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Broken autobox


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As I mentioned in my other thread, my autobox is making a rattling noise. After using some Freeze-Release (my new best friend and the testis-canus of un-stuck-bolting things) on the stuck screws:

05072007045s.jpg

I pulled the round plate off the bottom of the gearbox and poked a torch inside. The torque converter is bolted to the flex plate, which bolts through an adaptor to the flywheel. There are four t/c to flex plate allen-head bolts, which have come loose once before within 25 miles of installation. The chap who installed the gearbox stitched a hole in the bottom of the bellhousing to give better access, and put four 10.8 hex head bolts in instead, doused them in Locktite and torqued to f very tight.

Today's investigation of these four bolts shows:

05072007035s.jpg

05072007037s.jpg

05072007040s.jpg

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It seems the flex plate has fatigued around each bolt, which explains why it rattles but still drives. I'm not sure how far it'll go though (I've stopped driving it) but I've got to work out how to a fix it, and b stop it happening again. Is this a common failure, or is there something special on my car like a misalignment issue?

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I believe TDi's do flex plates in more often the V8's (probably all that vibration :ph34r: ), well that's what my LR mechanic told me when he done the flex plate in my old TDi auto disco.

Was a new flex plate fitted when the gearbox was done?

Although if the bolts where coming loose and now this it does suggest that there might be some mis alignment issues.

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No, the flex plate was second hand. Is this a normal way that they fail? I presume the engine has to come out to swap another one in? I can buy new (or rotate it 45degrees and redrill it?) but I can't hook the engine out at the roadside in London so it'll be a yellow-taxi breakdown up to my parent's place.

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Three comments from pictures. (1) It looks like washers have been put between the flex plate and the TC. This is not normal, but there is the temptation because often when fitting there is a gap there, which should be there (if a gap, then good news is that the TC is probably correctly seated, so no oil pump issue :D. (2) Looks like the TC bolts have spring washers on them. Again OE is not spring washers, just flat ones and loctite on bolts. (3) The torque on the TC bolts is not that great (can't remember exact figure), so if he torqued them to hell then the combination of these 3 are unlikely to have helped.

Any alignment issue, if any, will most likely come from your bellhousing adaptor plate (I assume an OE 300tdi auto flywheel and crank boss were used) . Was it a pro kit or a homemade one? A fairly unscientific test would be to feel the outside of the current flexplate where the breaks are and see if the broken bits are out of alignment with the rest of the flexplate (if you see what I mean :blink:). If it was out of alignment the the TC bolts would also be hard to install so hopefully you can rule this out.

As far as a fix, it is an engine or gearbox out job. For parts you will need to know which TC was used as IIRC the diesels and V8 are different sizes and so probably the flexplates. Warning as per other thread, just make sure on reasssembly that you seat the TC properly in the gearbox. You should have a gap (up to about 5mm) between the flexplate and TC as per point 1 above.

Sorry to hear the news and good luck.

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TC, this isn't unheard of. Unless alignment is spot on the flex plate wont run true and will fracture.

I'd also agree about the washer thing - the flex plate should mount to a flat surface and if there's a washer underneith it then it isn't flat and could explain the fractures you've got.

Time for a flat bed taxi and new flex plate IMHO. M&D might do an uprated V8 flexplate for use in its 2.8 kits and that might be worth a look - I've got a Tdi sized one and they're made of sprung steel and seem to be designed to flex a bit more than the standard parts. Mine was arround the £100 mark IIRC.

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re: the washers - i have the same.

When i first fitted the autobox (as an ashcroft conversion) i had a 4-5mm gap, the ashcroft info said to expect a 2mm gap. i bolted it up like that anyway, but i believe it pulled the tc too far forward & i had a clicky noise.

Now this gap is dependant on the shim that is fitted between crank & boss, so not easy to get back to.

I fitted 2-3mm worth of washers between my flex & tc & now the noise id gone.

So i'm running like that.

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Ashcrofts have them for a good price, just got one at work.

They do break but usually they go around the centre hub that bolts on to the crankshaft. We've had a few down here with not very many Tdi autos.

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re: the washers - i have the same.

When i first fitted the autobox (as an ashcroft conversion) i had a 4-5mm gap, the ashcroft info said to expect a 2mm gap. i bolted it up like that anyway, but i believe it pulled the tc too far forward & i had a clicky noise.

Now this gap is dependant on the shim that is fitted between crank & boss, so not easy to get back to.

The crank boss shim(s) are something completely different and there is a seperate measurement between the flywheel and bellhousing face on the block for them (the shims for this are thin and would need a lot to take up 2mm :blink:).

I guess it's what each person is happy with in their circumstance, but as with all things, once you veer from how it should be, you are exposing yourself to potential trouble.

