M5od-r1 tranny synchro key popped out of place

[PrattRanger96]

Has anyone ever had a synchro slider key pop out of place?
Mine did on the third-fourth gear slider causing it to be locked into fourth gear

 

[PlumCrazy]

Sometimes when a trans is locked in 4th its an indication that the input bearing has failed and the input and output shafts have welded themselves into one.

Is it stuck in just forth, or can you shift into another gear at the same time?

-PlumCrazy

 

[PrattRanger96]

I was able to slide the synchro ring back into neutral
By using the key down with a screwdriver.
It goes into third and neutral but not back into fourth.
At least it's drivable but I'm afraid to put it into fourth
because it will probably get stuck there again.
I think I'm due for a rebuild.

 

[PlumCrazy]

It may just need a top cover with all the shift rails and forks. It may have a bent or worn fork.

-PlumCrazy

 

[PlumCrazy]

You can pull the top cover and inspect everything without having to buy a gasket since it uses a reusable oring type gasket, but the tranny has to pulled to get it off.

-PlumCrazy

 

[PrattRanger96]

I already had it off without pulling the tranny, because it has a four inch body lift kit. I had to set aside the 4 high 4 low linkage. It came right up out of the floorboard. Pretty convenient! Anyway, thats how I was able to to see the synchro key popped out of place.

 

[PlumCrazy]

Oooo. I didn't know you could actually see the issue.lol. I though you were making an educated guess.

-PlumCrazy

 

[tx3nc]

The problem could be the inner hub of the syncro slider assembly (the part the key came out of) is stuck, sticking or seized on the main shaft. That hub needs to slide freely on the shaft to allow the synchro assembly to work properly. Do you experience any gear clash going into 3rd or 4th? There is a LOT of heat generated on the front end of the main shaft. When I rebuilt mine, the 3rd/4th shifter hub was stuck on the shaft. There was a little crunch sometimes going into third. When I reassembled it, 3rd wouldn't synch at all. A new output shaft and synchro ring/hub assembly solved that problem. I might not have needed both those parts, but I damn sure didn't want to take the trans out a 4th time. (Like I just did today because the kid burned up the clutch after just 8,000 miles )

 

[adsm08]

I've never had the key pop out except during a rebuild.

 

[tx3nc]

I've never had the key pop out except during a rebuild.

Me neither. But if you think about how it popped out during the rebuild... For me it's always been because I overextended the outer ring from the centerline of the inner hub. One way that could happen inside the transmission is if the inner hub is stuck at one extreme of travel and the outter ring is moved in the opposite direction to engage the other gear.

I guess if the transmission overheated it could cause the spring to relax and fall out which would also allow the key to fall out.