Any advice for trany cooler?

dieselenthusiast · **Posted:** Sun Sep 16, 2012 5:24 pm

I’m planning to add a transmission cooler to the KJ. Are there any good ideas or tips that I need to know before I do the install? I’m probably going to go with a DERALE.

Transmission Oil Cooler (DERALE Series 7000)
Recommended For:
* Towing or Hauling
* Stop and Go Traffic
* Mountain Driving
* Hot Temperatures

JJsTJ · **Posted:** Sun Sep 16, 2012 5:37 pm

i've had one similar to that since new and so far so good.

tjkj2002 · **Posted:** Sun Sep 16, 2012 7:43 pm

Only problem is your '07 already has a external trans cooler,the only trans cooler actually.Sadly you can not do the '02 radiator swap with the built in trans cooler then run either to OE stand alone or a aftermarket stand alone for the best cooling.

Not really going to gain anything by adding that AUX cooler unless you keep the stock stand alone but still only marginal cooling at best.

dieselenthusiast · **Posted:** Sun Sep 16, 2012 9:12 pm

tjkj2002 wrote:

Only problem is your '07 already has a external trans cooler,the only trans cooler actually.Sadly you can not do the '02 radiator swap with the built in trans cooler then run either to OE stand alone or a aftermarket stand alone for the best cooling.

Not really going to gain anything by adding that AUX cooler unless you keep the stock stand alone but still only marginal cooling at best.

I went outside earlier today to take a look and you are right, I already have an external cooler. :shock:

I don't even have the tow package. :lol:

I wonder why they added the external cooler on the 2007? Was this another model year change over for the KK?

tjkj2002 · **Posted:** Sun Sep 16, 2012 9:25 pm

dieselenthusiast wrote:

tjkj2002 wrote:

Only problem is your '07 already has a external trans cooler,the only trans cooler actually.Sadly you can not do the '02 radiator swap with the built in trans cooler then run either to OE stand alone or a aftermarket stand alone for the best cooling.

Not really going to gain anything by adding that AUX cooler unless you keep the stock stand alone but still only marginal cooling at best.

I went outside earlier today to take a look and you are right, I already have an external cooler. :shock:

I don't even have the tow package. :lol:

I wonder why they added the external cooler on the 2007? Was this another model year change over for the KK?

All KJ's with the 42RLE trans has that external trans cooler regardless of tow package/HD cooling or not since they deleted the in-radiator trans cooler that the 45RFE KJ's have.In '07 they put the radiator cap on the radiator so swapping in a '02 radiator is a no-go.

Personally in your case I would find a area to mount a trans cooler with a mini electric fan mounted to it for the best cooling possible.

Like this...............
http://www.jegs.com/i/Be-Cool-Radiators/134/96301/10002/-1?parentProductId=893135

That way it has it's own fan.

dieselenthusiast · **Posted:** Sun Sep 16, 2012 9:36 pm

tjkj2002 wrote:

All KJ's with the 42RLE trans has that external trans cooler regardless of tow package/HD cooling or not since they deleted the in-radiator trans cooler that the 45RFE KJ's have.

I didn't know that. :oops:

tjkj2002 wrote:

Personally in your case I would find a area to mount a trans cooler with a mini electric fan mounted to it for the best cooling possible.

Like this...............
http://www.jegs.com/i/Be-Cool-Radiators/134/96301/10002/-1?parentProductId=893135

That way it has it's own fan.

So would I keep the OE trany cooler and add the Cool Max External Cooler or run the Cool Max External Cooler by itself and delete the OE cooler?

tjkj2002 · **Posted:** Sun Sep 16, 2012 9:54 pm

dieselenthusiast wrote:

[
So would I keep the OE trany cooler and add the Cool Max External Cooler or run the Cool Max External Cooler by itself and delete the OE cooler?

Personally I would just run the trans cooler with fan and junk the OE cooler since with 2 stand alone coolers you can actually over-cool the trans.

