Mitsu FM145 questions

[rusty ol ranger]

Im getting closer to getting my 86 B2 ready to roll on the road (just the rear sill and a few wiring/brake issues left).

This is the first RBV ive owned without a TK5 speed. I know the mitsu is generally regarded as the worst for reliabilty manual used in these trucks. This one shifts smooth and is very quiet and id like to do my best to keep it that way.

1- What are the usual failure modes of this trans? So i know what to look out for.

2- Fluid type? I plan on changing it out.

3- If the trans does take a shit...the TK5 is a direct bolt in correct? Transfer case and all? Yes i know most guys swap a M5OD in but if the TK goes in directly ill use one...seeing as how ive never had any issue from one.

4- What is usually the biggest killer of these trannys? I dont plan on using it hard, just some minor trails, DD'ing and maybe very occasionally towing my little 6x10 trailer short distances with my quad on it (1500lbs total...maybe, my ranger tows it just fine)

5- Regarding the T-case (manual)...i know its a BW 1350 (or 54) but what fluid goes in that? Its also silent and works well but does leak a little. Id just like a concrete answer.

Thanks in advance.

 

[RobbieD]

From my notes.

The FM145 takes gear oil (GL-4 80W), which I had trouble finding. Other recommendations I found online were for Valvoline Synchromesh MTF, which is what I put in mine.

My trans (the 2WD FM132 version has a loud noise in 5th gear, which is caused by this:

I need to replace the bearing and sleeve in mine, but I haven’t checked for the updated parts since I found and copied the info in the image I posted. With my luck, these are probably not available anymore. Here is where I found that info:
https://www.drivetrain.com/parts-ca...kits-and-parts/ford-fm145-fm146-overhaul-kits

If yours is quiet, that’s a blessing. But be aware that the 5th/reverse bearing and sleeve are a known weak point in these transmissions.

My understanding is, that the Mitsu's weakness has a lot to do with ball bearings being used instead of roller bearings. I can buy that, but the Mitsu does do OK when it's healthy. What I do like about them, is that they are the smoothest and easiest shifting manuals, in my opinion.

Hope this helps.

 

[rusty ol ranger]

From my notes.

The FM145 takes gear oil (GL-4 80W), which I had trouble finding. Other recommendations I found online were for Valvoline Synchromesh MTF, which is what I put in mine.

My trans (the 2WD FM132 version has a loud noise in 5th gear, which is caused by this:

View attachment 111904

I need to replace the bearing and sleeve in mine, but I haven’t checked for the updated parts since I found and copied the info in the image I posted. With my luck, these are probably not available anymore. Here is where I found that info:
https://www.drivetrain.com/parts-ca...kits-and-parts/ford-fm145-fm146-overhaul-kits

If yours is quiet, that’s a blessing. But be aware that the 5th/reverse bearing and sleeve are a known weak point in these transmissions.

My understanding is, that the Mitsu's weakness has a lot to do with ball bearings being used instead of roller bearings. I can buy that, but the Mitsu does do OK when it's healthy. What I do like about them, is that they are the smoothest and easiest shifting manuals, in my opinion.

Hope this helps.

Awesome thank you.

It does seem to shift very smoothly. My TKs always felt a bit clunky....but this ones like butter.

Do you know the fluid capacity off hand?

 

[RobbieD]

Do you know the fluid capacity off hand?

Don't know, off the top of my head, and didn't see it my notes. Sorry.

When I have a minute I could pull the shop manual, and maybe somebody else will chime in.

 

[Shran]

Less than 3 quarts. IIRC something like 2.5ish. I second the Synchromesh recommendation - $11/quart at O'Reilly. I tried 80w oil in mine and it was very hard to shift in cold weather.

There is nothing wrong with these transmissions. Don't abuse it, don't use 5th gear under 55mph.

@RobbieD here is that bearing: https://www.ebay.com/itm/256118490056 I have used that exact one several times.

I don't buy the "ball bearings suck" argument about these. There are a LOT of older transmissions that have ball bearings supporting the input shaft. T18, T19, NP435, SM465's, toploaders............. you never hear about those being terrible because of that part.

