Need help to remove 5th gear from M5OD-R1

Maybe I'm getting too far ahead of myself with my self diagnosis. So let me start from the beginning. I've got my '93 4.0L ranger transmission (M5OD-R1) sitting on my workbench. Recently an unknown problem developed which resulted in the 5th gear malfunctioning. When in the 5th gear position the transmission acts as if it is in neutral (clutch engaged, of course). There is no sound that is produced that is different from when the transmission is in neutral The onset to the problem was the transmission "hiccuping" going in an out of 5th gear (this caused the truck to jerk several times with engine RPM jumping and falling). I recall it only acting up in this way about 4 times before 5th completely stopped working. All other gears (1-4+R) all work flawlessly and quietly.

Dissassembly observations: I removed the transmission from the truck, drained the gear oil and removed the top cover. No broken metal was found in the gearbox and all of the main gears were looking fine with light wear and no missing teeth.

5th gear inspection: Dog teeth look fine on the layshaft (I cant see inside the collar with out removal so that is still unknown. Then I moved the 5th and Reverse collar to engage 5th gear and the output shaft turns with the input shaft. This is opposite of how it acted in the truck. Then I though it might be associated with a warn out shifter so I put the cover back on and the shifter and the tranny is operating correctly.

Further inspection: Removed the tailshaft housing (4x4 model0 and everything still look great. I removed one of the plastic covers inside the tailshaft housing and I found lots of little black plastic pieces about 1/16" thick. What could this be? Maybe a shim that got chewed up and caused the collar not to engage 5th gear. But then, why would the transmission work when out of the truck. I need some help. Thanks.

last question: To inspect the 5th/Reverse collar I need to dissasemble the back of the tranny. How do I get the 2 blasted gear nuts off the two shafts in the tail housing? Should I lock the transmission into 1st and 3rd gear and put a pipe wrench on it? Will this damage anything?

All and any help is appreciated

i had a simialr problem with 2nd gear, i ordered a rebuilt from a auto recycler and replaced it, couldnt find much wrong with my old one other than the first gear inside the trans on the input shaft looked oil-starved (and the trans was low on oil when i bought it, shift rail plug issue) i suspect the plastic you found may have been the shifter bushings, was your shifter slopply? mine was though i never found the plastic bits. i fixed my shifter with a call to jegs, a little overkill bu works really nice not cheap, but durable and better i wish my trans problem would have been losing 5th, id have drove it to its grave as a 4-speed rather then spend 1,100 bucks and a cold winter weekend changing it out in a unheated drafty barn. dont have any other ideas, somewhere there is a detailed trans dissassembly plan, maybe a tech article or in the tech library. here, try this: http://www.therangerstation.com/tech_library/MazdaTransDissasembly.htm
________
Cruise-O-Matic

racsan said:

i had a simialr problem with 2nd gear, i ordered a rebuilt from a auto recycler and replaced it, couldnt find much wrong with my old one other than the first gear inside the trans on the input shaft looked oil-starved (and the trans was low on oil when i bought it, shift rail plug issue) i suspect the plastic you found may have been the shifter bushings, was your shifter slopply? mine was though i never found the plastic bits. i fixed my shifter with a call to jegs, a little overkill bu works really nice not cheap, but durable and better

i wish my trans problem would have been losing 5th, id have drove it to its grave as a 4-speed rather then spend 1,100 bucks and a cold winter weekend changing it out in a unheated drafty barn. dont have any other ideas, somewhere there is a detailed trans dissassembly plan, maybe a tech article or in the tech library. here, try this: http://www.therangerstation.com/tech_library/MazdaTransDissasembly.htm

Click to expand...

