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blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17391

2007 Defender 110 Puma 2.4 DCPU Stornoway Grey

jst wrote:
pin has collapsed in the front diff.

James, you win the coconut!

Took the old diff out and fitted the new Ashcroft ATB yesterday.

First off, a huge thank-you to the guys and girls at Ashcroft Transmissions who built and delivered a really beautiful diff in a very short time. What a pleasure to see a spotlessly clean diff which has been built and set-up correctly, and carefully wrapped and packed. I really couldn't have hoped for a better service (and at £400+ less than a Landrover 4-pinion diff it is tremendous value too)!

The old diff did indeed have a collapsed pin; in fact, I am amazed that the old diff could get so worn and knackered and still keep going for so long. If I get the chance to take some photos in daylight I will post them, but in a nutshell the obvious defects were:-

1) the holes for the cross-pin appeared to have been made with a slot drill - they are elongated to the extent that they are quite literally two diameters long in the wear direction,
2) the cross-pin is in two parts, having sheared clean through
3) all the teeth on both pinions and both side gears have about 40% material loss

It was not possible yesterday to ascertain what exactly has cause it to seize (it was getting dark and i wanted to get the new one in) but the entire differential is a sort of metallic mush. Curiously though the crownwheel and pinion and diff carrier bearings all appear to be in perfect condition still, so if anyone wants a pinion housing to build up into a locker let me know quick, it's yours for £100 (otherwise it'll go back to AT so I get the deposit back). Getting the swarf and fragments out of the axle case was possibly the longest single part of the job.

In case anyone is contemplating swapping out their front diff, it might be useful to know that it is possible to do without disturbing the brake lines, despite the workshop manual saying that they must be disconnected. If you jack the front end up so that the front wheels are only an inch or so from the ground, you can unbolt the swivel housings (don't remove the road wheels) and pull them out about 3" from the axle, then let the wheel take the weight. Put a block of wood under the track rod arm on the swivel hub to prevent it rotating downwards (which would stretch the brake hose). It isn't particularly easy getting the halfshafts back into the diff since you have to hold the swivel hub to stop it rotating, lift the wheel/hub/halfshaft assembly to slide it back in, but it can be done (and I was working without assistance). If you have ABS/TC (I don't) you may need to check the slack on the wheel speed sensor cable.

The whole job took about three hours working solo (in the rain, and for half the time in the dark too).

7th Dec 2011 9:27am

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8035

2011 Defender 110 Puma 2.4 USW Stornoway Grey

glad the cause was found.

correct, you dont need to take swivels apart of pull brake lines off to remove wheel stations sufficiently enough to get a diff out. Cheers

James
110 2012 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

7th Dec 2011 4:11pm

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17391

A couple of photos of the broken diff, in case anyone is interested. Note that the hole for the cross-pin is worn to the extent that it is nearly two diameters in the direction of thrust. Final failure came when the pin sheared allowing the two differential pinions to move. In the second photo the sheared pin can be seen, together with the well-mashed teeth of the differential gears.

Having now done the normal weekend mileage of 350 miles or so since fitting the new diff, it is clear that the improvement is incredible, perhaps not surprising given the state of the old one. What has surprised me though is the improvement that the new diff has made to the gearchange, which (even after the new clutch was fitted earlier in the year) was clunky and pretty horrible. Now for the first time the gearshift is almost as smooth as a normal vehicle. I really hadn't expected this!

If you are one of those unfortunates who has tried all the normal remedies for a clunky and horrible clutch/gearchange and still not found the problem, it might well be worth checking for driveline and/or differential wear.

Also, given that my vehicle hasn't (as far as I know) ever been systematically abused, and yet the diff has failed in this way at 87k miles, if you have a 90 or an early 110 with the 2-pinion diff you may want to consider popping the diff out to check it in case it has this advanced wear.

Click image to enlarge

12th Dec 2011 11:02am

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8035

blackwolf wrote:
the diff has failed in this way at 87k miles, if you have a 90 or an early 110 with the 2-pinion diff you may want to consider popping the diff out to check it in case it has this advanced wear.

sound advice, cant believe the state of that after the mileage.

have you owned it from new? Cheers

James
110 2012 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

12th Dec 2011 12:06pm

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17391

jst wrote:
sound advice, cant believe the state of that after the mileage.

have you owned it from new?

No, I am the fourth owner, but the first two between them had it for about 20k miles and 2 years. After that a very good friend of mine bought it and ran it for a year and approx 30k miles, but during this time I drove the vehicle regularly and I know how it was treated (I also carried out the routine maintenance on it, and oversaw servicing etc) So, unless it was monstrously abused in the first two years, it has had no particularly unusual treatment.

The oil level in the axle was correct when my friend bought it, and there was no metallic debris visible when I first changed the axle oils not long after.

Having said that, though, it is a bit of a mystery. I have seen many diffs from series Landrovers, including Series Ones, which are essentially exactly the same design and which have been much older and far, far higher mileage, which have been in perfect condition. Admittedly the engine power and torque is much higher on a Puma, and it is unlikely that earlier Landrovers would have been capable of the sort sustained high speed cruising that a Puma can manage (although my Series 1 86", with 2286cc engine, overdrive, etc can cruise at 70) but even so I am surprised at the extent of the wear.

It seems likely to me that most of the wear occurred first, then the pin sheared and the diff seized almost immediately after the pin sheared. I cannot think of a plausible failure scenario involving the pin shearing, then the wear, then the seizure. I think there must have been a considerable period when the pin was rotating in the differential carrier with one bevel gear seized to it, rather than the two gears freely rotating on a fixed pin. All a bit strange.

At least the outcome is that I now have a far superior diff fitted!

12th Dec 2011 12:46pm

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 8035

there was a bad batch of diffs on some of the very early vehicles.

wear first then the failure, no question. Cheers

James
110 2012 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

12th Dec 2011 2:28pm

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