about 2 weeks ago i was inspecting my drivetrain prior to a crosscountry trip and put the driveshaft back on the wrong way and it vibrated real bad. i then put it back the right way and still got vibration,

so i replaced:
carrier bearing
all ujoints with good napa ones
had the driveshaft dynamically balanced and heat straightened

so i think i caused collateral damage from geeking it off the get go with putting it back wrong and suspect it is coming from the transmission. the output shaft has play, and i have pinpointed the vibration to be coming from there.

is there a bearing inside there? how do i replace this bearing? its a 97 3 liter v6 with m5od manual trans.

thanks!

 

The '97 Ford manual shows an M5OD output shaft bearing and, at least on paper, it looks like a PITA to replace, requiring a bearing puller used in conjunction with a "remover/replacer tube" and a "TOD forcing screw".

 

hmm thanks rockledge. sounds to me like a book is worth every penny. there are tons and tons of threads and how to's ive checked out (including "other" sites), including a rear seal that goes there, but none so far for the bearing or bushing. and the parts stores dont seem to have this bearing, and its only furnished with a full rebuild kit. but oddly they do have input shaft bearings.

 

Danger_dave, can you move the yoke around radially? Specifically, can you grab hold of the driveshaft near the tail of the transmission, and make it move or wobble? There should be a very little movement, if any. If so, the bushing may be damaged, and possibly damaged the yoke. I have heard of using the new bushing to drive the old bushing forward onto the output shaft. I would then remove the tailhousing and remove the old bushing, and re-assemble. Or you can remove the tailhousing, and shlep down to your favorite garage or dealership and have someone with a press do the work. Machine shops should not charge a whole lot for that little work.
tom

 

there is small movement. from the research i have done on other transmissions sometimes this can be normal. i understand harmonics can be a tricky thing and where the vibration is isnt necessarily where the problem is, but besides the pinion bearing, this is all thats left because other than that the whole drivetrain has been rebuilt and proffessionally balanced.

funny thing about the whole situation is i brought my driveshaft back to the place 3 times. i insisted they didnt do a good enough job, and they said they have achieved runout that is within specs. but each time i brought it back and tried it out again on the truck, the vibration was less! so i am thinking they just fine tuned it better and better each time, while the actual problem elsewhere still exists. its like having a busted ligament kneecap but insisting the pain must be from the shoes, or the arch supports, or the socks, and those things help the pain, but the knee is still busted and youre just buttering the problem. they were complete gentlemen about everything and only charged me for the inital job, and i was recommended to the place from some good people who have had much more complex work done there than i did. so in the end i dont doubt my driveshaft is balanced as can be! and definitely cannot be the problem!

 

I would be testing in a few different ways. Get up to speed, and put the transmission in neutral. Coast and see if it still vibrates.
Add a good sized load to the bed of the truck. Check for vibration. You change the geometry of the parts when you add a load, as the angle from the nose of the differential to the crossmember where the carrier bearing is located will be different. This puts the U-joints in a different position at both ends. There can be some difference when under load and unloaded. If the transmission were to shift on the mounts due to oiled up mounts [weakened..] when loaded, it could un-shift when un-loaded.
If it weren't vibrating before, and you put it back together correctly, it shouldn't vibrate now. How much vibration are you getting? A bad U-joint will make you bounce up and down a little in your seat, and will also squeak or chirp in most cases.
tom

 

tom heres the full story....

the truck was fine and dandy
i pulled the driveshaft off to inspect ujoints and slip yoke grease
did not index it with chalk
put it back on the wrong way out of phase out of alignment
drove it that way 100 miles at 70mph
put it back on the right way
still vibrates really bad
drove it 1000 miles to florida still vibrating bad the whole way
had all new ujoints pressed in
had it balanced 3 times and straightened
its much better now but still vibrates and shakes at all speeds
some speeds worse than others probly due to harmonics

 

Get thee to a boneyard. With all the work you have done & had done, it is not getting back to the problem. A used unit might just fix you up fine. Dunno the $$.
Unless the drive took out the tailhousing bushing, or the bearing surface on the slip-joint yoke, or the center support (assuming you have a 2-piece) bearing is not doing its thing, allowing motion...
I don't know how the center support attaches - the method - as in should the rear wheels be on the ground when it is installed to get the correct positioning and angle? I don't know...
Was it put together the 'wrong way' end for end or a rotational matter of the crosses not being 90 off from each other or ...???

tom

 

i removed the 4 star bolts from the differential then disassembled the slip yoke boot, and slid it out,
upon reinstallation i did not match up the same 4 boltholes on the differential,
plus the spline on the slip yoke was off a couple teeth. so instead of the ujoints being parrellel with each other on the front and the back, they were worse than being 180 degrees off, or 90 degrees off.

