I am looking at transmission temperature gauges. I'm surprised to see that the VDO gauge goes to 400 degrees (F), while their engine oil temperature gauge only goes to 300 degrees. Is it possible that an automatic transmission can operate safely at 300 or above?

MrBSS

 

I would never go above 275F, and 250F is a better continuous limit, except for occasional excursions up to 275F. Above 275F, the life of the trans gets shortened, the fluid starts to turn brown and you know what that leads up to. $$$

 

The temperature rally should be lower than that. 150-170 is normal operating range. Up to 180-190 is not too bad, but for every 10 degrees above 190, you shorten the life of the fluid by 1/2. If you get the fluid up to 220-230, it's cooked and you need to change it out.

This is for dino fluid. I don't know if synthetic will take higher temps or not.

 

Thanks!

Does anybody know if the Ford Motorcraft Mercon V is synthetic, or part synthetic, or full "dino"? Is there a Ford recommended maximum temp for it?

MrBSS

 

Don't know about the Ford fluid. I do know we have a member who is a transmission engineer for Ford, Mark Kovalsky. You can see his inputs in the Super Duty-Heavy Duty Forum. His comments seem to favor the Mobil 1 synthetic fluid. I can't imagine transmission fluid going over 230 degrees F. The fluid would be burnt to a crisp, and the transmission. I pull a 26 ft. SunnyBrook TT with a 2000 F-250 V-10 and have never seen temps over 180 degrees. I do run a Hayden 679 Aux cooler and a Imperial electric fan, also Mobil 1 fluid.

 

I *THINK* the dealers have Motorcraft ATF that is dino, blend, and full synthetic. Your choice.

The factory fill MERCON V fluid is a synthetic blend.

I do not think Ford specifies a maximum temperature for the fluids.

Here's probably more info than you wanted, but it is handy, so here goes!
*******************

What is the Correct Transmission Fluid for My Transmission?

Automatic transmissions are very sensitive machines. Some of the smallest clearances machined into any vehicle are in an automatic transmission. Some of the clearances are in the tenths of thousandths of an inch. A fluid that is too thick or too thin can cause operational problems.

An automatic transmission uses friction to transfer torque. The friction material in the clutches and bands react against steel. The coefficient of friction between these surfaces is critical. A fluid change can make a large change in the frictional properties. If the new fluid is “slipperier” than the fluid that the transmission was designed to use the friction material will slip and the transmission
will fail in a short time.

Some fluids are not compatible with materials used in the transmission. Certain fluids can degrade the friction material or seals, leading to a transmission failure.

Ford has specified specific fluids for all of it’s transmissions. For the E40D and 4R100 transmission Ford specifies MERCON rated fluids. The owner’s manual and service publications warn against using MERCON V or a fluid that has both MERCON and MERCON V ratings.

The new TorqShift five speed automatic transmission uses an all new fluid called MERCON SP. This transmission will not operate properly on MERCON or MERCON V fluid.


Can I use a Synthetic ATF in My Transmission?


Ford does not make any specific recommendation about using synthetic fluids. The only recommendation is to use a fluid with the proper rating.

There are synthetic, synthetic blend, and non-synthetic blend fluids available in both MERCON and MERCON V. As long as you use a fluid with the correct rating your transmission will be happy.

There is a persistent rumor that you should not use synthetic ATF because it is too slippery. That’s not true. Any fluid that has a MERCON or MERCON V rating must meet Ford’s specification for coefficient of
friction, or “slipperiness.” If it is too slippery Ford does not allow the fluid manufacturer to put the MERCON or MERCON V rating on it’s product.

I believe that synthetic ATF is worthwhile for transmissions that are worked hard. A synthetic fluid has a stronger film, which lubricates better, it carries heat away better, and it does not break down from high temperatures as readily as conventional fluids.

I use Mobil 1 synthetic ATF in my vehicles that tow.

 

Thanks very much for the information.

Although I have always used Mobil Synthetic ATF in my GM vehicles and felt it was worth the extra cost, I went through a similar process with my Jeep GC for which Chrysler specifies "ATF+". Mobil synthetic specifically did NOT qualify, at least at that time.

As far as I can tell, Mobil Synthetic ATF does not qualify to Mercon V. If you have information to the contrary, I would appreciate hearing it.

MrBSS