why over heat ?

[MONMIX]

Driving down the road the other day looking at my tranny temp guage. Admiring the nice 150 temp. I got to wondering. Over heating is a symptom of what ?
Suppose my tranny over heats, I say " Oh **** I have gotta ___________ " Do what ?
What is the common cause of tranny over heat under normal driving conditions ?

 

[spindlecone]

Monmix
Where are you measuring the tranny temp? inline or at the pan?

 

[ExplorerDMB]

Most heat in the transmissions come from idling. When the fluid is going up to the cooler and so on, air isn't going over it. So when your transmission starts to overheat - say "I need to start moving". If your driving and it starts to overheat, you have either a cooler problem, restricted line, or possibly just a need for new fluid. The more strain you put on the transmission the more heat. That's my guess

-Drew

 

[toy720]

and besides that if you think 150 degrees is overheating it is not, That is pretty normal depending on driving conditions how high does your gauge
read?

 

[MONMIX]

random question

I am having no problems or concerns what so ever. Read my question you see I said " I got to wondering "

Just currious.

 

[toy720]

well your wondering is getting the best of you i would not worry!!!!!!!!!!!!!!!!!!!!1

 

[spindlecone]

Monmix
Where are you monitoring tranny temp?

 

[Glacier991]

HEAT. The number one transmission enemy. I think what MONMIX was pondering was where does it come from? And WHY do they overheat?

I'll add my 2 cents to the answer here.

Transmissions produce heat from friction. Friction takes many forms in an automatic transmission. Fluid movement friction (yes!) and surface contact (my term) friction.

The Torque convertor moves fluid around violently and directs it against impellers, stators, turbine etc... what does it spell ? HEAT, lots of heat. The TC is the biggest producer of heat in a non-lock up state. Lock it up and the heat production stops. So low speed non-lock up driving can produce a lot of heat.... like freeway rush hour driving, or offroad.

Surface friction.... slipping clutches and bands can produce a fair amount of heat...this is usually a failure mode in the making.... not an ordinary every day event... although with the newer trannies, they program in some slippage on shifts so THAT heat is normal.

The problem often is more one of "HOW do we get rid of the heat".

The radiator cooler is only "kind of" a cooler. It "cools" the trans fluid to the temp of the RADIATOR! Nice... on a cold day.... but an external cooler is the only way to go on a warm day. The Explorer towing package had one.... so should you. Even aftermarket.... and after radiator.

So if we have all that..... well... here is the worst case.... freeway rush hour stop and go.... 5 mph and stop, lather rinse and repeat.... no airflow over the radiator or aftermarket one either... no lockup.... HOT. (Does this also sound like off road?)

All other kind of "hot" has a problem lurking somewhere.

IDEAL ? Aftermarket cooler with dedicated electric fan. Essential for normal use? No. Nice.... uh huh. Offroad? Maybe past being "just a good idea".

There ya have my take on it.

 

[Albino 94LTD]

:d

 

[slravene]

where did you get that setup Albino...i need one, as my wheeling habits have begun to take a toll on my tranny i believe.

 

[Glacier991]

Now that's exactly what I am talking about! Sweet.

 

[MONMIX]

yeah Glaicer you are on my page.

It is like this, if my water temp guage reads hot, I know I need to check the fan, or the t-stat, or the fluid level. If my Oil pressure gauge reads low I know I need to check my oil level. If my tranny guage reads hot I really dont know what to check other than the cooler. No worries. My ex is running fine. Just want to learn " what if " Having the information from the guage is only part of the battle.

Spindle, I have the Perma-Cool filter with the temp sender in the filter mount. It is the first to see the tranny fluid on its way out from the tranny on its way to the coolers.

 

[Albino 94LTD]

Like this, right Kevin?

slravene, that's a Flexalite 4190 $153 from Summit. I went with the switch instead of thermostatic control in case I am in deep water, I don't want it to come on and bend up the blades trying to push water.

 

[spindlecone]

Thx Monmix
Next question, where is the best place to monitor tranny temps? what temp do's the tranny actually see?
I monitor temps at the pan, run 125/140, 150 max on a 90 deg day in traffic.
Is what I measure the true tranny temp?

 

[MONMIX]

Albino, yeah that is exactly like mine, just placed elsewhere and I painted my hose clamps back. ( yes I am that **** )

Spindle,
I put my temp sender in the place that made the most sence to me. For sake of ease the options were limited. Before or after all the coolers. No brainer right ?
It is usually with in 5 to 7 degresse of the ECM. Guage to the hot side. Close enough for me.

 

[Glacier991]

I think the answer to this one is "it depends". As best I can fathom it out, in the A4LD for example - and in a simplified analysis - the pump flows to the convertor and also to the pressure regulator valve. The convertor oil ends up flowing from there through the convertor valve and to the cooler, where it returns as case lubrication (front, center and back) and drains down to the pan. The overage from the pressure regulator is also redirected to the pan.

So is the pan the hottest oil? Probably not. Probably the TC flow is the hottest... so if you wanted to measure a peak temp, the line TO the cooler would probably be where you want to measure. At low speed operation the difference might be not insignificant.

But at freeway operation - steady state... with a locked up convertor and lots of oil flow.... I'm bettin the line to the cooler and pan ain't HUGELY far apart. I have never tested this theory though.

Would be an interesting experiment.

 

[spindlecone]

All Good info
Just trying to asertain if my oversize tranny pan makes a diff on actual tranny temps.
I have no baseline of OEM pan V/S aftermarket (3 additional QTS of fluid)
Would seem to me that the pan temp would be indicitive to the internal tranny temps.
Just curious