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Gearbox Fault. No drive!


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Hi there.


Was wondering if people could shed some light on my issue.


1996 P38 4.6 HSE Auto.


Was driving fine, though there was a noticible tapping coming from the bottom of the engine near the back .. though it could also be coming from the bell housing. Was difficult to determine the source, and I was going to look at it this weekend. Anyway. Gears selected fine. Light on the stick displayed. Went from High to Low as expected. Display on dash showed what gear I was in and everything. The girlfriend (her car tbh) left for an appointment Monday and got a few miles down the road when she slowed for a roundabout and lost all drive. Engine still starts and revs as per normal. Anyway she tried several gears until the display on the dash flashed up "Gearbox Fault". Car refused to select gears, and still no drive. When I went to look I had noticed the "tapping" noise had stopped. We moved the car out the way and I went out to look again to see if it has sorted itself out (sometimes these things happen). hoping it was a hot/low oil issue. No joy. It would allow gear selection, but no drive. Then after a minute or so of gear changing and such like the das flashed up "Gearbox Fault" again. I can home. We are going to recover it later when traffic is quieter. I am aware that to tow I have to fuse port "11" in the fuse box under the seat.


Now as for my problem my thoughts so far are:


Is the model number of the gearbox ZF 4HP24?


I have ruled out the selector as it will show the gears on the display until the "Gearbox Fault" message comes on. When selecting the gears you cannot feel the car do the usual lurch as the gearbox shifts (especially from "D" to "R"). This leaves me with three initial areas of concern


1) The oil pump has given out. There was a noticeable tapping knocking noise from the bellhousing area beforehand which has now gone. Obviously no pump no gear selection. I will start her up and pull a hose off and see if there is any pressure when I get a chance. Is the pump a known thing to go wrong on these gearboxes.


2) Something internal has given out and the entire gearbox is goosed.


3) The Torque Converter is goosed and not providing drive.


Either way I need to drop the gearbox, but I want to exhaust all avenues beforehand while on the car and able to feed power to it.


Apologies for the ramble, and I hope someone can enlighten me further.


Cheers

RatCav

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I can't help, but I shall watch this space with interest.

I bought a 4.6HSE auto about 9 months ago that was making a noise like a bag of spanners in the bell-housing area. I was hoping it was the flex plate and would be a simple fix. I get "gearbox fault" but I can still get gears and it still drives (I drove it onto the trailer). What's concerning me is that I was told with a flex plate issue, it is noisy until it starts, then i goes quiet. Mine is just plain noisy!

Mind you, I don't get a lurch either and it can take a while to get moving.

(Sorry, not intended as a thread hijack, but a similar problem!)

Cheers

Peter

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No problem buddy. If my issue helps others then that is a bonus.

Our tapping was always there and increased with the revs of the engine. Temperature and gear selection made no difference either. Car pulled like a train before hand. I originally thought the knocking was the dreaded slipped liners, but the noise has gone ... mysteriously at the same time the drive is gone. Have just towed it back home (in "Transfer Neutral") and the engine is running fine and dandy, purring nicely.

Sometimes it did take a couple of seconds to engage when pulling away i.e. we are in "D" and come to a stop. Stay in "D" and when you go to pull away the engine revs and then it hesitates and finally it pulls away.

More I think and research it sounds like torque converter. Will be pulling the gearbox off at the weekend, so will keep things updated.

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If it's a ZF4HP22 then the oil pump could be suspect, (very suspect on the HP22) if it's a ZF4HP24 then this isn't likely to be the problem as the oil pump was beefed up for this series, - when was the last time you replaced the gearbox filter and renewed the fluid?

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Working from memory as I sold my last P38 a while ago. On the back of the engine there is a cover plate for the flex plate / torque converter, remove this and it should be pretty obvious if the flex plate has failed.

I have also heard about (but never seen personally) of the torque converter bolts coming loose and falling out following a badly done gearbox change, again this should be pretty obvious with the cover plate removed.

The gearbox should be the HP24 unless the vehicle has been played with by an earlier owner, have a look at the Ashcroft website where it gives details on identifying gearboxes.

I am assuming you have already checked there is actually oil in the gearbox already.........

I bought a P38 with no drive a while back (it was very cheap), turned out the previous owner had broken the oil pump installing the gearbox so relatively simple fix, this made no noise at all from the gearbox area just no drive.

Other than that I think it is a case of gearbox out and see what you find. Wasn't a particularly difficult box to pull out just big and heavy and I did it on my back in the drive way with a selection of trolley jacks and quite a bit of swearing at various times!.

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It's an HP24.

And I'm going to stick my neck out based on your description and day your flex plate has shattered, classic symptoms. It connects the engine to the torque converter.

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Cheers for the replies. Will check Ashcroft for Identifying.

Yup plenty of oil in there. The truck had a full service just before we bought it but I don't know if that included the gearbox. My feeling it wasn't, as I had to top the oil up after we bought it, but then again they might of not put enough in after draining everything out. I am beginning to think Torque Converter more and more as the oil level when we bought it was very low (I had to put about 2 litres in to get it to the right level. If the TC was running dry then that could of been the beginning of the end. I think either way the gearbox is going to have to come off. Looks like a job for the weekend in the rain and sleet.

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Yup, sounds like the flex plate to me.

Sean f is right, there's an access plate to the bellhousing that's easy to take off. It's between the sump and the bellhousing, 6 or so bolts. You should be able to see what's wrong.

If the torque converter is dead, I'd expect to see discoloration, which you should be able to see through the access panel.

