diff backlash or driveshaft play?

[maverick]

Hi,
My Mk1 MOD has developed an annoying clunk form the rear when selecting reverse.It is coming from the diff area.
I have had a look and the nearside drive shaft has play of 1/2 inch in rotation,ie twisting the shaft side to side ,this is at the diff output joint and also produces said clunk.
This when car is parked normally
The off side has no play.
My Question is ,
Is the play likely to be diff backlash(I dont know how this is measured or what the tolerance is) is it the U.J on the drive shaft?

Any help welcome as I want to make sure I dont go buying a drive shaft when the diff is at fault or visaversa
Mark

[pompey272]

Hi Mark i have a clunk when i move away and was told it was probably driveshafts so i fitted Datsun driveshafts with new uj's but i still have the clunk my uj's on prop are fine so i think it's the diff or the manual gearbox or a combination of both if i do solve it i will let you know.
Regards
Trevor

[maverick]

Hi Mark i have a clunk when i move away and was told it was probably driveshafts so i fitted Datsun driveshafts with new uj's but i still have the clunk my uj's on prop are fine so i think it's the diff or the manual gearbox or a combination of both if i do solve it i will let you know.
Regards
Trevor

Thanks Trevor

[elvimto]

Even when you set the diff up with the correct backlash you will still get a clunk when changing selection nature of the beast, just keep going forward

cheers Stuart

[flying farmer]

It is most likely the outer UJ failing if there is little play in the other side. There is nearly always some movement on the splines, and this can be seen if you pull the rubber boot back so you can see the end of the splines. One problem is that mashed up bits of needle roller often take the play out of the UJ under hand pressure, and that can make the faulty uj hard to find, but it sounds like yours has gone past this stage and has spat out its rollers already.
Do something sooner rather than later as the centre of the uj can wear through the outer cup, or the cup can turn in the hub or driveshaft rendering them scrap.
I prefer to use EJ Wards expensive uprated UJ's as I have a tendency to destroy cheap ones in a few thousand miles
Neil

[maverick]

It is most likely the outer UJ failing if there is little play in the other side. There is nearly always some movement on the splines, and this can be seen if you pull the rubber boot back so you can see the end of the splines. One problem is that mashed up bits of needle roller often take the play out of the UJ under hand pressure, and that can make the faulty uj hard to find, but it sounds like yours has gone past this stage and has spat out its rollers already.
Do something sooner rather than later as the centre of the uj can wear through the outer cup, or the cup can turn in the hub or driveshaft rendering them scrap.
I prefer to use EJ Wards expensive uprated UJ's as I have a tendency to destroy cheap ones in a few thousand miles
Neil

Hi Neil,thanks was hoping I would get your imput.
Which do you mean by outer UJ.
Also would diff backlash show as play on both shafts assuming smashed up bearings not at play?

When rotating(to show the play ,wheel staionary) I am getting movement at the diff output flange,that why I asked about diff backlash as I dont know how much is acceptable and if it shows on one side or both.

Your destroying cheap UJs made me smile ,having read about your big engined Dollies etc
Thanks Mark

[maverick]

Even when you set the diff up with the correct backlash you will still get a clunk when changing selection nature of the beast, just keep going forward

cheers Stuart

Staurt Hi,
But mine didnt used to do it ,
Thanks Mark

[elvimto]

I had nothing to compare to but I did all the checks on the drive train from the transmission output,uj's, splines and outer hubs new bearings and seals in the diff and still get a small clunk so i am going to live with it. Good to hear that it might be something I missed as Neil pointed out I will check into this. next time I am under the car. Let us know what you find.

cheers Stuart

[flying farmer]

The outer UJ is the one hidden inside the trailing arm, but it is still possible to see movement between the two halves of the shaft
Diff backlash is not usualy a crownwheel and pinion problem, but there are little brass thrust washers that fit behind the smaller gears in the diff, and these wear quite badly by 100,000 miles. Fitting can be a DIY job, but the diff has to come out
The diff in my Stag engined TR has done getting on for 250,000 miles and they have been changed twice
See how far the diff input flange turns before the output flanges move, it is not unusual to see an inch of movement, but the backlash between the crownwheel and pinion often cannot be felt while the diff is full of oil
On my Stag the diff is freshly rebuilt with virtualy no backlash, but the driveshaft splines are buggered and this gives a clunk when going from overrun to acceleration
Neil

[maverick]

Cheers Stewart,
Will update when I know more
Mark

[maverick]

The outer UJ is the one hidden inside the trailing arm, but it is still possible to see movement between the two halves of the shaft
Diff backlash is not usualy a crownwheel and pinion problem, but there are little brass thrust washers that fit behind the smaller gears in the diff, and these wear quite badly by 100,000 miles. Fitting can be a DIY job, but the diff has to come out
The diff in my Stag engined TR has done getting on for 250,000 miles and they have been changed twice
See how far the diff input flange turns before the output flanges move, it is not unusual to see an inch of movement, but the backlash between the crownwheel and pinion often cannot be felt while the diff is full of oil
On my Stag the diff is freshly rebuilt with virtualy no backlash, but the driveshaft splines are buggered and this gives a clunk when going from overrun to acceleration
Neil

Thanks Neil,
Infromative and helpful,

More investigation reqd,
Much appreciated

Mark

[maverick]

DifferentialExploded.jpg

Thanks Neil,
Infromative and helpful,

More investigation reqd,
Much appreciated

Mark

Having replaced a suspect outer universal joint which temporarily improved my clunky rear end the clunking has now returned,after studying Don Kennedys excellent artilce and noting Neils advice on the bevel gear shims wearing ,I have now come to the conclusion that these shimms may well be the culprits of my diff clunking.

Question is can I remove the shaft with the roll pin (that the bevel/planet gears sit on) with the output shaft bearings(110515) in place,and can this job be done by just removing the backplate for access.

Does any one know if the correct gears for shimming are 153385/4 Planet gears?,are these the only shims reqd?

Thanks in advance,any help appreciated as I am desperate to sort out this,ironically the diff doesnt wine too badly !
Mark

[flying farmer]

The planet gear thrust washers wear far quicker than the sun gear thrust washers. The thickness should be stamped in but often wears off, however there is usually an unworn bit in the middle that can be measured for thickness
I think I once changed the thrust washers without removing the diff, though the bearing caps may have to come off to punch out the roll pin.
IIRC the roll pin will only knock out one way, from the crownwheel side I think, but I have a 50% chance of being wrong.
If you lower the rear of the diff and remove the cover you should be able to see if you can get a punch down the rollpin hole
Neil

[StagnJag]

Yes the roll pin will only come out one way. It is actually a solid pin and the end of the diff carrier is dented in to hold it in place. I was bashing it for ages before I realised it would only come out one way!

I refurbished my diff a year or so ago, it was a real sod of a job and one i wouldn't wish to do again!

Rgds

Dave

[maverick]

Yes the roll pin will only come out one way. It is actually a solid pin and the end of the diff carrier is dented in to hold it in place. I was bashing it for ages before I realised it would only come out one way!

I refurbished my diff a year or so ago, it was a real sod of a job and one i wouldn't wish to do again!

Rgds

Dave

Thanks Neil and Dave ,
Neil by bearing caps do you mean part 110515,if not could you let me know which part from the diagram above ?Also wondered if I can do this job without a spreader or any other special tools and will the shaft come out with just the pin removed?

Thanks again for your help.
Mark