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The crank boss shim(s) are something completely different and there is a seperate measurement between the flywheel and bellhousing face on the block for them (the shims for this are thin and would need a lot to take up 2mm :blink:).

I guess it's what each person is happy with in their circumstance, but as with all things, once you veer from how it should be, you are exposing yourself to potential trouble.

Well if you have a better way of setting the TC in the correct position - i'd be interested to hear it...

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Most of the above gives the 'correct' (as per LR manual) way do do it. Although Ashcroft give 2mm as the gap, in practice 2-4mm seems normal. I would question whether we need a 'better' way?

I pointed out the shimming issue because when you have the combined weight of the flywheel and torque convertor spinning at 6k I think being aware of and sticking as close to factory specs as possible is wise :) .

Would be interested to know what causes the increase in gap, maybe the flexplate curves over time?

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Most of the above gives the 'correct' (as per LR manual) way do do it. Although Ashcroft give 2mm as the gap, in practice 2-4mm seems normal. I would question whether we need a 'better' way?

I pointed out the shimming issue because when you have the combined weight of the flywheel and torque convertor spinning at 6k I think being aware of and sticking as close to factory specs as possible is wise :) .

Would be interested to know what causes the increase in gap, maybe the flexplate curves over time?

I doubt they curve over time as then you'd find people who'd have no gap and I've never heard of that, more likely just a combination of tolerances and TC postioning on the splines.

BogMonster, when I've heard of failiers its normally in the centre of the flexplate. My guess with Turbo's failier is that vibrations (due to the flex plate not being up against a flat surface) have caused the flex plate to fracture.

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I'm not sure what my transmission is made up of. I know the flex plate is a V8 part, but as I understand it the Tdi auto doesn't usually have a flywheel as such. I have a solid flywheel, then a spacer machined to bring the t/c closer to the flex plate by about 50mm. The chap who actually did the install suspected that the gap was too large, hence the washers. However, the photos show that the snapped half-moons around each bolt are now standing proud which suggest that the plate wants to be closer to the t/c than the washers allow. Maybe that would give a 2-4mm gap? I'll have to see once I've ordered a new plate.

Any idea how much ££ this latest rattle will batter my flexible friend by? Yellow taxi is free and an engine crane will be forthcoming - can I get away with dropping the gearbox back 6" or so and slipping the new plate through the gap? The bottom of the bellhousing is removable which will help access:

05072007029mods.jpg

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I'm not sure what my transmission is made up of

It is made up of an engine at one end and axles at the other with some big toothy bits in the middle that all squish together :D

Pretty sure the Tdi doesn't have a solid flywheel, the V8 certainly doesn't, the mass of the TC acts as a flywheel and when I converted my old Discovery I dumped the flywheel because it was no longer needed.

The flex plate will set you back somewhere round about 100 quid from Ashcrofts, you can more than double that if you get a genuine one.

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The crank boss shim(s) are something completely different and there is a seperate measurement between the flywheel and bellhousing face on the block for them (the shims for this are thin and would need a lot to take up 2mm :blink:).

I guess it's what each person is happy with in their circumstance, but as with all things, once you veer from how it should be, you are exposing yourself to potential trouble.

Er - no - on a 300 auto the shims are in the region of 2mm ish thick.

As others have said this points to a misalignment issue, but its odd, as they normally go round the middle. Were the bolts overtorqued and have casued a failure that way?

Jon

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Thank you for the concise description of what goes on underneath, I had always wondered.

I know I've got plenty of mass down there - a flywheel, torque converter and a flex plate.

Is it really £100 for a flat disc of metal with ten holes in it? I'm incensed, I could make it myself. Hmm.

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Thank you for the concise description of what goes on underneath, I had always wondered.

I know I've got plenty of mass down there - a flywheel, torque converter and a flex plate.

Is it really £100 for a flat disc of metal with ten holes in it? I'm incensed, I could make it myself. Hmm.

Yes - it is (or appears to be) very high tensile stuff so I assume it is expensive to make. I always thought it was a bit pricey for an oversized baked bean tin lid too, but Ashcrofts are a hell of a lot cheaper than Land Rover's. Try a bit of 3mm plate in there and see what happens :)

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Ashcroft only have 300Tdi flex plates in stock, M&D do their own version of the V8 one that I need.

I'd like to canvas some other suppliers for their opinions - does anyone have a part number for the flex plate? It's the flat disc type and doesn't carry the toothed starter ring. Cheers in advance.

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The bit I want looks much more like part 6 - it's a V8 box, t/c and flex plate.

Does anybody make a flex plate to attach a V8 autobox to a Tdi engine? I doubt Land Rover do, which might explain why it was bodged in the first place :)

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