Bent Input Shaft...
Discussion
Hi All,
A very brief question after the gearbox on my laguna failed a couple of days ago. On the dual carriageway, it suffered a couple of sharp jolts, as if there was some air lock in the fuel. A few seconds later it's lost all drive and i was having to coast down to a lay-by. Couldn't put it back into gear while coasting, it would just crunch up as if there was no clutch.
When parked you can put it into any gear slot with the engine running and nothing happens.
So the garage has had the gearbox taken off to inspect....and he says it's clearly the input shaft that's bent. He says other mechanics have looked at it and concurred that it must be a lack of lubrication.
Has anybody seen this before? From my understanding a lack of lubrication would produce a whining noise when at speed for a while, and then chunter up and seize, perhaps throwing teeth off the gears. I can't see how gear teeth could bend the shaft. Perhaps there's something else I'm not thinking of.
Would anyone with experience care to share kindly?
Thanks.
A very brief question after the gearbox on my laguna failed a couple of days ago. On the dual carriageway, it suffered a couple of sharp jolts, as if there was some air lock in the fuel. A few seconds later it's lost all drive and i was having to coast down to a lay-by. Couldn't put it back into gear while coasting, it would just crunch up as if there was no clutch.
When parked you can put it into any gear slot with the engine running and nothing happens.
So the garage has had the gearbox taken off to inspect....and he says it's clearly the input shaft that's bent. He says other mechanics have looked at it and concurred that it must be a lack of lubrication.
Has anybody seen this before? From my understanding a lack of lubrication would produce a whining noise when at speed for a while, and then chunter up and seize, perhaps throwing teeth off the gears. I can't see how gear teeth could bend the shaft. Perhaps there's something else I'm not thinking of.
Would anyone with experience care to share kindly?
Thanks.
A bent input shaft can't stop the gearbox getting drive of some sort even if it wouldn't really want to rotate very nicely. Either the clutch is not engaging at all or some other fundamental part of the drive system has completely broken. This could be the diff or the input shaft is snapped just inside the box or maybe a driveshaft is broken which would then fail to transmit any torque to the other side too.
Never fail to underestimate the stupidity of garage mechanics. Their comprehension of cause and effect is as close to zero as makes no odds.
Never fail to underestimate the stupidity of garage mechanics. Their comprehension of cause and effect is as close to zero as makes no odds.
Pumaracing said:
This could be the diff or the input shaft is snapped just inside the box or maybe a driveshaft is broken which would then fail to transmit any torque to the other side too.
I see your point...he's stated the clutch is fine currently. I may have to inspect that myself to be sure. I would have thought it was clean broken, somewhere before the selector forks hence not being able to select any gears. I would think the bent shaft is a result of some other catastrophic failure anyway?Have you seen root causes to this? Sounds like fatiguing to me. I'd be quite surprised if lubrciation issues caused the shaft to snap.
Pumaracing said:
Never fail to underestimate the stupidity of garage mechanics. Their comprehension of cause and effect is as close to zero as makes no odds.
I agree...I've had experiences before including blazing arguments with a mechanic over why a list of issues were popping up on an engine on a previous car. Some are good and advise they do not know the whole story....others are right a lot of the time and understand the cause...but then you get ones like this who see an issue and don't understand the term "failure mode" let alone the difference between primary or secondary and the likes.stevieturbo said:
I find it impossible to believe a clutch would be fine after running with a gearbox with a bent input shaft.
The friction plate will have suffered some damage. It would be impossible not to.
Good point, even witohut seeing it, i was dubious myself but felt slightly convinced by his manner over that on the phone. This could well prove the incompetence of those involved at his end.The friction plate will have suffered some damage. It would be impossible not to.
2woody said:
I have seen both bent input and mainshafts. BUT only as the result of a big engine or transmission failure - and by big, I mean broken casings, parts impacting the road, propshafts piercing floor panelsl etc.
Go have a look at the stuff for yourself would be my advice.
Thanks, I would definitely like to before it's torn down for the report so I can get a feel for his description, as he suggested I do. Unfortunately work commitments and trying to recover from money lost on Tuesday as a lack of getting to work are stopping me from making it over.Go have a look at the stuff for yourself would be my advice.
He actually described it as the mainshaft as bent (and I asked around at work too, so i thought he meant input shaft). There's a bit of conflicting nomenclature around - can you describe which definition you mean by input and mainshafts? So I know - I call them input and output, but i've heard layshaft / sub-shaft and all sorts.
Cheers.
CarsGoVroom said:
So if the gears reside on the mainshaft....what is on the input shaft then?
On many transverse FWD gearboxes, the input shaft is what would be the "layshaft" on a RWD box. It has the fixed gears incorporated into it, and possibly the fifth gear synchro hub on the end. The "output" shaft has all the other "free" gears and synchro hubs (and a fixed fifth gear)
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