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Shudder/Vibration Around 40-45 MPH, then 60 MPH +

19Walt93

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It sounds like you need to try some angled shims under the spring pads and see what happens, a couple of degrees can make a huge difference. If you switched the Explorer axle spring pads to the top of the axle it is critical that they are on the same plane, if one is tipped it will cause vibration. I know you said the original rear also had the shudder, we has a new Bronco II delivered with incorrectly positioned spring pads from the factory. I chased hundreds of driveline vibrations over the years, Ford released a troubleshooting guide for Fairmont vibrations that often said to substitute a "known good" part and that a new part is new, not "known good". It might also be worth neutralizing the engine and trans mounts- loosen them all, jack the weight off the mounts,then lower them back down and retighten the mounts. It's easy and free.
 


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I'd say start with some of the tests that have been suggested.

Get the truck up on jack stands, put it in gear and check for vibration and to make sure none of your wheels/tires are out of round.
Failing there, drive it around in FWD with the rear driveshaft removed (also make sure the 4WD isn't remaining partly engaged, the front driveshaft should rotate freely while in 2WD). It seems there has to be a simple answer to this.

Post a pic or two of your rear driveshaft (u-joint angles), maybe someone here can spot something amiss there.
 

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Ok, so today I had a chance to do most of the tests. The only one I didn't get to do was 'drive' the truck on jack stands. I figure this would be best to do with someone else's help so I can inspect while someone else drives it. Anyway, here are the tests I did get to do and their conclusions.

-Rear driveshaft removed, hubs locked and driving in 4WD (FWD). Not much difference, it was hard to say for sure because it drove quite differently like this. The issue still seemed to be there around the same 40-50 range though.
-Clocking the driveshaft on the t-case flange. Rotating the driveshaft 1/4 turn or one bolt hole on the t-case flange changed the shudder a little. It was noticeably less shaky, not perfect but a noticeable improvement. Rotating it another set of bolt holes, now 1/2 turn from stock position, felt similar to the original position. Rotating it to 3/4 of a turn or one final set of bolt holes, it felt about the same again as stock or 1/2 turn. So I ended up leaving it in the 1/4 turn position because it did at least seem to make some improvement.
-While I was under the truck I was looking at the transfer case dampener and remembered reading how some Rangers came without them and some came with them and no one really knows what Ford's reasoning was. So I figured why not try removing it and seeing what happens? Well it was definitely noticeably worse, so needless to say I definitely need that dampener.
-I loosened the motor and trans mounts, then ran the engine for a minute or two revving it up and holding it at different rpm's to get it to move around and settle out. Then re-torqued the mounts. This made little to no difference as far as I could tell.
-I double checked the angles on the spring pads on the rear axle since it was mentioned that if they are off from each other that it could cause a vibration if they weren't perfect. They were pretty much dead on, at worst maybe 1/4 of a degree off from each other. But I have a couple different sets of pinion angle shims so I tried using a 1 degree shim only on one side to see if it helped. I installed it on the drivers side, both directions at different times, so that it would point that side up or down one degree. Both of those tests made the problem worse, the shudder now started sooner around 35 or so and up to 50 as before but noticeably worse. So I believe that is not my issue.
-Since I have a couple sets of pinion shims I tried different angles to see what happened. As mentioned before, setting it to perfectly equal and opposite the t case flange, or 0 degrees pinion angle, the vibration is quite bad. I used a set of 1 degree shims to angle it down 1 degree, and it does help a little. I also have a set of 2.5 degree shims so I swapped out for those instead, and it made no difference compared to the 1 degree of pinion angle. Better than 0 but still shaky.
-Also, I recently reverse leveled my truck with a shackle flip first of all because I had the parts and wanted to get rid of the lean BUT also because I wanted to see what it would do given to the driveshaft operating angle and pinion angle would change. The driveshaft angle was reduced, it went from something like 7 degrees down to around 4. (The t-case flange originally pointed 3 degrees down, the driveshaft measured to be 10 degrees, so 10-3 equals 7 degree operating angle unless I'm misunderstanding that). This also changed the pinion angle to a super dramatic 6 degrees nose down compared to the t-case flange. I figured why not try driving it like this even though I believe 6 degrees is way too much. And surprisingly, this was the smoothest the truck has been yet. Not perfect but much better. Because 6 degrees seems excessive, I tried installing the 2.5 degree shims again, this time to bring the pinion back up so it now has 3.5 degrees of pinion angle. However, it feels about the same as having 1 or 2.5 degrees down. 6 degrees down was the smoothest, although not perfect.

So I haven't fixed the problem yet but have found ways to at least tone it down a few notches. But, the weirdest part to me is that having 6 degrees down was the best result so far. Am I mistaken that 6 degrees down is way too much pinion angle? Or better yet, does having that much angle tell of some other issue that having the excess angle masks/remedies somehow? To me most of these tests were rather inconclusive but I think that one part is the most interesting to me.

