P38A Stall speed monitoring gearbox fault

marjon said:

I thought the Can Bus was Range rover, not just the 4.6 (at a certain year) but that basically the Hp22 was the same electronic control as the Hp24 and also has the learn function.
But willing to read a bit more on it when I have time .

J

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No learn function on the HP22 ECU as far s I'm aware, I will re-read RAVE this evening

marjon said:

I thought the Can Bus was Range rover, not just the 4.6 (at a certain year) but that basically the Hp22 was the same electronic control as the Hp24 and also has the learn function.
But willing to read a bit more on it when I have time .

J

Click to expand...

Datatek said:

I have been out and re-checked the sensor readings. I'm a bit embarrassed to find I have a broken lead that goes open circuit at certain angles on my DVM which resulted in the readings I gave you. The re-test shows 307 ohms both ways round. sorry about that.
Have you checked from either pin to the auto box metal work?
Chasing a fault on my auto box I swapped the ECU with no problem. It didn't cure the fault though.

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Thanks for doing that!

I checked from either pin to the gearbox casing with the ECU plug (C1320) disconnected and have infinite resistance there. I do get readings with the ECU plug connected but that's not the correct way to measure I think because then you're measuring the ECU side.

(I do all my measurements with a needle probe from the C0745/C0988 connector under the center console)


I still think it's weird that there is the same DC voltage between either pin and ground. (It's weird that there is any DC voltage there tbh, why not use a normal inductive sensor..). My voltage readings during driving seem to suggest something is happening, but I would expect the same amplitude regardless of speed. So maybe that's just noise.

Datatek said:

View attachment 310884View attachment 310885

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Whoa! So they snuck in a little canvus technology on the '99 gearboxes? Naughty.

Every day is a learning day.

So I finally found time to continue on my quest.

Took the pan off, and took the sensor out. Then stuck a borescope in the hole. Not good news.




Seems like indeed the bolts for the trigger wheel came loose. Hopefully they didn't do too much damage inside.

Now I need to have a think about how I can get those back in their holes. I don't fancy taking the back end of the gearbox as that means that exhaust, props and transferbox need to come out...

The trigger wheel bolts to the parking brake wheel, in above pictures it needs to move slightly to the left. The parking brake wheel is on the left. (Left = back of gearbox)

ar1g3 said:

So I finally found time to continue on my quest.

Took the pan off, and took the sensor out. Then stuck a borescope in the hole. Not good news.

View attachment 311733
View attachment 311734

Seems like indeed the bolts for the trigger wheel came loose. Hopefully they didn't do too much damage inside.

Now I need to have a think about how I can get those back in their holes. I don't fancy taking the back end of the gearbox as that means that exhaust, props and transferbox need to come out...

The trigger wheel bolts to the parking brake wheel, in above pictures it needs to move slightly to the left. The parking brake wheel is on the left. (Left = back of gearbox)

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Well found that guy

Anyone know if its possible to reach into the rear housing where the park gear is from the intermediate housing, if the valve body is removed? I've spent two hours searching for photos or videos and poking the gearbox with the borescope but can't get a conclusion on whether this is possible or not.

ar1g3 said:

Anyone know if its possible to reach into the rear housing where the park gear is from the intermediate housing, if the valve body is removed? I've spent two hours searching for photos or videos and poking the gearbox with the borescope but can't get a conclusion on whether this is possible or not.

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I'm quite sure that this is not possible and I will have to drop the transfer box. I'd like to avoid taking the front exhaust pipes (with the cats) off, contrary to RAVE procedure. Only reason why this may be required that I can see is the wiring to the lambda sensor. Anybody know if there's enough length there so that it doesn't hang up when the engine+box is tilted to get to the top bolts on the transfer box?

If the exhaust is standard, the front cat pipes go over the gearbox cross-member & then join before the centre box. So you cannot tilt the engine with the cats connected. Best way is to unplug the sensors & then disconnect the downpipes.

Whether this gives enough room to get the transfer & gearbox out remains to be seen.

Easier access to top bellhousing bolts can be done, by removing the engine mounts & lowering the whole things a few inches with an engine crane (or a spare gearbox jack if the car is on ramps).

pwood999 said:

If the exhaust is standard, the front cat pipes go over the gearbox cross-member & then join before the centre box. So you cannot tilt the engine with the cats connected. Best way is to unplug the sensors & then disconnect the downpipes.

Whether this gives enough room to get the transfer & gearbox out remains to be seen.

Easier access to top bellhousing bolts can be done, by removing the engine mounts & lowering the whole things a few inches with an engine crane (or a spare gearbox jack if the car is on ramps).

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Thanks!

I will be removing the crossmember so there will be nothing in the way of the downpipes. I will also not be taking the gearbox out, I'll leave that in place. I can get to the sensor trigger wheel from the back of the gearbox so I will remove the rear extension housing from the gearbox with it still underneath the car.

So I'm close to pulling off the transfer case now, probably something for tonight or tomorrow.

What I was wondering: my car has 263k km on the clock, when I have the transfer case off any things I should change while I'm in this far? VCU, chain,..? Just to prevent having to do this job again after the next 1000km.

ar1g3 said:

So I'm close to pulling off the transfer case now, probably something for tonight or tomorrow.

