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Member
- Joined
- May 28, 2017
- Messages
- 5
- Vehicle Year
- 1994
- Transmission
- Manual
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 4.0 countershaft is slightly larger and almost 1/8" wider than the 2.9'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!
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 4.0 countershaft is slightly larger and almost 1/8" wider than the 2.9'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!
I only know transmissions at the animation and cut-away level, i.e. never had one fully apart on the bench, BUT... as Shran said, HOW would things MESH? Even with a 2 tooth difference, either the DIAMETER is going to be off, or the tooth PITCH and/or DEPTH is going to be off, either way, it seems the opposite of meshing would occur, i.e. NOISY lock-up, followed by sheared teeth, before you even got out of neutral. 