Here are some pictures of the driveshaft and angles and all that, it's hard to picture under there because either the gas tank or the exhaust block the view.

Looking at the rear from the drivers side:


Looking at the front from the drivers side: (don't mind the blob of grease, whenever I do a sloppy job greasing the u joints it flings everywhere lol)


Looking at the rear from the passenger side:


Looking at the front from the passenger side:


A shot of the whole shaft: (or as much of it as I could get)


Angle finder on the t-case flange: (reads about 4 degrees down)


Angle finder on the pinion flange: (reads about 1 degree up, giving around 3 degrees of pinion angle currently)


Angle finder on the shaft itself: (reads around 8 degrees, making the operating angle 4 degrees unless I'm misunderstanding that)


Normally I remove the driveshaft to measure the angles to be more accurate but you still get the point for the purpose of these pictures. Any thoughts so far?
 

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But a mechanical gauge never needs batteries or charging, generally won't be damaged if you drop it or get grease on it, and it can't ever spy on you (it also has that neat magnetic base so both your hands can be freed to take pictures). :D



I wish I had an answer for you, but nothing in your pictures seems to jump out at me. (I do see what looks like significant rust on the shaft that's been painted over, but I recall you said they were able to balance it, which if so, it shouldn't be an issue).

What doesn't make sense to me is how the vibration is significantly changed when you make tiny changes to the rear pinion angle, but at the same time the vibration remained when you drove it in FWD (eliminating anything to do with the rear pinion angle). I have the feeling you might have multiple issues presenting similar symptoms, which maybe the test while up on jack stands might help reveal (sticking it in 2nd or 3rd gear and then letting the engine idle while you look for anything that's off-kilter should be sufficient).
 

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But a mechanical gauge never needs batteries or charging, generally won't be damaged if you drop it or get grease on it, and it can't ever spy on you (it also has that neat magnetic base so both your hands can be freed to take pictures). :D



I wish I had an answer for you, but nothing in your pictures seems to jump out at me. (I do see what looks like significant rust on the shaft that's been painted over, but I recall you said they were able to balance it, which if so, it shouldn't be an issue).

What doesn't make sense to me is how the vibration is significantly changed when you make tiny changes to the rear pinion angle, but at the same time the vibration remained when you drove it in FWD (eliminating anything to do with the rear pinion angle). I have the feeling you might have multiple issues presenting similar symptoms, which maybe the test while up on jack stands might help reveal (sticking it in 2nd or 3rd gear and then letting the engine idle while you look for anything that's off-kilter should be sufficient).
Yeah so when I had dropped off the driveshaft to be balanced I figured they would say it was too rusty but they said it balanced fine after the slip & spline was replaced so I imagine that is okay. In hindsight I do wish I just had them rebuild the whole shaft just so I could know for sure it's not problematic. And yes the pinion angle changes really messes with my head. It didn't make any difference to me from being anywhere between 1-3 degrees down but having 6 degrees down it smoothed out a bit which is odd. I will do the test drive while on jack stands soon when I get a chance, and I realized I hadn't tried indexing the driveshaft on the differential side, just the transfer case side so it's worth a try.

This might just be a crazy thought of mine, but I'm just trying to look into every possible option so I figure it's worth asking. I suspect the input shaft bearing is going out. It never pops out of gear or anything, but the transmission is very noisy especially in 4th gear. It also is very noisy in neutral and if you push the clutch in the noise goes away. The noise in neutral sounds like knocking, it really just does not sound good. The noise when in 4th gear I can best describe as it sounds like there are a bunch of marbles rolling in my transmission. That probably sounds super weird but that's the best way I can describe it. So, there are two reasons I mention this. One is that I will be making a long road trip soon half way across the country and I'm starting to worry about driving at highway speeds that long with potentially a bad input shaft bearing because I don't want to end up breaking the transmission and being stuck without my truck. The 2nd reason I bring it up, although I haven't found anyone claiming it can cause vibration in my research, is could that possibly be the source of the vibration? I could imagine that it could be possible, but I could also see it not being possible.

Again, the vibration/shudder happens around 40-50 and can happen in any gear, but I'd say it's worst in 4th. Lately I've been noticing that if I creep up to 40 in 4th, say I shift into 4th around 35 MPH, the vibration/shudder is worse than if I were to shift into 4th at say 45 and keep accelerating. Also something I've noticed, if the shudder starts, it's near impossible to get it to stop unless I accelerate past 50 or decelerate under 40 unless I push the clutch in or toss it in neutral. If the shudder starts, it will shake when accelerating or decelerating in gear. Less so on deceleration but still noticeably, and then pretty much gone when in neutral. Also, if I accelerate very slowly, giving it very little throttle, I can get it to not shudder around those speeds. It definitely gets worse under load. The more gas I give it, the harsher it gets. These are the reasons I was suspecting motor mounts possibly but I'm still doubtful that's the problem. I've had bad motor mounts in the truck before (obviously since I replaced them) and the only symptom I had from that was not being able to shift easily because the motor would move so much. So anyway, what I'm wondering is if there is any chance whatsoever that a worn out input shaft bearing could cause this issue? It could make sense because that issue would still show during the FWD test. And to me, getting out of gear stopping the vibration could also make sense with that being the issue. Also, should I at the very least worry about doing a rebuild anyway as prevention of a catastrophic failure?
 

