|
|
Nov 11, 2021 16:40:22 GMT
|
Hello all,
A friend of mine has an 1980 VW LT van in which he mounted a younger engine.
The current engine is a 2.5 common rail diesel from a crafter with a manual six speed gearbox.
He had a propshaft made to fit between gearbox and original rear axle. New uj's and a sliding piece were used by a respectable shop.
Flange-angles are within a degree or so of eachother.
Unfortunately carnage happened this week. After coming from a mapping session he lost his propshaft on the freeway.. gearbox flange broken off, bolts snapped off the rear flange, rear flange damaged, exhaust and floorpan damaged and a few following cars were damaged as well.
Rather then just fixing it we would like to know what happened and if we van prevent this..
The car had a very slight vibration at about 65mph that would get less if you went faster. At the moment of destruction het was just passing a lorry and the vibration got worse for a second and then it gave up.
|
|
|
|
|
|
|
Nov 11, 2021 16:51:33 GMT
|
|
|
|
|
|
|
Nov 11, 2021 17:03:15 GMT
|
It seems to me that the gearbox axle broke, with the car still driving it would initially been kept in place by the bearing from the gearbox and start flapping around, damaging the gearbox housing with the flange untill it gets free. Then the axle hits the bottom and bends and shears the bolts off. And either before or after this it also seperates at the sliding joint, the pieces were found apart from eachother.
My question is; would the gearbox be ok with a single propshaft under a bit of an angle? Normally i see 2 piece propshafts with the front piece in line, not under an angle. Maybe now there was to much force in a wrong direction?
Since the van is a short wheelbase and engine and box are rather far back the propshaft is not very long. That's why it's a 1 piece now.
We would love your input..
|
|
|
|
|
|
Nov 11, 2021 17:29:30 GMT
|
'kinell!! That looks nasty Vibration at between 30and 60 can be propshaft related iirc It doesn't look from the photos if the sheared gearbox output shaft has any discolouration around the break? That would suggest that the output shaft itself was already damaged IE cracked Are you sure that the propshaft uj's were phased properly? Bit difficult to tell now!
|
|
|
|
Dez
Club Retro Rides Member
And I won't sit down. And I won't shut up. And most of all I will not grow up.
Posts: 11,784
Club RR Member Number: 34
|
Driveline destructionDez
@dez
Club Retro Rides Member 34
|
Nov 11, 2021 17:46:07 GMT
|
It looks like the original failure point was the gearbox output shaft, rather than the slider, as it appears to have been smashed into the floor a few times before it came apart.
My input would be that becuase of the conversion. there is now no ‘Cush’ in the system. That gearbox originally had a big rubber donut on the back, now it hasn’t it’s getting a lot of shock loading from the drivetrain. Given the break profile on the shaft (it looks shattered), I’d say this would be a major contributing factor.
|
|
Last Edit: Nov 11, 2021 17:47:43 GMT by Dez
|
|
|
|
Nov 11, 2021 18:30:16 GMT
|
It doesn't look from the photos if the sheared gearbox output shaft has any discolouration around the break? That would suggest that the output shaft itself was already damaged IE cracked Are you sure that the propshaft uj's were phased properly? Propshaft is made by a professional who does this for a living. I assume they were in phase.. Will tell the owner to look for the discolouration.
|
|
|
|
|
|
Nov 11, 2021 18:32:54 GMT
|
It looks like the original failure point was the gearbox output shaft, rather than the slider, as it appears to have been smashed into the floor a few times before it came apart. My input would be that becuase of the conversion. there is now no ‘Cush’ in the system. That gearbox originally had a big rubber donut on the back, now it hasn’t it’s getting a lot of shock loading from the drivetrain. Given the break profile on the shaft (it looks shattered), I’d say this would be a major contributing factor. I'm not really sure if there is a rubber donut on the gearbox originally. It's a 4 bolt flange. The original LT driveline definitely doesn't have a donut.
|
|
|
|
|
|
Nov 11, 2021 18:40:18 GMT
|
I guess he's having a conversation with the propshaft manufacturer? Not necessarily to blame, more for their input?
