Quick search (all of 2 minutes) provided two owners having cooler system issues in this thread: BMW X5 Transmission Problems - Bimmerfest - BMW Forums

If you want to compile data, by all means feel free as I don't have the will nor the time, however, I still stand by my temperature comments, and have yet to see anyone even post the most basic information supporting your claim as to a cooler not being beneficial: actual transmission temps.

My platform is cooler running transmission temperatures provide better longevity for both the fluid and components, which encompasses pretty much every car from a 1960s ford to the newest SSTs.

Yours is "I have no data, but the stock cooler is fine, even for towing, because..."

I would agree with you stating: "Don't throw an auxiliary cooler on the car if you're going to implement some half-assed kit, as you can just create problems"

Why would having the convertor locked be beneficial? Using your above statements about the cooler being more than adequate, I would think that keeping it locked (which reduces heat) wouldn't be a concern..

My experience and knowledge of auto trannies and towing is with the Ford 7.3L intercooled turbodiesel, circa 2000, whose auto tranny was the weak link in an otherwise marvelous towing machine. The standard solution there was (1) add a temp gauge (2) use synthetic Mercon ATF, changed every 30k miles (3) track the temps carefully and (4) watch the temp rise to dangerous levels [230F+, as I recall] when towing uphill at speeds that didn't lock the torque converter. If towing heavy in such conditions, with temps approaching the danger zone, you added an auxilary cooler. I only got close to this temp once, hauling uphill in the Rockies on a gravel road at over 8k feet elevation towing maybe 14k lbs of horse, tack and gooseneck trailer. Mine usually ran in 180-190F area. Later years [I think starting sometime in 2001] Ford added a aux cooler in the radiator, which mitigated the problem. I don't pretend to know the operating temps of auto trannies in E53s, or its torque converter lockup tendencies, but if I had an auto tranny and towed heavy, regularly, I would look to add a temp gauge and learn about optimal operating temps and work from there. On my Ford, there was a bung on the side of the auto tranny where you could insert the NPT threaded sending unit. One other advantage - with this, an exhaust temp gauge, and gauge to measure turbo boost, you got to add a cool three-pod gauge mount to driver's side front pillar! Required if, as I did, you had chipped the truck to maximize its towing/hot rod performance. Good times ....

Those aren't towing issues. The first shows what happens when the transmission cooler thermostat malfunctions. Demonstrates the effectiveness of the design. The second shows what happens when the temperature sensor fails. Both problems were resolved by fixing the problem. I take it as a given that the vehicle should be functioning properly before commencing towing

We have seen innumerable transmission internals at high mileage when specific problems are being addressed. Clutch plates are typically good, fluid is not burnt. Additional cooling only helps when the cooling system is marginal.

Yes, but only if transmission temperatures are too high. How many of those Cruisomatics, Selectomatics, FMX, C4, C6, etc transmissions in older Fords had temperature sensors? Or were designed to tow up to 7800 lbs without additional coolers? Or had lock up torque converters? Or backed off the power during shifting? Apples and oranges.

That isn't my position.

Any kit that overcools on cold start and thus accelerates wear during the period of highest wear is, by definition, half assed.

First step is to avoid the transmission hunting for a gear on a climb. Second is to avoid excess heat by taking advantage of the lock up mode. Both are driver controlled. If heat can be reduced, it is a good thing, in general. The benefits of driving properly come for free. Putting a second cooler on it and accepting increased wear on cold start, just because one doesn't want to operate the machinery correctly, is dumb IMO. And in the absence of a history of accelerated transmission failures relating to excessive heat, additional coolers are a solution looking for a problem.

Oh good. Another debate about who knows more about how auto transmissions work, in what otherwise appeared to be an informative thread for the OP and others.

Why don't you guys open a thread titled something along the lines of "I know more about auto transmissions than you do", and compare d!ck sizes to your hearts content.

The OP founded this site in March 2005. The first post was gently mocking the aftermarket hitch, and was posted in mid 2005, coming up on ten years ago.