I'm thinking of adding a thermostatic oil cooler bypass to bring the transmission temperature to a steady 170F.
What do you folks think?
Ok david85...here goes....
Disclaimer...I am no 'expert' and do not claim to be...and...although I try to keep up with the latest in the industry...I have not been working in the field for over ten years...so...the latest on fluid development is not in my quiver...
I did get a chance to have a pretty long conversation with Dr. Philip Landis of Lubeguard fame...back in '88 at the Trans Expo in Memphis...really smart guy...everybody else was drinking and dancing and I was getting all of my questions answered...
So...that being said...
Says the new fluids handle temps just fine.
It is the seals in the transmission that you should be worried about...that is the weak link in the chain...
I agree with trackspeeder on the temps...nothing to worry about so far...
I would not add the oil cooler bypass and add extra complexity and possible failure point to your system...
...a lot of the factory systems that do that very thing are giving the aftermarket transmission industry more stuff to address when they rebuild a unit that failed from one of those clogging up or failing in some way...they are having to either bypass the factory system or add aftermarket corrections to get them to work...
As far as losing MPG with colder oil...U2slow is probably correct but losses occur with not only pumping...as in resistance to the flow into and out of the actual pump and torque convertor...but also parasitic losses once the fluid leaves the cooler and cools the geartrain and bleeds off into the sump...My opinion is that sure...dead cold in the Great White North you are going to loose some efficiency...but you are also losing it until your engine fully warms up so trans losses are the least of your problems...and...the minor difference you would see between, say...130F and 195F of fluid temp...well...you would need to test that under more exacting methods than just filling up to the top at the filling station...you would need a way of measuring BSFC and run repeatable tests...probably on a chassis dyno...
On the factory cooler...to use it or not....I had come to the conclusion that factory coolers...the ones in the radiator surrounded by engine coolant....were a cheap and convienient way to
facillitate quick warm-up...and not much else...especially in the colder northern climates...
Yes...they have the capability to actually
cool transmission oil in some conditions...but they cannot cool the oil any lower than the temperature of the engine coolant that surrounds it...so...if you work your unit hard and the oil leaving the torque convertor is hitting in excess of 200-230F...then yes...it can help bring it down to around 190-195F...but not lower than the surrounding coolant temp...
I tried a test on a truck that the owner had me install a guage for the trans....(where you put the sensor makes a difference in your readings, too...)...and I found out pretty quickly how fast you can peg the needle and how long it takes to get that heat back out of it...
It only take seconds of powerbraking to generate massive amounts of heat....
Once you see 280F on the guage...well....you know that it is easy to ruin a unit-load of fluid...and...once you get the heat in it...well...you hope like hell you can get it back out of it....but you will dig your fingernails in the steering wheel for a good while before you see the guage needle drop any significant amount...
Factory coolers have their place...in average conditions...
..we (those of us with IDI's) are generally pushing our trucks past what Ford envisioned them to do...and running them longer than 'They' wanted us to...we are not running in 'average' conditions...
When it comes to factory coolers...you have to consider whether you want to run the risk of it fracturing and totally hosing your precious automatic transmission...the industry term for a coolant-contaminated unit was 'strawberry milkshake'...
Yes...you can get lucky and some coolers will last longer than others...but it is only a matter of time before it springs a leak...when copper or aluminum heats up and cools down (thermal cycles) it is bound to open up a crack at some point...and coolant will ruin your week...or month...I would just install aftermarket coolers on most of the trucks I fixed...
He said he purposely deleted the external cooler. He sees trans temps near 200. Saw 1.5-2 mpg increase from running a hotter trans.
Sure...but how long is it going to last before he cooks the seals...I would counter with he better save that money in a jar for his eventual rebuild....and...we really don't know if it actually is something else he is doing to achieve the extra mileage...and...where in the unit is he actually measuring the temperature..?
Speaking of fluid...you have synthetic and you have regular paraffin based oil and you have synthetic blends...one of the differences was the uniformity of the molecules that make up the fluid matrix...
As I understood it...synthetic fluid was more resistant to damage from heat...but the damage would be localized...where the overheat occurred...and not affect the whole chain of fluid...synthetics have a much higher heat tolerance before damage would occur...
With regular paraffin-based oils...the heat damage would affect the whole chain...so...overheat your fluid and you are kinda hosed from here on out until you change it...
Speaking of overheating fluid...remember the older dipsticks and tubes...? Pretty simple affairs...tube and a stick...with markings...
Remember later in the late 80's-early 90's...when the sticks had a lever that you would push down and the stick would lock to the tube...? Want to know why..? Because overheated fluid could
Flash
and pop the stick out and burp fluid on the exhaust...especially the catalytic converter...and catch a vehicle on fire...
'They' fixed that by eliminating the tube and stick...
On the warmup thing...with units not shifting and no lockup until they reach a certain temp...Can't Write brought that up...yes...'we' were told in continuing education to watch out for that...can't remember what make or model it was...and not waste any time and money trying to 'fix' that factory strategy for a customer...
Now...on the internal seals that make up a large part of the hydraulic integrity of the unit...depending on what kind of material they were made of...that is going to be the limiting factor in your transmission longevity...there are a few different types of rubber that the aftermarket uses...as a rebuilder...you just had to go with what you had a 'feel' for...whatever you had good luck with...certain brand names of kit suppliers were reliably good...and some would cheapen up and cause you trouble...I don't want to name names here...but I was told by my suppliers that I was one of the pickiest guys they knew...
The breaking point is how much heat the seals could stand before they break down...and it is my belief that the breaking down process starts as soon as heat and wear start ...and the effects are cumulative...you might be able to get away with a little overheating here and there...you are thinking...but you would be wrong...you will pay for it in the long run...
You ever go to a tire warehouse and smell that new-tire smell...? You know what that actually is..? The solvents or otherwise volatile ingredients in the tire rubber compound that keep the tire pliable...
...well....transmission rubber seals are made up much the same way...and when the volatile ingredients are cooked out of the rubber...from heat...then what is left is the solids that the synthetic rubber is made of...and the seals shrink....
Heat is the enemy of transmission longevity.
You want the thing to last..? Limit it's exposure to heat...
You are not going to totally protect your unit from the effects of heat...but you can...as they say...manage the decline...
last winter I noticed it would hold 3rd a LOT longer.
I suspect you are correct but I would attribute the delay of shifting higher than third to the TCM calculating a higher load when things are colder...and then delaying the upshift...and/or the possibility of the colder, thicker fluid not wanting to flow though the VB plate orfices as quickly as it would at normal operating temps...the way to figure out which it is would be to tap in an LED signal monitor to get a visual as to when the computer sends the upshift signal.
This is all I have for you at the moment...
Bottom line..? I would leave it alone...if you have a good grade of synthetic fluid in it and your filter seal is holding up...you are good.
Happy guage watching....