|
|
|
|
|
|
Nov 11, 2021 18:43:48 GMT
|
That's gearbox failure rather than prop failure, what was the map like? If they're spiky with boost they can cause carnage.
|
|
|
|
|
|
Nov 11, 2021 18:52:47 GMT
|
I guess he's having a conversation with the propshaft manufacturer? Not necessarily to blame, more for their input? Yeah, he is going there with the van to show him the remains and hopefully to get advice on how to prevent this from happening again.
|
|
|
|
|
|
|
Nov 11, 2021 18:55:42 GMT
|
That's gearbox failure rather than prop failure, what was the map like? If they're spiky with boost they can cause carnage. They stopped mapping early due to some problems.not really sure what. 420nm max torque is not very high i think.
|
|
|
|
|
|
Nov 11, 2021 19:01:26 GMT
|
to me that looks more like the flange on the diff end let go, need more images of that end, with that loose the gearbox end will flail around and break the shaft.
I'm guessing its a short wheelbase vehicle as these tend to have a centre bearing especially the twin wheel vans.
|
|
|
|
|
|
Nov 11, 2021 19:05:12 GMT
|
the end flange is missing totally off the weld here.
|
|
|
|
|
|
Nov 11, 2021 19:15:01 GMT
|
The uj is fixed to the rear axle flange with 6 bolts. These are all snapped off now and the flange has bend a bit.
I can't see how the rear of the propshaft would have come out first. To shear off the six bolts and bend the flange you need quite some force. And then it would more likely just slide off the sliding part immediately.
The damage to the bottom of the van is above the front part of the shaft.
|
|
|
|
|
|
Nov 11, 2021 19:19:07 GMT
|
I'm guessing its a short wheelbase vehicle as these tend to have a centre bearing especially the twin wheel vans. It's indeed a short wheelbase with twin wheels. Originally these old ones have a 1 piece shaft with a sliding piece in the gearbox. With the modern engine and box the slider had to go into the shaft.
|
|
|
|
|
|
Nov 11, 2021 19:50:55 GMT
|
it looks to me like the gearbox output shaft has failed first, in the picture above there seems to be a series of fine lines around what looks like it was a step in the shaft, these will be cracks forming under fatigue, it looks like it got to the blue line then and at that point fractured almost instantaneously. To be sure you would need to look at the fracture face under a microscope. The next question would be why did it fail, the initial cracks look like they are the result of bending which would indicate a significant balance problem, eccentric loading or the joint not having enough articulation, its also possible it's a historic crack which has propagated while being held at load on the dyno. I don't think you should consider using a rubber coupling, they don't have the articulation to be used with a one piece prop and a live axle.
|
|
|
|
|
|
Nov 11, 2021 20:23:36 GMT
|
Ouch….. should think there matching underwear damage in the driver and possibly following vehicle drivers…
Assuming that the shaft maker knew enough to size the tube for the torque and length and it wasn’t whip that did it….
l’m also of the opinion that the initial failure was the gearbox shaft. Possibly it had damage from its past life? Was the flange checked for runout before installation. Could be it came from an accident damaged donor or was dropped at some point?
Can you post a close-up of the fracture surfaces?
Nick
|
|
1967 Triumph Vitesse convertible (old friend) 1996 Audi A6 2.5 TDI Avant (still durability testing) 1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
|
|
|
|
|
The owner was not having the time of his live at that moment, that's for sure 😊
He didn't share with us if he needed new undies afterwards but i would not be surprised if that was the case.
I asked him for some better pictures on the fracture to show you guys.
Thanks for all your insights. More eyes means more views.👍🏻
|
|
|
|
|
|
|
Nov 12, 2021 10:51:53 GMT
|
Definitely output shaft failure caused all the other damage.
Why did it break though? Was the prop not balanced properly? Was it another reason?
Can't answer for you but some advice would be to fit a prop hoop about 1/3 distance from the gearbox - if it ever failed again this will contain the prop and stop the collateral damage to his and other cars.
|
|
|
|
|