M5R2 (M5OD-R2) Rebuild Deep Dive | Page 3 | Ford Explorer Forums

  • Register Today It's free!

M5R2 (M5OD-R2) Rebuild Deep Dive

Okay I was all wrong for the output shaft bearing, it's actually super easy. When you remove the snap ring from the third gear side, the 3/4 synchro assembly, third gear, and needle bearings all just lift off. Then you can rest the back of second gear on the cradle of a press, and press on the first gear/output side of the shaft. This effectively pushes the shaft through the first and second gears, the 1/2 synchro assembly, and the output shaft bearing. I'll make a point to take pictures when I do the 2wd.

I got the countershaft front bearing race off too. I really snugged the separator down and just kept cranking. It got a little nerve wracking, but eventually the race "popped" and it came off easily from there.

Now it's time to clean the shafts, gears, and sliders. Then I can start reassembly with fresh brass rings and bearings. I think that should all go pretty smoothly as long as I don't get anything mixed up.

The only other tricky disassembly I have to do is for the shift tower to get the 1/2 and 3/4 rails free so I can swap the 1/2 fork. That'll deserve it's own section.
 



Join the Elite Explorers for $20 each year or try it out for $5 a month.

Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.





You've got me curious. I looked for a drawing or diagram of one and came up with an 18 page PDF document. M5R2 diagrams
M5R2.PNG
 






Yes, that looks like the one I found too. Lots of good info in there!
 






Got new races onto the countershaft and the bearing pressed onto the new input shaft. Then I started working on the output shaft and ran into something that made me pause.

The second gear and 2 side of the 1/2 synchro assembly are totally different between the 1997 output shaft assembly that came out of my transmission and the 1999 output shaft assembly that I grabbed from the salvage yard. The 1997 parts are pretty simple, just one brass synchro ring and symmetrical teeth on the gear.
1000003851.jpg


But the 1999 parts have two brass rings and a steel ring between them (they all nest between the gear and synchro hub) and they engage second gear differently than the 1997 setup. Also, the 1999 second gear has asymmetrical teeth, basically a mirror of the third gear teeth.
1000003850.jpg


I've never read about this later-revision second gear and synchro setup. Both second gears have the same tooth count, so I think the overall output shaft assembly is interchangeable. Unfortunately, my rebuild kit doesn't include the parts to replace the brass rings in the later assembly.

Since the 1999 parts are in so much better shape, I think I'm going to use them, even though I'll have to run with the used brass rings. I don't think a new brass ring in the 1997 assembly will help much because the gear teeth and synchro slider teeth that would engage it are all chewed up. I'm also hoping there was a good reason why Ford/Mazda switched to a more complex and surely higher-cost design, and I get better shifting as a result of it.

It'll be interesting to see which setup is in my 1998 2wd transmission when I dive into that next!
 






Sure enough, there's a different synchro ring kit for later transmissions.
It's out of stock though, so I'm sticking with my previous decision to forge ahead with used second gear synchro rings.
 






So now that you are inside th slush box maybe you can help me understand my synchro issue
In my sport trax, no idea what year the m5od-r2 is or how many miles
Sucker shifts great until it gets warm… after a highway run shifting into third gear gets grindy… it gets worse and worse until basically I cannot downshift into third because it just grinds. I can force past the grinding… but after a few years of this it’s getting worse

Is this a synchro issue you think?

Keep up the good work! I have two of these transmissions right now for my own personal al use… with my luck I grabbed the one with the 3rd gear grind hahahaha
Any way to tell what year they came from just by looking at them?
 






That does sound like a synchro issue, at least in part. Something probably getting hot and causing part(s) of the 3/4 synchro assembly not to move the way it should.

Since the 3/4 synchro moves between the last gear of the main shaft (third) and the only gear on the input shaft (fourth), there's a lot going on there. There's a caged roller bearing that runs on the front of the main shaft and inside of the back of the input shaft. There's a thrust bearing there too. If the input shaft front bearing is worn (they usually are), there'd be more load transfered to that roller bearing. My guess would be that it's building up heat, things are expanding, and clearances are getting too tight as you try to slide off of fourth gear and into third.

But it's probably a combination of things. I think that 3/4 synchro is especially prone to wear since it slides between gears that aren't on the same shaft. That roller bearing should keep things concentric, but as parts wear, I'm sure things get sloppy and start to move in ways that they're not meant to.

That said, I know very little about transmissions and I'm not a mechanic. Just my best guess after staring at parts for hours haha.
 






Pressed on the output shaft bearing.
1000003853.jpg

I've been able to do all the bearings with just two pieces of sch. 40 PVC and the old races.

1000003854.jpg

Third gear, the 3/4 synchro assembly, and the thrust bearing get held in by a snap ring.

Then put on the roller bearing that @410Fortune likely cooked in his 'trac.
1000003855.jpg


And drop it all into the case. Don't forget to slip on the 4th gear brass ring first (I did...oops).
1000003856.jpg


Then you can wrestle things around to get the shafts where they need to be as you slide in the front and rear/mid bearings and races. This took some patience and finesse.
1000003857.jpg
Then reinstall the plate over the rear/mid bearings to hold them in.

