Thread: Puma rear P38 diff lock

Granted it is not a great diff, IMO it may be getting hyped bad press Aulro style.

Consider total number of P38 type rear diffs in use, consider total number of failures on Aulro

Seems alot of the failures are due to set-up. The question you need to ask yourself is:

Have you had it fail yet?
Has it been set up properly?
does it have good oil with regular changes?

Now if you answer No to the first, unsure to second and yes to third, it is probably serving you fine. Locking it will probably kill the axles first if you dont upgrade those.

The other thing to remeber is a Rover type diff was never offered in a 110 or 130 so it wont be legally load rated. If a built P38 type isnt good enough, skip the Rover type and just put in a Sals....this is what they had after all. Either way it will mean a prop shaft change.

Originally Posted by grover7488

Hi
i'm pretty keen to put lockers (prob Ashcroft) front and rear into my Puma but am hearing different stuff relating to the rear.

How many here are running rear lockers in Puma's with the P38?

Is the P38 that bad? Seems that the big downfall is the short pinion.

Is it possible to swap in a Disco 1 rear axle (disc to disc) and get a new (shorter) rear driveshaft

thanks for your thoughts

Grover you are not alone.

I bought an Ashcroft locka, axels and flanges because I wanted to make the rear reliable. I got the impression from here and others that the rover front was the weak link, so by building what I thought would be a bomb proof rear, I could get home from tricky areas like the desert.

Not so sure after peoples recent P38 experiences on here, but the locka and bits was still half the price of a second hand Sals that may need money spent on it anyway.

As others have said, it's not like all P38's are dyeing, just like not everyone's gear box in a puma drops it load.
I am going to run with my standard P38 rear diff with Ashcroft additives. I also bought new flanges for the front to run the axels in oil. I may upgrade the ring and pinion in the rover diff, but haven't done enough homework. It may need CV's and axel to make it all work strongly. If that's the case I will wait till it fails.

I would replace the Rover carrier before I replaced the Rover ring and pinion.

Originally Posted by uninformed

I would replace the Rover carrier before I replaced the Rover ring and pinion.

Forgive my ignorance, is the carrier the guts of the diff, what would replaced by a locka?

Is there worth regarding reliability using reverse cut gears in the front for normal use. I mean average off road 2,3 times a month. I'm guessing most upgrades are for competition, towing trailers or heavy loads cross country.

Originally Posted by newhue

Forgive my ignorance, is the carrier the guts of the diff, what would replaced by a locka?

Is there worth regarding reliability using reverse cut gears in the front for normal use. I mean average off road 2,3 times a month. I'm guessing most upgrades are for competition, towing trailers or heavy loads cross country.

Yep it is the guts that is supported by the carrier bearings. There are 2 half round machined spots in the removable 3rd casting that the bearings sit in. The carrier is placed in these and then bearing caps are fitted over creating the other half to form a full circle for the bearing, then they are bolted to the 3rd casting. The ring gear is bolted around its diameter to the carrier. The pinion is supported by bearings around its shaft that fit inside the nose of the 3rd cast housing.

A carrier has 2 side gears, which the axle shafts fit inside of. The Rover OEM carrier only has 2 other gears that rotate off the side gears. This is the Minimum a Differential can have. It is also the weakest by design. Along with material etc. The Rover carrier is known to fail more than and cause failures of the R+P.

There are a number of different carriers on the market, Diff locks or lockers, will generally be a better carrier by nature. Lokka is a brand so maybe dont refer to lockers as locka Some people like LSD or ATB diffs and some prefer lockers. LR actually do have a 4 pin upgraded open diff carrier as an option for the Rover type diff.

In the front application reverse cut gears are better because the tooth is loaded on the correct drive side, rather than the back side of said teeth.

It is my personal opinion that the R+P the last part needed to be upgraded in a Rover type diff. I would do carrier, shafts, flanges, cvs and run in oil before changing the R+P (either in front or rear) Many stock Rover and modded Rover diffs running OEM R+P.

Now if you are competing or hard core, or just changing ratio then it would be wise to change to a HD reverse cut for the front.

There is also no point building a bullet proof or even HD rear or front diff and leaving the other one stock.

Many here have toured using all stock OEM axle assemblies. But for my liking and knowing how many axles have been broken just from road miles, I personally would change these out.

Back when it was just the RRC and the Landrover 110 the cvs were ok. Now the modern 90's, 110's and 130's all have a smaller, shorter weak CV. This also makes the inner axle shafts weak because they are forced to be the small 32 spline at CV end (weak point) So if I was doing the front on a budget, I would do axles and CV's first. You can no longer buy genuine AEU2522 CV's but can get ok AM types for about $150. Throw these in and save up for the Ashcroft Cromo AEU2522. Now you can just upgrade the axles in the front, but they are compromised by the 32 spline CV. The AEU2522 set up is best, because it is all based on Stock replacement parts.

Get a locker for a stronger carrier. Ashcroft seem the Best ATM. Even if you cant afford to hook it up and get a compressor, atleast it is in the diff.

Have the diff set up by a specialist!!!!

Heavy loads and towing in normal road conditions dont normally add to much stress. It is when you start having to reverse up steep grades, load one wheel more than another etc.....

Most important thing you can do is proper maintainence and drive with mechanical sympothy.

Some pictures of a Rover type 3rd member. You can see the cast carrier with 2 side gears (bigger) inside it. Also note the carrier bearings held in postion with caps and bolts.

and pictures of a much better quality carrier for the Rover type diff. This is a MD locker.

Originally Posted by uninformed

Granted it is not a great diff, IMO it may be getting hyped bad press Aulro style.
Consider total number of P38 type rear diffs in use, consider total number of failures on Aulro

Seems alot of the failures are due to set-up. The question you need to ask yourself is:

Have you had it fail yet?
Has it been set up properly?
does it have good oil with regular changes?

Now if you answer No to the first, unsure to second and yes to third, it is probably serving you fine. Locking it will probably kill the axles first if you dont upgrade those.

The other thing to remeber is a Rover type diff was never offered in a 110 or 130 so it wont be legally load rated. If a built P38 type isnt good enough, skip the Rover type and just put in a Sals....this is what they had after all. Either way it will mean a prop shaft change.

Well deserved in my experience. I would go as far as to say they are a failure waiting to happen. Rubbish design for a hard working vehicle. The reason more Rangies don't ruin them is that most of them aren't used very hard, and nearly all P38as are automatic, which helps a lot...

Sorry Serg, i won't defend these diffs at all. I am actually very disappointed in LR for this backward step. I am quite hopeful Dave Ashcroft and his associates can come up with a solution for a drop in unit, as the sals is really too big and adds too much unsprung weight but at least is an easy and stronger alternative at present.

JC