Diagnosing finicky shifting

[Thew]

Howdy,

New to TRS, will do an intro post with pics of the project soon. Been using the site/forum as a major resource throughout the build/repair process.

Truck is a new to me (april), 1994 xlt 4x4, 3.0 5spd, 260k original motor and trans (to my knowledge). It was in a million pieces from april through august while I picked off various tasks and cleaned 30 years of grime

Shifting has been a bit temperamental, not atrocious, but leaves some to be desired. Bit clunky to shift into 2 & 3, sometimes accompanied by slight grinding when it engages, double clutching and feathering gas helps. Basically refuses to go into first if its rolling, or sometimes "engages" but then pops out. Reverse can take several tries, even when stopped, does similar fake engage and pop out like 1st. Shifts fine with engine off.

Changed the fluid ~300-400 miles ago, old fluid with pretty dark with some signs of wear but no big chunks. Bled clutch w/ vacuum pump 50 miles ago, didn't pull too much air out, but the old fluid was pretty dirty. Did a shifter rebuild/changed the bushings. I can pull the clutch pedal up towards me a few inches (not sure if this is normal or signs of a faulty master).

The problems persist, so I looking for some advice from those more knowledgeable and acquainted with quirks of the M50D.

Is it just the wear on the synchros? Failing master? quirks of the trans itself?

any input is much appreciated

 

[franklin2]

Sounds like it is wore out. The only thing you might do is go to Walmart and get some synthetic gear oil. If it's possible for your transmission to shift smooth, this oil will do it. or possibly you used that type already. If you used regular gear oil I would try it. It's not cheap though. Walmart sells the Valvoline Flex fill full synthetic 75w-90 for about $15.48. Two of these would probably do it.

Another check you can do, get the truck and trans fully warmed up from a drive, and then sit in the driveway in neutral, clutch out, engine running. Push the clutch in and wait a couple of seconds, and try reverse. if it scrapes, wait a little longer and try it. If it never goes in no matter how long you wait without scraping in reverse, you might have clutch problems.

 

[Thew]

Sounds like it is wore out. The only thing you might do is go to Walmart and get some synthetic gear oil. If it's possible for your transmission to shift smooth, this oil will do it. or possibly you used that type already. If you used regular gear oil I would try it. It's not cheap though. Walmart sells the Valvoline Flex fill full synthetic 75w-90 for about $15.48. Two of these would probably do it.

Another check you can do, get the truck and trans fully warmed up from a drive, and then sit in the driveway in neutral, clutch out, engine running. Push the clutch in and wait a couple of seconds, and try reverse. if it scrapes, wait a little longer and try it. If it never goes in no matter how long you wait without scraping in reverse, you might have clutch problems.

I put mercon V in it when I changed it, was debating synchromesh or synchromax after hearing some reports of it helping on other forums but hadn't pulled the trigger on it yet.

It does shift into reverse, just sometimes it takes a couple tries, sometimes it does it first try, haven't figured out any consistent circumstances for either yet.

 

[scotts90ranger]

It should have Dex/Merc not dex V, I've heard about that causing hard shifts...

I've never had an M5OD that was hard to shift or popped out of gear but if it does any of that it's likely worn shift forks or something

 

[Shran]

Popping out of gear is only caused by a couple of things - something is bent or worn and it's not completely engaging the gear, then under load it gets pushed out. Shift forks usually. Can also be really sloppy bearing(s) making the gear train shift up/down/side to side under load. It COULD also be the shifter stub being really worn... is it still really sloppy after new bushings or does it feel pretty tight?

I like using thicker engine oil like 10w-40 in worn out M5OD's that grind in between shifts and that might help with your 2-3 issue but I don't think any oil will help with the bigger problem of it popping out of gear - to me that would almost certainly call for a teardown unless it's the shifter stub.

 

[Thew]

It should have Dex/Merc not dex V, I've heard about that causing hard shifts...

I've never had an M5OD that was hard to shift or popped out of gear but if it does any of that it's likely worn shift forks or something

I'll likely switch it to something thicker then

Popping out of gear is only caused by a couple of things - something is bent or worn and it's not completely engaging the gear, then under load it gets pushed out. Shift forks usually. Can also be really sloppy bearing(s) making the gear train shift up/down/side to side under load. It COULD also be the shifter stub being really worn... is it still really sloppy after new bushings or does it feel pretty tight?

I like using thicker engine oil like 10w-40 in worn out M5OD's that grind in between shifts and that might help with your 2-3 issue but I don't think any oil will help with the bigger problem of it popping out of gear - to me that would almost certainly call for a teardown unless it's the shifter stub.

It's pretty loose shifting. doesn't pop out of gear often, more of a kinda fake engage into first, only happens while rolling, where as soon as i apply gas it pops out. Could I have reinstalled the shifter stub incorrectly (ie, not fully seated)? I did do the bushing replacement with it in gear accidentally and had to slide things back into place to put the stub back.

 

[Shran]

The stub only goes in one way, if you get it backwards then the rest of the shifter won't be oriented in the right direction.

Did you replace those two little pins that keep the stub oriented? If those are worn, that can make it pretty sloppy. Maybe see if you can round up a junkyard stub to troubleshoot. Try to stay with like 94 or older, sometime in the 90's the stub length changed and they're not interchangeable.

 

[Thew]

good to know, it's in right then

Did you replace those two little pins that keep the stub oriented? If those are worn, that can make it pretty sloppy. Maybe see if you can round up a junkyard stub to troubleshoot. Try to stay with like 94 or older, sometime in the 90's the stub length changed and they're not interchangeable.

i did replace them, used a dorman shifter repair kit that had bushings, pins, and the top seal plus its screws. Seems like i can get a new stub plus all the bushings and pins for about the same price as the stub alone. I probably do that plus some thicker lube. Hard for me to get to a junkyard with a 9-5 and them all being 40 minutes away

 

[franklin2]

Listen to the other guys, I forgot your trans takes auto trans fluid.

If it finally goes into reverse without having to force it, the clutch is probably releasing ok.