P38A Gearbox Fault. No drive!

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RatCav

RatCav

Member
Posts
48
Location
Preston
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
 
Nope ... level is fine and pink. No leaks. All seems normal, apart from no drive, and no feeling of gear engagement when shifting the lever. Also now it sounds spot on as the loud tapping ratchety noise has gone.
 
Take off the wee cover at bottom of bellhousing and see if any bits fall out? Drop gearbox sump and again see if bits fall out. If nothing obvious then I reckon drive plate.
 
Hmm ... no little cover on the bottom (hole about 3" diameter allows me to see the TC and a very small section of the Flywheel/Drive Plate/Flex Plate.

If anything was ratting around there then it has fallen out.
 
I would suggest you get a diag read on it (only thing is i think prior to '99 the EAT ECU isn't CAN linked to ECM. BECM is obviously throwing something up on the dash). The fault code may help with this - volt read outs for the EAT pins definitely will.

However, as you say no drive is selected in any gear, meaning no clutch packs (pretty much ruling out a single solenoid failure) engages i would agree with the pump failure is a likely route.

Should have gone into limp mode, and locked into 4th gear though.

Is the transfer motor engaging? Sport mode (again not sure if it will be on your earlier model) lighting up? If it doesn't, then the fault code should help with why the ECM has stopped the clutches engaging.

If you don't have diag equipment, volt meter to EAT connector - try engaging each gear and get the readings and compare to w/shop manual (fairly sure there is a table with pin numbers and correct readings)

Thats what i would do before any dismantling! Hope this jargon helps!
 
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Yup that makes sense. I have no diagnostic though. Cannot find anything that is less than an amazing high amount of money. I appreciate that in the long term it may pay for itself, but money .. time of year yada yada.

When I towed it I fused port "11" as your meant to under the seat. Got the "Transfer Neutral" message. That gave some hope. Engine starts and runs fine and dandy. Handbrake works. Gear lever moves and before it records the "Gearbox Fault" message I get the moving light on the stick and display of gear on the dash. Even "shifts" into High and Low normally .. until it realises there is a fault and then it just displays "Gearbox Fault". Before the error message. Even though it thinks it is changing gear I get no drive what so ever. Engine picks up and drops normally. I don't get the normal "lurch" as the box actually engages the gears internally. I just move the lever and nothing happens in any gear High or Low. The metallic rattly noise that was there was there all the time with the engine running. That noise has completely gone now .. well it is now quietened so much I cannot hear it above the sound of a 4.6 V8 engine with a slight exhaust blow.

I think regardless of what the diag would say the issue is between the engine and the transfer box. Only leaves a few things. As you say the chances of all the solenoids going is very slim. Clutch plates again you would get something .. it is all heading to one of a few areas. The engine is obviously running so the crank is doing its thing. That means it has to be something between the crank and the gearbox oil pump. I am going to drop the box at the weekend and see what is happening. I feel that to fix it I am 99.99% likely to have to drop it anyway.

Thank you all for your time so far.
 
Fair enough, but plenty of stuff can be done with the volt meter and manual - after all all fault codes are is a change in voltage!

Lets try a rudimentary method - engage drive - try to push the vehicle backwards. Do the opposite for reverse and again in neutral. That should clear up with what the box is locked in (if anything - make sure the F11 is out though).

So you hear the motor engaging ye? Did you have any symptoms prior? Kickdown not working, poor performance, gear selection etc?

Hmmm. I honestly can't see it been a "failed" torque convertor. If the rotor/stator had come off (which is very very very slim) you would hear quite a lot of noise in the housing! The pump is in the housing though…

I would honestly get a diag to it…where do you live? Maybe someone in the area will help you out.

In the box you have a pressure regulator, 2 shift controls and there should be a lock up (all solenoids) - you may have pressure but its not doing anything.

The ECU obviously knows something is up!
 
I am in Preston. There is a guy round the corner with an ever increasing number of LR's (two disco's, P38, and a Forward Control .. all light metallic blue, apart from the light grey 101). Might go and knock on his door and ask. Other than that is trying to find a garage or such like who will most likely charge through the nose. I don't know anyone here that would have something .. in fact I have only just moved here so know very few people at all.

We did move it a few feet to the side of the road when it initially broke down. Had the selector in "N" for that and I pulled it very slowly with my 4x4. No more than a couple of mph and literally off the road. It was all I could do to get it off the road and stop it being an obstruction, as I had no tools and it was close to rush hour. It moved with ease and no disconcerting noises. I assumed that even though the selector was in "D" when the calamity happened, as the car was stationary it was internally in a neutral state. My gut feeling at the time was the oil pump (rattly noise was a failing pump and finally giving up the ghost. No pump then no drive or ability to change gear). I then read up and learnt about the fuse trick to tow it home. I was also armed with spanners then to remove prop shafts if necessary as I was aware you cannot tow them without doing something. The F11 trick did work though so at least I know that side of things work.

Before it failed completely it drove absolutely fine. However it did seem to hesitate to "engage" i.e. you select "D" but it would take a second or two to actually move. It always had the metallic tapping rattle noise. Ryhmic not intermittent. Gets louder and faster with engine revs .. not speed. Now when you select a gear you get nothing. No feedback through the car at all. It is as if the gear selector isn't connected to the gearbox. It registers the gear changes on the stick housing and the dash, up until the ECU registers there is an issue and then flashes up "Gearbox Fault"
 
I would take the sump off first and check that the filter isnt blocked or fallen off . Then the valve block and make sure there are no broken springs and no sticky valves any where and the selector valve is still connected to the seletor lever after that its box out and pump drive checked then see any shafts and clutches have failed
 
I also wonder if it's the flex plate that has failed... that could explain the tapping you heard - and why the engine is running ok, you get the gear indications as normal. the oil pump is usually only damaged if the torque converter has been removed and then not lined up properly again on install, so instead of driving the oil pump it destroys it.

I'd definitely remove the bell housing cover at the bottom and shine a torch up in there and have a look. Also, I think there is a rubber bung on the front of the bell housing (under starter motor somewhere) which can be pulled to get a better look (I have one on mine - though it is a later 01 model - I'm not sure if the earlier ones had it). If you can get a look in there, you might be able to see if the flex plate has cracked/broken up and causing the problem.
 
Place in park, hand brake engaged. Start engine. Lift car to high, put a stands under chassis. Get under with a torch look in through access hole and see if torque converter is spinning. If it is oil pump is duff. If it's not flex plate has failed.
 
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Hi wammers. Your the man to speak to apparently. :)

I bit the bullet today. Only the bell housing bolts to go and the gearbox is off. Got slightly delayed fixing my other truck. I have a new flex plate. Turns out, it is just as cheap getting them from LR dealership. Hopefully I will drop it later this week. My theory is no matter what is wrong, it has to come off.
 
I have the later sump apparently. The extended one with the two holes. I have poked, prodded, and rummaged. Tried even to see if there is any play in the TC. No play, and nothing visually untoward.
 
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