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M5OD rebuild..an odd occurrence??

94Sport5

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I'll start off by saying this is a very long post, but to get straight to the question go to paragraph #8.. I have a 1994 Explorer Sport 4x4 5 speed. A junkyard 1994 Explorer M5OD is in it right now and has been for about 5 years.

Since the moment it was put in, 2nd and 4th gear would grind no matter how much the clutch was bled or what kind of fluid was used. Also the first 2 drain/fills were totally metallic goo, I'm surprised this thing has lasted 5 additional years of abuse! Okay, recently 2nd gear started making a terrible noise when engaged, a loud and fast rhythmic knocking, but it does have power flow through the gear albeit it doesn't feel right, so I assume it's toast and have been shifting from 1st-3rd religiously for the past year.

Anyways, I recently have come to figure out that the original transmission that was installed when I got the Explorer, was a unicorn..a 1992 Ranger 2.9 4x4 M5OD. As most of you may know, this transmission is a direct swap for the 4.0, as the bellhousings are the same, and they also have steeper 1-3 gearing than a 4.0 geared trans, with 4th 5th and reverse having the same ratios. Also, it's incredibly hard to find as nearly all 4x4s used the Mitsubishi transmission in the Ranger.

So several years ago, the 2.9 trans locked up while backing out of a parking space, leading to me installing the current junkyard 4.0 transmission. The locked up 2.9 trans sat in the trunk of my car for years without me knowing it was in fact a 2.9 M5OD trans.

Getting to the point here..I need to replace this junkyard 4.0 trans that's on its way out, so I found a cheap rebuilt 3.0 4x4 trans on eBay. I didn't know at the time it was a 3.0 version, as it was listed as a 2.9 m5od (sucked figuring that out when I got it delivered, but I should have known being it's as rare as that one is). Regardless it was pretty cheap and rebuilt, so oh well.

So I get around to cracking my old 2.9 M5OD open and totally disassemble the it, leaving an empty case. I took this time to degrease, pressure wash and remove the old black paint from it with a 1" wire brush and drill. Once reconditioned, I set that case to the side being it's ready to be built. So then, I get to opening the 3.0 transmission and see it's VERY new on the inside, literally no wear on much of anything, and I start disassembling that one too, to place all of it's internals into the older 2.9/4.0 case that's reconditioned.

Well I get it all apart. I have 2 fully disassembled transmissions laying in front of me and I start looking at and counting the gear teeth on the main shafts and also the countershafts. Here is where I come across something very odd! I'm counting the gearset teeth on the 2.9 transmission, and it lines up with what I read it should be, tooth count-wise. Then I get to counting the 3.0 case's gearset, and find out whoever rebuilt it, put a 4.0 gearset in it! Okay, but that may not be ideal for someone who planned to use it for a 3.0..considering it's supposed to have the shorter 1-3 gears.

So okay here's the big one. I'm counting the countershafts now..10+ times btw just to make sure what I'm seeing is true..and find out that the 2.9 transmission, had a 4.0 countershaft in it the entire time! Also, the 3.0 cased rebuilt transmission, which has 4.0 internals installed, was mated with a 2.9 countershaft?! What? In my mind that shouldn't really work should it? The two countershafts have different tooth counts obviously for 1-3 gears, but wouldn't you think the 2.9 gearset would only mesh and work correctly with the 2.9 countershaft? Same with the other, 4.0 gearset should only mesh and work correctly with a 4.0 countershaft??

I'm so confused, have called a few transmission shops and Ford shops, they are all confused on what to say. I explained that if I brought my trans to them, a 2.9 trans, and said my countershaft broke and needed to be replaced, they said they would order a 2.9 countershaft without even thinking twice about it. My mind just doesn't calculate this correctly, but regardless both gear sets ran and meshed perfectly together, even though neither technically had the correct countershaft installed for their gearsets.

So this leads to another question! People that have completed the low gear swap on the m5od, if you had a 4.0 set and did that swap, did you also change your countershaft to a 2.9 one? Or is it known knowledge that the 2.9 gearset will work fine with a 4.0 countershaft and vice versa? Someone please chime in on this, I know it's a huge post, but I have seen bigger and just need some opinions on this.

I had wanted to use the new 2.9 countershaft with my old 2.9 gearing, due to it being new, but the master ford tech I called for advice said even though that sounds like the right thing to do, to keep the 2.9 set matched with the 4.0 countershaft. It worked, didn't cause odd wear issues, none at all actually, and is actually a little bigger anyway. The largest gear on the 2.9 countershaft is slightly larger and almost 1/8" wider than the 4.0's. Of course this must mean, that the 2.9 trans mated with a 4.0 countershaft (which I'll remind everyone was originally in my vehicle for 2 years no problems at all) must have a slightly different gear ratio than a 2.9 set w/ 2.9 shaft OR a 4.0 set w/ 4.0 shaft, it must be a hybrid gear ratio between the two.

If someone could calculate the ratio of the 2.9 gearset/4.0 countershaft combination, that would be great. Please help guys! I can add pics later if needed as everything is still apart. This is a confusing one to me, just want to put the rest together so half of my living room isn't littered with transmission components. Thanks to anybody that attempts to help!
 



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RangerX

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Whew, that’s a pretty rare question! It might be better suited for the transmission section, and I’d be happy to move it there if you would like, but it works here too, so your call.
Also just to throw in a couple thoughts after reading it, although it’s all slightly above my knowledge as I’ve never seen the inside of a transmission lol, is it possible that ford (Mazda) used the same part (countershaft)in all three transmissions? Realize I don’t know what that part looks like. Also, have you considered buying the correct 2.9 countershaft?
 






