101 Front Driveshafts

[101RRS]

Sorry for the long post.

Like most 101s my truck has the noise and vibration from the front end on over run. I have read widely on this and the simple solution most agree is that the angles in the front driveshaft are too great for the UJs and the vibration is caused by pulses from the hardworking UJs (not a CV so speeding up and down with each revolution). However no one seems to know for sure what exactly is the problem and there is a lot conjecture. If it is a driveshaft issue, not one can answer why the vibration only comes from the front driveshaft when the rear shaft is shorter, has a steeper angle and the same sideways angle as the front. So why is the problem only with the front when the rear should be worse. Also the answers given for the vibration should also apply in all circumstances not only when the engine speed is matching road speed with no torque being applied - the vibration goes if torque is being applied by the engine to the drive train or voce versa when the wheels are providing torque when power is removed from the engine.

Some of the relevant issues were dicussed by Ron here.
http://www.aulro.com/afvb/fcs-military-variations/74986-101-front-shaft-fix.html

I did some tests and the rumble is only above 60kph and gets worse the faster you go - it is not speed related but related to slightly backing off the throttle. At 100 kph the front drive shaft is doing 3300 rpm where other landies - depending on diff ratio and tyre size, are doing between 2800 rpm and 3300rpm so the 101 does have a high from shaft rpm. The rumble goes immediately the clutch is pushed in indicating it is related to engine power vs road speed.

For me the rumble makes driving the 101 tiring and does nothing for fuel consumption as you have to constantly backoff or drive through the rumble.

I discussed issues with my driveshaft guy and considered dual CVs but the cost is prohibitive as were double carden joints. So he built a drive shaft with much larger UJs, with more needle bearings that can handle the angles. Also the yokes etc are much larger and have a greater operating range. The slide splines are 1 1/2 times the diameter and size of the originals and are about 5" long rather than the 2" on the original shaft. The tube is 1/2" larger in diameter and the female splines and mounted in rubber inside the tube to assist in taking out noise and vibrations.

So I put this new driveshaft in and there is basically no difference :mad: - there is still the sound but vibrations are reduced because of the rubber in the driveshaft. Now this shaft has new parts and has nothing worn so most of the reasons for the rumble do not apply. So is there something else actually causing the rumble which is being magnified through the shaft?

When putting in the shaft I noticed that when I moved the pinion flange on the front diff there a lot of noise even though it is full of oil - is the diff adjusted up correctly? Is the noise in fact the crown and pinion teeth bashing each other on trailing throttle and the noise is coming back up to through the drive shaft - is the noise in the diff actually being caused by the drive shaft speeding up and down when rotating when there is no load on the diff. Likewise is the noise actually from worn bearings in the CDL end of the transfer case.

I will try turning the drive shaft around to see if that makes any difference. Likewise at the moment the UJs are lined up with each other so that the pulses from them when the shaft turns reinforce each other - the splines are set up so that the UJs can be setup to be 45 degrees offset which would result in twice as many pulses but at a much lower intensity and could result in the rotation of the drive shaft being smoother - who knows until I try.

So this is my experience thus far - what is clear is that whatever the noise is, the driveshaft does not seem to be damaged by it - with the driveshaft I took out, the UJs and splines were all in excellent condition.

So is there anyone out there with a 101 that does not have the rumble??

Garry

[101 Ron]

Garry your work is proving what I have been saying all along and no one (especially the poms) will listen to the truth.
The fix is not easy...........landrover would have done it if they could with the design and money constrains of the time.
Fix 1
Roll the front diff and use a tailshaft with a double cardon joint on one end at the transfercase.
Lower right hand side front engine mount slightly.
Fix 2
Double cardon joint on each end of the tailshaft.
( the whole thing will most likely be slightly weaker and will become very unsteady when worn.)
Fix 3
Drive the vehicle and dont wory about it like 95 percent of 101s on the road.

