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The shudder

collinbrewer

Sr. Member
Joined
Jan 23, 2007
Messages
529
Loc.
Austin
I never drove my Bronco before I lifted it because when I bought it, it was in shambles.

Now that it's all put together and drivable, I finally got the front driveshaft lengthened to match the new drivetrain and lift, and installed.

Here's the deal. When the hubs are locked, but 4WD is disengaged, I get a slight bit of vibration, and when I engage 4WD, she really shudders, even at low speeds as low as 20 mph.

I'm praying it's something simple like maybe the machine shop didn't balance my driveshaft. Would that be enough to cause such a bad vibration even at low speeds?
 

Skiddy

Bronco Guru
Joined
Oct 8, 2003
Messages
11,557
i would say maybe your front axle shaft u-joints. with the just the hubs locked in and not in 4x4 the drive shaft doesn't spin just the axles
 

dave67fd

Contributor
Bronco Guru
Joined
Sep 24, 2010
Messages
2,863
I agree. If it's fine "without" hubs locked and not with i would suspect axle u-joints. Any clicking or racheting or when turning in 4wd?
 

DuneBuster

Sr. Member
Joined
Dec 14, 2004
Messages
423
Loc.
Canton
Are both the front and rear tires the same brand and type?
Check tire pressure and then actually measure circumfrence of all 4 tires.

I had a friend that found that their old Bronco II had a similar problem and it wasn't until after a lot of work that someone found the front and rear tire circumfrences were different (same brand and model of tire too!!)
They wound up putting 2 new fronts on.

DIfferent circumfrences mean the larger tire wants to travel more than the other tires and that puts a straing ont he transfer case, and the shorter tires are being dragged.

** if you aren't in 4WD, never mind, you have other problems**
 
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collinbrewer

collinbrewer

Sr. Member
Joined
Jan 23, 2007
Messages
529
Loc.
Austin
Before I had selectable hubs, and a front driveshaft, I drove it for three months with zero vibration even at 70mph... would this rule out axle u-joints?

Need to check to see if it clicks when turning in 4wd.

I'll measure the tires when I get home.
 

jrnymn

New Member
Joined
May 17, 2009
Messages
37
Loc.
Hamburg, MI
Seeing that you got it in shambles, did you verify the gear ratios? Possibly a slight mismatch such as a 3.55 in one axle and a 3.73 in the other?
 

Skiddy

Bronco Guru
Joined
Oct 8, 2003
Messages
11,557
Before I had selectable hubs, and a front driveshaft, I drove it for three months with zero vibration even at 70mph... would this rule out axle u-joints?

Need to check to see if it clicks when turning in 4wd.

I'll measure the tires when I get home.

can you clarify selectable hubs?:?
 

Skiddy

Bronco Guru
Joined
Oct 8, 2003
Messages
11,557
Seeing that you got it in shambles, did you verify the gear ratios? Possibly a slight mismatch such as a 3.55 in one axle and a 3.73 in the other?

wouldn't matter if he's not in 4wd
 

Greg_B

Bronco Guru
Joined
Apr 15, 2010
Messages
2,087
Loc.
Cohutta, GA
Before I had selectable hubs, and a front driveshaft, I drove it for three months with zero vibration even at 70mph... would this rule out axle u-joints?

Need to check to see if it clicks when turning in 4wd.

I'll measure the tires when I get home.

I am going to say front drive shaft... I bet the slip joint is worn out... Or the driveshaft was not balanced properly.

I had a worn slip joint that would make the truck shake like an earth quake...

Greg
 
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collinbrewer

collinbrewer

Sr. Member
Joined
Jan 23, 2007
Messages
529
Loc.
Austin
Selectable hubs as in the hubs that you can turn to select whether the hub is engaged or disengaged.
 
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collinbrewer

collinbrewer

Sr. Member
Joined
Jan 23, 2007
Messages
529
Loc.
Austin
It wasn't *that* much in shambles but I suppose the mismatch could be an issue. I'll make sure to look into that.