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If you got "marbles in your trans", then I would strongly suggest forget about the vibration for the moment and focus on that (yes, I know that sound well, a friend's Toyota did that just before he lost all gears but 4th).
To start, check the fluid. If it's gray and metallic-looking, then you got problems. I would not suggest trying to drive halfway across the country like that regardless of the vibration.

As for a bad input bearing causing the vibration, I s'pose anything is possible... though something on the input side I would think would show up at a specific engine RPM, rather than road speed. If it's really bad (and it sounds like it might be if it makes noise in 4th) the shaft may be wobbling, which would cause a vibration.

If the vibe persists after the trans is squared away, it might then be easier to find where it's coming from.
 

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If you got "marbles in your trans", then I would strongly suggest forget about the vibration for the moment and focus on that (yes, I know that sound well, a friend's Toyota did that just before he lost all gears but 4th).
To start, check the fluid. If it's gray and metallic-looking, then you got problems. I would not suggest trying to drive halfway across the country like that regardless of the vibration.

As for a bad input bearing causing the vibration, I s'pose anything is possible... though something on the input side I would think would show up at a specific engine RPM, rather than road speed. If it's really bad (and it sounds like it might be if it makes noise in 4th) the shaft may be wobbling, which would cause a vibration.

If the vibe persists after the trans is squared away, it might then be easier to find where it's coming from.
Yeah this was my exact thought. I hadn't really put much thought to the noisy transmission until recently as it seems to be getting worse and I started worrying about it surviving such a long trip haha. Interestingly enough, when I originally did the clutch in this truck I changed the fluid and the fluid looked totally normal then, I'll be curious how it looks now.

And that was my thought too, if it's bad enough, I could see the input shaft wobbling causing noticeable driveline vibration possibly. There's only one way to find out I suppose, as I'm going to rebuild the trans before I go for some peace of mind. So, hopefully after doing so I gain some insight to this problem!
 

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But a mechanical gauge never needs batteries or charging, generally won't be damaged if you drop it or get grease on it, and it can't ever spy on you (it also has that neat magnetic base so both your hands can be freed to take pictures). :D
That may be, but how many people today don't have their smart phone within arms reach? How many people treat them like they're gold?

I've NEVER broken a phone. Ever. Mine is charged at night when I'm asleep and lasts for nearly 48 hours easily. Plus it's always on me.. I get it greasy, oily, and covered with crap all the time while working and it's still never failed me...

The driveline angle app worked great for me and just verified what I already knew.. Plus it has a LOT of other cool functionalities. Gear ratio calculators for different Tremec transmissions, etc.. Definitely a good app to have if you're not purely a junkyard parts hound.
 

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Well, things only get stranger now... I got a chance to drive the truck on jack stands. I didn't drive it up to 40 MPH and try to mimic the vibration just yet. I started by just letting it idle in 3rd gear and looked around and here's what I found.


It should be obvious in the video, but the whole wheel/tire and brake assembly wobbles side to side in sync as it spins. It makes it look like there is tire wobble, as you can see in the video I film the tire rotating and wobbling side to side. But it's not just the tire, the wheel and the rotor and caliper all seem to do it in unison. So what I'm trying to figure out is - is this a severely warped rotor, or a bent axle? The bearing still feels good as I can't find any play. I will be investigating further soon as I have the gasket and gear oil to change out the rear diff oil. But anyway, does anyone have any guesses as to if this is a bent axle shaft vs warped rotor?

Also, I had noticed that my higher speed wobble had come back which was originally fixed by getting the rotors turned. I'm assuming whatever is causing this wobble caused that issue to come back, unless the rotor got warped again and it's the rotor causing all of this wobble but I'm doubtful. What I'm trying to figure out is if this issue is solely the higher speed wobble issue, or both the cause of the 40-50MPH shudder and the higher speed wobble. As I said I will investigate further, but has anyone seen anything like this before?

I'm also bummed seeing this because when I swapped this rear axle in, I installed all new brake parts, and I'm betting those caliper guide pins are fucked now because that is a lot of play. I'm also confused about this because my vibrations and shudder hadn't really changed from before I swapped the axle in and after... so with that being the case I don't understand how this problem didn't seem to affect these vibrations.
 

