shelled M5OD

[LittleHorse]

there weren't any complete faces in there, but there were a lot of shreds of friction material, like someone had put it through a cheese shredder. It definitely didn't wear down as dust like usual. Whatever happened was sufficient to remove the faces from the disc and shred them into pieces.

Maybe after trashing the transmission, they tried to take off in 4th gear by revving it up and dumping the clutch?


With a 2.9L M5OD, changing from 5th to 1st will spin the clutch at 4.2x what your engine RPM was before the shift...so if you're cruising at 3000RPM and shift to first, your input shaft will be turning 12,600. It's even more dramatic with the 4.0 gearset because 1st gear is a higher reduction.

 

[Sevensecondsuv]

No, 1st on a 4.0 M5OD is numerically lower than a 2.3/2.9/3.0 tranny. The gear ratios are also closer together with the same 4th and 5th. I've been seriously contemplating rebuilding the M5OD in my turboranger with the 4.0 gear set because the 2.3T hits redline in 1st faster than you can push the clutch in to shift into second. In case anyone was wondering, the gears in the 4.0 aren't actually any stronger, just different ratios.

As for your problem, I'd just get a junkyard tranny. Around here they go for 100 bucks if you pull it. Maybe 250 if they have to. M5OD's are nearly indestructable if you keep them full of clean fresh ATF and don't drive around with a non working slave jambing it into every gear. Dumping the clutch at 4000 RPM with a 4.0 or a 2.3T is about the only other way to break one. They'll withstand it OK (still not recommended) from a lower output engine.

 

[LittleHorse]

No, 1st on a 4.0 M5OD is numerically lower than a 2.3/2.9/3.0 tranny.

you're right, I was merely glancing at the TRS transmission page when I said that and for some reason thought the 4.0L was listed second since it was built later. My bad.

I've been seriously contemplating rebuilding the M5OD in my turboranger with the 4.0 gear set because the 2.3T hits redline in 1st faster than you can push the clutch in to shift into second. In case anyone was wondering, the gears in the 4.0 aren't actually any stronger, just different ratios.

As for your problem, I'd just get a junkyard tranny. Around here they go for 100 bucks if you pull it. Maybe 250 if they have to. M5OD's are nearly indestructable if you keep them full of clean fresh ATF and don't drive around with a non working slave jambing it into every gear. Dumping the clutch at 4000 RPM with a 4.0 or a 2.3T is about the only other way to break one. They'll withstand it OK (still not recommended) from a lower output engine.

I'm actually sort of a glutton for punishment, and was kindof looking forward to rebuilding it for the experience. I've rebuilt many engines but never a transmission. I figure my choices are $100-$250 for a junkyard tranny of unknown and unverified condition, $500-$600 for a rebuilt with a 1 yr warranty, and $280 for a rebuild kit, intimate knowledge of it's internals, and a transmission that I know the condition of all the parts inside.

I still haven't decided whether I'll change to a 4.0 gearset - it really all depends on if I can find out what all parts I need to do it and how much extra they will cost on top of the rebuild kit. I know for sure I'll need 1, 2, and 3 mainshaft gears and of course the countershaft but I don't know what, if anything else.

 

[thegoat4]

I've heard of that in a big truck but not a little one. It is something people don't think about though. If you are going 70mph in 5th at 2500rpm, you push in the clutch and move the shift lever to 1st the clutch plate is going to accelerate to almost 11,000 rpm. But he should find them in there if it did. I don't think it's enough rpm on a Ranger clutch. A big truck would have a much greater speed difference.

It's a whole lot easier in a big truck due to the higher gear ratios and larger clutch plate diameters, but it's still entirely possible in smaller vehicles. It's called "burst RPM." You can contact the clutch manufacturer to find out what it is for a particular clutch.

In the big trucks it's very common to do it in reverse when rolling backwards and not fully engaging the clutch. In passenger vehicles it's usually when somebody tries to downshift and gets the wrong rail, so first instead of third or second instead of fourth. It can also happen when somebody successfully "upshifts" form OD to reverse--that's why most trannies have a little interlock to block that and intentionally make the reverse synchro a little weak.

