P38a diff in 'fender problems

**justinc** · 4th May 2007, 09:41 PM

As most here are aware, the defender post 2002 uses the P38a differential in the rear. I have been informed quite some time ago by Mal of MD that they are very weak and have a propensity to damage crownwheels etc due to the fact they are so thin. I have at present one that is on its second pair of pinion bearings, and the C+P are both damaged by bearing particles, enough to make them U/S. The vehicle has 77,000km on the clock and apart from towing a trailer for work use, sees no offroad work.(YET)

I have obtained a new C+P, and will get the carrier refaced to ensure it is true ( It has an ARB air locker carrier)fit new Brgs obviously, and put it up for sale. The whole unit including Airlocker, disc to disc including ABS sensors etc will be up for grabs as we are fitting an ABS Salisbury from a 2000 Defender in its place.

My reason for mentioning this is that the rear end on this vehicle made some interesting twanging noises for a while before the first set of pinion bearings were replaced under warranty. If any of you with '02 on 'toy' differential equiped Defenders notice a twang when taking off particularly after reversing, then get it looked at ASAP, ESPECIALLY if it is under warranty.

Mal at MD has fitted some 4.11 gears to a few of these diffs, and has expressed disgust at their weakness, wondering why they went away from the salisbury, and his opinion was that the original rover diff was stronger as a fine spline unit, even without MD innards.

Why do LR insist on going backwards with these things?

JC

**discowhite** · 5th May 2007, 10:25 AM

how do you know its a p38 diff?? whats the diff(no pun) between the rover diff and the p38 one?? i was under the impression the p38 diff was a 4pin??

my 03-04 90 has a rover diff, just clocked 50 000k's, did half that on the oe center and bearings, everything perfect, the other 25 was done with new bearings and a detroit, same thing, perfect.

cheers phil

**discowhite** · 5th May 2007, 10:26 AM

i thought the p38 diff was the same as the D2 one?? looks like the rover diff but has a bigger diameter pumkin??

cheers phil

**Slunnie** · 5th May 2007, 11:38 AM

Aus D2's are all Rover diffs, the P38's I'm certain came only on the 4.6V8 models which were in the US market I undertood the P38 to be a 4 pinion centre, not the normal Rover 2 pinion centre, and it to have a different design for the CW flange, with CW/P to suit. The P38 diff doesn't fit through the slot into the Rover housings. The CW dia is the same though.

**justinc** · 5th May 2007, 03:18 PM

Simon's right, I would be happy if I could've fitted a Rover centre to the 110's rear, as it has one in the front!!!

Phil, it isn't a side gear issue, especially now with an ARB air locker 4 pinion carrier, it is a pinion bearing and crown wheel design weakness. I would also invite you to have a chat with Mal at MD, he has some interesting things to say about them.....

They are a disaster of a differential to be putting in a vehicle like a Defender.

I would suggest people examine the thickness of the crownwheel compared to the Rover diff, and you'll see exactly what I mean. It is about 40% thinner. This equates to way more deflection under high loads, and thereby loading up the pinion bearings and at worst case will break off some crown wheel teeth. If ever there was a need for 'pegging' this is it.

I guess a 90 wouldn't have the same loads applied due to its tare weight and most won't be lugging heavy trailers as much as a 110 because they aren't really a 'work' truck.

All I will say is that LR made an error fitting these to a Defender110 due to its inherent weaknesses.

JC

Most P38a RR's are used for 'light' duty ( Yes I know some aren't !!) and therefore they haven't yet seen too many failures.

**Slunnie** · 5th May 2007, 03:35 PM

In the aftermarket diffs like the Maxi and the ARB etc, have they made the CW flange thicker to prevent distortion? I just wonder as Tusker on here has a P38 rear diff in his Defender running 35's, 50% low range, gets used hard and has not suffered diff damage, but has twisted a maxi rear axle.

**justinc** · 5th May 2007, 03:44 PM

Originally Posted by Slunnie

In the aftermarket diffs like the Maxi and the ARB etc, have they made the CW flange thicker to prevent distortion? I just wonder as Tusker on here has a P38 rear diff in his Defender running 35's, 50% low range, gets used hard and has not suffered diff damage, but has twisted a maxi rear axle.

Is Tusker using MD 4.11's? If so I think they are upgraded CW thickness. AFAIK the mounting flange on the ARB etc is designed to fit a standard CW 3.54 ratio.
Mal has had a fine time trying to make these diffs worthy of his lockers!!

JC

**Slunnie** · 5th May 2007, 04:02 PM

Tusker I think was initially on MD lockers and 3.54's, but is now using Ashcroft 4.11's. I was under the impression that MD didn't really do CW/P sets anymore??? I'm not sure of this though.

**Redback** · 5th May 2007, 04:56 PM

Doesn't JMac do a Hilux CW&P for Rover diffs

**Slunnie** · 5th May 2007, 05:28 PM

Yes, but its easier to do the conversion yourself than to deal with Jeff. JacMac uses a low pinion front and rear with their own front housing, but you can do it youself with a Landcruiser hipinion front diff and no special housing. You'll also need axle halfshafts to suit.

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