What I was wondering: my car has 263k km on the clock, when I have the transfer case off any things I should change while I'm in this far? VCU, chain,..? Just to prevent having to do this job again after the next 1000km.

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VCU maybe but some last for ages, depends I think if you keep the tyre wear even front to rear and whether it's road or off road use.
Some say the Morse chain but IMO unless the car has had a hard life towing or off roading I suspect it will be OK but it's all a matter of how far you want to go.

Datatek said:

VCU maybe but some last for ages, depends I think if you keep the tyre wear even front to rear and road or off road use.
Some say the Morse chain but IMO unless the car has had a hard life towing or off roading I suspect it will be OK but it's all a matter of how far you want to go.

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Agreed, I've got 254k miles on my old tank and she stomps around like Errrr a Tank

Thanks! I think I will not touch those, both the chain and VCU are quite pricy and the car is a bit of a shed atm. For that price I will just deal with the extra work should they go wrong.




She's out!

Now I need to get the transfer case off that jack so I can jack up the gearbox, it's currently resting on a part of the rear casing which needs to come off to get to the sensor trigger wheel.

Question: what do you think about supporting the gearbox on the oil pan? Of course with a bit of wood to spread the load evenly. Normally I would not do that but as this oil pan has a nice flat part I'm tempted..

ar1g3 said:

Thanks! I think I will not touch those, both the chain and VCU are quite pricy and the car is a bit of a shed atm. For that price I will just deal with the extra work should they go wrong.

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She's out!

Now I need to get the transfer case off that jack so I can jack up the gearbox, it's currently resting on a part of the rear casing which needs to come off to get to the sensor trigger wheel.

Question: what do you think about supporting the gearbox on the oil pan? Of course with a bit of wood to spread the load evenly. Normally I would not do that but as this oil pan has a nice flat part I'm tempted..

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Take it to the and of the pit, jack it up a little higher and slide it onto the garage floor
As for the g/box, lift it on the sump but try and support well so it doesn't roll off on you. They really are effing heavy

Mark Piercy said:

Take it to the and of the pit, jack it up a little higher and slide it onto the garage floor
As for the g/box, lift it on the sump but try and support well so it doesn't roll off on you. They really are effing heavy

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Thanks! I have suspended the transfer box from the blue bar you can see in the photos, then I could slide everything to the back of the pit on wooden planks.

I jacked the gearbox up on the sump with a wooden block and some brackets to prevent the jack from slipping.


Then I could take the rear extension housing off and get to the P gear and pawl. And to those two bolts.



The two bolts are 'locked' in place with a wavy spring washer. For anyone installing a replacement gearbox in their car: take the park gear out and put loctite on these bolts. It's an easy and quick job when the box is out. It's not an easy and quick job when you need to get to it with everything in the car.

Thanks everyone for all the input until now!! Helped me lots!

I'll update on the reassembly, now I need to wait for parts (seals, gaskets,..)

Excellent, get stuck in there

ar1g3 said:

So I'm close to pulling off the transfer case now, probably something for tonight or tomorrow.

What I was wondering: my car has 263k km on the clock, when I have the transfer case off any things I should change while I'm in this far? VCU, chain,..? Just to prevent having to do this job again after the next 1000km.

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I would have a look at what they do for the Ashcroft's refurbed transfer boxes. Definitely VCU and chain, you'll be amazed how much quieter a new chain is. I think there's a bearing as well. By the time I priced it all up it wasn't far off the refurbed price from Ashcroft's at the time so I got one off them. Unfortunately the output flange on their replacement was pitted and chewed through the output seal (and two replacements subsequently put on by me) until I pulled the flange and polished it with some Wet & Dry and engine oil. Seal after that has been fine since.

Grrrrrr said:

I would have a look at what they do for the Ashcroft's refurbed transfer boxes. Definitely VCU and chain, you'll be amazed how much quieter a new chain is. I think there's a bearing as well. By the time I priced it all up it wasn't far off the refurbed price from Ashcroft's at the time so I got one off them. Unfortunately the output flange on their replacement was pitted and chewed through the output seal (and two replacements subsequently put on by me) until I pulled the flange and polished it with some Wet & Dry and engine oil. Seal after that has been fine since.

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Yeah they seem like a good deal! But given the price and the state of my car I will go the cheap route now. I just want to get her driving again, she needs to prove that she's worth spending this kind of money first

Well after weeks of waiting for parts the first steps to getting everything back together were made today.

These are the little f***ers that get loose over time:

Partnumber TYP000010, still available at Land Rover. I bought new ones as they include a wavy spring washer, which on the old bolts might have lost some springiness. Didn't want to take a chance on these. I also degreased everything and used loctite on the threads. Not prescribed by RAVE but less likely to rattle loose.


Another issue was that this parking gear together with the sensor trigger wheel doubles as an oil sprayer for the output bearing. The sprocket slides over an O-ring on the shaft, and the collar you can see on the picture above around the shaft hole slides over a piston ring type seal. This creates an oil chamber and a small hole in the sprocket allows oil to spray onto the bearing. For this reason the o-ring on the output shaft needs to be replaced, this is STC4602 which is not produced anymore, not by LR or aftermarket brands. I settled for a 25x2mm FPM o-ring which was the closest match to what I think is a 1"x5/64" O-ring.