M5OD-R1 usually pops out of 5th

[TheAbstracted]

So I bought a rebuilt M5OD-R1 for my '88 2.3, and it's a lot better than my old one - except that it refuses to stay in 5th, at least most of the time. Sometimes it will stay on the first try, but usually it'll pop out 3, 4, 5 times or more before it stays. I've been trying to research why it would do this, but every answer I've seen pop up seems to relate to it never staying versus usually not. I think maybe I might have messed up the shifter mechanism because it was really difficult to get the stick onto it and I was really banging on that sucker, but I really wouldn't know if that would have anything to do with it, transmissions are not my forte. I did see one answer saying the shift fork for 5th can be adjusted by a star nut on the outside of the transmission, but even though my old one has that and I could see what it was doing while I turned it, my new one just tightens and loosens that same nut instead of it adjusting anything. Don't know, I do have a warranty on this if all else fails but I'm really hoping this is something I can fix myself without too much trouble, as it was a royal PITA to get my old one out and this one in by myself, which is what would be happening again if I need to do that.

 

[SenorNoob]

Can you get pics with the shifter out? Might give somebody something to work with. IDK?

 

[Shran]

Popping out of gear means that gear is not fully engaged or something is worn so bad (bearings, etc) that it's causing other things to move around.

Did your new transmission come with a shifter stub installed already? Is that the part you were hammering on or are you talking about the longer/upper part of the shifter?

IMO you are probably looking at a 95% chance that it was assembled incorrectly or assembled with worn out parts. There is a small chance that the adjustment eccentric star nut will do the trick. I don't remember ever needing to mess with that when I worked on one of these. I do remember finding worn out 5th/reverse shift forks and it's possible that the 5th/rev slider ring got installed backwards. It's possible that the top cover is bunged up somehow. I think I would suggest taking advantage of the warranty right now rather than trying to fix it.

 

[gw33gp]

I have been fighting this through 3 rebuilt transmissions and 1 refurbished one. Each time except for the refurbished replacement, it was a worn 5th gear cluster. It started when I had my original transmission rebuilt. It was working properly but they said my reverse/5th gear cluster and slider were warn and needed replacement. A year later it started popping out of 5th gear. They replaced the 5th gear cluster under warranty. It worked again for a year and started popping out of 5th again.

I then ordered a refurbished transmission from Zumbrota. I also had the 5th gear cluster replaced for the 3rd time in the original transmission to have as a backup. The Zumbrota transmission also only lasted one year and was replaced under warranty. So far, the Zumbrota replacement it has held up for nearly 2 years without failure.

The failures have been blamed on lower quality aftermarket gears. On the last 5th gear cluster replacement on the original transmission, I had the gear and slider cryo-treated to see if that would help. It also lasted about a year and failed.

I hope you don't run into the same issue. I wish I could give you a solution to the problem but right now I am just driving in 4th gear. I would put the last Zumbrota transmission back in but am tired of changing transmissions. someday i will get around to it.

 

[Roert42]

I have been fighting this through 3 rebuilt transmissions and 1 refurbished one. Each time except for the refurbished replacement, it was a worn 5th gear cluster. It started when I had my original transmission rebuilt. It was working properly but they said my reverse/5th gear cluster and slider were warn and needed replacement. A year later it started popping out of 5th gear. They replaced the 5th gear cluster under warranty. It worked again for a year and started popping out of 5th again.

I then ordered a refurbished transmission from Zumbrota. I also had the 5th gear cluster replaced for the 3rd time in the original transmission to have as a backup. The Zumbrota transmission also only lasted one year and was replaced under warranty. So far, the Zumbrota replacement it has held up for nearly 2 years without failure.

The failures have been blamed on lower quality aftermarket gears. On the last 5th gear cluster replacement on the original transmission, I had the gear and slider cryo-treated to see if that would help. It also lasted about a year and failed.

I hope you don't run into the same issue. I wish I could give you a solution to the problem but right now I am just driving in 4th gear. I would put the last Zumbrota transmission back in but am tired of changing transmissions. someday i will get around to it.

Can you change the 5/R cluster with the transmission in the truck?
I helped my brother rebuild his a few weeks ago and it looked like you could do everything needed by just removing the tail housing.

It's interesting to hear about the issues you've had with the aftermarket gears. The engagement gears on my brothers R had the points worn off, but we reused them because we didn't want to wait for a replacement set. Maybe it's better we left the originals in there.