P38A Driving with front propshaft removed

pwood999 · May 18, 2023

Had lots of rumbling when going uphill while driving back from Bournemouth yesterday. Checked today & UJ's definitely need replacing. The one on front diff has lots of slack. Ordered hardy-spicer replacements & bolts for all four.

So while I wait for the parts, are there any issues driving with front prop removed ? Seems to be different opinions out there ?

Pete

kermit_rr · May 18, 2023

Unless I'm being dim, there's no diff lock, so the front output would just spin?

marjon · May 18, 2023

I have looked at this a few times, IMO I would only do it to get it in and out of the garage or to a safe place.

As there is no diff lock it relies on the VC to lock and give drive.
The rear drive goes through the diff to the VC, which I believe is why some say its no problem. But the front drive is also taken from the diff and passes through the outer of the VC, hence where it sees the difference and locks up.
So I would say no personally.

Its strange why they fitted both a diff and a VC as surely they could of just fitted a diff and a bloody diff lock

I have never had 1 apart so am just working on manuals and (my

) knowledge and workings of things.

But I am all ears if somebody can tell me different

.

J

Datatek · May 18, 2023

marjon said:
I have looked at this a few times, IMO I would only do it to get it in and out of the garage or to a safe place.

As there is no diff lock it relies on the VC to lock and give drive.
The rear drive goes through the diff to the VC, which I believe is why some say its no problem. But the front drive is also taken from the diff and passes through the outer of the VC, hence where it sees the difference and locks up.
So I would say no personally.

Its strange why they fitted both a diff and a VC as surely they could of just fitted a diff and a bloody diff lock

I have never had 1 apart so am just working on manuals and (my ) knowledge and workings of things.

But I am all ears if somebody can tell me different.

J

Driving with the front prop removed risks ruining the V CU so except for a very short distance, it's not something I would do.
The VCU is the cheap excuse for a diff lock, it serves no purpose in normal road driving. They could have fitted a proper diff lock but that would have cost more.

300bhp/ton · May 18, 2023

Datatek said:
Driving with the front prop removed risks ruining the V CU so except for a very short distance, it's not something I would do.
The VCU is the cheap excuse for a diff lock, it serves no purpose in normal road driving. They could have fitted a proper diff lock but that would have cost more.

I'm not sure the vehicle would move, you'd have to try it and see.

Your 2nd point makes no sense at all. The RR (p38) was the most expensive and flagship model..... Other lesser models like the Discovery and Defender had centre difflocks. So the lack of one on the RR is not a cost thing...

With the LT230 with the diff open, on a slippery surface or with a wheel off the ground, you would essentially end up with 1wd (yes one wheel drive).

With the viscous unit is it more like having a limited slip differential, you will always have power to both axles and a minimum of 2wd pretty much.

Therefore in slippery conditions the RR will have more traction than a Disco with an open diff.

As a consequence of being a limited slip device, you also get a better turning circle with the viscous unit compared to a locked LT230.

pwood999 · May 18, 2023

ok, will wait for the new UJ's to arrive.

In the meantime, the bolts at the transfer case end seem to be the wrong way round to me ? Doesn't appear to be enough room between the prop flange & the TC shell to remove them ??

Datatek · May 18, 2023

300bhp/ton said:
I'm not sure the vehicle would move, you'd have to try it and see.

Your 2nd point makes no sense at all. The RR (p38) was the most expensive and flagship model..... Other lesser models like the Discovery and Defender had centre difflocks. So the lack of one on the RR is not a cost thing...

With the LT230 with the diff open, on a slippery surface or with a wheel off the ground, you would essentially end up with 1wd (yes one wheel drive).

With the viscous unit is it more like having a limited slip differential, you will always have power to both axles and a minimum of 2wd pretty much.

Therefore in slippery conditions the RR will have more traction than a Disco with an open diff.

As a consequence of being a limited slip device, you also get a better turning circle with the viscous unit compared to a locked LT230.

The car can be driven with the front prop removed many have done it, the VCU locks to ensure drive.
I'm sorry but the VCU is just a cheap and rather nasty alternative to a diff lock, no control needed electronic or manual. Unlike a locked diff, it requires loss of traction on one axle before it can lock and is therefore less effective than a proper diff loc.

Datatek · May 18, 2023

pwood999 said:
ok, will wait for the new UJ's to arrive.

