definitely not an issue. But if someone does it because they read it here, that might not be as good. I'm just pointing out this mod is not for everyone.

 

[roaniecowpony]

They deleted the thermostat, but not the heater. Yes, plenty of jeeps start up and drive off with cool/cold temps. The same can be said about coolant temps and engine oil temps, but you wouldn't want to run your engine too cool. Engine coolant and engine oil heat up to a controlled set temp. Keeping a modern engine at 140 or 160 is not good either. The same is true for the transmissions now.

And while I understand what you're saying about not wanting the temps to get too hot wheeling, I wouldn't want my temps staying too cool for normal on road driving. Just something to keep in mind. A lot of people still think cooler is better like the old days when an auto trans wasn't computer controlled with a bunch of servos controlling pressure and flow. Out on hot rocks and in the desert where you are running too cold is probably not an issue LOL. But, plenty of others might think they need to purchase or perform a full bypass because it's available. The ZF transmissions are designed to work properly and efficiently with heat in them, more heat than in the past. If you know what you're doing and why it's definitely not an issue. But if someone does it because they read it here, that might not be as good. I'm just pointing out this mod is not for everyone.

I get your point.
But to counter your point, 1) There is no evidence these transmissions don't work perfectly fine and last just as long at lower temperatures than the normal OE temps, 2) There is plenty of evidence that these transmissions will definitely fail if overheated. The new valve body, designed without the thermostat and put into production and which superseded the old valve at a huge cost, and now being sold at a very much lower price from Mopar, validates this, 3) I doubt many owners will lift a finger to pre-emptively change from the original thermostat equipped heater valve body to the new one without the thermostat, let alone modify it, 4) this is a forum that thrives on modifications (many of which have as much or more negative potential than this modification) on a vehicle that has a huge modification culture ownership base, 5) I did suggest people that live in cold climates may be better off leaving the heater functional in post #52 above.

In the end, I think everyone should get the new heater assembly without the thermostat, before their thermostat sticks and fails the transmission, especially so if they are out of warranty where FCA will not cover the transmission replacement if that thermostat sticks.

Eliminating the heat input of the engine coolant is something each owner should evaluate based on how they use their JL. Bypassing the heater will eliminate heat input to the transmission and is easily done by disconnecting the engine coolant lines from the heat exchanger and just looping it as the OP of this thread did. Machining a bypass plate to replace the heat exchanger is only necessary if you have a clearance issue with an aftermarket driveshaft as the OP did. I made the bypass plate just in case my new driveshaft had a clearance issue, as I'm retired and have a machine shop at my disposal and these kinds of projects keep me busy, just like some old people garden or take up art. I don't know if I will need the plate for clearance yet. But it may go on there anyway.

That's my wall-o-words and I'm sticking to it.

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