It doesn't happen a lot, but it does happen.

 

[LittleHorse]

While I don't at all doubt the fact that it can happen coasting in too low of a gear, given the condition of the transmission, and knowing that they either had to break at the same time or the transmission first (since it wouldn't be possible to strip the teeth off the input shaft with no faces on the clutch), I doubt coasting is what did it. I'm leaning toward the "trying to start in 4th gear" theory.

 

[rurouni20xx]

well it still sux no matter what happened, your in the same dilemna as me. im looking for a 3.0 m50d to get rid of my pos a4ld, the tranny is good and shifts but it shifts all over the place and never when i want or need it to. if i can find one cheap enuff ill attempt redoing it w/ 4.0 internals that way itll hold up to the turbo 3.3 engine. i never meant for it to be implied that i said its stronger, just a better ratio for more power output due to dif 1 2 3 ratio. as far as rebuilding a manual automobile tranny, i have never changed a clutch much less messed w/ a tranny, so itll be an experience for me all the way around. if im going to do it im going to do it right the first time w/ as much info as possible. hell if you werent 7 hours away littlehorse i prob would have trkd it up there and helped you w/ it one wknd that way we could both learn from the experience.

 

[LittleHorse]

CARNAGE PICS!!! NOT FOR THOSE WITH A WEAK STOMACH!!!

I'll start with more of the clutch.

Here is the "clutch cheese" that was piled in the bellhousing. Some of it had already fallen out at this point.

Here is the flywheel - showing wear but no apparent damage from the rivets.

Then I took the extension housing off...

And the top cover.

Wait, what's that I see toward the front there???

As it currently sits

So the diagnosis was correct - the gear on the input shaft is totally stripped, and there is heavy damage on the corresponding countershaft gear.

The output shaft seems to be dragging on something when I spin it - I cleaned some metal shards out of Reverse and it got a lot smoother, so I imaging there's probably some more in the bearings or the 5th gear on the countershaft. Hopefully there isn't any another gear damage on any of the gears I wasn't planning on replacing.

 

[rurouni20xx]

looks like first gear in a honda trx500 when you pull 28 inch tires and a lift kit. spinning in mud grab a stick all of a sudden clickity clickity... how do the synchros look? if they are busted and all you have is one gear (4th like my friends trk...) she ended up revving the piss out of 4th and taking off to get it home, doing the same thing your trk is experiencing. they just didnt keep driving it like what looks what happened to yours. cheers buddy, and changing to a 4.0 gearset is pointless if they skrewd 4th and 5th since they are the same as a 4.0 anyway. its still interesting to see tho. i love carnage...cheers to successful diagnostic b4 teardown!

 

[rboyer]

I have seen transmission carnage exactly like that several times but that clutch is definitely something new to me. If you are indeed going to rebuild that thing then I would suggest scrubbing down that case while you have it all apart.

 

[LittleHorse]

I ended up buying a used replacement from a '92 Explorer w/ 4.0. I've received interest in my case and main shaft of the old trans, so I disassembled it last night.

I must say, I am GLAD I didn't try to rebuild this thing. A lot of those bearings as well as the splined synchro ring for 3-4 were pretty tough to get off without whatever tools a transmission shop would have been using, and though the gears probably weren't reusable anyway due to digesting input shaft pieces, if they would have been fine, I'd have ended up replacing 3rd gear and the 3-4 synchro assembly anyway.

 

[AllanD]

Somebody coasted in gear with that thing and flung the clutch faces off. Seen it before. The giveaway is that despite the clutch faces being gone, the rivets are not ground down.

The tranny probably dies from low oil and a failed bearing that led to ground-off teeth.

Actually it's far more likely someone burned it most of the way off struggling around in a tranny witha burned input gear and thus only 4th.
and after the friction material was compromised it shattered.

Remember that "4th" isn't actually a gear at all but rather "direct drive"
a locking collar that connects the input to the output.

Also remember that when the pressure plate bolted to the flywheel
it won't actually come close to touching the flywheel

I blew the friction material off ONE SIDE of a disc and it wouldn't drive at all.

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