94Sport5

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Whew, that’s a pretty rare question! It might be better suited for the transmission section, and I’d be happy to move it there if you would like, but it works here too, so your call.
Also just to throw in a couple thoughts after reading it, although it’s all slightly above my knowledge as I’ve never seen the inside of a transmission lol, is it possible that ford (Mazda) used the same part (countershaft)in all three transmissions? Realize I don’t know what that part looks like. Also, have you considered buying the correct 2.9 countershaft?
As a matter of fact this whole question began when I wanted to use the newer looking countershaft from the rebuilt trans I bought, but when I counted the teeth, that's when I started realizing some very odd things. The two countershafts are different part numbers, and state very specifically when you go online and buy either that the 2.9 shaft is for the 2.9 gearset and the 4.0 shaft is for the 4.0 gearset. The 4.0 shaft as I said is ever so slightly larger in some dimensions than the 2.9 shaft..but I was told that to be safe, use the gearsets/countershafts that were already meshing and working together. As for moving the thread, whichever you think will get the most attention is what I would like! Thank you for the reply! If you could tag people that are knowledgeable in this subject that would be great!
 






wankel1308

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As a matter of fact this whole question began when I wanted to use the newer looking countershaft from the rebuilt trans I bought, but when I counted the teeth, that's when I started realizing some very odd things. The two countershafts are different part numbers, and state very specifically when you go online and buy either that the 2.9 shaft is for the 2.9 gearset and the 4.0 shaft is for the 4.0 gearset. The 4.0 shaft as I said is ever so slightly larger in some dimensions than the 2.9 shaft..but I was told that to be safe, use the gearsets/countershafts that were already meshing and working together. As for moving the thread, whichever you think will get the most attention is what I would like! Thank you for the reply! If you could tag people that are knowledgeable in this subject that would be great!
You need to match the countershaft to the gearset. When I built mine I assumed it was a 4.0 gearset and cluster. So that's what I ordered. 3rd and a cluster for a 4.0. When I slapped it back together the assembly was incredibly tight and hard to spin. Come to find out I had the 2.3/2.9/3.0 gearset and the 4.0 parts did not play nice. Ordered 2.3/2.9/3.0 gear and counter, everything was peachy.

2.3/2.9/3.0 gears need to go with 2.3/2.9/3.0 counters. 4.0 gears go with 4.0 counters. The tooth count is not the same. You can put it all together... It won't spin right.

Here's the breakdown.... Ford Ranger Manual Transmissions – The Ranger Station
 






94Sport5

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You need to match the countershaft to the gearset. When I built mine I assumed it was a 4.0 gearset and cluster. So that's what I ordered. 3rd and a cluster for a 4.0. When I slapped it back together the assembly was incredibly tight and hard to spin. Come to find out I had the 2.3/2.9/3.0 gearset and the 4.0 parts did not play nice. Ordered 2.3/2.9/3.0 gear and counter, everything was peachy.

2.3/2.9/3.0 gears need to go with 2.3/2.9/3.0 counters. 4.0 gears go with 4.0 counters. The tooth count is not the same. You can put it all together... It won't spin right.

Here's the breakdown.... Ford Ranger Manual Transmissions – The Ranger Station
I'm pretty sure that you trying to put a 4.0 gearset's 3rd gear with a 2.3/2.9/3.0 gearset is what made it so tight. That gear differs by two teeth vs a one tooth difference on 1st and 2nd gear..Please read a bit more in my first post, because both of the transmissions I took apart had no funny wear at all, no tight assembly, spun easily, and we're actually running in vehicles..one for 1 year, the other for two years.
 






wankel1308

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You need to match the countershaft to the gearset. When I built mine I assumed it was a 4.0 gearset and cluster. So that's what I ordered. 3rd and a cluster for a 4.0. When I slapped it back together the assembly was incredibly tight and hard to spin. Come to find out I had the 2.3/2.9/3.0 gearset and the 4.0 parts did not play nice. Ordered 2.3/2.9/3.0 gear and counter, everything was peachy.

2.3/2.9/3.0 gears need to go with 2.3/2.9/3.0 counters. 4.0 gears go with 4.0 counters. The tooth count is not the same. You can put it all together... It won't spin right. That might explain the metallic goo when you drained the junkyard unit..... Surprised it lasted this long....

Here's the breakdown.... Ford Ranger Manual Transmissions – The Ranger Station
 






94Sport5

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You're still misunderstanding my post. I know it's confusing, but you have to pay attention to what I'm already saying. First of all the metallic goo that I drained never came out of either the 2.9 trans with the 4.0 countershaft, or 3.0 trans with 4.0 internals & 2.9 countershaft, it came out of the 4.0 junkyard transmission that has been in my explorer for 5 years and currently still is. It was in the very beginning, when I first drained and re-filled it after running it for a week that this happened.
 






wankel1308

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You're still misunderstanding my post. I know it's confusing, but you have to pay attention to what I'm already saying. First of all the metallic goo that I drained never came out of either the 2.9 trans with the 4.0 countershaft, or 3.0 trans with 4.0 internals & 2.9 countershaft, it came out of the 4.0 junkyard transmission that has been in my explorer for 5 years and currently still is. It was in the very beginning, when I first drained and re-filled it after running it for a week that this happened.
Good luck with y
I'm pretty sure that you trying to put a 4.0 gearset's 3rd gear with a 2.3/2.9/3.0 gearset is what made it so tight. That gear differs by two teeth vs a one tooth difference on 1st and 2nd gear..Please read a bit more in my first post, because both of the transmissions I took apart had no funny wear at all, no tight assembly, spun easily, and we're actually running in vehicles..one for 1 year, the other for two years.
Could very well be. It didn't work for me. Your mileage may vary.... Good luck finding your information.
 






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