jschira, you are correct. There are no available studies that temperatures up to 248 degrees have any ill effects on 4R100s. (I can get information on GM trannies done by GM, but they didn't use the 4R100, and so would not apply.)

However, other than Ford, every single repair, maintenance, or consultation firm, company, or individual that I have read about or spoken with (including auto trans engineers from GM) recommends that transmission longevity is enhanced by 1) proper maintenance, 2) non-abusive driving, and 3) low running temperatures (recommended peaks range from 210 to 230, recommended normal temps range from 150 {gotta love those engineers!} to 220.

I have to wonder why Ford's recommendation is so high. They know more than anyone else? Naturally, unlike the oil companies and oil cooler companies who are only trying to sell you something, Ford makes absolutely no money on 4R100 parts or remanufactured transmissions, so there would be no motive whatsoever to exaggerate specifications.

I have pulled apart a couple of auto trannies with fried clutches and hardened and cracked seals, and have seen what excessive temperatures and burnt oil can do. Not being a mechanical engineering expert, as you apparently are, and having little faith in claims of near-magical, high-temperature resistance that runs counter to everything else I can find, I long ago decided to err on the side caution.

While there is no direct evidence currently available that 4R100s are best run below 200 degrees, there is overwhelming indirect evidence that the 4R100 is no different than any other auto trans when it comes to proper operating temperatures - and I can't find anyone that recommends 'normal' temperatures nearly as high as Ford does.

Oh, and sorry. I can't come up with clever, derogatory names to call people like Jimmy Joe Bob, or lemmings. I'm not big on patronizing, either, though I have made rare exceptions.

 

By the way, could you please provide a link to the comprehensive study Ford did that proves the 4R100 is happy at 248 degrees? I couldn't find it. Just the owner's manual reference - the one near the other one that states "under no circumstances use Mercon V in your Ford transmission as severe damage may result".

Perhaps it was published with the recent Ford statement that Mercon V is now okay to use in a transmission that it could have caused severe damage to 4 months ago.

 

Useful information, because many swear that "every single repair, maintenance, or consultation firm, company, or individual that [they] have read about or spoken with (including auto trans engineers from Brand X) recommends that transmission longevity is enhanced by" keeping tranny temps below 200.

Actually, what Ford recommends is in line with what you are hearing from GM, etc. 248* is allowed only for brief amounts of time (30-45 minutes). Sustained temps should not normally go above 230*.

Also, DCX says 190* in "normal" operating temp. So they are on the higher side of your range.

So where is the 175* or 180* coming from? Jimmy Jo, I suspect. And therein lies my point. People throw all kinds of numbers out. Very few (you are a rare exception) have any intelligent information on which to base their recommendation. Yet, the "because Jimmy Jo says so" group can be quite vocal. The net result of which is that people who have never see their tranny get above 210 or even 200 (and even then, only briefly) are told that more cooling is an absolute necessity and go out and spend money chasing a fititious number that does absolutely nothing to enhance the longevity of their tranny. At those temps, the tranny is absolutely operating within design parameters, and the Ford engineers may not be the brightest, but I suspect that they are smart enough to specify materials that will withstand temps within normal design parameters.

BTW - My "cheap, useless" Ford tranny temp gauge operates within the temp ranges that you (and Ford) specify.

 

Well, my trans gauge is about 65 above ambient with towing a trailer weighing 8000#

 

when i am just driving around my trans. temp gets up to the 170's is that okay???

 

Yes. Perfectly normal.