trans temp

JL Rockies · **Posted:** Mon Jun 01, 2009 1:57 am

Would a transmission in a vehicle traveling 75 mph have a higher operating temp than one in a vehicle traveling at 65 mph all else being equal?

JeepinJarhead03 · **Posted:** Mon Jun 01, 2009 2:13 am

difference should be negligible

CRDMiller · **Posted:** Mon Jun 01, 2009 5:46 am

Driving faster = more fuel burnt, = more btu. An obvious answer for a gasser, but in the crd it means MORE BTU INTO THE INTERCOOLER, = more heat for every component behind the intercooler. Proximity to a hot object in some conditions can easily warm up the trans fluid? Like tailwind.

I'm pretty sure the transmission cooler is in front of the IC.

Also there is no way that more movement = less friction. It's the opposite, more revs = more friction, especially in a transmission. The hopes being that they are negated by additional airflow over your trans cooler, right?

Well higher speeds also = greater fluid flow. And more loss to moving that fluid. = more heat.

I'd say your inner trans temps are higher at higher speeds It is going to get hotter before it has a chance to get even cooler (if everything is working well and assuming that greater airflow is more than = to the increased btu).

hrogi · **Posted:** Mon Jun 01, 2009 12:16 pm

The simple answer is Yes.

But is their more to the story?

JL Rockies · **Posted:** Mon Jun 01, 2009 1:20 pm

Now that the weather is warming up I have higher temps shown on the gauge at first confined to times I climb long steep grades. I plan to install an additional trans cooler since I came to the conclusion that since the temp gauge would sit at high noon all the rest of the time, heat soak from all the coolers being in proximity was the problem. I think an additional trans cooler is a lot cheaper than a new tranny for a CRD. I suspected the trans because the engine RPM would not change but the temp would spike. My logic is the trans must be under greater stress up hill.

On a trip home yesterday from the front range of CO to my home in SLC, UT I had the usual temp spikes as I climbed through the grades on I 70 that I expected. When I got to the desert area of SE Utah, the temp gauge stayed at the border of the red zone with the cruise set to 80 mph and backed down to 3/4 when I set it at 75 mph (the speed limit). I turned off the AC, no change. I turned off OD, no change. Reduce speed to 70 mph the needle drops to high noon again.

This was not a problem at all in the winter months, in fact, the needle sat below noon no matter speed or grade. This was also never a problem the entire year I live out here back in 2007. Here are some changes to the Jeep I made while in FL before moving out here again:

4.10 gears; engine revs higher than it did back in 2007, I don't know if this affects trans temp but I guess the engine would be hotter
ARB bumper; with the winch controller and PIAA lights, it can't possibly have the airflow it used to

Things I have done to address the issue:
trans flush
cooling system flush
pulled apart the front end t make sure everything was clean

Since pulling out the gears, taking off the ARB or trading in my CRD in for a Prius is not an option, I thought the trans cooler would help increase the cooling efficiency over all. I planned to add one from Summit that has a fan attached to it.

I have also read that the CRD has a crappy fan clutch. I don't know how to test this but i know that the fan turns. When the engine was cool (and off) I taped one of the fan blades to the shroud and started the engine. After some time as the engine warmed, the fan broke the tape and was spinning. I am not sure what I proved there except the tape flapping around meant the fan was turning.

I don't know if the cooler will fix the problem but I know it can't hurt either.

JL Rockies · **Posted:** Mon Jun 01, 2009 4:10 pm

Kinda sux that someone moved this here. It's really not CRD specific.

RTStabler51 · **Posted:** Mon Jun 01, 2009 4:28 pm

I don't see a difference according to my gauge. Temp is measured from the bottom of the pan.

warp2diesel · **Posted:** Mon Jun 01, 2009 7:11 pm

As soon as I get on the highway the trans temp drops 20 F.
Of course I have a big PML pan and not a stock steel pan.