My shifter was a little sloppy and I now that you mentioned it I did find some broken rubber/plastic pieces near the ball pivot. I don't think this would have caused the transmission to not fully engage 5th gear. I did notice an unusual star nut on the 5th/reverse lever. Is this an adjustment? I like your shifter by the way. I've got a 2000 Trans Am with a really nice Hurst Pro Billet shifter and that thing is rock solid!

im not sure what that is, if it worked before and doesnt now, theres got to be something more "wrong" than just a adjustment. i dont think the missing bushing in the shifter would cause it either, i had no bushings when i took mine apart and it still would shift all gears, it just was a sloppy feel.
________
buy easy vape vaporizer

racsan, thanks for your help; here and over on RPS. I'm getting ready to take the transmission apart to check out the 5th/Reverse slider collar. It is the only thing that I can't see that could possibly be causing the problem. Even though it is acting correctly on the workbench, I'd hate to reinstall it only to have the same problem. I found these diagrams over at drivetrain.com. It doesn't look like there are any spacers or shims that could have worn out. If its not the slider then I have no what else it could be. Has anybody bought the shifter bushing kit? From the diagram about it looks like I'd need (2x)109 and (2x)106.

Check your shift fork to make sure it's not broken.

Alright, I think I've figured it out and I believe the countershaft 5th gear is broken. The dog teeth part of the gear have separated from main part of the gear. I still haven't gotten the nut off of the back of the mainshaft but I did turn the dog-teeth of 5th gear and the main part of the gear didn't turn. There was enough friction between the two that everything seemed to be working correctly but in reality when the slider collar engage the dog teeth the dog teeth would not turn the gear (with the applied torque coming from the tail tailshaft; backwards)

I don't see it in the diagram but sometimes the dog teeth are connected with the main gear with some steel keys. Could it be that the keys have sheared in mine (if it has keys of course)?

Tranny is apart! Looks like the weld broke between the countershaft 5th gear and its dog gear. The gears look good. I know it not a typical weld but does anybody repair these? Its lookin' like $100 for a new gear and $30 for the 5th gear bearing and $15 for the two nuts that I destroyed :banghead:.

Technically you are supposed to replace the nuts anyway.

I've seen the doog teeth broken off the gear twice on third gear.
I've never seen it done to 5th.

AD

And I wouldn't suggest welding a hardened gear or it won't be hard for long.

Just buy a new (or used but good!) 5th/counter-5th pair. Your favorite local transmission rebuilder should have a shelf full. Or you can buy new ones from an online source such as Phoenix Hard Parts (though I really would suggest a careful inspection prior to purchasing, which doesn't work by mail order).

The effect of welding on the heat treating is the least of the worries.

As a practical matter it's impossible to get the parts that have torn loose from each other parallel, concentric and "Square" to one another without the factory welding jigs.


Typically when 3rd breaks like that the two pieces will "Friction weld" themselves back together, but the synchro dog teeth are invariably "crooked" relative to the gear.
making it difficult to get into gear and prone to hopping out.

and making a nasty noise in any gear OTHER than that gear.

AD

Advice taken so I'm looking for a new gear. How do y'all feel about the prices that I found from drivetrain.com? Are there any cheaper alternatives for the same quality part? Also, I found that there is an 'updated' 5th gear available. Does anybody have any info on the 'updated' version of this gear and what else is required to make it work? I appreciate all the help so far.

The updated version might be the one you require.

Count the number of synchro dog teeth on your gear.
Your gear should have 30dog teeth, that IS the "updated" gear, the earlier 5th gear has 36teeth and it isn't compatible with your synchro assembly or reverse gear.

Unless they Updaed it AGAIN for the current production carbon faced synchro rings that they adopted ~2002

AD

Allan, thanks to you and all others for the great input! My gear does have the 30 teeth you described. I found a transmission rebuilder that will sell me a lightly used gear for $40 and I'm checking with him on ordering some of the other parts for the transmission like shifter bushings, the three metal plugs, and the main/countershaft nuts.

Before I order this stuff, I want to know if there is anything else that I should consider doing while the transmission is apart? I read through the tech library writeup and found out about the three plugs so I'll be fixing that problem. All of the brass syncros look great but I did notice that there is more play with the input shaft than with the output shaft. I know the input shaft is supposed to be 'centered' by the pilot bearing on the crank centerling so how much input shaft play is allowable with regards to front bearing, the one just behind the slave cylinder?

I've got this exact problem on my '97, lost it in the exact same manner and it's been a "4 speed" now for over a year. I'd like to get 5th working again in it for the obvious economy reasons.

How did you make out finishing up your rebuild, squealingtires? I'm debating rebuilding mine on my own...