Need Help With Clunking noise when Driving

[82ndparatrooper]

Hello Guys, quick question While traveling at highway speeds I started to hear and feel a clunking noise coming from the rear/ front of trans area. I can feel it through the gas pedal also. I felt it in the gas pedal for a while but didn't think anything of it. It just started getting to the point where I can hear the clunking when driving beside another car or jersy barrier just a faint noise though. Any ideas what it might be???

 

[chubble]

is it persistant, is it quick or slow. When you are on the gas accelerating or just cruising?

Some of the other guys might know better than me but they will probbly need more info.

Also, what part of NC are in you in?

 

[82ndparatrooper]

is it persistant, is it quick or slow. When you are on the gas accelerating or just cruising?

Some of the other guys might know better than me but they will probbly need more info.

Also, what part of NC are in you in?

Im in fayettville...yes its consistant moderate clunk and its just when cruising

 

[chengny]

Look at the universal joints (double-cardan maybe).

Failing universal joints, CV joints and even wheel bearings usually sound worse when not loaded.

For example, if a loose u-joint is under a steady load (as when accelerating) it may not sound bad because the bearings are held tight against the caps in one direction.

But when the drive train is in a state of constant load/unload (as would be the case when cruising at a steady speed) the cross-memeber of the u-joint kind of bounces back and forth within the caps.

 

[82ndparatrooper]

Look at the universal joints (double-cardan maybe).

Failing universal joints, CV joints and even wheel bearings usually sound worse when not loaded.

For example, if a loose u-joint is under a steady load (as when accelerating) it may not sound bad because the bearings are held tight against the caps in one direction.

But when the drive train is in a state of constant load/unload (as would be the case when cruising at a steady speed) the cross-memeber of the u-joint kind of bounces back and forth within the caps.

you know what that makes perfect sense. I will take a look at it, also would I be able to feel that vibration through the gas pedal?? also if that is the prob is that something I need to take care of asap?/is it serious

 

[chengny]

I guess a loose u-joint might be felt in the gas pedal - its for sure that the gas pedal isn't generating it's own vibration.

You know how pain in one part of the body can radiate out to a larger area - it's the same with harmonics (vibrations in solid objects) in the drive train of a vehicle.

As far as the urgency of the repair (if it is in fact a bad u-joint); you shouldn't ignore it.

But if you are just recently noticing a rhythmic noise - when you are driving along a Jersey barrier with the windows open - you probably can drive for a few weeks anyway.

If at some point you feel/hear a severe "clunk" felt when shifting into reverse - that would be when you need to deal with it.

 

[82ndparatrooper]

I guess a loose u-joint might be felt in the gas pedal - its for sure that the gas pedal isn't generating it's own vibration.

You know how pain in one part of the body can radiate out to a larger area - it's the same with harmonics (vibrations in solid objects) in the drive train of a vehicle.

As far as the urgency of the repair (if it is in fact a bad u-joint); you shouldn't ignore it.

But if you are just recently noticing a rhythmic noise - when you are driving along a Jersey barrier with the windows open - you probably can drive for a few weeks anyway.

If at some point you feel/hear a severe "clunk" felt when shifting into reverse - that would be when you need to deal with it.

when I shift back and forth from drive to reverse there is sort of a delay then it clunks in to gear. Not to sure what to do from here. I got underneath the truck yesterday and gave it a shake.. nothing really moved except for when I rotated the front shaft...not sure if it's suppose rotate to much but it did about 1inch clock and counter.

 

[chengny]

Received from the OP:

When I shift back and forth from drive to reverse there is sort of a delay then it clunks in to gear. Not to sure what to do from here. I got underneath the truck yesterday and gave it a shake.. nothing really moved excepr for when I rotated the front shaft...not sure if it's suppose rotate to much but it does about 1inch clock and counter

You will not easily be able to identify excessive wear in a u-joint with the truck wheels on the ground. Even if one is bad - if the other is tight and the tires are on the ground the whole drive train will be locked up.

Lift the rear end and then (with both wheels clear and the transmission in neutral) you can check for slop in the drive components. Play around with it at different places.

The tires are a good place to start. They're easy to grab, and when you rock them back and forth the drive shaft really moves.

An easy way to get a good inspection of the u-joints is by inserting a screwdriver through each of them - one at a time.

Using the screwdriver as a lever arm:

Pry up/down and back/forth on the cross member note any apparent motion - if the roller bearing are good, there should be none at all.

Keep the screwdriver inserted through the joint - this is a good time to use it as a lever to rotate the entire drive shaft and rear axle.

The added lever arm of the screwdriver will allow you to rapidly and forcefully jack the drive train in both directions.

Watch and listen for and undue motion or banging noise. It is sometimes helpful to have an assistant rock the drive train while you look around.

As far as the front drive shaft:

I don't know much about Suburbans. What kind of transfer case do you have? The front hubs, are they manual locking?

With the t-case in neutral and the hubs unlocked, the drive shaft should be free to rotate forever. That is true even if the wheels are on the ground.

If the hubs are locked and the transfer case is in N - the free play you describe would be considered normal.

Same thing goes for if the hubs are free and T-case is in 4H or 4L.

Hubs locked and T-case in 4 wheel - you will still have considerably more play than the rear drive.

There is generally more play in the front drive train than in the back. This is due to the fact that there are an additional set of u-joints at the axel ends and the hubs are engaged by splines.