The front plate will come later.
 






I got all the 5th/reverse countershaft components together. Just followed what the manual says.
1000003884.jpg

1000003886.jpg

Not staked yet though.

Manual says add sealant to the 5/R shift rail retaining bolt, so I did even though the bolt had none from the factory.
1000003875.jpg


The oil tray bolt gets some sealant too.
 






Examples of worn gears and synchro rings.

Old 5th
1000003871.jpg


New 5th
1000003873.jpg

Note the crisp edges on the ramped teeth for the synchronizer. Those are what wear out, not the actual gear teeth that mesh between the shafts.

Old synchro
1000003879.jpg

1000003880.jpg

The teeth look worn on this one, but most of the rings didn't look as bad. The grooves on the inside have worn from peaks into plateaus over time though, and I believe that's what leads to the hesitant, notchy shifting (or grinding if you try to push through it).

New synchro
1000003881.jpg

1000003882.jpg

Nice and crisp all around.

Old reverse teeth are absolutely gone
1000003878.jpg


New reverse
1000003877.jpg
 






Measuring for input shaft shim. Follow the manual as best as you can.

Case must be upright
1000003887.jpg


Measure race protrusion
1000003888.jpg

I took four measurements around the race and averaged. A depth micrometer would be a far superior measurement tool for this, but I don't have one. I took my time with the caliper and checked each measurement at least three times.

Measure cover bearing pocket depth
1000003889.jpg


Then follow the equation in the service manual to figure out what shim thickness you need to get the recommended 0.002-0.006" clearance. You remember algebra, right?

Mine did need the thinnest shim in the shim kit to get into spec.

The countershaft front bearing clearance measurement follows the same process. I measured mine and it's actually a little too tight compared to the 0.006-0.010" spec. Since I didn't change the countershaft (unlike the input shaft), I just lightly sanded the old spacer and will run it as is. They don't sell shim kits for it, so I don't have anything available to do otherwise.

Then I got confused on which way the input shaft spacer, shim and seal go on top of the input shaft bearing. Good thing I have my 2wd to take apart and check. Except I cracked the cover pulling it off...thought I backed all six bolts out, but one was hanging on. I guess I'll be making another trip to the salvage yard tomorrow. I sure hope the cover from that 4.6 trans I pulled is still laying there -- I really don't want to pull another transmission!
 






Kits are here!
View attachment 466633
Nice stuff. The same Japanese NSK and Nachi bearings as what Mazda originally used, SKF seals, freshly machined synchro rings, and new locknuts. Also the new reverse gear and slider. The price tag hurt, but you get what you pay for...and you don't want to pull transmissions more often than you need to.

It's about time to get rebuilding!

My father used to sell Nachi bearings to the OEMs.:chug:
 






I went back and checked my fifth gear clearance to the split washers. One of the split washers barely fit in and the other slid in easily, but I couldn't slip a piece of paper in between it and the gear. The spec is 0.000-0.002", so it seems good.

Then I checked clearance between the new reverse gear and the thrust washer.
1000003892.jpg

I measured 0.022" and the spec is 0.010-0.014". That's not ideal. I put the old reverse gear on and measured the clearance at 0.016". Obviously I'm not going to run the trashed old gear just because it's thicker, but I'm not sure what to do. The manual says you can get a thicker thrust washer, but that won't change the clearance because the washer is already bottomed against a shoulder on the shaft.

I guess I need to make a 0.010" washer with an ID that fits over the shoulder of the shaft. That way the clearance between the gear and thrust washer would be cut down to 0.012". But I'm not sure what'd actually be worse: a sloppy reverse gear or a shim that might fall apart and leave bits of steel in the transmission. I guess the only time the countershaft reverse gear sees any kind of side load is during the shift itself as the synchro teeth bump their way into place, and the countershaft is ideally not turning at that time. So maybe the shim won't actually be under much stress?
 






Very interesting stuff and great pics!! Thank you
 






No problem! Hopefully all of this helps someone someday. I've been asking myself a lot of questions, but I'm slowly figuring things out. I am going to make a washer/shim for the reverse gear out of some stainless shim stock. The stock is cheap and it'll be good to keep around.
 






Shim stock is on the way! In the meantime, I'll get my 1-2 shift fork replaced.

But this afternoon I went back to the salvage yard to grab the front bearing cover to replace the one I cracked. Thankfully, it was right where I left it. I grabbed some other M5R2 bits I had left behind too.

I also made a point to check the new arrivals and got an AC line I need for my V8 swap from a 2000 mountaineer. But what's cooler is I found a dual shift boot in an '89 Ranger.
1000003895.jpg

This 2.9L Ranger must have had the Mitsubishi trans, not the Mazda because the shifter base is further back than what's in my rigs. But in a M5R2/BW4406M swap, you could just move the whole bezel forward and not have to stagger the tcase shift lever so much (like I did in my '99 Mounty). For $3.30, it's my best bargain in a while.
 






Featured Content

Back
Top