shelled M5OD

[LittleHorse]

wow this sucks.

I bought this '90 Bronco II with what I thought was a bad clutch. My suspicion was right, the clutch is the worst I've ever seen - BUT the clutch was hiding a transmission that only has 4th gear.

When I spin the input shaft in 1-3, 5, or R, I can hear a metal on metal rubbing sound and the shaft drags intermittently, output shaft does not move. The way it drags feels like the a shaft is broken and grabs whenever the break is lined up.

When I spin it in 4, I still hear the sound but the output shaft moves with the input shaft.

Is this a common thing? Does anyone have an exploded diagram of the transmission so I can start figuring out what in the world is going on?

I've had a manual transmission apart before so I'm ok with fixing it if it's a simple remove and replace sort of thing...though I'm not sure I want to get into a full rebuild with setting gear lash and washer thicknesses, etc.

 

[z3ro]

pics of clutch or gtfo

 

[LittleHorse]

ask and ye shall receive

 

[rurouni20xx]

it would be the same as a full rebuild kit, just reuse your shims and change the gearsets out. i hate to hear this but at the same time i want to see pix of this gearset and clutch assy cuz this sounds like some wicked carnage. i want to know what destroyed this tranny, the m50ds are the strongest sticks you can get for an rbv besides a 4.0 gearset for one. it must have had a bad clutch or slave cylinder and the partial shifting and half shifting must have ground down the gears over time.

 

[z3ro]

That clutch needs this sticker

 

[LittleHorse]

no kidding. I've never seen one with no friction material at all.

I really don't know how, but the pressure plate and flywheel managed to not have ANY grooves from the rivets. I could grab the hub and freely move the disc around while the pressure plate was still bolted on, and it spun freely before I took it apart, just barely even grazing the flywheel and plate. I haven't examined the pressure plate fully yet but I figure the clutch disc must have grenaded and got a piece of material jammed in the springs so the pressure plate couldn't clamp what was left of the disc.

 

[rboyer]

That is the most beautiful clutch I have ever seen.

 

[LittleHorse]

So apparently by possessing this clutch I've accomplished something :icon_rofl:

I feel like my best bet is going to be sourcing another trans from salvage. I don't know if these prices are typical but drivetrain.com is selling master rebuild kits for $360, and its listing just bearings, bushings, washers, and nuts and doesn't include the $110 syncro ring kits or appear to include any of the shafts, which are each $60-$130 if any are broken, or gears.

 

[Beanmachine7000]

I priced out a 4.0 M50D-R1 rebuild kit at Autozone and it was right about $500 including synchros... The Ford stealership wants almost $300 just for the 1-2 synchro (which supposedly the only one they can get?)

 

[LittleHorse]

ouch.

off to the salvage yards I go....

 

[LittleHorse]

I talked to a friend who's somewhat of a transmission wiz...and according to him it could very likely be that the input shaft has had all of it's teeth stripped off of the gear that drives the countershaft. This would make perfect sense since 4th gear is the only one that works - being direct drive from input shaft to mainshaft.

There's a rebuild kit on ebay that includes all the bearings and such, along with an input shaft and countershaft. It's $280. There are rebuilt transmissions all over ebay for $500. Now to decide whether doing it myself is worth $220.

My body says no but my brain says yes

 

[LittleHorse]

i want to know what destroyed this tranny, the m50ds are the strongest sticks you can get for an rbv besides a 4.0 gearset for one.

besides different ratios, what is different about the 4.0 gearset? If I'm rebuilding the transmission and replacing the countershaft anyway, would it be worth swapping to 4.0 internals?

Besides the countershaft and the gears themselves for 1-3, are there any additional parts I would need to swap over?

I've also seen parts lists with references to 5th gear and reverse "upgrade kits". Any idea what the upgrade is?

 

[thegoat4]

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.

 

[LittleHorse]

I agree, the input shaft bearing is definitely shot. The shaft has quite a bit of play. I imagine the bearing allowing the gears to move apart allowed the contact surfaces of the gear teeth to get just small enough that they were no longer strong enough to handle the load.

Hopefully I'll have time to tear into it tonight for a visual confirmation of diagnosis.


So you think perhaps someone was at highway speed, had to slow down for a stop and just shifted into first at 60mph, holding the clutch released the entire time? I can imagine the input shaft would be FLYING in that type of situation.

 

[Will]

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.

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.

 

[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.