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M5OD - M5R1 ....?


Madman54

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So I recently did a full engine rebuild on my sons 91 Explorer sport With the 4.0 OHV with a manual trans and 4WD that we acquired from an impound yard for $200. it was in such bad shape that i thought I had better see what the transmission looks like...
to my surprise, there are several shattered gears..... theyre all missing teeth...first gear looks like all the teeth busted off and they kept driving it like that for years...
i have pictures if anyone wants...
Im pretty well versed as far as everything else goes in these things, but i really dont know anything about the trans/transfer cases. the only problem ive ever come across is the electric shift motor problem....
so, can i please get some guidance here?
am I better off looking for a different transmission entirely, or is it just as cheap to replace all the internals?

can a 2WD transmission be used if i put the tail housing from my 4WD on it?

last but not least, will an automatic bolt up and work the same as a manual?
 


RonD

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Yes, thats odd to see any "gear" in an M5R1 do that
The input shaft gear and it counter shaft gear was known to do that, but not common just "known"
But you only have 4th gear when that happens

M5R1s use ATF not gear oil, so a few were lost when people put in gear oil instead of ATF, its just too thick of an oil to lubricate this transmission

A used M5R1 would probably be better/cheaper than full rebuild, especially if the cause of the failure is not apparent, and used M5R1s are pretty safe bets

1990-2011 M5R1 from a 4.0l Ranger/Explorer or Mazda B4000 4x4 would be plug and play
4.0l OHV and SOHC used the same bolt pattern for transmission bellhousing
2001 and up had a different shifter so get the shifter with transmission, your 1991 shifter wouldn't work

You can change an M5R1 2WD to a 4WD but you also have to change the output shaft as well as the tail shaft housing, so some disassembly is required, output shaft is shorter on a 4WD trans

You have a BW1354 transfer case which was used in Ranger thru 2011
1997 and earlier have speedometer cable hook up which you need in 1997 and earlier Ranger and Explorers

Automatic can be used, but must be 4WD version because the main/output shaft can't be swapped without full disassembly, so possible to convert just not practical, lol
1986 and up Ranger/Explorer automatics(A4LD model) need computer control, so you would need to get a 4.0l computer that matches the year of that automatic transmission, up thru 1994, 1995 and up would require full engine wiring harness change

1983 to 1986 Rangers with 2.8l engine used a C5 automatic, no computer needed, but no OD either, they did come in 4WD versions, and 2.8l used same bolt pattern as 4.0l and same transfer case bolt pattern
And you could use a universal floor shifter(cable operated) to replace manual shifter

If you look for used parts, car-part.com is a good place to see whats around your area
 
Last edited:

Shran

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Every time I've rebuilt an M5OD I end up having $500+ into it. Junkyard transmissions are usually a couple hundred bucks at most... if you can find one that looks reasonably clean, pull the top cover off, eyeball everything inside and check the input shaft for slop. Run it if it looks good. @RonD is correct about the shifter but I think it is different before 2001, the stub changed lengths in the mid 90's somewhere and then the retaining bolt was in a different spot shortly after that. I have one from a 98 2wd Explorer that has the newest style shifter.

Auto swap is a lot of work, A4LD is a waste of time and the C5 requires driveshaft length changes and a lot of other little things. I like the one I put in mine but it is NOT highway friendly anymore, basically at 3000+ RPM all the time...and I have 3.73 gears and tiny tires on that rig.
 

Madman54

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Make / Model
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Transmission
Manual
2WD / 4WD
4WD
My credo
Stop skipping steps and get it done right the first time.
thanks for all the info. love this forum and its people.

I did forget to mention what i 'think' might have been the cause...
when i opened up the transmission. there was about 3 ounces of ATF left in there. there were no signs of recent leakage....

your guess is as good as mine, but id bet money that no fluid was the likely culprit.
 

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