 

there is 1 other thing i suspect besides the trans. they balanced the driveshaft as a whole unit with all pieces together, except 1. one which they said does not matter, but i think it does matter. the flange on the differential. the steel drum with the center nut holding it to the differential that the driveshaft bolts to via 4 star shaped 12mm bolts. this is a little steel drum rotating at high speed connected to the driveshaft so i think it has to matter
all the stuff ive read online so far says when you remove the driveshaft you must index this piece with chalk as well, and put it back the same way. which i did not.

 

Two things: 1) the flange [flat plate with the four holes] is already balanced, and is of such small diameter, and so well supported by the nose of the differential that it can hardly shake any at all. 2)you have one chance out of 4 to get it right. remove, rotate 90deg and put it back on again.
I suppose it is possible that the pinion flange is balanced to the driveshaft. In a way, it seems unlikely as that would mean balancing, and then keeping that pinion & flange together with the rest of the driveshaft as the differential and carrier is assembled. Not the way I'd do it..

It would make sense to check for the parts being concentric... at least one of the rear wheels in the air, spin it and watch the nose of the differential to see if it wobbles as it rotates. watch the driveshaft at the same time. If it doesn't run true, try the 90 degree turn thing???
Beyond me...

tom

 

interesting update:

that runout near the output shaft was before i had this balanced. it shook near the trans like a paintshaker. like i said i brought it back to that shop and had it balanced and heat straightened a total of 3 times. each time the truck felt differently. they said it is good. hmm.....

i crawled under there today and put the rear up on jackstands and this is what i found:
grabbed the whole trans and shook it with force. shes tight. grabbed the output shaft, slight up and down movement, none side to side. seal leaks fluid. carrier bearing is tight. (after all the carrier bearing is new) ran it in 1st gear idleing. cant run it any faster because the rear end makes a horrible noise and cant decide which wheel to spin. i watched the rear half of the driveshaft near the differential dance like patrick swayze. the front half of the shaft is smooth as silk. the flange on the differential also was smooth. this guys video is pretty darn similar to what i saw.

YouTube - driveshaft runout

so now i put a scissor jack under the driveshaft and cranked it up to where its barely touching. rotating the shaft by hand i watched it hit the same high and low spots. did this all along that half of the shaft just incase of any imperfections in the metal from 13 years of age. so i marked the high and low spots. an article i read online says to rotate the shaft in the flange on the differential halfway around, then bolt it back up and measure the high and low spots again. if they trade places it is a bent pinion or flange. if they stay the same it is the shaft. they stayed the same. so it is definitely the shaft. what i dont understand is how the shop was unable to fix this, notice this, or point this out to me after 3 times, and after they were such gentlemen and didnt strike me as a shady place one bit.

 

Maybe they are not competent. That has occurred upon occasion in the auto repair business. If you can see much more runout than the video showed, it is broken. [a technical term if I ever heard one..]
If you took the driveshaft out, and laid it on a flat surface, you could determine if it was bent, or the rearmost yoke/flange/U-joint was not installed or centered properly. If one of the needle bearings fell out of place, and it can happen!, it could off-center the bearing cross. *Some* people make things fit even though they should not. Brute force and awkwardness are effective if not efficient...
"We're gonna need a bigger hammer, Bud."
I think I would attempt to check the shaft for straightness, and then measure the heck out of the rear yoke/flange to see if the shaft was centered on the cross, or offset. If offset, that would explain the runout. If the wrong bearing was installed, such as one with a smaller than factory cross, it could allow the shaft to move in and out of the bearing caps. Wrong part specified and installed? I just remember taking the 12 point bolts loose on an Aerostar, and needing a foot long breaker bar to get them loose. I don't remember marking the part for re-installation, but had no vibration problems...
tom

 

I agree the shop may not fully competent. Case in point, I had a driveshaft rebuilt by a shop, and they claimed to balance it. When I reinstalled it, it shook like a dog passing a peach seed. After 3 attempts to get them to fix it, I gave up.
I ended up taking to another shop, and they discovered the joints were not centered. After they solved this problem, a spin on their balance machine showed the shaft was balanced perfectly BEFORE the other shop added their weight. Removing that weight returned the shaft to it's factory balanced condition.

Just because a shop "specialises" in a feild, doesn't mean they actually know what they're doing.......

 

hmm lol that sounds like my situation!


yes i love hearing people say "i do this for a living" or "ive been doing this for 25 years" and they say it with such emphasis.

and i say, "sorry pal, but yove been doing for 25 years and doing it for a living THE WRONG WAY"