Jeepjeepster · **Posted:** Mon Jun 01, 2009 7:16 pm

If the torque is locked I would assume it shouldnt change. Other than more air going through the cooler.

tjkj2002 · **Posted:** Mon Jun 01, 2009 7:31 pm

The gear change is not at fault,you didn't go deep enough to raise the rpms to the engine overspeed leval.I would say a fan problem is more at fault though extra cooling for the trans is never a bad idea.

kskj · **Posted:** Mon Jun 01, 2009 8:36 pm

When I was out in colorado last year my trans light came on a few times on long steep climbs in four wheel low. But I did find a hairline crack in the plastic part of the radiator when I got home and it was running hot when the trans light came on. So When I bought a new radiator last year I got a 02 with the trans cooler in the radiator and I just found the fittings last week to run the trans lines through the 02 radiator cooler first then into the stock 04 cooler so I don't think I will have any problems this year. (Thanks Troy for the good idea, and the how to instructions)

I should get it installed this weekend.

gmctd · **Posted:** Mon Jun 01, 2009 11:59 pm

If DCJ hadda tho't depleting KJ CRD radiator capacity by adding an internal w-o heat exchanger was a good idea, they would not have designed the external a-o heat exchanger in front of the radiator - nearly all other DCJ lines use the internal w-o heat exchanger because of the rapid heat transfer in the liquid medium..........................

JL Rockies · **Posted:** Tue Jun 02, 2009 12:20 am

For the record, I have never seen a trans temp light while driving. It's all needle.

gmctd, thanks for the reply, is there a decoder ring that goes with your post?

gmctd · **Posted:** Tue Jun 02, 2009 10:22 am

Glad you asked:

Water-over-oil heat exchanger, mounted in radiator for max thermal transfer, also affords stable oil temps when coolant system is sized accordingly - your CRD engine-oil heat exchanger is cooled by engine coolant, additional thermal loading not designed into the gasser (patooie!) system

Air-over-oil heat exchanger, externally-mounted, hopefully in air-stream produced by forward motion of vehicle, efficiency also subject to ambient air temps - intended to reduce thermal loading on engine coolant system

Turbo-Diesel engine BTU thru-put can be 300% greater than that of a same-displacement gasoline engine, even if turbocharged

'Nuther words, not even a good idea to substitute the gasser (yk!) version radiator for your larger capacity CRD radiator, even tho the mounting convenience is similar

danoid · **Posted:** Tue Jun 02, 2009 11:31 am

Also, engine coolant is usually hotter then the transmission sump temperature. A trans cooler that 'rejects' to engine coolant is known as a trans cooker.

1st law of thermodynamics: brown stinkies rolls downhill...

2nd law of thermodynamics: things go from bad to worse...

CATCRD · **Posted:** Tue Jun 02, 2009 11:58 am

RTStabler51 wrote:

warp2diesel wrote:

As soon as I get on the highway the trans temp drops 20 F.
Of course I have a big PML pan and not a stock steel pan.

Mine too...

What temperatures are you guys seeing? 150°F? 170ºF?

RTStabler51 · **Posted:** Tue Jun 02, 2009 12:02 pm

warp2diesel wrote:

As soon as I get on the highway the trans temp drops 20 F.
Of course I have a big PML pan and not a stock steel pan.

Mine too...

yakers · **Posted:** Tue Jun 02, 2009 1:10 pm

warp2diesel wrote:

As soon as I get on the highway the trans temp drops 20 F.
Of course I have a big PML pan and not a stock steel pan.

AFAIK that pan will not work with the regular Jeep skid plate, right? I want/need to keep my skid plate.

CATCRD · **Posted:** Tue Jun 02, 2009 1:15 pm

Wow, how did my last post get inserted above the one it was quoting?

JL Rockies · **Posted:** Tue Jun 02, 2009 1:28 pm

yakers wrote:

warp2diesel wrote:

As soon as I get on the highway the trans temp drops 20 F.
Of course I have a big PML pan and not a stock steel pan.

AFAIK that pan will not work with the regular Jeep skid plate, right? I want/need to keep my skid plate.

No worky

trans temp

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