 

[82ndparatrooper]

I had the truck on a lift today...all you joints were checked and seem to be good to go. There is still a sort of delay and clunk noise when shifting from drive to N to reverse. Now that you mentioned the front hubs..I do have manual locking hubs. Also I did notice when backing off the lift I asked my buddy was the front drive shaft rotating, he said roger that lol. That being said front hubs are engaged while in 2WD. I've heard that driving like that isn't that much of a problem but some say yes and no. Tomo I will disengage the hubs and see if that will eliminate some of the noise and vibrations I'm hearing. I didn't even think to check the front hubs lol....thanks Chengny I'll let you knw what happened tomo

 

[Driver4r]

Umm, an idea. Even if your hubs are unlocked, its possible that your tcase might actually still be turning the front dshaft(cause its free mooving). A buddys dodge does this.

 

[82ndparatrooper]

Umm, an idea. Even if your hubs are unlocked, its possible that your tcase might actually still be turning the front dshaft(cause its free mooving). A buddys dodge does this.

ok cool I'll double check that as well...thanks man

 

[chengny]

Just to be sure clear, I'm not sure that I follow you when you say:

That being said front hubs are engaged while in 2WD.

The locking/unlocking of the front manual hubs is not influenced by the position of transfer case drive selector.

In other words, whether the T/C is in the 2H position or the 4H/L position - it has no effect on the wheel hubs. Even though the transfer case and locking hubs are the main components of the 4WD system, neither one has any control over the other.

The transfer case can best be described as the driving unit while the front wheels would be the driven unit.

The T/C output shaft (when in either of the 4WD positions), drives the front drive shaft. The torque from the front drive shaft drives the pinion in the front differential. The pinion splits the load and drives the two halves of the front axle. At the end of each axle are the hubs.

It is only when the hubs are engaged that the torque from the transfer case is allowed to reach the front wheels.

While in 4WD with the hubs set to FREE, the driveshaft and axles spin but no power is transmitted to the front tires. They appear to be driving the wheels, but are actually just along for the ride.

If the T/C is in 2WD and the hubs are locked, the front wheels (as they roll along on the road) will back feed the axles and drive shaft and cause them to rotate. But because the T/C is not mechanically connected to the driveshaft, they are just freewheeling.

Driving around all the time with the front hubs locked is not harmful to any part of the front wheel drive system.

Many people up north do this - mainly in the winter. It eliminates the hassle of climbing out and locking the hubs when road conditions warrant 4WD - and then getting out again to unlock when say they are getting on the highway.

If 4WD is temporarily required (and the hubs are always engaged) it can be utilized simply by engaging the transfer case. The only drawback is that there is a minor increase in total engine load due to the force required to drive the weight of the drive shaft and axles.

 

[MrMarty51]

1988 ???
Does this unit have independnt front suspension ???
If so, does it have the "Torsion bars/rods holding the front end up instread of leaf springs ???
If it is in fact a " Torsion Bar " front end, be sure to give those torsion bar mounts, to the frame, a good lookover.
Sometimes if those mounts gets bad, they can do some mighty funky things.

 

[82ndparatrooper]

Just to be sure clear, I'm not sure that I follow you when you say:

That being said front hubs are engaged while in 2WD.

The locking/unlocking of the front manual hubs is not influenced by the position of transfer case drive selector.

In other words, whether the T/C is in the 2H position or the 4H/L position - it has no effect on the wheel hubs. Even though the transfer case and locking hubs are the main components of the 4WD system, neither one has any control over the other.

The transfer case can best be described as the driving unit while the front wheels would be the driven unit.

The T/C output shaft (when in either of the 4WD positions), drives the front drive shaft. The torque from the front drive shaft drives the pinion in the front differential. The pinion splits the load and drives the two halves of the front axle. At the end of each axle are the hubs.

It is only when the hubs are engaged that the torque from the transfer case is allowed to reach the front wheels.

While in 4WD with the hubs set to FREE, the driveshaft and axles spin but no power is transmitted to the front tires. They appear to be driving the wheels, but are actually just along for the ride.

If the T/C is in 2WD and the hubs are locked, the front wheels (as they roll along on the road) will back feed the axles and drive shaft and cause them to rotate. But because the T/C is not mechanically connected to the driveshaft, they are just freewheeling.

Driving around all the time with the front hubs locked is not harmful to any part of the front wheel drive system.

Many people up north do this - mainly in the winter. It eliminates the hassle of climbing out and locking the hubs when road conditions warrant 4WD - and then getting out again to unlock when say they are getting on the highway.

If 4WD is temporarily required (and the hubs are always engaged) it can be utilized simply by engaging the transfer case. The only drawback is that there is a minor increase in total engine load due to the force required to drive the weight of the drive shaft and axles.

in other words Part time 4 WD....I checked my hubs today and they were disengaged. I guess I will drive around untill something more drastic happends so I can identify the noise and vibration.So that did answer my question earlier about the spinning front drive shaft. I guess that would make sense that it would spin all the time even with hubs disengaged..I guess kinda of waiting there just incase you need to lock them if that makes any sense. Thanks for clearing that up bubby.

 

[82ndparatrooper]

1988 ???
Does this unit have independnt front suspension ???
If so, does it have the "Torsion bars/rods holding the front end up instread of leaf springs ???
If it is in fact a " Torsion Bar " front end, be sure to give those torsion bar mounts, to the frame, a good lookover.
Sometimes if those mounts gets bad, they can do some mighty funky things.

I have leafsprings all the way around