Changing the position of the sliding joint, unijoints, shaft size etc will not solve the problem as the basic laws of operation of the unijoint have not changed.
Diffs and transfercases have operational play in between the gears for safe operation.
Diffs and transfercases run at constant speeds per revolution.
The tailshaft itself does not not run at a constant speed, but speeds up twice and slows down twice per revolution and this speed up and slow down effect increases with angles of operation.
For a normal tailshaft to deliver a constand speed per revolution from one end to another using two normal UJs the angle of operation of the UJs must be the exactly the same , but opposite to one another to cancel each other out.
Even with a correctly set up and angled tailshaft using two UJs as operating angles are increased you will lose constant drive efect though the tail shaft as the maximum possible angle of operation is 45 degrees for constand drive effect.

[101 Ron]

At high angles of operation the tail shaft is speeding up and slowing down and as is the tail shaft weight or inertia.
The effects of inertia increase with speed.
The 101 runs low diff ratios and the tail shaft runs at higher speeds than most 4WDs if driven down the highway like we tend to do in civilian use.
When a load is on the tail shaft like on drive or backing off and using engine braking all the play in the diff pinion gears , transfercase and tail shaft sliding splines is taken up by the forces of the drive and the effect of no play.
When on the float going down a hill or coasting any inertia effect and slight misalignment causing more speed differential effects will unleash themselves in the play in sliding splines and gear clearances as there are no forces to control them until the play in the drive system is taken up and it will then release and find the play in the other direction.

[101 Ron]

The effect of reducing gear clearances in the the front diff is interesting.
I did this when I fitted my front locker.
The standard front diff pinion gear clearence is something like 12 to 6 thou and mine was reduced to 4 thou ( I didn't mention this on my locker thread).
The effect was it made to front tail shaft vibs higher in pitch and and any thing slightly worse than before as the frequency effect had less play to bounce from one side of the gear clearence to the other.
The effects on the drive drive with this viberation is one that the tailshaft bolts and drive flange nuts will tend to come loose and wear in the drive flange splines will be heavy and this in turn will lead to the seal on the transfercase leaking.

Tailshaft splines and any other part of the front drive on a 101 will wear quicker than normal.
I note the front tailshaft on my defender, whisle it doesnt viberate or cause a noise, it does suffer from the above problems to some extent for slmilar reasons.
When replacing the diff pinion seal or front transfercase seal use a Loctie produce on the drive flange splines and nuts.
Use Nyloc UNF nuts with Loctite on the tailshaft bolts and check bolts frequently.

[101 Ron]

The effect of a overdrive with standard tail shaft and diff ratios is interesting.
When going down a moderate hill in a 101 cruising at 80 kph we tend to back off as the vehicle is picking up speed at getting out of the friendly engine rev range.
If we float down this hill we tend to induce the the tailshaft buzz, so we tend to back right off and use the engine braking effect to load up the drive line again and stop the buzz,
The problem is with the low gearing the engine braking is too good and we have to drive though the buzz and put the power on again and the cycle starts.
With a overdrive you would tend to be cruising higher down the hill anyhow at say 100 kph.
Due to the increased wind drag (box shape) and drive lines losses you need to keep the power on and can do it for as long as needed as the motor is not reving too hard.
A good example was driving my 101 down to the Hawksbury on the F3 freeway.
A normal 101 would have to back off going down keeping to 90 kph.
On my 101 I kept a small amount of power on all the way down (just enough to stop the buzz) and reaching 120 kph on the bridge at the bottom and then used the momenum to help carry me up the other side.
With overdrive the engine revs are less than 3800 rpm at 120 kph

[101RRS]

Thanks Ron - most of what you have said ties in with what I have found, however I do not believe a double carden will actually fix things in the front. As you have indicated there is more that one thing going on which manifests itself in the noise and vibration.

If it was just a drive shaft issue - the rear drive shaft would be worse - in all the forums I have posted this issue the same question has never been acknowledged or answered - and that is if the rear drive shaft is shorter and steeper than the front, why is it that it is only the front shaft that has the issues. I suspect it has something to do with a rear salsbury diff being put in the front but I have no evidence.

