How to check?

[michibronc]

Hi All,

My '96 gets a shimmy around 68 mph and above. It seems to get worse at times and better at times, but is always present to some extent. It's almost like a harmonic vibration that goes in and out. I don't think it's the tires because it did the same thing before I got my new meats.

I've had the truck to a reputable front end shop - they claim it's not in the front end and that all of my front suspension and linkage are within specs.

I don't feel the shimmy much in the steering wheel, but i feel it in the door panels and the seat of my pants plenty.

Wheels have been balanced by two reputable places with no improvements or changes.

I'm wondering if it might be the CV joint at the front of the rear driveshaft. I've heard that a driveline vibration can be caused by that going bad. Problem is, I don't know how to check or rebuild if that is the case. Does anyone have any experience in the matter (or any ideas of anything else to check?)

Thanks for any advice you may be able to offer.

 

[BroncoJoe19]

I'm only repeating what I've read here before.

Since I noted that you have autolocking hubs, this would be yuor proceedure.

Put her into 4x4 high and go forward a few feet to engage your auto hubs.

Block your tires, all that neat stuff, and pull your rear drive shaft.

Take her for a spin in front wheel drive.

Take your rear driveshaft with you just in case your auto hubs disengage.

IF the vibration is gone, well you know that it is in the rear driveshaft, either the u-joints, or the shaft itself is out of balance.

To check the ujoints, once you have the driveshaft out, you can try flexing the joints in all four directions, if you feel ANY grittiness at all, they are bad. IF there is ANY play at all they are bad.

I *think* that the only true way is to take them apart and look at them. IF the shafts that the needle bearings ride on are not PERFECTLY smooth, then they need to be replaced.

I hope this makes sense.

joe

 

[BroncoJoe19]

I'm only repeating what I've read here before.Since I noted that you have autolocking hubs, this would be yuor proceedure.

Put her into 4x4 high and go forward a few feet to engage your auto hubs.

Block your tires, all that neat stuff, and pull your rear drive shaft.

Take her for a spin in front wheel drive.

Take your rear driveshaft with you just in case your auto hubs disengage.

IF the vibration is gone, well you know that it is in the rear driveshaft, either the u-joints, or the shaft itself is out of balance.

To check the ujoints, once you have the driveshaft out, you can try flexing the joints in all four directions, if you feel ANY grittiness at all, they are bad. IF there is ANY play at all they are bad.

I *think* that the only true way is to take them apart and look at them. IF the shafts that the needle bearings ride on are not PERFECTLY smooth, then they need to be replaced.

I hope this makes sense.

joe

Here is an excellent post on how to dissassemble a U-joint and that double cardan joint.

http://broncozone.com/forums/index.php?s=&...ost&p=63810

 

[michibronc]

Thanks for the post , BroncoJoe.

Seems logical, but one question....

Is it good to go 70 mph with only the front axle working? That's the speed where the shimmy occurs at.

I'm only repeating what I've read here before.Since I noted that you have autolocking hubs, this would be yuor proceedure.

Put her into 4x4 high and go forward a few feet to engage your auto hubs.

Block your tires, all that neat stuff, and pull your rear drive shaft.

Take her for a spin in front wheel drive.

Take your rear driveshaft with you just in case your auto hubs disengage.

IF the vibration is gone, well you know that it is in the rear driveshaft, either the u-joints, or the shaft itself is out of balance.

To check the ujoints, once you have the driveshaft out, you can try flexing the joints in all four directions, if you feel ANY grittiness at all, they are bad. IF there is ANY play at all they are bad.

I *think* that the only true way is to take them apart and look at them. IF the shafts that the needle bearings ride on are not PERFECTLY smooth, then they need to be replaced.

I hope this makes sense.

joe

 

[Redneck86]

I dont know about drivin it with the rear shaft out, i would say no at high speeds. But those CV joints on the rear shaft are a b*tch to swap out U-joints in, mine are bad too.

 

[BroncoJoe19]

I dont know about drivin it with the rear shaft out, i would say no at high speeds. But those CV joints on the rear shaft are a b*tch to swap out U-joints in, mine are bad too.

The toughest part we had in doing ours was getting the bolts out that held them to the rear. They are 12mm 12 point bolts, and I needed to put a pipe on my 1/2 in drive breaker bar to free them.

If you are going to do it, hit them with PB Blaster the night before. That *might* make things go easier for you.

 

[BroncoJoe19]

Thanks for the post , BroncoJoe.
Seems logical, but one question....

