Samwell

I have a 1993 F-150, 4x4, 4.9 with the m5od-r2. The transmission seems to be leaking, I think the rear gasket has been slightly compromised. It isn't leaking heavily, but enough to keep everything in that area on the transmission pretty wet. I have looked around a little bit trying to find out the best fluid, lots of places seem to suggest Mercon V ATF fluid.

So, my question is, is it okay to top off my transmission with that Mercon V ATF? I have no idea what type of fluid is in it right now. I really don't have the time to repair the gasket right now either otherwise I'd just do that and flush the transmission and fill it up with fresh fluid. Although I have also heard that flushing and filling will new fluid will sometimes cause a transmission to go out. Not sure what to believe, mainly I just need to know if topping it off with that Mercon is going to hurt anything.

This is my first post here, I created an account just for this as I am stumped. However I have had quite a few Ford trucks over the years and have always found answers here, you all are a great community!

Thanks for any help or suggestions in advance.

-Sam

BLDTruth

Are you talking about where the transmission bolts to the transfer case?

You can top it off with Dex/Merc ATF, which is what is specified for that transmission. I can't remember if Mercon V is the backward compatible stuff but if it is you can use that too. It only holds about 3.5 quarts of fluid so I'd go about fixing that gasket sooner than later. If it is leaking as bad as you say it won't take long for it to run dry.

Samwell

Whichever gasket that is just to the right of the Drain plug in this picture.
[img]

djfllmn

iTrader: (1)

Merc V is just fine to use

BLDTruth

Dang that looks like the tailshaft housing. That's only going to get worse, unfortunately.

You can always try to just snug down those bolts a little tighter - it might slow it down but it could also make it worse.

BareBonesXL

Might be the rubber shift rod access plugs in the top plate. They are known to dry out and leak. You can find stories around the internet. On a 93 you can reach them from inside the cab, you don't have to drop the transmission.

The fluid does two things - lubricates and lets the synchros work right. You could probably blend up any of a number of fluids and be fine with lubrication. Worst case your shifting action gets difficult if you add a different fluid.

And, Mercon V ATF has its own fishy kind of smell. Other gear lubes smell more like sulfur. Might be a clue.

Samwell

Hmm hm, it does seem to be coming from the top of the housing and running down the side, from what I can tell anyway, would that be consistent with an access plug failure?

Thank you to you other two for the info by the way! Taking all comments into account here.

BareBonesXL

Post #13 below shows the three plugs on the left of the top plate/cover. Round rubber. I think that some people with shiny flexible spaghetti arms have done them from underneath.

But, the earlier M5OD's tend to have shift fork problems. Might be worthwhile to just remove the cover and check the forks while you're replacing the plugs. Some people get fancy with aluminum core plug type replacements but I think that the rubber ones are still available.

https://www.f150forum.com/f10/transm...-plugs-137284/

Steve83

I think it's the shift rail plugs, and I wouldn't mess with the t-case or tailhousing bolts. You'll waste more time & end up with the same or worse leaks if you try to work blind with dirt & ATF in your eyes. Do it right, or pay someone to do it right for you.

BareBonesXL

Your link just comes through as a small picture when clicked on. On my computer anyway...