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My 98 ranger would violently shake at those speeds and all because one of the bolts that goes from the sway bar to the lower control arm was snapped
 

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Well, things only get stranger now... I got a chance to drive the truck on jack stands. I didn't drive it up to 40 MPH and try to mimic the vibration just yet. I started by just letting it idle in 3rd gear and looked around and here's what I found.


It should be obvious in the video, but the whole wheel/tire and brake assembly wobbles side to side in sync as it spins. It makes it look like there is tire wobble, as you can see in the video I film the tire rotating and wobbling side to side. But it's not just the tire, the wheel and the rotor and caliper all seem to do it in unison. So what I'm trying to figure out is - is this a severely warped rotor, or a bent axle? The bearing still feels good as I can't find any play. I will be investigating further soon as I have the gasket and gear oil to change out the rear diff oil. But anyway, does anyone have any guesses as to if this is a bent axle shaft vs warped rotor?

Also, I had noticed that my higher speed wobble had come back which was originally fixed by getting the rotors turned. I'm assuming whatever is causing this wobble caused that issue to come back, unless the rotor got warped again and it's the rotor causing all of this wobble but I'm doubtful. What I'm trying to figure out is if this issue is solely the higher speed wobble issue, or both the cause of the 40-50MPH shudder and the higher speed wobble. As I said I will investigate further, but has anyone seen anything like this before?

I'm also bummed seeing this because when I swapped this rear axle in, I installed all new brake parts, and I'm betting those caliper guide pins are fucked now because that is a lot of play. I'm also confused about this because my vibrations and shudder hadn't really changed from before I swapped the axle in and after... so with that being the case I don't understand how this problem didn't seem to affect these vibrations.
Thats a bent axle.
 

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So you have the same gear ratio front and back right?
 

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Thats a bent axle.
That's what I'm thinking. I just don't know how it bent because I don't beat on this truck and it didn't strike me as looking bent when I had the axle apart.

So you have the same gear ratio front and back right?
Yeah of course. I swapped the front to 4.10 also at the same time as I swapped this rear axle in.
 

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Well, things only get stranger now... I got a chance to drive the truck on jack stands. I didn't drive it up to 40 MPH and try to mimic the vibration just yet. I started by just letting it idle in 3rd gear and looked around and here's what I found.


It should be obvious in the video, but the whole wheel/tire and brake assembly wobbles side to side in sync as it spins. It makes it look like there is tire wobble, as you can see in the video I film the tire rotating and wobbling side to side. But it's not just the tire, the wheel and the rotor and caliper all seem to do it in unison. So what I'm trying to figure out is - is this a severely warped rotor, or a bent axle? The bearing still feels good as I can't find any play. I will be investigating further soon as I have the gasket and gear oil to change out the rear diff oil. But anyway, does anyone have any guesses as to if this is a bent axle shaft vs warped rotor?

Also, I had noticed that my higher speed wobble had come back which was originally fixed by getting the rotors turned. I'm assuming whatever is causing this wobble caused that issue to come back, unless the rotor got warped again and it's the rotor causing all of this wobble but I'm doubtful. What I'm trying to figure out is if this issue is solely the higher speed wobble issue, or both the cause of the 40-50MPH shudder and the higher speed wobble. As I said I will investigate further, but has anyone seen anything like this before?

I'm also bummed seeing this because when I swapped this rear axle in, I installed all new brake parts, and I'm betting those caliper guide pins are fucked now because that is a lot of play. I'm also confused about this because my vibrations and shudder hadn't really changed from before I swapped the axle in and after... so with that being the case I don't understand how this problem didn't seem to affect these vibrations.
That is a bent axle shaft for sure (a warped rotor normally wouldn't have the wheel & tire also wobbling).
I don't know how long you've had the axle, but I'd suggest check with where you got it and see if they'll give you another shaft & caliper (and also a rotor too if needed).


This is one of those things anyone buying a junkyard axle should always check for. With the number of vehicles that get decommissioned & parted out due to collisions, unseen (or concealed) damage like this is quite common.

Case in point:
When I bought the '99 Explorer axle for my BII, I originally went into a local yard looking at a nice low price on a 3.27-geared unit with an open diff (plan was for 5.13:1 gears + ARB locker). They brought the axle out, set it on my tailgate, and I looked it over, rotating all the components. BOTH sides had a wobble exactly like yours (it was obvious that it must've been involved in a pretty good collision). They took the axle back into their yard and then produced a 3.73 geared unit with a Traction-Lok diff for the same price. I looked it over, all seemed good, which is the axle I've now had under there for over 15 years.


As for how you had vibes before, and nothing seemed to change much, remember you had those bubbled-out tires before too. So this is exactly what I said earlier, you had multiple issues causing the same symptoms. As you nail each one down, you should eventually get to the bottom of it all and finally have your truck riding smooth.
 

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