Removing rear driveshaft question

[luca1014]

I've been having a vibration on the highway (65mph+) and have been trying to hunt it down for awhile now. I been thinking maybe my driveshaft is out of balance for some reason so I decided to remove it for a quick test drive with the truck in 4x4 hi. I figured having the front end pull the truck for a short drive should be fine. Is this correct? In my head, it seems like it should work without any issues with just the front end pulling in 4x4 hi.

When I started the truck up and put it into drive, the truck was extremely jerky. Once I got over 10 mph or so, it drove normal. I decided it didn't feel right because of the jerkiness, so I just took it around the block and parked. The jerkiness would only occur at slow speeds when coming to a stop or just starting to accelerate. If the truck was stopped and I was holding the brake, it didn't feel like it was surging or anything. Any ideas why it would do this? I'm wondering if it's an issue in the transfer case or front diff?

The truck is a 01 4.0 EB. Thanks in advance.

 

[1997XLTRollover]

I'm not sure how the 4.0 T-case is but when you pull the rear driveshaft doesn't all your transfer case fluid pour all over the place if you pull it? The driveshaft usually seals the transfer case.

 

[SoNic67]

On my AWD, the CV on the rear shaft (close to TC) was busted and made the same noises (and even more after a while).

 

[luca1014]

The 4.0 4WD transfer case has a flange for the rear shaft. The rear shaft doesn't have a CV in it. It has a ujoint near the transfer case and one near the rear diff, with a slip joint some where near the middle (closer to the transfer case).

The front shaft does have a CV in it, but I removed the front shaft and drove it for a week like that and the vibration was still present. I think that probably eliminates anything in the front shaft.

 

[SoNic67]

Sorry, I was thinking of the front shaft. Yeah, the rear has always U-joints.
I have done both shafts on my truck. The rear just as preventative thing, they looked OK when taken out, but it cleared some rumblings.
One of my friends though, had this on his shaft:

 

[Flash]

Vibration at 65mph is classic wheel imbalance.

 

[SWIGIN]

My Mustang had a high pitched whine at 90 mph and with most noises it had a slight vibration when the noise started.

Long story short, the factory Spicer u joints ford uses has thin plastic discs in the end of each bearing cap.

These plastic discs with start getting chewed up for whatever reason and produce a whine or slight vibration at a specific speed. My stang was 90 my daughters 02 EX was 60-65mph.

I always start with new u joints if they are original Spicer solid u joints and have miles on them.

I'm not knocking Spicer joints, I think they are the best solid joint for the money, but those end discs do create problems.

 

[luca1014]

The tires are only a year old and have been balanced twice already by two different shops. The vibration was unchanged with the old and new tires. The wheels have also been rotated many times and the vibration was still unchanged. All the ujoints are pretty new (less than 6 months) in both the front and rear shaft. The vibration has been unchanged after all the work I've done on the truck. The vibration is felt in the seat. Not so much in the steering wheel. Any other ideas?

Does anyone know if the truck should drive normal without a rear drive shaft installed?

 

[Meat_PoPsiclez]

Are you lifted? Possibly you were feeling cv joint binding that might not be noticeable with the rear wheels powered. Makes sense it would smooth out with speed. Completely a shot in the dark though.

 

[Flash]

Does anyone know if the truck should drive normal without a rear drive shaft installed?

It should be ok.

 

[mitch1204]

A couple easy checks. Parked and the emergency brake on see if there is any play in the drive shaft by attempting to rotate with your hands. It might reveal the culprit.

Also jack the rear up off the ground and place jackstands under both sides. Place you a fixed object about 1/8" or so from the side of the tire and rotate them. Watch the gap on your fixed object and see if you notice any change.Also wiggle the tires and see if there is any play.
Being the vibration is in the seat and not the steering wheel indicates the problem is on the back side or even the transfer case. I wouldn't consider the rear end unless it has high mileage, towed alot or abused.

 

[luca1014]

It's not lifted and I've taken the CVs out and rotated by hand to feel for any binding. Didn't feel anything if that counts for anything.

I'm thinking it's something in the transfer case. It seems like the vibration is coming right from underneath the driver's seat. Any suggestions for anything to look for in the transfer case?

The rear end looks good. I opened it up and changed the fluid over the past summer and everything looked good. I also did the rear axle bearings at the same time since one was bad and I had all the fluid out.

The truck only has 90k on it, which isn't much considering its 15 years old now.