Seems like it's either the slip yoke, unbalanced driveshaft, or a mismatch between the tires/gearing.

Do you think the lack of balance would cause such a severe shudder at low speeds?
 

garberz

Bronco Influencer
Joined
Jun 24, 2007
Messages
6,856
Loc.
Conejo Valley, Ca.
i would say maybe your front axle shaft u-joints. with the just the hubs locked in and not in 4x4 the drive shaft doesn't spin just the axles

If the axles are spinning the drive shaft is spinning, so it still may be a drive shaft balance issue or too worn of the slip yoke.

Take the front drive shaft off, drive it with and without the hubs being locked to narrow down the source.
 

Greg_B

Bronco Guru
Joined
Apr 15, 2010
Messages
2,087
Loc.
Cohutta, GA
It wasn't *that* much in shambles but I suppose the mismatch could be an issue. I'll make sure to look into that.

Seems like it's either the slip yoke, unbalanced driveshaft, or a mismatch between the tires/gearing.

Do you think the lack of balance would cause such a severe shudder at low speeds?

When mine did that I could grab the drive shaft in the center with it on the truck and move it back and forth... you could see the slip yoke wobbling back and forth...

I had my rear drive shaft slip yoke lock up and it also made a bad vibration. It wouldnt go in or out or wiggle.... it was frozen solid. It also eat U joints like crazy.

Greg
 

rustbucket

Bronco Guru
Joined
Mar 22, 2004
Messages
1,579
All good advice above, but a few questions. Are you driving on dry pavement in 4wd? Do you have a locker? Are you sure the gear ratio is matched front to rear? If you have a limited slip in the front, do you have a friction modifier in the gear oil?
 
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collinbrewer

collinbrewer

Sr. Member
Joined
Jan 23, 2007
Messages
529
Loc.
Austin
I don't think you can clock the joints incorrectly with a double CV... I can't see how anyways.

The slip yoke is my suspicion still... I just got done taking out the DS so I can take it back to the machine shop in the morning.

rustbucket: I am driving on dry pavement. No locker(that I know of). I'm not sure of the gear ratio, need to lift it to find out because I can't find any markers. I don't know if I have limited slip in the front(how can I tell?), but I have standard gear oil in it.
 

ScanmanSteven

Bronco Guru
Joined
Dec 19, 2010
Messages
1,129
Driving in 4wd on dry pavement could be part of the problem. The Dana 20 is gear driven, so when in 4wd there needs to be some slippage for things to work right. The slip joint could be the problem. Try running down a gravel road as it will allow the needed slippage.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,275
I don't think you can clock the joints incorrectly with a double CV... I can't see how anyways.

It's easy. The slip yoke has splines. If you pull the two halves apart and put them back together one or more splines off, your joints are out of phase. The two upper joints are still fine, but the one by itself is now misaligned compared to the other two. Just as important on a double-cardan type CV shaft as it is on a single.

As far as angles go though, your pinion angle could be so severe as to have a typical u-joint bind situation. That would give you a vibration too.

Your shaft can definitely turn with just the hubs locked. If you have a limited slip, your shaft should turn all the time.
Even with an open diff, you can get enough spin to maybe overcome the resistance of a bound up joint.
And if the transfer case is actually in 4wd high and you don't know it, you're for sure going to feel it.

It's not easy to get a pinion that far out, but it's possible. How much lift, and what c-bushings did you install. Also, did you install longer radius arms or drop brackets too?

Paul
 

stpdhurts

Jr. Member
Joined
Oct 2, 2012
Messages
79
Loc.
Havre, Montana
This thread has been quiet for a while so I am going to hijack it!!! I recently traded a bronco for a dirtbike and am trying to work the bugs out. The roads are icy and 4x4 would be nice in town right now but I am having the same shudder. I am pretty sure it is the pinion angle but I am not sure what C's are in it. The bronco has a 3.5 lift with radius arm drops. Is there a way to ID the C's???
 
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