M50D and t case HOT to the touch?

[cstarbard]

Just got back from a short 2wd trip doing errands, nothing crazy, and noticed the transmission (manual) and t case are really hot to the touch. Not enough to burn you but very uncomfortable to hold onto. Hotter than I would think is normal.

Is that bad? Normal? I have new fluid in both (whatever the owners manual reccomends- Merc V I think), which is topped off (literally just checked yesterday).

Thanks

 

[4x4junkie]

Fluid spec for a 1997 M5OD is Mercon. This fluid will normally be branded as "Dex/Merc" nowadays.

Ford however, for some time now has been wanting you to believe Mercon V is a complete replacement for Mercon, but for some applications (such as the M5OD), there's been a number of reports of hard-shifting issues, probably because it's too slippery for the synchros in a manual trans to function correctly. I generally recommend sticking with Dex/Merc fluid for any M5OD specifying Mercon.

Use of Merc V however would have little or no bearing on operating temperature. It's perfectly normal to see manual trans temps well over 150°F, maybe even 200° after being subjected to a sustained load in any gear but 4th. Figure that the engine it's attached to is already running at 190-195°F as well.

 

[adsm08]

How hot do you think the trans should be getting, or not getting?

I can usually hold a hand on a trans, but my tolerance is pretty high.

Like Junkie said, you have loads and fluid sheer, and things happening in all gears but 4th, and you have the trans bolted right up to an engine that is running on the high side of 200*F. Metal likes to transfer heat. You also have the exhaust radiating a good bit of heat, although not 200*, into the same area as the trans.

 

[cstarbard]

Thanks guys. I realize it was kind of a stupid question. I never thought that hard about hows hot a manual trans might get after use and just got nervous.

Thanks for the helpful info on MERC V. I would not have known.

 

[4x4junkie]

Yeah Ford yanked the license for the name "Mercon" some time around 2007 IIRC, and then stipulated Mercon V as a replacement.
Funny thing is... prior to this, Ford themselves actually stated never swap or mix these fluids, they are not compatible (and will void warranties because of it too). IMO they should've just stuck with that advice.

Fortunately the aftermarket oil brands recognized there being an issue and have continued to make the original Mercon fluid, but because of the licensing crap, they now have to call it "Dex/Merc" (same shenanigans took place simultaneously with GM's "Dexron III" fluid, so is why the name. The two fluids were essentially the same).