Another Driveshaft Question

#21
Rockin302,

From what you describe it could either be bad U-Joints and/or the transmission output yoke.

Just replacing the driveshaft may fix the U-Joints and output yoke because these come with the FMS DS. However, you may pick up new and different vibrations due to pinion flangle runout. I have an FMS DS and am still working to get all the vibs out. The balancing must be done on the DS using info from both these sources. I'm getting very very close to perfection but it takes a while to work it out. Check this out:

http://www.geocities.com/dbennettya/Mustang_PCM/Driveline_field_balance_procedure.doc

Also be sure that your driveshaft is indexed properly by matching up the yellow dots on the pinion flange and DS.

Good Luck, Don
 
#22
gt90stang said:
Rockin302,

From what you describe it could either be bad U-Joints and/or the transmission output yoke.

Just replacing the driveshaft may fix the U-Joints and output yoke because these come with the FMS DS. However, you may pick up new and different vibrations due to pinion flangle runout. I have an FMS DS and am still working to get all the vibs out. The balancing must be done on the DS using info from both these sources. I'm getting very very close to perfection but it takes a while to work it out. Check this out:

http://www.geocities.com/dbennettya/Mustang_PCM/Driveline_field_balance_procedure.doc

Also be sure that your driveshaft is indexed properly by matching up the yellow dots on the pinion flange and DS.

Good Luck, Don
Click to expand...


Don, whenever DS balance threads come up, i think of you. :)

Rockin, if interested with playing with the old DS to try to get it better, i might suggest reading Don's DS threads - he has had some real good ideas and is pretty adamant (that is a compliment, Don) about getting this cured. IIRC, a lot of the info was on a thread Don started (shortens the searching process).

good luck bud (and Don - how did your end up? still playing with it?)
 
#23
Thanks for the thread Don and hissin50. I didn't have anytime to jack up the car today to have a look but I managed to get under the car far enough to grab hold of the drive shaft to check for play.

I could actually move the shaft up and down just a tad and it would twist ever so slightly to the left and right, so basically a vague loose feeling on the shaft. After doing this, I go over to my 93 vert and do the same with no play at all. So does this help you guys diagnose my problem anymore?

Sorry for being so inquisitive, but I just want to solve this problem as much as anyone else out there! =)
 
#24
Rockin302 said:
I could actually move the shaft up and down just a tad and it would twist ever so slightly to the left and right, so basically a vague loose feeling on the shaft. After doing this, I go over to my 93 vert and do the same with no play at all. So does this help you guys diagnose my problem anymore?

Sorry for being so inquisitive, but I just want to solve this problem as much as anyone else out there! =)
Click to expand...
dont be sorry - i enjoy this stuff, as i think most of us do. the pursuit is half the fun. :)

while i'm no Don or Yount, ill toss out my two cents.

if you notice ANY movement in the joints, think about that same slack at high RPM's (with centrifugal forces and whatnot). i would certainly think that freeplay could create a nice imbalance.

so for 8 bucks each (or so), you could try new joints. or if more comfortable with doing a new DS, that route obviously might work. your call. if you do new joints, be sure to mark the relative position of the DS, as well as the position at each half (that you split to do the joint). the stuff is loosely balanced at the factory, so the goal is to try to keep it that way. :)

good luck and good info on what you found. :)
 
#25
"I could actually move the shaft up and down just a tad and it would twist ever so slightly to the left and right, so basically a vague loose feeling on the shaft."

As I said in my first post in the thread -- "Driveshafts don't usually just 'go out of balance'. Occasionally they'll throw a balance weight or you'll bang the underside of the car and slightly bend one (only takes a few thousandths to throw one out). But unless something has happend, they don't just start vibrating.

Given what you're describing as symptoms, I'd check your ujoints. When they start to go, they'll make a helluva vibration especially under no/low load. If that's it, get 'em changed, cause the vibration will break other things too. "
 
#27
Holy Crap!!! I just crawled under the car to confirm any doubt and what did I find???? One of the bolts that connects the driveshaft to the differential is missing!! Good thing I haven't really gone balls out on the car or I'd possibly have a driveshaft sitting in my trunk!!
 
#28
It could just be that it's loose. Those need to be fine thread, grade 8 bolts, but I'd try tightening it up and see what happens. Hopefully driving around with it that way hasn't hurt the ujoints, tranny or rear end.

I've had ujoint failure during a race (SCCA) cause vibration bad enough that I cracked a tranny tailhousing. I 'spose I should've come in and put it on the trailer. :)
 
#29
if not mentioned before, ya might want to threadlock the DS to pumpkin (Happy Halloween folks) bolt threads.

those bolts are infamous for backing out. good luck.
 
#30
Rockin302,

You can get new DS bolts from Ford under N800594-S100. They are special bolts with a 12mm x 1.75 thread and a 12pt 12mm head. You may have to get a tap to clean out the threads depending on how long it has been out.

Good Luck, Don
 
#33
Michael Yount said:
Is the flange threaded on the Stang guys? Mine's got bolts/nuts.
Click to expand...
i think so. the rear of the DS meets up to the flange (on the rear end). the flange bosses are threaded - no need for a nut on the rear (though one of my older Euro cars incorporate that same idea so i know what you mean). im not sure which method is better.
 
#35
Michael Yount said:
Not sure one's better than another - although, when you bugger one up, you can just replace the nut/bolt with a Grade 8 replacement. Always hate having to break out the tap for threaded holes in things.
Click to expand...
yes, but think of all the added weight with the 4 nuts on there. :) (I'm kiddin).

i do like the nut idea myself - also gives one more thing to use a wrench on. i do recall tight clearances when doing R/R on mine though (to get to the nut).
 
#36
Usually I'd probably go ahead and attack the problem myself but I've been real busy lately. Do you think a shop that does general repairs can fix the problem or do you guys recommend a driveline shop, although there aren't that many driveline shops where I live. Don't really want to take it to the local ford dealer and get ripped off.

Does anyone know what the going rate is to r/r the u-joints and maybe replace the seals?? I also didn't notice any fluid leaking out of the differential housing.

I'm starting to get hooked on this site!! :D
 
#37
Yeah, on mine there are eight threaded holes in the flange. So when I was indexing the aluminum DS I had to clean out the 4 unused holes so the bolts wouldn't bind when using those positions.

Don
 
#38
Michael Yount said:
Driveshafts don't usually just 'go out of balance'. Occasionally they'll throw a balance weight or you'll bang the underside of the car and slightly bend one (only takes a few thousandths to throw one out). But unless something has happend, they don't just start vibrating.

Given what you're describing as symptoms, I'd check your ujoints. When they start to go, they'll make a helluva vibration especially under no/low load. If that's it, get 'em changed, cause the vibration will break other things too.
Click to expand...



I would first agree with U-Joints. Take the shaft off and have the U-Joints Pressed and replaced. Most auto repair shops will cheaply R/R your U-Joints off of the car for next to nothing.

If that doesn't fix it, then I would look into the tail shaft bushing as a "possibility". I really doubt that your shaft is out of balance if you have never removed it.

Chris
 
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