IMO and I am not an engineer but I think the input bearings on these AND the M5OD's fail because the input shaft is only supported by the transmission case in one spot (the input bearing) and the rest of it is supported by the pocket bearing which is supported by the output shaft. Any amount of wear in any of the bearings will cause some deflection in the input and output shafts... thus compounding any wear. Those old 3 and 4 speeds usually have really short output shafts so that may contribute to their longevity.

I think a better design would have included a second support for the input shaft but that of course is complex, costs more and would make the transmission longer. I guess the argument could be made that the pilot bearing provides that support yet we see problems and a bad reputation develops.

In any case one of these in good condition is very capable of many years & many thousands of miles of trouble free operation.

 

[RobbieD]

@Shran

@RobbieD here is that bearing: https://www.ebay.com/itm/256118490056 I have used that exact one several times.

Thank you!

 

[rusty ol ranger]

Less than 3 quarts. IIRC something like 2.5ish. I second the Synchromesh recommendation - $11/quart at O'Reilly. I tried 80w oil in mine and it was very hard to shift in cold weather.

There is nothing wrong with these transmissions. Don't abuse it, don't use 5th gear under 55mph.

@RobbieD here is that bearing: https://www.ebay.com/itm/256118490056 I have used that exact one several times.

I don't buy the "ball bearings suck" argument about these. There are a LOT of older transmissions that have ball bearings supporting the input shaft. T18, T19, NP435, SM465's, toploaders............. you never hear about those being terrible because of that part.

IMO and I am not an engineer but I think the input bearings on these AND the M5OD's fail because the input shaft is only supported by the transmission case in one spot (the input bearing) and the rest of it is supported by the pocket bearing which is supported by the output shaft. Any amount of wear in any of the bearings will cause some deflection in the input and output shafts... thus compounding any wear. Those old 3 and 4 speeds usually have really short output shafts so that may contribute to their longevity.

I think a better design would have included a second support for the input shaft but that of course is complex, costs more and would make the transmission longer. I guess the argument could be made that the pilot bearing provides that support yet we see problems and a bad reputation develops.

In any case one of these in good condition is very capable of many years & many thousands of miles of trouble free operation.

That makes me feel better about it.

I know the TK uses a ball bearing too and like i said ive never had an issue with one. I just know after being here for 20 years it seems the mitsus seem to be second only to the A4LD in serious issue/failure rate.

I have a habit of not hitting O/D untill im at cruising speed anyways. So no big change for me on that one.

When i change the fluid ill hunt down that syncromesh stuff. Since itll be on DD duty (most likely) and ill need it to go even if its -10 out lol.

 

[bcschief]

Worn out shifters that are unavailable new except the core shifters that may or may not be available.

 

[Shran]

I know the TK uses a ball bearing too and like i said ive never had an issue with one. I just know after being here for 20 years it seems the mitsus seem to be second only to the A4LD in serious issue/failure rate.

IMO it's a lot of hearsay and people repeating something so many times that it becomes true. I will fully admit to ragging on these until I had a chance to rebuild two of them and now I understand how they function.

It broke because I lugged it around in 5th at 40mph
It broke because it has 300,000 miles on it and worn out
It broke because I never changed the fluid
It broke because the rubber shift rail plugs shrunk & let the oil out
It broke because I dumped the clutch/neutral bombed it to spin the tires
It broke because it was severely overloaded many times and I didn't care

etc... it all boils down to "it's junk" without knowing the facts of why it broke.

 

[rusty ol ranger]

IMO it's a lot of hearsay and people repeating something so many times that it becomes true. I will fully admit to ragging on these until I had a chance to rebuild two of them and now I understand how they function.

It broke because I lugged it around in 5th at 40mph
It broke because it has 300,000 miles on it and worn out
It broke because I never changed the fluid
It broke because the rubber shift rail plugs shrunk & let the oil out
It broke because I dumped the clutch/neutral bombed it to spin the tires
It broke because it was severely overloaded many times and I didn't care

etc... it all boils down to "it's junk" without knowing the facts of why it broke.

good points

 

[gearfather]

shran has nailed it. my company built and sold ALOT...of these units in the 90's and early 2000's for shops and especially Ford dealers in the U.S. and CANADA. by far the most common problem was driving too slow in 5th, too thick or lack of lube and some 5th/reverse syncro hub wear in the center of the hub. Not a bad unit for what they were designed..