In the meantime, the bolts at the transfer case end seem to be the wrong way round to me ? Doesn't appear to be enough room between the prop flange & the TC shell to remove them ??

No need to remove them, there is no problem reusing the existing bolts, I know this is not the fashionable choice but they will be just fine.

pwood999 · May 18, 2023

Datatek said:
No need to remove them, there is no problem reusing the existing bolts, I know this is not the fashionable choice but they will be just fine.

Yes I figured I'm stuck with that, but it would be nice to replace them just in case !!

pwood999 · May 18, 2023

According to RAVE, it looks like the bolts are the correct way round. Flange has to come out to change them.

Datatek · May 18, 2023

pwood999 said:
Yes I figured I'm stuck with that, but it would be nice to replace them just in case !!

I have done the props on 2 and never changed the bolts and not had any problems. All this bolt changing is a modern thing. The prop bolts are in shear so not likely to fail.

norseman · May 19, 2023

Datatek said:
The car can be driven with the front prop removed many have done it, the VCU locks to ensure drive.
I'm sorry but the VCU is just a cheap and rather nasty alternative to a diff lock, no control needed electronic or manual. Unlike a locked diff, it requires loss of traction on one axle before it can lock and is therefore less effective than a proper diff loc.

A theory exists that it was done for the benefit of owners that want everything to happen automatically, rather than having to move a lever & sometimes shunt the car a bit to ensure engagement, because that requires thinking ahead

Being 'old school' I'm with you on the diff-lock option.

300bhp/ton · May 19, 2023

norseman said:
A theory exists that it was done for the benefit of owners that want everything to happen automatically, rather than having to move a lever & sometimes shunt the car a bit to ensure engagement, because that requires thinking ahead

Being 'old school' I'm with you on the diff-lock option.

The RRC also used a viscous unit.

I don't know of any circumstances where it is a hinderance. And they generally out perform LT230 vehicles in off road competitions.

Datatek · May 19, 2023

300bhp/ton said:
The RRC also used a viscous unit.

I don't know of any circumstances where it is a hinderance. And they generally out perform LT230 vehicles in off road competitions.

My P38 on road tyres struggles to climb the grass slope from my parking to the road when wet or frosty. My Pajero with a centre diff lock and LSD rear diff and my Galloper with no centre diff and LSD rear diff on similar road tyres climbed out with ease. The P38 sounds like a machine gun with the TC firing which helped not at all.

300bhp/ton · May 19, 2023

Datatek said:
My P38 on road tyres struggles to climb the grass slope from my parking to the road when wet or frosty. My Pajero with a centre diff lock and LSD rear diff and my Galloper with no centre diff and LSD rear diff on similar road tyres climbed out with ease. The P38 sounds like a machine gun with the TC firing which helped not at all.

That doesn't sound related to the centre diff if I'm being honest. Tyres, suspension, tyre width, wheel base and other things would all have a major impact.

A rear LSD could also make a big difference too, although the TCS on the P38 is really an electronic way of simulated an LSD (in this situation).

I've off roaded my p38 quite a bit, plus being doing off road competitions for nearly 25 years in various Land Rover products. I've seen lots and lots of classic RR's with the viscous centre diff do very well. And it is the transfer box of choice for all of the V8 powered 80" coiler purpose built competition vehicles. I've not struggled for traction in my p38.

Can't say I noticed any traction issues myself....

norseman · May 19, 2023

300bhp/ton said:
The RRC also used a viscous unit.

Well the later years anyway.

Had one in my '93 RRC & that required replacement as it had started to seize.
All 3 of my 3.5efi's had/have the diff lock. Personally I prefer manual control, but it's a matter of choice.

pwood999 · May 20, 2023

Props off & fitted four new Hardy Spicer UJ. Vibration & rumbling seems to be gone up to 60mph on local dual carriageway, but needs a motorway blast tomorrow to be sure.

Balance weights appear to be missing on the diff end of front prop, and transfer case end of the rear prop ? Might need to get them balanced.

marjon · May 20, 2023

pwood999 said:
Props off & fitted four new Hardy Spicer UJ. Vibration & rumbling seems to be gone up to 60mph on local dual carriageway, but needs a motorway blast tomorrow to be sure.

Balance weights appear to be missing on the diff end of front prop, and transfer case end of the rear prop ? Might need to get them balanced.

I see a wt at the diff end in your last pic?

J

pwood999 · May 21, 2023

Tired typing. Was the other end !!

P38A Driving with front propshaft removed

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