Odd manual transmission problem

[BWDuty]

I've just experienced something new to me, and I'm hoping for some insight from some more experienced mechanics.

Brief backstory -- I replaced my clutch, pressure plate, pilot bearing, flywheel, slave cylinder and throwout bearing (and rear main seal and most of the seals in the tranny since I already had it dropped, I don't like to half-ass stuff) about three or four months ago. Everything has been perfectly fine since. I gravity bled the slave cylinder. I know the check valve on the end of the line from the master cylinder holds in the fluid, but I still checked the fluid level after a test drive and again after a few hundred miles.

I had completely smoked the clutch by pulling a Durango that wouldn't go into neutral fully.. basically pulled a 6400 pound vehicle while it was still half in gear for about five miles. My bad, yeah it was stupid, especially since I was still on my original clutch.

I've driven it thousands of miles since I replaced the clutch system and everything has been great. Now today I jump in to go to Taco Bell and it doesn't want to go into reverse. Finally get it in with some grinding. The whole way there it was *very* difficult to shift gears. The pedal seemed too spongy as well. The clutch did seem to be properly engaging once it was in gear. I could idle with it in gear and the clutch depressed. No slipping either.

It actually died on me twice while I was fighting to get into first.

After the second time it died and I started it back up, everything was perfect again. I'm not one to let something like this slide, something was obviously wrong.

I checked the fluid as soon as I got home and it was still completely full. My first guess was, of course, air in the hydraulic system. However, with the system still being completely full and not having any problems for thousands of miles, this seems strange. If air was trapped in there wouldn't I have problems before now? Nearly all of my driving consists of constant clutch usage. I'm thinking I should pull the master cylinder and replace it with a new one which I already have after bench bleeding it (bought it just in case before my clutch replacement and didn't use it). It actually surprised me when I found that there is NO leak from the master or slave cylinder as that seemed like such an obvious cause.

What could have possibly caused this? The clutch had to be ALL the way to the floor to shift, and even then it just would NOT go into gear or a couple times would just grind like crazy. Then after restarting the vehicle the second time it was perfect.

If I had a newer vehicle I'd think it was something with the computer/electronics, but being a 2000 that seems less likely than a mechanical problem to me.

Thanks for your time!

 

[JamesH]

I would say it sounds like you have a worn syncro key or the scncro's them selfs. You said you resealed most of the trans, did you open it up and look at the syncro's? When was the last time the fluid was changed? How about the input bearing and pocket bearings. What is the milage on the truck?

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[BWDuty]

The only seals I replaced that were actually *in* the transmission were the slave cylinder seal (the one you have to knock that ring off behind the slave cylinder to get to) and the one on the top of the transmission itself that seals the top cover. Also checked those three plugs on top and cleaned them up really good, and opted to RTV them back in as they showed no signs of dry rot instead of pounding in metal plugs. I did look inside there, but didn't see anything that looked unusual. I mean, no broken teeth or anything crazy, but I wouldn't know *exactly* what to look for. I changed the transmission fluid with all new Royal Purple Max ATF (my manual specifies Mercon ATF for the manual tranny, and the Royal Purple meets/exceeds those requirements). I'm not even sure what the input and pocket bearings are, so looks like I have some more research to do! The mileage is right around 202,000.

Thanks!

 

[JamesH]

The input bearing it the one that the input shat rides in that goes into the clutch disc. The pocket bearing is inside the gear on the inside of the input shaft where the output shaft rides, the input shaft is usually 4th gear (1:1) and the syncro locks input and out put shafts together eliminating the need for power transfer through the countershaft.

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[BWDuty]

Thanks! It sounds like you know quite a bit more about transmissions that I do. I didn't change any bearings on the input shaft, just the pilot bearing behind the flywheel. I'm guessing your original assessment of something wrong with the syncho/key area would be pretty likely. From my limited experience, I would think that if the problem were a bearing there would be some kind of noise or something before it failed? Also, since the shaft just rides on the bearings, I don't understand how that would effect shifting into gear? Maybe a completely blown bearing throwing off the angle of the shaft?
Even still, it just seems really odd to me that everything went back to perfect all of a sudden after it got really bad and I had to restart the truck two times. As soon as I started the truck again the problem (at least temporarily) completely went away. I suppose that could have something to do with something vibrating back into place. I guess I'll end up dropping the transmission again either way which I was hoping to avoid.

