p38 axle questions

[chuggaman]

hello guys

i am desperatly in need to clarify a few things before i start my new projest.

i know the p38 axles have the diff housing moved to the opposite side on the front.

do the diffs still drive/coast in the same directions ??

am i correct in believing they have a combination of 4 and 2 pin carriers

are they really 4.10 diff ratio

all help appreciated

mike

[David Sparkes]

Ok, as there is plenty of scope for confusion, I'm going to adopt the pedantic approach, and spell out what might be assumed.

Right and Left are used in the conventional automotive approach 'as viewed from the drivers seat, looking forward'. This also equates to 'as if standing at the rear of the vehicle, looking forward'.

I'm going to omit any reference to clockwise and counter clockwise. That will be for the reader to decide, AFTER deciding on their terms of reference (looking from the rear of the vehicle, or looking at the pinion, from the drive flange).

Yes, all previous chassied Land Rovers have the axle differentials on the right of the vehicle centreline.

The 38A has the axle differentials on the LEFT of the vehicle centreline.

The 38A axle ratio is always 3.54 :1.

The question about 'drive / coast' directions presumably refers to the relationship of the pinion to the crownwheel.

Viewed from the rear of the vehicle, the crownwheel in the front axle is to the right of the pinion.

Viewed from the rear of the vehicle, the crownwheel in the rear axle is to the left of the pinion.

I have checked this on my own 38A, specifically to answer this question.

I have no idea what the relationship is on any other chassied Land Rover, that has the axle differentials to the right of the vehicle centreline.

The differentials came as both 2 pinion and 4 pinion flavours from the factory. The fitment followed the pattern of Traction Control fitted.

Thus early diesels, and 4.0 petrols, had no ETC, and therefore 2 pinion differentials in both axles.

As ETC was introduced to the rear axles, those axles gained 4 pinion differentials.

Where 4 wheel ETC was fitted, both axles had 4 pinion differentials.

I do not know of any way of identifying the number of pinions from the outside, nor of telling from the axle case whether ETC was used. The toothed wheel and ABS sensor exists on all axles, as 4 wheel ABS was standard across all models. ETC was a function of the ABS ECU and the valve assembly, not the axle design.

Time has showed that even without ETC, the rear 2 pinion differential can fail. Certainly if anyone purchases a replacement differential ASSEMBLY from Ashcrofts, a 4 pinion differential will be supplied, and bolts straight into the axle.

Note ASSEMBLY. This is the differential, crownwheel, and pinion, all built into a case.

'Start a new project' implies a vapour element. Be aware that these units are very heavy, intended for a vehicle that weighs well in excess of 2 tonnes, and can pull a lot more. If the project vehicle is a lot lighter then you should consider whether you need the strength of these units, and the large unsprung weight the associated axles will represent.

Hope this answers all the questions.

[chuggaman]

Ok, as there is plenty of scope for confusion, I'm going to adopt the pedantic approach, and spell out what might be assumed.

Right and Left are used in the conventional automotive approach 'as viewed from the drivers seat, looking forward'. This also equates to 'as if standing at the rear of the vehicle, looking forward'.

I'm going to omit any reference to clockwise and counter clockwise. That will be for the reader to decide, AFTER deciding on their terms of reference (looking from the rear of the vehicle, or looking at the pinion, from the drive flange).

Yes, all previous chassied Land Rovers have the axle differentials on the right of the vehicle centreline.

The 38A has the axle differentials on the LEFT of the vehicle centreline.

The 38A axle ratio is always 3.54 :1.

The question about 'drive / coast' directions presumably refers to the relationship of the pinion to the crownwheel.

Viewed from the rear of the vehicle, the crownwheel in the front axle is to the right of the pinion.

Viewed from the rear of the vehicle, the crownwheel in the rear axle is to the left of the pinion.

I have checked this on my own 38A, specifically to answer this question.

I have no idea what the relationship is on any other chassied Land Rover, that has the axle differentials to the right of the vehicle centreline.

The differentials came as both 2 pinion and 4 pinion flavours from the factory. The fitment followed the pattern of Traction Control fitted.

Thus early diesels, and 4.0 petrols, had no ETC, and therefore 2 pinion differentials in both axles.

As ETC was introduced to the rear axles, those axles gained 4 pinion differentials.

Where 4 wheel ETC was fitted, both axles had 4 pinion differentials.

I do not know of any way of identifying the number of pinions from the outside, nor of telling from the axle case whether ETC was used. The toothed wheel and ABS sensor exists on all axles, as 4 wheel ABS was standard across all models. ETC was a function of the ABS ECU and the valve assembly, not the axle design.

Time has showed that even without ETC, the rear 2 pinion differential can fail. Certainly if anyone purchases a replacement differential ASSEMBLY from Ashcrofts, a 4 pinion differential will be supplied, and bolts straight into the axle.

Note ASSEMBLY. This is the differential, crownwheel, and pinion, all built into a case.

'Start a new project' implies a vapour element. Be aware that these units are very heavy, intended for a vehicle that weighs well in excess of 2 tonnes, and can pull a lot more. If the project vehicle is a lot lighter then you should consider whether you need the strength of these units, and the large unsprung weight the associated axles will represent.

Hope this answers all the questions.

Thankyou very much

you have been very helpfull indeed.my plan is to put p38 axles under my jeep cherokee.landrover moving the front diff to the opposite side means less fabrication of the donor axles.

the drive/coast question is to determine which way the pinion turns to get forward motion clockwise/anticlockwise.with the crown wheel being on the right side it will mean that the pinion turning anticlockwise will produce forward drive,which is also a result....

the weight and size is perfect for my plan and the axles will have to be upgraded to accomodate large wheels by changing the ratios etc.

the plan is to do a four link setup on the front and to copy that to the rear.

the p38 uses trailing arms and a panhard rod at the rear ??

many thanks

mike

[David Sparkes]

"the p38 uses trailing arms and a panhard rod at the rear ??"

Yes, and Yes.

Note that the trailing arms are composite (think glass reinforced plastic). They are designed to twist along their length, to give a certain amount of roll stiffness. IE They perform the function of an anti-roll bar as well as axle location.

This may or may not matter with your proposed design.

Cheers.

[Dr Gneil Pipely]

"the p38 uses trailing arms and a panhard rod at the rear ??"

Yes, and Yes.

Note that the trailing arms are composite (think glass reinforced plastic). They are designed to twist along their length, to give a certain amount of roll stiffness. IE They perform the function of an anti-roll bar as well as axle location.

This may or may not matter with your proposed design.

Cheers.

It doesn't sound as if road-performance is high on your list of priorities, but JE Engineering retrofitted a Watts linkage to P38s as part of their suspension upgrade. (Also, they moved the damper mountings outboard too, requiring wheel spacers to create room.)