Transmission/Differential Fluid

BobGPz

Registered User
I put in my transmission mount/crossmember bushings kit from MN12 this weekend and decided to change my transmisssion fluid. It has never been done since I have owned it. :eek: :eek:

The moron at the parts store sold/told me I need 7 quarts of Auto Trans Merc III. I say Moron cause it only took just under three, not 7 :rolleyes: , and think he sold me the wrong kind.
I thought there was a friction modifier that was suppose to go in there, but they didn't have any "Friction Modifier". So, what is it? :confused: Slick 50 for the tranny or something? Should I have gone with Merc 5 instead of 3?
Also "Moron Man" was trying to sell me 80w/90w for the rear differential and I am pretty sure it is the same as the transmission, isn't it?

BTW, the trans mounts weren't that badly worn, nor were the bushings but at least 3 less things to worry about going bad. Shifts a little bit better but there is still some serious slop somewhere. Thinking the diff/rear suspension bushings are needed next to get rid of the slop.
 
Bob, Dexron III or Mercon is the specified fluid from Ford on the M5R2 transmission. If you look at the service publications for certain years, it will also suggest the friction modifier additive, C8AZ 19B546 A, which was originally used for the traction-lock rearends.

For the differential, 80W90 gear oil is the correct fluid. Ford also sells synthetic 75W140 gear lube, which they recommend for newer vehicles ... it can be substituted as well.


cheers,
Ed N.
 
BobGPz said:
.. decided to change my transmisssion fluid. It has never been done since I have owned it. :eek: :eek:
With the 5 speed, shouldn't be a worry.

BobGPz said:
The moron at the parts store sold/told me I need 7 quarts of Auto Trans Merc III. I say Moron cause it only took just under three, not 7 :rolleyes: , and think he sold me the wrong kind.
Not sure about the 5 spd, but the AOD absoultely requires Dexron/Mercron III and not Mercron V which is used in most new vehicles. Also, since your trans was built in 90, there wasn't Mercron IV or V, so stick with the III. Your sales guy must have been thinking AOD; but in fact the AOD takes 12 or more with the converter and all; 7 is about the most you can squeeze out w/o draining the converter.

BobGPz said:
I thought there was a friction modifier that was suppose to go in there, but they didn't have any "Friction Modifier"...

Also "Moron Man" was trying to sell me 80w/90w for the rear differential and I am pretty sure it is the same as the transmission, isn't it?
Absolutely don't put any friction modifier in your trans and don't put any Mercron in your differential :eek: The diff oil is really heavy oil (80/90 is correct) and the friction modifier is proportional to the 20 oz or so of fluid. Best thing is to check the diff fluid by taking the plug out and sticking your finger in to check the level. The proper level is just slightly below the threads. Add enough 90w to it and a bit of friction modifier. Do a forum search for the proper amount as I don't know for sure off the top of my head. Bear in mind the amount of friciton modifier is usually stated for a complete fill.
BTW, newer vehicles with transaxles will often share the same type of trans fluid in the differential. My wifes sienna van uses Mercron III for both. Thats also convenient since the SC uses Mercron III as well. :D
 
TbirdSCFan said:
Absolutely don't put any friction modifier in your trans
You're supposed to, if you have the fiber syncros. If you have brass syncros you don't add any friction modifier.
 
Bob - if you are unhappy with the shifting using the Dexron 3/Mercon , then try adding between 2-4 ozs of the friction modifier. I believe all the stock 5 speeds came with the fiber blocker rings and only re-builds used the brass ones, because that's what is available (from the F-150 I believe). Total capacity is only 3.15 quarts (bottom of fill plug). I've had best success using synthetic gear oil, like Redline's MTL + their modifier; but now I believe Redline recommends their D4 synthetic ATF. So it's a question of personal success and cost - synthetics being about $8 qt.
For the diff, which I assume being a 5 speed is a limited slip (traction lock) you'll need just 3 pints (1.5 qts) of 75w90 plus 4 ozs of friction modifier & as mentioned fill to just below the plug level. Currently Ford recommends using a 75w140 synthetic diff lube; but with an older car and high miles I'd just stick with the regular hypoid gear oil unless you're getting some noise, in which case a higher viscosity might help. In my '93 which just passed the 200,000m (and my '90 which had 246,000m) I've always used the Redline MTL in the gearbox and, after putting new 3.27 gears in the rear (plus new seals and clutch pack) I've been using Richmond's 75w140 synthetic which already has the modifier included.
 
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Wew! Glad the right stuff is in there.

I'd hate to drain the tranny again, and glad I didn't mess with the rear end. It's a pain getting my car up on the ramps, stands, and two big floor jacks just incase (Paranoid underneath cars :eek: )
Thanks for the part numbers Ed, I will see if my local Ford dealer carrys this stuff, as I'd like to make it shift a little easier. :)

Also, thanks for the info: Richard, Chris and Jim. :)
 
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