aerofabrique
Active Member
Personally, Not on p38 most common one here i think will be psi. Try the defender forum as i believe theyre quite popular there. Someone may come back here though...
Power boxes and auto boxes on rr are not a happy marriage as you'll find out
I don't know for sure the torque limit of the 4hp22 box, from what i read its either 340nm or 380nm.
The m51 when stock has 265nm and i can't tell the numbers of a mine with chip and bigger intercooler but should be around those 340nm.
But i can tell from the tuned Td5 that i drove that it has much more torque than mine and it has been like that for around 60k miles.
So although the numbers (if they are correct) may say that the box will die, in real life most of them survive.
The m51 when stock has 265nm and i can't tell the numbers of a mine with chip and bigger intercooler but should be around those 340nm.
But i can tell from the tuned Td5 that i drove that it has much more torque than mine and it has been like that for around 60k miles.
So although the numbers (if they are correct) may say that the box will die, in real life most of them survive.
aerofabrique
Active Member
Even on my r380 manual the clutch cant cope with the extra output from a psi Slips whenever the throttle goes hard over halfway. Clutch is good and replaced by ashcroft couple of months back. You have to keep the revs well up in a lower gear to match the clutch with the flywheel speed and torque for it to work to its full advantage. Not good for engine or box...if LR could produce more power at the wheels from the m51 and thought the drive train could cope im sure the ecu would have been written that way in the first place.
Hypocritical of me but i think powerboxes are false economy especially if youve ever opened one up. For the price i expected intel processors and diamond encrusted PCBs not a homebuilt project built on a breadboard.
Hypocritical of me but i think powerboxes are false economy especially if youve ever opened one up. For the price i expected intel processors and diamond encrusted PCBs not a homebuilt project built on a breadboard.
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Datatek
Well-Known Member
No they do not under estimate the max rating, they give 2 figures, an absolute max and a recommended limit. Anything over the recomended figure reduces life expectancy.
Failure on the 4HP22 on chipped diesels is not down to poor maintenance, at least not in every case. Mine had been properly maintained but started to give up when shifting with the power box fitted. Removing the power box and adding Lucas Transmission Fix improved things but soon I will have to swap the box. If you use the extra power of the power box, don't expect more than 60K miles from the box, even if you don't use all the power, the lack of torque reduction on shifts will shorten the life of the box.
The fact is that the auto ECU requests a torque reduction when a shift is about to occur, fitting a power box effectively nullifies the torque reduction as it takes over control of the fueling thus over loading the box during shifts
Incidentaly, ZF stands for the Zeppelin Foundation the same lot that built the Hindenburg and the WW1 Zeppelins.
These days they prefer ZF Fahrwerktechnik of Friedrichshaven. The Zeppelin Foundation still own a sizeable chunk of the company as does the city of Friedrichshaven.
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jamesmartin
Well-Known Member
id agree with datatek it is the harshness of gear change ,its usually the diesel boxes that fail
Mike v.t.s
Active Member
Mine died 6 month after fitting the PSI box, I set off from work up hill then put foot down and it kicked down from 2nd to 1st and bang the spragg clutch failed so now when I stop I have to set off in 1st then over 10mph select drive.
Saying all that though I'm still keeping the psi box fitted when I change gearbox as its worth a box every now and then, I couldn't cope with the under powerd slug monster with out it, gets embarrassing when mopeds overtake.
ShotmaKer
New Member
From what I gather, 4HP22's max torque is usually said to be either around the 300 Nm mark as Datatek stated, or around the 380 Nm mark - found posts on other forums backing the latter. Either way, official specs are not easy to find it seems. Confusing...
Dave from Ashcroft Transmissions seems to believe fitting a bigger oil cooler for the gearbox might help, as heat is usually the issue with these bad boys, or so I've been told.
Dave from Ashcroft Transmissions seems to believe fitting a bigger oil cooler for the gearbox might help, as heat is usually the issue with these bad boys, or so I've been told.
StuckAgainSteve
Well-Known Member
Don't Ashcroft offer an upgrade service to fit the bulk of the 4HP24's stronger internals into the 22? They should be well aware of its failings and aware that a larger oil cooler is just masking an inherent problem. The number of them that have gone pop in chipped-up diesel P38s is more than enough evidence to suggest there are already near their torque limits standard. Well maintained 4HP24s are practically bullet-proof.
Datatek
Well-Known Member
Datatek
Well-Known Member
Ashcrofts do indeed offer upgrades to various parts of the HP22, have you seen the prices
ShotmaKer
New Member
380Nm is the recommended figure I have for the 4HP24 with an absolute max of 450Nm
Cheers for that
Ashcrofts do indeed offer upgrades to various parts of the HP22, have you seen the prices
Am I mistaken in thinking that, given the prices, somebody has at least tried to rebuild the HP22 with the stouter HP24 internals on their own?
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Cheers for that
Am I mistaken in thinking that, given the prices, somebody has at least tried to rebuild the HP22 with the stouter HP24 internals on their own?
Biggest fail points on the 22 are the one way clutches. I believe Ashcrofts do up rated ones for it. But don't hold me to that.