I find the 101 extremely tiring to drive in undulating country where you are constantly trying to either drive through or slow down through the rumble - as it does not appear to actually damage the shaft I find I am no longer driving through it just driving at a speed appropriate to the conditions - my new earmuffs help.

When someone can work out why the front shaft rumbles and not the rear when it should be the rear shaft that makes all the noise then we may be on the track. The rubber in my new shaft certainly takes most of the vibration out but not the noise.

Garry

[101 Ron]

As for the rear shaft I have experimented here and so did Landrover.
The prototypes had rear tailshaft problems and so the 101 short bell housing was developed to lenghten the rear tailshaft on production models.
I have played with UJ joint angles in the rear by the use of castor correction wedges under the rear springs to see if I could induce vibs in the rear tailshaft or see if any effects the rear shaft could have on the front being a constant 4WD system.
The rear shaft has no effects vibs wise on the front one, but I could easly induce vibs from the rear shaft by slightly placing the UJ angles out.
The fact is the rear shaft is on its limits too and I think we are luckly it is not more of a issue as well.
The front tailshaft has more play advailible to it for harmonics due to the presence of the front axle CV steering joints.

[101RRS]

The front tailshaft has more play advailible to it for harmonics due to the presence of the front axle CV steering joints.

Thanks Ron - good information - I am beginning to find I am getting more out of you and the other 101 owners in Australia than all of the 101 owners in the UK.

I am with you on the front end - while the noise and vibration may manifest itself in the front drive shaft - I think the entire front end has to be considered as a unit as I think all components contribute to the issue.

I will be interested to see how Peter P's new drive shaft works in his truck when it gets onto the road.

Cheers

Garry

[abaddonxi]

Dunno the first thing about this stuff, but I'm curious if anyone has put a locker in the front of a 101? Just as another way of changing the setup.

[101RRS]

Dunno the first thing about this stuff, but I'm curious if anyone has put a locker in the front of a 101? Just as another way of changing the setup.

Ron has an ARB locker in the front of his 101. I also have one to go in once I get the replacement side gears that will fit the axles delivered.

In a couple of posts up Ron said "The effect of reducing gear clearances in the the front diff is interesting. I did this when I fitted my front locker.
The standard front diff pinion gear clearence is something like 12 to 6 thou and mine was reduced to 4 thou ( I didn't mention this on my locker thread). The effect was it made to front tail shaft vibs higher in pitch and and any thing slightly worse than before as the frequency effect had less play to bounce from one side of the gear clearence to the other."

Garry

[abaddonxi]

Sorry 'bout that, thought I was paying attention in the thread, obviously not.

[PeterP]

Thanks Ron - good information - I am beginning to find I am getting more out of you and the other 101 owners in Australia than all of the 101 owners in the UK.


I agree Garry, perhaps user 101Ron should be modified to Yoda101Oz!


I will be interested to see how Peter P's new drive shaft works in his truck when it gets onto the road.
Probably not as interested as I am. Hope it cures the issue as I am told it will. I have also been told the double cardin shaft should work but when they stuff up they do it in a big way.
Very interesting how the 4 thou clearance in Rons diff changed the harmonics. Possibly more effect than cause?
I have some thoughts on this issue overall. but will reserve comments until CanDo can do a few k's. May even make it to Canungra.

Peter

[djam1]

Ok I hope this post isn't too irrelevant but I have a Stage 1 that originally came with a double cardan joint.
I replaced the double cardan with a standard Rover type shaft that was the right length, for ages I chased a rumble that obviously related to the tailshaft sadly I couldnt fix it with balancing or anything else.
I had a new clutch put in in Geraldton by Wyatts and they put the shaft back on with the spline at the transfer case end.
Problem gone its not perfect but its a as good as any Stage 1 I have driven.