Is it good to go 70 mph with only the front axle working? That's the speed where the shimmy occurs at.

I don't know, as I said I was only repeating what I had read here.

But now that the question was raised, I am starting to think that the problem may not be a Ujoint, but more likely a balance issue.

When your U joints start to go, one will notice the vibration with acceleration, ie when there are torque forces on them. A high speed vibration is usually a tire balance issue. Since you stated that was addressed, now I am starting to think that it is more an issue with balancing of the driveshaft.

Since there is no authoritive consensus that it is ok to drive in Front wheel drive at 70, try this... rotate your tires from front to rear. See if the vibration remains, and if it does not switch to the steering wheel.

IF it remains, and you still feel it in your pants, then it is likely a driveshaft issue. Perhaps one of the balancing weights got knocked off, maybe you hit it on something and bent or dented it a little bit.

Does that make sense to you?

 

[swampthing]

just my 2 cents..normally when the cv joint goes bad you will get ahigh pitch chirping/squeeling noise sounds almost like a bird...grab your driveshaft and shimmy it a little see if it has some play in it

 

[shift1313]

you can drive in just front wheel but i wouldnt recommend it unless its an emergency and i personally wouldnt do it at 70.

Drive shafts are balanced, its possible that yours is out of balance.

For checking the joints ive always just grabbed a hold of the drive shaft and rotate it a bit and watch for play. Ive never had an issue swapping out joints on my trucks, but you need a press for sure.

also joe i think a 12point 1/2" fits the ujoint u bolts. At least thats what i always use. Box wrenches.

Is there actually a CV joint on the driveshaft of a 96? or is it the same U joint setup as the older ones?

in case you are wondering this is a CV joint, typically on FWD cars and RWD with independent rears.



here is a u joint

the ends of the U joint are little caps with roller bearings in it.



Two of these are bolted to the ****** with u bolts are you tranny and rear end. the other two "cups" are pressed into the yolks on your driveshaft. To replace them you need to press the u joint one way until you can remove one cup and then press it back the other way to remove the other from the actual joint. There are also to clips that do not allow the cups to come loose. You have to remove these before you start pressing the joints out.

 

[BroncoJoe19]

Matt,

Nice pictures.

Of U joints and vs CV joint.

Yeah, you're right the broncos have U-joints.

The third picture of the series that I posted a link to above shows how to use a heavy duty C clamp to press the U-joints apart and back together again.

Autozone (and I guess others) will loan you the tool. Their deal is currently, You pay for the tool (about $100) and use it, and if you return it within a month you get your money back, so it is really a secured loaner program. Using the proper tools certainly makes the job go a LOT easier.

Now as a REAL shade-tree mechanic, one would pull the drive shaft, and lay it on the ground. Use a BIG socket as a reciever cup, and a smaller one to insert within the yoke, but on top of the bearing cap of the Ujoint and beat the snot out of it with a BFHammer. One can use a lighter weight C-clamp in the $20 range, and teh sockets as outlined above. If it can't generate enough pressure coaching it wih a hammer would usually work. Just make sure that you don't miss and hit the drive shaft. If you dent it, you may create a new vibration. :blink:

So now I guess the question is... how does one determine if the drive shaft is out of balance?

Doe it have to be taken to a machine shop, and put on/in a lathe?

 

[shift1313]

it will have to be spun at a drive shaft shop as far as i know. If you look around your drive shaft there is a little metal plate that has two spot welds holding it to the drive shaft, this is how they balance it from the factory. Not sure what the DS shops do

 

[michibronc]

Wow! Lots of discussion! Thanks a lot for all your information, fellas.

The cv joint I speak of is a "double cardan" u - joint. There's two separate U joints that act as one unit. Whatever that darn thing is called, I'm worried to break into it. I've changed regular U joints before (in fact the rear one when I bought the truck), but this one at the front of the rear driveshaft has a spring (which I assume is really strong) keeping the two u joints in alignment. That spring is what scares me. I think I can get the unit apart (I seem to be really good at disassembly!), but I don't know if I'll be able to put it back together if that little spring is a bugger.

I guess I should probably take the whole driveshaft off and take it to a shop for them to test it.

What sort of a shop should be able to do that? Any ideas there?

One other thing dawned on me today....

