i believe it's wobbling on clutch takeup, hence the bucking when starting to move, but that's really just a guess. I'm waiting for a diagnosis now.

thanks for the tip on used M5 prices, but how do i know it's a "good" M5, and what constitutes "good" in this poor design? In my view, a one year warranty on a product with a bad history is hardly evidence of "good" - it appears the life of this thing is all too often significantly less than 100K miles, even when properly and used maintained... not my first choice. Yeah, there are many that last much longer, but based on my research, that's a roll of the dice against bad odds, and there are better products available - the auto, or the ZF5... so I'm looking at costs. I'm willing to trade money for reliability; depending on how much money.

If there were aftermarket mods that could make up for the M5OD problems - such as a stronger input shaft; a more reliable shift mechanism, then I'd be interested. but i have a hard time accepting spending money to get to the start point of a short lived product.

 

we had a m5 with 275k the only thing it needed was to replace the rubber plugs with copper ones

i also have one in my garadge with 180k on it was perfect but i wrecked the truck it was in

first/reverse syncronizers arnt the best in the zf5 ok for daily drivin but heavy wheelin n towing u can take them out in no time

and ive blow brand new auto tranys in less then 20k miles sticks are far supirior to automatics

think of it this way the more u ad the more complicated it gets and the more stuff to go wrong

 

251k miles, nothing done to it. Not properly used or maintained. More like abused an beat up.
You're ignorance is getting in the way of the real problem.
It's a truck and no matter what it's gunna have these problems. You want a Cadillac, go buy one.

 

Joe, I've got 141k on mine now and it's solid as a rock. A lot of problems such as you describe are actually clutch assembly, flywheel, and pilot bearing related. If your slave is going, you might as well get a full clutch kit and a pilot bearing, pull the flywheel and get it bench ground, and replace the rear main seal while the flywheel is out.

I haven't exactly treated the tranny easy either - 4 summers ago I did a LOT of towing.

Story - bear with me. I bought the truck with 55k on it in Sept 06. 1 week after the 90 day warranty expired, I blew the slave in my driveway, it had 64k on it. I crash shifted it over to the shop on the other side of town. I've known the head mechanic since he was in high school. We discussed the situation, and he recommended that I replace the whole clutch assembly due to the labor situation (why tear it down again later to replace the clutch) - and the possibility that fluid may have contaminated the clutch. I agreed. The only clutches he could get without waiting a few days were a no-name reman or a heavy duty Brute Power. I told him to go for the heavy duty. A couple months later, it started chattering. Come to find out he didn't bench grind the flywheel, he ground it in place with a hand grinder. He also used cheap universal ATF in it (Pennzoil). The next summer I went back and forth from Chicago to Joplin towing a packed to the brim 5x8 enclosed trailer and with the bed full to the rails. I was over all ratings - tow weight, GVWR, and GCWR. I towed in 5th with cruise control. Other than the annoyance of a chattering clutch, I had no issues. At 100k I had the tranny fluid changed to a universal full synthetic (BG), and it actually smoothed the shifts out. Finally, at around 120k, the pilot bearing started sticking so I decided to get the job done right. I took it over to Ford, and they put a complete OEM clutch kit in it, a new flywheel, pilot bearing, and rear main seal (which WAS leaking). It drives like a new truck and the tranny feels just like it did when I bought it.

 

On the one hand, your response is much more useful, and effective, than being called "ignorant".
on the other hand, here's what i hear - short life, again. the trans you describe went out at 64k miles, and required major work again withtin 60k miles... not what i want to hear. mine is going out at 76k. this is typical of what i've found on the M5OD - they don't last. as i mentioned earlier, and as mr. "ignorant" ignored, it's not how many last, it's how many break. and too many of these break. no amount of name-calling or anecdotes to the contrary is going to make me happy with transmissions that can't be counted on to go over 100k before any work is required. it doesn't have to be a cadillac to get there; too many examples exist of transmissions that routinely do exactly that - as far as i can tell, EVERY trans used in the F150 but the M5OD can be counted on to do exactly that. "Truck" does not equal "unreliable" - Ford and Toyota have demonstrated that repeatedly. The M5OD is unreliable.

on the third hand, i really, really, hope it's all clutch related - and what you describe makes me think that's my real problem; not a worn input shaft as i feared; in which case, it is definitely worth fixing when compared to the cost of a swap.
thanks, and as soon i get a diagnosis, i'll let you know. your clutch experience makes me hopeful. won't be satisfied, but it'll be a workable solution.