That's why having a in-radiator cooler is so nice,it actually helps the trans warm up faster in sub-zero temps and when then run through a AUX cooler will cool it to a better temp for long life.The in-radiator cooler will also keep temp spikes in check better then a stand alone cooler will,but a deadicated fan on the stand alone cooler will do a pretty good job.Most will say that a in-radiator cooler keeps the trans to hot with the higher temps engines see these days but the in-radiator coolers are in the return side of the trans which is usually 40-50 degrees cooler then the inlet side which is the 210+ degrees the engine is running at.

dieselenthusiast · **Posted:** Sun Sep 16, 2012 10:04 pm

Okay, thanks Troy. I probably should get a transmission temperature sending unit and see what my temperatures are first. I hate to swap out parts until I take some data on the current system. Where is the best place to put a transmission sending unit to get the most accurate temperatures? I have the PML trany pan which has a cast boss for a sending unit.

dieselenthusiast · **Posted:** Sun Sep 16, 2012 10:11 pm

tjkj2002 wrote:

The in-radiator cooler will also keep temp spikes in check better then a stand alone cooler will. Most will say that a in-radiator cooler keeps the trans to hot with the higher temps engines see these days but the in-radiator coolers are in the return side of the trans which is usually 40-50 degrees cooler then the inlet side which is the 210+ degrees the engine is running at.

I wonder if the Mopar engineers wanted to increase the cooling efficiency of the 3.7L cooling system by not running the transmission line through the radiator. I would think that a standalone trany cooling system would take a lot of added stress off the cooling system.

tjkj2002 · **Posted:** Sun Sep 16, 2012 10:27 pm

dieselenthusiast wrote:

tjkj2002 wrote:

The in-radiator cooler will also keep temp spikes in check better then a stand alone cooler will. Most will say that a in-radiator cooler keeps the trans to hot with the higher temps engines see these days but the in-radiator coolers are in the return side of the trans which is usually 40-50 degrees cooler then the inlet side which is the 210+ degrees the engine is running at.

I wonder if the Mopar engineers wanted to increase the cooling efficiency of the 3.7L cooling system by not running the transmission line through the radiator. I would think that a standalone trany cooling system would take a lot of added stress off the cooling system.

I think it was a cost saving thing and the fact that most owners never tow with or offroad a KJ.I know that almost every trail run here those KJ's with the 42RLE trans and the stand alone cooler only would have the trans over temp lights come on and in most cases that was before even getting to the trail,even those with HD cooling.Those of use with the 45RFE never had that issue,ever.

I remember we did a clean up of Eagle Rock trail and had to stop twice to let those with the 42RLE's cool down on old stage road,a actual road and not the trail.

JJsTJ · **Posted:** Mon Sep 17, 2012 1:21 pm

fwiw, I had the trans temp light come on once (while in 4wd Hi but never in 4wd Lo) prior to swapping over to the larger aftermarket cooler and never again since (in either mode). (knock wood)

dieselenthusiast · **Posted:** Mon Sep 17, 2012 5:18 pm

JJsKJ wrote:

fwiw, I had the trans temp light come on once (while in 4wd Hi but never in 4wd Lo) prior to swapping over to the larger aftermarket cooler and never again since (in either mode). (knock wood)

I need to add a temperature gauge and take data; otherwise I’m shooting in the dark. I'm still surprised that there’s no differentiation in the OE cooling system between the towing package and non-towing package.

Here’s a list of the modifications that I have done so far to help improve the cooling system:

1. Transgo Shift Kit
2. PML aluminum transmission pan

Here’s a list of modifications that I could do to help further improve the cooling system:

1. Add a transmission by-pass filter (spin-on) or inline filter (Magnefine).
2. Add a heavy duty transmission cooler with auxiliary fan.

JJsTJ · **Posted:** Mon Sep 17, 2012 7:53 pm

not sure about all years but my 03 had the larger fan shroud w/ clutch fan that came w/ the towing package.

dieselenthusiast · **Posted:** Mon Sep 17, 2012 9:10 pm

JJsKJ wrote:

not sure about all years but my 03 had the larger fan shroud w/ clutch fan that came w/ the towing package.

I added the Mopar Heavy Duty Fan Kit to my "non-tow package" 2007 KJ. The HD kit contained the larger shroud, HD mechanical fan and electric fan. It really flows the CFM.

Any advice for trany cooler?

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