I get a jingling noise from the driver side front tire when I go over bumps. It's always been there, but it's getting worse as time progresses. The front end shop said it wasn't due to any of the steering linkage or the suspension. It literally sounds like a clip banging into a flagpole in the wind. I believe it is my auto hub taking a ****. The truck still locks into 4wd fine, but I think there's some play.

Could that be the cause?

If so - very good way to justify to the boss the cost of getting some warn premiums. She loves it when I dump money into Gertrude. Good thing I live 20 miles away from JBG!

 

[BroncoJoe19]

That spring is what scares me. I think I can get the unit apart (I seem to be really good at disassembly!), but I don't know if I'll be able to put it back together if that little spring is a bugger.

Oh.. go for it! IF you can't get it back together... I'll apologise /emoticons/[email protected] 2x" width="20" height="20" /> LOL

I guess I should probably take the whole driveshaft off and take it to a shop for them to test it.
What sort of a shop should be able to do that? Any ideas there?

Not really. When I bent the driveshaft in my Ford motor home, I was in Blackwell, OK. I stopped in at a chevy dealership and asked if there was anyplace I could get a driveshaft balanced (cause I was already on the phone with Ford, and they claimed that there was not one available anywhere in the country! My unit was too new!) The gal behind the parts counter sent me to a shop in Enid, OK., 2 hours away, limping along at 30 mph I got there first thing in the morning. They dropped my driveshaft, cut both ends off, and welded a new pipe inbetween, balanced it and sent me on my way. They really saved my butt, AND my vacation. Lucky for me... they were a machine shop that specialized in making driveshafts for farm machinery, pumps, and I guess anything that breaks.

OK.. so that was a long story to say, you might call a local Ford dealership, or a local parts store to find out where they would recommend.

Don't know about your jingle bells though.

Run into any reindeer lately?

 

[shift1313]

we have drive shaft shops here in VA, there is one about 25mins from me.

i would look into the u joints first before worrying about the balance. The chance of it being out of balance is pretty slim unless you hit something.

As for the spring. Ive never removed one so im not help there, sorry.

 

[BroncoJoe19]

As for the spring. Ive never removed one so im not help there, sorry.

Yeah.. I read through that post from BroncoBill78 which was from the Ford Service Manual. I see the picture that includes the spring, but no mention is made of it in reassembly. IF it was particularly difficult to put in, wouldn't they make mention of some type of trick, or comment on it?

 

[michibronc]

Well, I would hope so. Everything's always going well in the Chilton's guide until step 6 doesn't seem to flow into step 7 so well for a novice such as me.....

Here's a pic of my driveshaft. First pic I've posted. Not sure if it'll come out.

Mine's a little different and looks to be harder to reassemble (but I don't know that for sure) than the ones in BB78's post for the earlier FSB's. The double cardan in front has that spring mounted on some little assembly between the two U's that just seems like you'd need some kind of a jig or something to manage it. There must be some trick. I wouldn't think the spring would do much if it weren't amazingly stiff.

I guess worst case scenrio I could take the shaft (disassembled) in and have a shop reassemble if I couldn't manage. Eat some crow and figure out how.

BroncoJoe, I hope you're right though - someone on this forum would've found out about what a pain this thing is and publicized it - right?

/emoticons/[email protected] 2x" width="20" height="20" />

Thanks for the continued advice everyone. Makes troubleshooting a little more bearable for sure.

By the way - I'm getting some Warn Premium Lockers and some Polyurethane sway bar bushings from JBG in a few minutes. I've wanted them for a while anyhow - this just gives me a good enough reason to purchase! Front only. My machine doesn't seem to have one in the rear. Going on this week or weekend depending on work.

I'll post if that seems to fix the problem (the hub(s) that is).

Yeah.. I read through that post from BroncoBill78 which was from the Ford Service Manual. I see the picture that includes the spring, but no mention is made of it in reassembly. IF it was particularly difficult to put in, wouldn't they make mention of some type of trick, or comment on it?

 

[desert4wheeling]

Hi all,

I just had to replace my CV joints (including the rear axle u-joint also, I figured it only made sense to do them all.) The first symptom i had that they were going bad was a clicking sound (only noticable at slow speeds). At this point i really didn't know what the noise was. Then my tranny suddenly seemed to take longer to shift from 1rst to 2nd gear. Finally, there was a loud metallic vibration and squeaking when accelerating. Of course by this time i was concerned it was my tranny or torque converter, even though i had absolutely no shifting or stalling problems. Based on my experience, I would say you more likely have a tire or suspension problem if you only notice it at a higher speed. Just my 2 cents.