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Perplexing Loss of Drive.


ajh

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I have just found the strangest problem I've ever run into. Vehicle is a D1 that was a V8 converted to a 200TDI mated to an R380 and LT230. It was working fine; then one day when the clutch was depressed there was a sound like a spring being released from pressure. This resulted in loss of all drive. I removed the slave cylinder and the pushrod moved freely as if there was no clutch present at all.

Normally you'd thing something like the centre has torn out of the friction plate or the basket has failed... not needing it right away it sat for a while and I finally got around to opening it up today and nothing.. every single part of the clutch looks perfectly good. The entire setup probably has fewer than 10,000km on it, so it should look like new and it does. The friction plate is fine, the shock springs are good... the clutch basket fingers have slight wear but nothing that would explain a failure... and the only possible failure mode I can come up with is the clutch basket somehow getting 'stuck in the released position, but I'm not sure I've ever heard of that happening with this design.

The transmission input shaft when turned manually results in movement at the LT230 output flanges, so that seems good.

The only different thing is this has a cast clutch fork and the slipper pad area does seem to be a slightly different size than the pressed fork type... I can only imagine the issue was somehow related to this... does anyone know if I can just swap in a standard pressed fork instead with the removable slipper pads (I would need to replace the pushrod with one without the pin on the round end or at least grind it off, but is there anything else to consider when doing this?

Ideas?

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I thought of that, and will try with more force in the morning, it just looks perfect and springs back as expected... No clue how it would do that, also... That would not explain the slack pushrod.

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The pushrod and fork will always be slack with the slave cylinder removed as there is nothing to hold them in position against the fingers of the clutch pressure plate.

I didn't think the cast V8/Td5 type fork was interchangeable with the pressed steel Tdi style one. The release bearings are the same (FTC5200) though so that end at least must be the same dimensions. Is it a V8 or Tdi gearbox/bellhousing?

If the slave, fork, pushrod or bearing failed it wouldn't affect the clutch's ability to transmit drive - only the ability to actuate it and change gear. Unless of course it fell apart and damaged the friction plate somehow, but I would think that fairly unlikely.

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Depending on the box & clutch combo I'm pretty sure there is a different release bearing for V8 and TDi in some setups - only because I know we had one of each on the shelf in the lab and somehow the wrong one got fitted and it jammed the clutch permanently "released".

I can't remember if it's V8/TDi or LT77/R380 but I know there's two different lengths of bearing (that you'd struggle to pick apart if you didn't put one next to the other).

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Not sure about LT85 or other gearboxes but for the standard LT77 and R380 both V8 and Tdi variants use the FTC5200.

There is a special shorter bearing (UTJ100210) for the stumpy bellhousing variant of the R380. And according to the parts book there is a separate bearing for the Mpi engine in Discovery applications - FTC2772.

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I'm pretty sure I figured it out. V8 manual Disco are rarer here than forward control FFRs, (I know of 2 or 3), it turns out the previous owner didn't know the fork required a retention clip (571163) so it was held in place only by the plastic cup and hope... Something must have shifted allowing the behaviour, but I still can't really figure out what was actually happening... it's mostly back together now and seems to be working. if it happens again I'm boring a scope port and figuring out exactly what's going on. Thanks for all the input/ideas.

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