Need Advice: Best Transmission Upgrade for a 4.0L – FM vs. M50D R1

[93ranger4.0l]

Hey everyone,
I’m trying to figure out which transmission is the better choice for my 4.0L Ranger. I’ve been looking at the FM and the M50D R1, but I’m not totally sure which one is more reliable, stronger, or a better fit overall.

If anyone has experience with either transmission behind the 4.0, I’d really appreciate your opinions—pros, cons, common issues, or what you would recommend.

Thanks for the help!


 Thanks

 

[SenorNoob]

FM series was only ever used with the 2.9.

The only real option is an M5OD. At least you can get shifter parts for them.

 

[93ranger4.0l]

Ok i was just wondering what was better and what lest longer it's fm145 and if I should rebuild it but I'll just throw the t case in it and wait for the trans to need to be rebuilt


But the trans in my ranger is the m50dr1 so

Thanks

 

[lil_Blue_Ford]

So, I have an FM-146 behind a 4.0 in my Choptop and it’s lived there longer than a few motors despite my shenanigans, but I’m well aware that it’s living a charmed existence. When it dies, if I don’t happen to have another FM-146 sitting around, it’s getting an M5OD like it should have. From my understanding, an 01-11 4.0 actually has an M5OD-HD

 

[93ranger4.0l]

I think the fm 145 came out of a 83 dont judge me on that with the 2.9

 

[scotts90ranger]

The 2.9 was only '86-92, before that was a 2.8, there was an FM145 and 146 and if I'm not mistaken the 145 is 4 speed and the 146 is 5 speed but I've just paid attention to the M5OD's...

From what I gather the M5OD is the heaviest duty transmission offered, the 4L versions even got their own gear ratios with a taller first through 3rd gear to handle the torque of the 4L better...

 

[19Walt93]

Of the two, the M50D is by far the best.

 

[Shran]

Toyo Kogyo/Mazda 4 & 5 speeds were found mainly in early/mid 1st gens
FM145's were usually in 86/87 trucks
FM146 & FM132 (same thing, 132 is 2wd) were in '88-1990 or so
M5OD was found in 1988+ 4 cylinder trucks and 90+ V6 trucks

M5OD's are much easier to source parts for. FM-145's are physically shorter so it makes swaps more complicated. FM-146 and M5OD are the same length. My personal opinion is that none of them are bulletproof. I have rebuilt several, the internals are all about the same, no major strength advantages in either model. All of them have well known, documented issues with fixes. I have put a FM146 behind a 4.0 and it held up just fine... don't abuse any of them and they should last.

I like the FM units, they shift really nice and IMO they got a bad rep back in the day because they simply wore out and people assumed they were junk. Well now we have a million worn out M5OD's... same same in my mind.