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It's an HP24.

And I'm going to stick my neck out based on your description and day your flex plate has shattered, classic symptoms. It connects the engine to the torque converter.

Bowie you beat me to it. I am inclined to agree with you. The knocking is consistent.

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This is quite reassuring. Broken flex plate is an easy thing to diagnose and fix ... just a matter of bolts. Also relatively cheap as well.

Just an aside. I have heard people say "Drive Plate" .. same thing I guess, just different peoples terminology. I would of called it a flywheel personally :D

Will have a quick look after work and pull that inspection plate off.

Thanks for the advice so far lads/lasses.

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The flex plate is separate to the flywheel, it bolts onto a middle spacer piece at the crank, and takes the drive out to the four torque converter bolts, it is flat, and has no teeth on it.

The flywheel is mounted directly to the crank, with a toothed edge, this is why you can still start the car and test it ;)

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Ahh ... I haven't had that before. Usually (read Ford Explorer, and Nissan Z31 300ZX) the TC was bolted to the flywheel directly. Interesting. Mind until about a year ago I have never owned an automatic gearbox car before. Only ever had manuals.

Anyways. I have been out and looked under the car. Found that the inspection hole has lost its cover. All I have is a hole about 3" across. I can see the TC, and if I get at the right angle I can see the flywheel. Nothing untoward. Also lack of cover plate means anything in there has probably fallen out.

So looking at pictures. The flex plate is simply a flat metal plate with 9 holes in. Looking at pictures. There is a bush bolted to the crank with 6 off allen head screws. Then there is a ring, followed by flywheel, followed by flex plate, lastly another ring and all of these are held on with 4 off bolts through the lot into the crank bush. Then the TC is bolted to the flex plate with another 4 off bolts.

If the flex plate is a solid (albeit thin) metal plate. How can it completely break to then not provide drive to the TC. That would be a serious amount of damage for something so simple.

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Anyways. I have been out and looked under the car. Found that the inspection hole has lost its cover. All I have is a hole about 3" across. I can see the TC, and if I get at the right angle I can see the flywheel. Nothing untoward. Also lack of cover plate means anything in there has probably fallen out.

That isn't the cover we meant, the actual access cover looks like it's part of the engine side bellhousing, lower left here: http://www.rover-classics.co.uk/images/reference/thumbnailv8/autobox/gallery/images/Drive%20Plate,%20Torque%20Converter%20&%20Housing_jpg.jpg

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I thought I was going crazy. I looked for that plate and couldn't find it. Went back out just now and I was right. I have one of these sumps on the engine:

s-l1000.jpg

I assume they removed that plate so they can fit an extra large sump onto the engine. I looked through the two access holes. without having any tools to rotate the crank I still cannot see anything untoward. The little tabs on the back face that I could see and feel through the access holes seem fine though. Unfortunately I didn't have a view through the holes on the flywheel to see the bolts that hold the TC onto the flex plate.

One thing I did notice which alarmed me is the engine and gearbox have been apart at some point. It was easy to deduce as there are no bolts between the sump back plate and the gearbox bell housing.

I can start to understand what may have happened. The engine and gearbox could be flexing apart at the bottom. That would make the line of the crank and the input shaft of the gearbox be out of true. The weakest point on the drive train would be the flex plate (as history tells us). Any play that would allow the TC to flex the ... errm .. flex plate more than usual will put additional stress on the plate and cause it to fracture. Anyway I won't know for sure until it is apart.

Does answer my question of how to get to the TC/Flex Plate bolts. That was bugging me as I couldn't find the inspection plate before.

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Strange, so you have the post-'99 sump on a '96. There are indeed two rubber plugs to allow you to access the flex plate bolts then, as you have already found.

I doubt that the sump to bellhousing bolts missing has much effect on flexplate longevity, especially as the earlier sumps didn't have that connection at all.

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Ahh .. I have a weird one then. Its a Gems as far as I can tell with the black box inlet with "4.6" cast into it .. replacement engine maybe?

Missing lower bolts, rubber bungs, and the inspection plate. Some right cowboy with the biggest stetson in the world has been at this truck it seems.

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  • 3 weeks later...
Plot thickens clear.png


Firstly apologies for the delay. Bad weather, stray kittens, many trips to the vets etc etc. Long story short I managed to get the box and TC off finally. Initial discovery is the flex plate is fine. No cracks or splits or anything. In fact it is pretty unmarked. Thoughts are now heading towards Torque Converter or Oil pump. I have no idea how to test either, but I do have a good auto transmission shop near me. Two other things I have discovered. It is a second hand box. Someone has written 4.6 V8 in yellow scrappy pen on it. Also another bell housing bolt is missing (top drivers side). The TC output shaft has been chewed slightly. Anyways photo's:


IMAG0387.jpg

IMAG0389.jpg

IMAG0390.jpg

IMAG0391.jpg

IMAG0392.jpg

IMAG0397.jpg

IMAG0399.jpg

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The damage on the torque convertor is a classic sign the gearbox was installed badly and the oil pump has been damaged, almost exactly what I had on the vehicle I bought.

The TC should be fully engaged in the gearbox when fitted to ensure exactly this doesn't happen (Ashcroft give measurements to confirm it is fully fitted). What has probable happend here is the TC wasn't lined up with the drive for the oild pump and the gearbox was fitted then pulled up using the mounting bolts and in doing so has broken something on the oil pump.

Have a word with the auto gearbox people they may be able to just change the oil pump depends on if anything else has been damaged as well.

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