91' Ford Ranger 2WD 3.0L V6 5speed manual 162,000 miles.
Not sure of the trans code. Mitsu or Mazda? Anyone know...

Really never post here on the forums, but I am a long time Ranger owner. For about two years my Ranger has been leaking from the rear of the transmission. Recently I refilled the case with gear oil 75W/90 because the trans was starting to whine and shifts were a bit notchy. Well, most of the fluid I have added has leaked out again. Today when I was changing the motor oil and filter I decided to look into the trans leak and I noticed that it is coming from the rear of the trans towards the top is where it is really messy and wet. For the longest time I thought it was the seal at the end because thats where the drip was coming from, but after researching I found out that the problem could be the three shift rail plugs on top.


Anyone change these plugs ever? Looks like its a common problem on this model trans, so was wondering what you guys have done to fix the leaks. If I were to drop the trans, I would might as well replace it, its kind of worn I bet from running out of fluid, but still gets me around OK, input shaft is a bit noisy when the clutch is disengaged. I am looking for the cheapest fix, was thinking I could take out the shift boot and reseal the plugs from the top then refill the gearbox.

Also what is the proper fluid for my trans? I am using 75W/90 dino gear lube but have heard that others use ATF Mercon III




Pics of said shiftrail plugs: (Not my trans)

 

Changed them on 2 different Rangers with R-1 trans. you can buy replacement plugs i think dealer idk if reg stores have them or not. VERY simple to replace can do it from top threw the floor plate or under side with some small hands. its just 3 rubber plugs they pull out and push the new one's in. put some lube on the plug so it goes in easier some trans fluid you have to refill will work

ATF is the fluid she needs

 

Awesome, thanks for the quick reply ^^^.

I will probably coat the plugs with some RTV and install them. Hoping that my leak is at the plugs and I can take care of them through the top. Will be sure to refill with ATF this time.


Here is a DIY Link: Ford Ranger Shift Rail Plug Maintenance

In case anyone else has the problem. Seems common.

 

Looking to refill my gearbox soon. Still haven't gotten around to replacing the shiftrail plugs. Ford sells them for $6 ea. What kind of ATF should I refill with? I checked the owners manual and it calls for gear oil which I used last time, but the shifts suck and I have read people use ATF. What should I buy?

 

With a 3.0, you should have the M5OD. Ford still used Mitsubishi transmissions in some trucks in '91 though, which is why you saw gear oil in the manual.

70W90 is WAY too thick for the M5OD and could cause bearing damage. Dump it for ATF or a suitable MTF (ie Royal Purple Synchromax) as soon as possible. You can use any Dex/Merc ATF, most universal ATFs, Mercon, and Mercon V.

 

If it is a 1991 5 speed its a Mazda. Trust me... I had to replace mine at 180k. They are hard to find too!