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4HP24 Gearbox Failure


JohnnoK

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After dropping the brats at school, I stopped in front of my gate to open it, left the car idling in Neutral, and when I got in and selected Drive it made a weird "grumbling" noise and didn't go into gear.
Reverse was brief and then any selection after that was a no-go. Revving it in Drive got a short hop, enough to get it moving, and then back to nothing.
The oil level is good and the GEARBOX FAULT message comes up, but not every time I tried to work through diagnosis.

To add insult to injury, my Nanocom won't come on when plugged in. It works on my Disco, not the P38.

Any ideas, please?

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Cheers for the replies, folks.

Considered opinions all seem to point to the flex plate as the likely culprit. Apparently they either break and lose drive to the TC or they warp under load and disconnect the torque converter from the lugs of the pump drive causing pressure loss.

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If you do remove the gearbox be aware that the torque converter is only pushed onto the input shaft & will happily fall off if not locked into position by some external means. I'd suggest making a 'T' shaped piece of metal with the arms of the 'T' drilled to match up with two of the small bolts that hold the small round cover onto the bottom of the bellhousing & the shaft of the 'T' bent so it goes up inside the bellhousing & presses against the torque converter. Use a piece of 3mm plus steel as the weight of the torque converter will bend thin sheet & then it falls off. (Guess how I know - albeit a 4HP22)

When refitting, the tc MUST be on the gearbox and seated to the appropriate depth which is measured from a straightedge across the bellhousing mouth to the front of the 4 bosses on its front. If not it will fit but will break the pump & you get to take it all off again. Distances given on Ashcroft's site if you don't have the LR manual. Although the manuals show it being fitted with the box horizontal it's MUCH easier to seat if the gearbox is vertical. Once seated use your 'T' tool to keep it in place.

I also recommend making up the LR jack to gearbox mounting plate as these are big heavy unbalanced units. 

Edited by paintman
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5 hours ago, paintman said:

I also recommend making up the LR jack to gearbox mounting plate as these are big heavy unbalanced units.

Thanks for the tips regarding the tool, will definitely do that.

Can you point me at a drawing for this plate, please?

This is going to be a slow "as funds permit" job, so don't be surprised if it goes quite for a while...

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Apologies for not getting back sooner.

Mine is the RRC which has the 4HP22 & the diagram for that is in the factory workshop manual.

I've had a look & all I can find for the P38 is reference to a LR Special Tool LRT-99-007 with some pics in the online manual but no dimensional drawing. 

http://www.landroverweb.com/Pdf-files/Manuals/Workshop-Manual-P38-Range-Rover.pdf Page 651

 

Edited by paintman
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  • 2 weeks later...

Paintman,

Thank you, sir!

The boxes are essentially the same, barring the electronic control and some internal differences, so that will serve as a starting point for a project.

Edited by JohnnoK
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Don't know if this will work for you but I've done a few bits & pieces to the internals of mine & used this UK company for the parts. They were very quick on delivery & very good on prices too. I replaced the steel sealing rings on the input shaft with the Teflon ones which would have cost a fortune from ebay (USA only) but were pennies from them.

Has very good exploded diagrams of the boxes.

https://jpat.co.uk/zf.html

https://jpat.co.uk/uploads/1/0/3/5/103549764/89__zf_1_4hp22-24.pdf

This might be of interest:

http://bmwe32.masscom.net/moswald/zf4hp22_rebuild/zf4hp22_rebuild.html

http://www.cowdery.org.uk/zf.php

Edited by paintman
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  • 2 years later...

So, I finished it up yesterday, new front seal, filter and sump gasket, 11 liters of Ravenol Dex III and started her up.

Not happy on 2 year old fuel, but got the old bag to idle eventually, and shifted through the gears a few times to get the oil nicely into the gubbins and the torque converter. Then, set off for a drive around the block to get some fresh fuel and see what else has decided to quit on me since I parked her.....                                                                   Such a great feeling driving the Rangie, big smile on the dial until I got back to the house, around 5km of smiles...... pulled up at the gate to allow it to open, and, back to the top of the thread..... NO DRIVE AGAIN!!!🤬 Feckitall, bollox and similar un-nice words of a blue tinge.

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14 hours ago, Snagger said:

How about reverse?  Have you tried the other forward selections?  I remember that the spray clutch can cause trouble if the cams invert, but I thought that was a 22 problem, eliminated on the 24.

No other gears, not in high range or low range, NOTHING at all!

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  • 3 weeks later...

Right, so I went out and bought a transmission to fit to the Rangie....

Cue the installation of it today and..... the bellhousing is different to my GEMS engine one...🤬🤬

My understanding of the engines is that they are all the same from a bolt holes and layout point of view, so what am I missing? The only difference between the GEMS and Bosch engines is the intake, ECU, CPS and some ancillaries, but the blocks should all be identical, right?? Yet, my bellhousing has the bolt below the starter motor almost 3/4" out of the corresponding hole in the block.

The burning question now becomes.... is the gearbox also somehow different or can I just swap bellhousings over? Can it be that simple?

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Just now, elbekko said:

Did you buy one off a diesel maybe?

I don't think so, it has a monster torque converter in it that almost fills the bellhousing.

I am all showered up and on my first beer, so will crawl under the old 131TCH tomorrow and check while I place the kindling in position.

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The oil pan is different on the Bosch as well. But the bellhousing should fit, we fitted a bellhousing from a (manual) GEMS to go on a Bosch engine without trouble. And a mate uses a Bosch V8 block with the original autobox and bellhousing. So the boltholes should match all V8s, at least on the block if not on the sump.

Diesel bellhousing is indeed completely different, but should be obvious as it has the starter on the left instead of on the right. 

I have GEMS blocks and bellhousings from both GEMS and Bosch lying around, if there's anything you'd want me to check/measure to help you out let me know.

Filip

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I also have many ZF gearboxes to fit the V8s in all the colours and all the sizes, and I have not noticed any differences in the bellhousings ????

Diesel one is so obviously different and the starter is on the other side of the engine.

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7 hours ago, smallfry said:

I also have many ZF gearboxes to fit the V8s in all the colours and all the sizes, and I have not noticed any differences in the bellhousings ????

Diesel one is so obviously different and the starter is on the other side of the engine.

As Captain Mainwaring of Dad's Army would say.... "Stupid boy!"...

I had my bolt in the "extra" hole below the starter bulge in the bellhousing. Small wonder it wasn't lining up properly, and it never would have, too. The bolt is now in the right position and progress can proceed accordingly...

Duh.jpg

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