[101RRS]

The 101 does have the splines at the tfr case end - indeed I am thinking of changing it around to see if anything changes if I put it at the diff end - I do not think so but who knows.

Unfortunately everyone in the 101 community seems to have an idea on what the problem is and how to fix it - however I have not come across anyone who actually has fixed it and this is after nearly 40 years after the 101 was designed.

If it was just the front driveshaft - the rear driveshaft would be causing issues as well. When I ask the question why the rear driveshaft has no issues on the UK forums the question is just ignored - the only one to even discuss it has been Yoda101Oz.

I have tried one approach that has been not been successful - though the rubber damper seems to have helped a little. It will be interesting to see how Peter's new shaft works.

Garry

[101RRS]

To do some other work on my 101, I have removed my rear driveshaft. I then decided to see what impact this would have on the 101 rumble. I have previously driven the 101 with the front driveshaft removed - no rumble but increased drivetrain backlash.

When driving with the rear shaft removed there was virtually no drivetrain backlash at all, however the rumble was substantially increased and started at a much lower speed. Normally in my 101 the rumble is not heard below 80kph and is very soft increasing in volume as speed increases. On this test run, the rumble started much lower at 60 kph and was very loud.

So in some way the rear driveshaft has an impact on reducing the front rumble - not sure why this should be so though.

Garry

[PeterP]

Garry,

How was it to drive with the front shaft only? I would think it would be much heavier than normal.


however I have not come across anyone who actually has fixed it and this is after nearly 40 years after the 101 was designed.

I have come across two people who are confident they have fixed the issue in their 101's. When I mentioned it to Anthony in Vic he bushed it off with "I just dropped the right side of the motor, not an issue"
Bill from Great Basin Rovers in US Quote - "101's have driveshaft harmonic issues and you can cure it with double cardon shafts."
The other fix I have seen is rotating the front diff housing up but this is a a biGGG dockyard job.

While no expert on driveshafts I have read what I can find on them.
Most information infers that the input/output should be parallel to cancel the change in speed of the UJ's as per below.

https://www.aulro.com/afvb/images/imported/2009/11/1161.jpg

Wlile I have not done any measurements a spirit level tells me the motor/gearbox of the 101 slopes up This would make the make the front output shaft over-parallel to the input like this -
https://www.aulro.com/afvb/images/imported/2009/11/1162.jpg

The rear would be obviously under-parallel like most rear wheel drive vehicles. I think the physics of being under parallel is a lot more forgiving than over-parallel. Both dropping the RHS of the motor or tilting the diff housing addresses this issue precisely.

Be interested in peoples thoughts.

Peter

[101 Ron]

Peter you are on the money.......the standard angles are not quite right and the only way to fix is roll the front diff at great cost or a Double ended double cardon shaft.
Perryscope Photos - Removing and Modifying a Landrover 101 Axel (http://www.perryscope.com/photos/thumbnails.php?album=16)

[101 Ron]

https://www.aulro.com/afvb/images/imported/2011/03/32.jpg
https://www.aulro.com/afvb/images/imported/2011/03/31.jpg
https://www.aulro.com/afvb/images/imported/2011/03/30.jpg

[PeterP]

Nice pics, rotating the diff centre is something that is not going to happen with mine quickly.
I have done 30k's with the DC shaft (DC coupling on the transfer case end, did not fit the other way) and nothing to report yet. Removing the groaning rear diff and sorting this weekend, then I might be able hear/feel any vibs from the front end.
Dropping the RHS of the motor has to be seriously considered if the DC shaft proves unsuccessful. Need to ask Anthony how much and how it was achieved.

Peter

[101RRS]

Garry,

How was it to drive with the front shaft only? I would think it would be much heavier than normal.

Peter

Actually drove very well - next to no drivetrain slack at all. However as said the rumble was much louder and came in a slower speed - the other variable I had not considered was that the diff lock is in - is this an issue? When my truck is on the road I will test on a high speed dirt road to see if having the diff lock on or off makes any difference.

Garry