 

[chefduane]

I would take a look at u-joints. I had a bad vibration starting at about 35 up to 65 where it became downright scary. I checked my rear driveshaft balance and wheel balance.
Turned out to be the front u-joint on the driveshaft. I replaced both (u-joints) as a preventative measure and no more vibration. Get your vehicle up to speed when the vibration starts, and then back off the power. Does it go away or lessen? If it does... u-joint. Also, get it up to speed, then carefully shift into neutral, and gently rev the engine. If the vibration goes away then it is most likely drivetrain (non-engine) related. If the vibration persists when coasting, then is most likely NOT drivetrain related and could possibly be engine and/or brake related. This process worked for my diagnostics and may not determine your issue, but I'm still thinking u-joint.

 

[luca1014]

I've replaced all the ujoints (front and rear) last summer. There was no change in the vibration. They didn't feel bad, but were pretty rusted up so I decided to change them anyways since I was so fed up with the vibration issue.

There's no change in vibration whether on or off the power, swerving left or right at speed, transmission in neutral on the highway (only for a short period since I've read you aren't supposed to do that), or pretty much anything else you do.

I've measured the frequency of the vibration to be about 15-19Hz at 70MPH. (I'm actually an electrical engineer by trade that does a lot of work on control systems for gimbal systems to reduce NVH, go figure I can't even figure out the vibration in my on truck). 15Hz is about 900 RPM. I measured it using a vibratach and also using a basic app on my phone that uses the accels built into the phone (not sure how accurate that is though). Knowing the frequency of the vibrations didn't really help me figure it out since I don't have a chart or specs for each and every bearing (need to know the ball pass frequency for each bearing).

I've had the vibration issue for over a year now and it hasn't really gotten worse, which I find odd. You'd think that if it was a bad bearing, it would just degrade over time and use.

 

[rb142]

You are right in range for a first order wheel vibration at that frequency. Check the tires, wheels, hubs, etc.

 

[chefduane]

Luca, given your response I'd say that u-joints are NOT the issue. So, freq stays the same regardless of acceleration/deceleration and engine rpm? Odd. I utoobed 15hz to 19hz and that's way down there. It's mechanical not electrical?

 

[luca1014]

I was really thinking wheels since at 70mph first order wheel vibration is around 12-13Hz, but I've brought it to two different shops and both shops balanced the wheels with no change in the vibration. I guess I could try another shop. Maybe I'll do that this weekend.

The frequency is speed dependent. It stays the same regardless of engine rpm. If I shut overdrive off, the vibration is the same. Same if I put it in neutral. That eliminates the engine and most likely the transmission. The vibration is the same whether or not your on the throttle or not, as long as your speed stays pretty consistent (like off the throttle but coasting down a hill).

The vibration is definitely mechanical. Since you can actually feel the vibration in the seat, I think that pretty much eliminates electrical. 15Hz is way down there in terms of electrical frequency and audible frequency, but it's a pretty sweet spot for vibration. It's low enough in frequency to actually feel it. Unfortunately, a lot of things are rotating in that frequency range (Wheels, axles, hubs, bearings, etc.)

 

[Oranguice]

I would take a look at u-joints. I had a bad vibration starting at about 35 up to 65 where it became downright scary. I checked my rear driveshaft balance and wheel balance.
Turned out to be the front u-joint on the driveshaft. I replaced both (u-joints) as a preventative measure and no more vibration. Get your vehicle up to speed when the vibration starts, and then back off the power. Does it go away or lessen? If it does... u-joint. Also, get it up to speed, then carefully shift into neutral, and gently rev the engine. If the vibration goes away then it is most likely drivetrain (non-engine) related. If the vibration persists when coasting, then is most likely NOT drivetrain related and could possibly be engine and/or brake related. This process worked for my diagnostics and may not determine your issue, but I'm still thinking u-joint.

Awesome Diagnostic Solution ChefDuane!! I've become really worried about the vibration I've recently been having on my '96 4x4.....(300k+ miles)...... While under power, horrific shaking and vibration. Lay off the gas, smooth as silk...... Slight gas applied......."Vibramax 3000" starts right back. Took my baby off the road the other day and transferred all my work stuff to my '98 Jeep Grand Cherokee that I hate to use for work.....(only 75k miles on it). But I REALLY hate sitting on the side of the road somewhere here in the Carolina's..... #FearOfBanjoMusic. :^). Have yet to rip it all apart, but am now confident that rebuilding both front & rear drive shaft ends will resolve the issue..... Many Thanks!!!

 

[chefduane]

No problemo!

 

[pjtoledo]

have you had a friend drive beside you and look at your wheels?

did any of the shops do road force balancing?