91 Mazda Navaho w/ 4.0, M5OD, BW 13-54 (electronic shift).

Tranny locked up due to lube leak - on disassembly, front input shaft bearing had puked it's rollers and eaten up inner and outer race. I've got all the stuff back of the bulkhead pulled, and have the mainshaft loose, but I don't have a manual (well, I have a Haynes, but that's not really a manual - all I have on the tranny innards is just a schematic), and can't figure out how or where the input shaft separates from the mainshaft - any help out there? Also, how is rear mainshsaft bearing removed from shaft (there's about 2mm of slop in the bearing - almost went the way the front did)?

Thanks in advance....

 

Hi thefasteddy and welcome to FTE

The input shaft seperates from the mainshaft right behind the very front gear which is on the input shaft. It is the gear that drives the countershaft.
After you have 5th and reverse off you can see the output shaft rear bearing. It takes a long puller to remove it. After it is removed from the back of the transmission there is a plate that holds the rear main and countershaft bearings into the case. Remove that and you can then remove the rear countershaft race. Remove the cover off the front of the transmission and then you can remove the front countershaft bearing race allowing the countershaft to drop a bit into the case. Then you pull the input shaft as far into the bellhousing as you can which will allow you to remove the input bearing race. This makes enough room to tilt the mainshaft down in the back and remove it up through the case. After the mainshaft is out you can remove the input shaft.
Be careful with the shims in behind the front cover and in the back of the transmission too. Make sure to keep them where they belong.
Let me know of this helps or if you need more info. It's been a while since I've had one apart but a few years ago it seemed like I was doing 2 a week for while.

 

Thanks for the welcome!

I've got all the stuff off you list, but the input shaft won't come off the mainshaft. I suspect a fried shaft bearing buried down in the guts of the mainshaft/input shaft. Does the mainshaft separate behind or ahead of the syncro engagement partial ring on the gear on the input shaft, or behind it? Schematic is not clear. All bulkhead mounted bearings are loose - countershaft bearings are out, destroyed front bearing on mainshaft and race are out, and outer race on rear mainshaft bearing is out.

 

It does sound like maybe the input shaft "pocket" bearing is welded to the mainshaft
The input shaft seperates from the main shaft in between the front synchro ring and the synchro hub.

 

Well I guess I'm going to cut off the input shaft - the gear is nicked up anyway - and see if there's clearance to get the mainshaft out. Thanks for the help! Nice folks on this board....

 

Let us know how you make out.

 

When stuck, go to the pros.

Southern Gear (South Atlanta Road, Smyrna, GA) whanged off my input shaft, microscoped the teeth on and rejected my cluster gear/countershaft, polished the front boss on my mainshaft (and saved it), installed my previously purchased rebuild kit parts on the mainshaft, and the races and bearings on everything new (input shaft and cluster gear), all for the princely sum of $225 for complete rebuild kit and rear bearing retainer plate, plus $220 for the input shaft and cluster gear. I took the bench guy about 20min to do it all, including roughness test on mainshaft front boss, microknurling and truing the boss, and polishing the renewed boss on the lathe. He had 7 other M5OD's skitting there on the floor, and another he pushed out of the way while he did mine while I waited. VERY nice folks, work, and prices. They do any manual transmission, any transfer case, and sell aftermarket drivetrain parts.

Thanks for the very useful advice, and I'm off to stuff it back together and hoist it back into the Cave of Strain.

 

Sounds like a good place to deal with

 

take the top cover off transmission, and tail extension housing. once you can see inside you want to turn input shaft so the flat spots are horizontal then pull out input shaft by angling it horizontal and out. youtube m5od rebuild. I got a kit for 161.00 bearings and synchs. you can get a kit includes same plus input shaft and counter shaft for 316.00