 

[JamesH]

Sorry for that one. The only reason I think it might be bearings, I've seen it, only once, and I still can explain it, a bad pocket bearing that looked just fine to several of us made the truck shift like it was full of rocks. Usually what your describing is keys, from what I have seen. I actually have something similar on my 89 b2, all original, and it only seems to happen with my wife in the truck... Lol,

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[BWDuty]

Haha.. well I just went back out to mess around a bit with some recent mods I've done (put a stabalizer bracket on the front mount hitch I put an 8,000 pound winch on, plus Amazon just delivered some recovery gear -- an upgraded 18,000 pound hook, 30,000 pound tree saver strap, and some 57,000 pound shackles) and I figured I'd get it all organized in a nice little box in in the cab of the truck. Everything shifted perfectly again. I guess I'll start doing some research in case I need to change out that synchro key. That or just start thinking about pulling a tranny from a lower mileage vehicle and transferring whatever newer parts I have over to it. I just hate not knowing for sure *why* this happened, knowing that every time I get in my truck it might be perfect or it might not shift!

I also hate the idea of coincidences.. I mean, I did just replace a ton of components a few months ago. Maybe the strain from the newer components put too much pressure on the older components, maybe I did something wrong -- that's why I was hoping it would be something simple like the clutch master cylinder or an air bubble somehwere, especially since it started working fine again.

 

[Mark_88]

I don't know much about transmissions but that has happened to me a few times too. In my case it was the 1988 M5OD that was working perfectly up to that point. Well, I should correct that because one time my Master went through the floorboards so shifting was a bit challenging and I thought it was the clutch. That required fixing the flooboards.

I do know that you won't get that problem with anything after 1994 or so when they mounted the clutch onto the brake pedal assembly and not directly on the firewall...anyway...moving forward...

In my case it was simply old transmission fluid that was low on top of being less than necessary. Once I topped the transmission fluid up it never missed a beat.

Since you recently rebuilt the transmission I would have to assume you filled the fluids up with the proper stuff...and since it is working properly again...probably not low transmission fluid...unless you were parked on a slant that time and the fluid was low but now the vehicle is level...

So...might check the level of the fluids.

I have read one other post on this and there was an intermittent shifting/engaging gears issue that cleared up for no apparent reason. Otherwise, these transmissions (M5OD) amazingly tough and durable.

 

[BWDuty]

My driveway is on quite a slant, and I'm 99% sure that I put the proper amount in (I filled it through the gear shift area with both the drain and fill plugs in, much easier that way) and used the amount that the owner's manual called for -- but you do have a good point, it can't hurt to pull the fill plug and make sure it's all the way up to it while on a level surface. Can't hurt, will only cost a few bucks, and if there's any chance of it saving me from droping the transmission I'll give it a go!

 

[tomw]

Did you happen to have rain? Did you let the truck sit for a few days?

Did you try to start with the transmission in gear, clutch pedal to the floor?

I have had the clutch disk 'weld' itself to the flywheel momentarily after letting the truck sit for a while, to the point that after starting I could not get the transmission into gear. Ranger S 5-speed 2.3l EFI
My solution was to put the transmission into a likely gear, say 1st, and start the engine. The truck would try to lurch forward, but quickly gave up on that, and started normally. The clutch worked fine and still does subsequent.
I have had this happen two times that I remember since 1985... Yeah it & me are old.
tom

 

[BWDuty]

Just an update for anybody with a similar problem who stumbles across this post.

Drove the truck to work and home last night and shifting is absolutely smooth as silk. After I installed the new clutch and pretty much every related component it was a bit hard to shift sometimes, sometimes it even grinded a bit. I chalked it up to all of the new parts. Ever since whatever happened yesterday happened it is shifting better than it has in the 15 years I've owned it.

I did buy a couple more quarts of Royal Purple Max ATF (damn that stuff is expensive) but I haven't checked the transmission fluid level yet. I know I put the right amount in and I'm pretty certain I don't have any leaks but I'm going to check it anyway when I get a chance.

At this point I'm going to go with my original assessment -- air in the hydaulic line. I think I had bubble(s) that needed to work themselves out. Perhaps starting up the truck pressurizes the line and forced whatever air was giving me trouble to the top of the reservoir. That just seems to make the most sense to me, hopefully I'm right.

I will definitely update again if the fluid was low, or if the problem comes back and I need to replace any parts. If I don't update within the next few months I think it's safe to say that I just had a stubborn air bubble that worked it's way into a bad area for a little while.

Thanks for all of the input, I really appreciate being able to consider all of the options and I always love learning a new thing or two!