 

Joe, my TRANS didn't go out - EVERY issue was clutch-related. Or did I misunderstand you?

The pilot bearing is in the flywheel, not the tranny. Are you possibly confusing it with the input shaft bearing?

 

I have put serious miles on an M5. Currently on my 3rd truck equipped with the trans and have nothing but positive things to say about it. I've put them through some abuse towing, mudding, and so on. I've gone through slave cylinders, clutches, shifter forks, and a synchro. The factory salve cylinders were by default a bad design and since have been improved. My clutches went out do to normal wear, blew a shifter fork due to resting my hand on the shifter in fourth while driving in town and blew a synchro pulling a seriously heavy trailer and, out of habit, put it in fifth. Although I have heard of the shaft wobble, I have never experienced it. I owned a 97 4.6 4x4 and personally put 430k miles on it with the M5. Outside of the things listed above, I never had a serious problem with it. No wore out input shaft or the such. It did what I needed it to. If I were to guess, I would have to agree with glc in his advice to check out your clutch system. Clutch, slave cylinder, pilot bearing etc. Did you buy this truck brand new or are you a second hand owner? I ask because sometimes its difficult to really diagnose a problem if you are uncertain about its history. I've seen bad slave cylinders slick out a clutch in a hurry. Glaze one over and its a matter of slip and grab "bucking." I wish you luck in whatever you find.

 

based on what the two of you have to say, I'm beginning to be optimistic about the problem being confined to the clutch - i sure hope so. the slave cylinder dumping fluid onto the clutch just never occurred to me; that seems a much more likely cause of my symptoms than a worn input shaft - even with a reputation for a weak shaft, getting that much wear so soon does seem incredulous. i hope.
I'm still waiting on the diagnosis, which is now into three days so I'm beginning to get anxious about it. i called once, it was on the lift and going through testing. FWIW, the diagnosis is not limited to the trans; they're chasing down a valve-train issue as well.
your comment about "The factory slave cylinders ... and since have been improved" - what is that improvement, and is it possible to get that improvement in my trans?
I'm the second owner, i got it at 57000 miles.
thanks so much for your time, i really appreciate what I'm learning here.
jg

 

The slave cylinder is part of the clutch, not the trans!

You pull the tranny - then inside the bell housing you have the clutch assembly - pressure plate, disk, combo slave cylinder/throwout bearing. The current clutch kits SHOULD have the improved slave. The problem with the original one is premature leakage.

Honestly, the 4.2 doesn't have enough power to kill input shafts unless you beat the crap out of it with full throttle clutch dumps.

Parts and labor to do a full clutch rebuild and do it RIGHT is about $1200. Unless you have a part failure or slip the hell out of the clutch, an OEM clutch should last at least 150k.

 

The last slave cylinder I bought had a stronger spring, bigger throwout bearing, and a rubber dust cover over the spring. it felt much better than the stock one ever did and yes they're not as prone to leak as the stock ones were.

 

See I just got my slave last summer and it was the old style. Kind of made me angry when I found out there is a new style available.

 

Dude that sucks. It should last a while though. Note the bigger bearing and such. Much better design IMO.

 

I'm pretty sure mine has a larger bearing and spring. I don't remember how but with my old one still connected but the trans halfway out of the truck a buddy stepped on the pedal and blew the bearing off the cylinder. Funny to see.
I hope the new one lasts a long time, but I don't mind dropping the trans, I haaaattteeee bleeding the system though.

 

You know how to back bleed it?

Get a pump-style oil can. Fill it with brake fluid and attach a hose to the spout and the bleeder screw. Take the top off the master cylinder and stuff a bunch of rags under it. Crack open the bleeder screw and start pumping.

 

Yeah I know all about reverse bleeding. Now. After it matters.
Same with the slave. Oh well, I'll know for next time.