Can I trust my Puma front diff?

[primal]

I own a 2010 Puma 90 with 270000kms. The friday before Christmas I had a rear diff disintegrate 6 hours from home with a 2 tonne van on the back. I was faced with having a local mechanic build a new diff (if he could get the parts), having it towed 3+ hours to a specialist diff or Land Rover mechanic, or ordering a diff from Ashcrofts in the UK. I went the Ashcrofts route. The diff was not that expensive, but freight, import duty and GST doubled the price.


So the rear has a super strong Ashcroft pegged ATB diff with heavy duty axles and drive flanges.


Most of the kms to date has been freeway driving, where you would expect the diff not to be doing much so I am assuming the initial cause of the damage was crown wheel related. (The mechanic had thrown away the shattered parts before I got to pick up the vehicle).


The main use in the future will be as a tow vehicle, with a lap on the cards within the next 18 months.


I am assuming the centre diff is symmetrical and has a 50/50 torque split ratio. If this is the case, and given that the rear rover diff has just destroyed itself, can the front rover diff be that far away from doing the same?


Are the loads on the front and rear diff significantly different when there is 150kgs on the rear tow ball?

Thanks

[DazzaTD5]

the rear P38 diff are prone to failure.
I rebuild them, ashcroft ATB, cap bolt for the crown wheel, you really dont need to get them pegged. I keep them in stock as I do enough of these (i dont ship them anywhere).

The front Rover diffs like most Defender diffs of old are not prone to failure, so yes can be trusted.
But they are good with a Ashcroft ATB also

There is plenty of other items that will fail well before the front diff ever does...

[primal]

Thanks for the reply


you really dont need to get them pegged.

I suspected the pegging was overkill, but it was a 180 pound optional extra, so not that expensive when ordering from Ashcroft directly. In comparison it is $875 in Australia for a modified diff housing and pegging kit from Kingpin Fabrications.

On the plus side, the drivetrain backlash has gone. From new this vehicle had a severe rattle when lifting your foot off the gas. I put it down to the "charm" of the Defender. Turns out it was the rear diff. The front diff does not have the same rattle, so that is good.

[Red90]

the rear P38 diff are prone to failure.

He has a 90. 90s have traditional Rover diffs, not P38. Pegging is a good plan if you drive off road.

The bigger issue on the late style front axles is where the halfshafts go into the CV joints. They are tiny at that location. I would carry spare shafts and a CV joint, if I were to stay stock. If you are just road driving, as mentioned, this is probably fine. If you do upgrade, an Ashcroft 4 pinion is good choice.

[DazzaTD5]

Thanks for the reply



I suspected the pegging was overkill, but it was a 180 pound optional extra, so not that expensive when ordering from Ashcroft directly. In comparison it is $875 in Australia for a modified diff housing and pegging kit from Kingpin Fabrications.

On the plus side, the drivetrain backlash has gone. From new this vehicle had a severe rattle when lifting your foot off the gas. I put it down to the "charm" of the Defender. Turns out it was the rear diff. The front diff does not have the same rattle, so that is good.

*as was already mentioned the 90 has a rover rear diff, i simply didnt read that.
*the rover diff front or rear again rarely fail, so i wouldnt be too concerned.
*as you say pegging is overkill, 99% of us that use a Defender on or offroad wont ever load it up enough to flex a rover crown wheel enough to break it.
*as you mention the pegging wasnt much more.
*yes all 110 / 90 2007 on Defender models are prone to a lot of clunk clunk, the diffs are parts of that issue.

*the front fine spline on a late rover diff half shafts, again for most of us you are unlikely to break them.
*when I broke a front course spline half shaft on my 110 Perentie I "upgraded" it to later fine spline with a ashcroft ATB and I have well abused it more without a issue.

[Toxic_Avenger]

*the rover diff front or rear again rarely fail, so i wouldnt be too concerned.
*as you say pegging is overkill, 99% of us that use a Defender on or offroad wont ever load it up enough to flex a rover crown wheel enough to break it.


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[goingbush]

Of course the Rover diff is prone to failure, Its virtually unchanged since the 1948 Landy & before that in the PreWar Rover car it was designed to run with 18HP . A few minor improvements along the way like metric bearings & updated carrier cup locks do nothing to increase strength.

[MLD]

the D90 Puma carrier was a 2 pin design. Not as strong as the front 200/300tdi and Puma 110HD/130 4 pin (not sure what TD5 was and given it had a change over in 2002, could be anything from the parts bin).

To the OP, understanding torque helps with explaining breakages. Torque is a twisting force. An engine produces torque based on demand. Driving on flat land the engine produces less torque than when going up hill. Also weight is the real killer of diffs. Heavier you are, more torque (twisting force) is generated from the extra resistence from the contact with the ground versus the engine trying to turn the wheels. Shock loading then also comes into play but not really a problem for a tow vehicle.

To the OP, your comment of symetrical torque bias 50/50 front to rear only happens when the CDL is engaged and that does not account for the left to right bias. Torque follows the path of greatest resistence. If 1 tyre has more weight on it or has the highest contact (grip) with the ground, a higher proportion of the engine torque is in the driveline at that wheel. Torque is constantly moving around the driveline. for example if you are facing down hill into a left hand bend, the front right will have proportionally the most weight of the 4 tyres and thus the twisting force of torque is temporarily the hightest on that corner.

[DazzaTD5]

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yes and no amount of pegging or anything else is going to prevent that sort of damage.
shock loading through abuse or a sudden lock up of the wheel is what destroys diffs.
I'd also likely believe the half shafts or at least one has signs of excessive movement on the splines.