MikeR
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| posted on 7/11/22 at 11:55 AM |
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propshaft - too short? should I panic?
So as I understand it the rule is push the prop all the way in and pull it out 20 to 25mm.
I got mine second hand and it's got 36mm movement. It's behind a crossflow. I'm guessing it's fine as is got about 55mm of
engagement measuring the splined section inside the yoke. Should I get the prop extended to add 15mm engagement to take it to about 70mm?
My instinct is no. But I thought I'd check with the collective wisdom here. Safety is more important than the 150+ vat Dave Mac has quoted to
extend the prop (now panicking I said drive shaft and not prop when I spoke to him) but id much rather not have to do the job and save the cash.
[Edited on 7/11/22 by MikeR]
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theconrodkid
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| posted on 7/11/22 at 12:18 PM |
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in a non scientific way i would say the prop is too short, can you move the engine / box back a tad ?, if not i would get another prop
who cares who wins
pass the pork pies
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Mr Whippy
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| posted on 7/11/22 at 12:28 PM |
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I'd not be keen on having no clearance as if you hit a speedbump hard you could ram the prop into the back of the gearbox. 55mm seems plenty imo
especially if it's not loose on the splines. I mean really your asking, could this thing fall off the splines and kill me and no it can't.
That 25mm rule you quote is more dependent on the suspension type and travel and how much suspension movement affects the prop length. Most of my cars
with propshafts were landrovers and the suspension positioning was all over the place offroad and nothing fell off...well the propshaft anyway, so you
might be worrying about nothing really.
[Edited on 7/11/22 by Mr Whippy]
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dmac
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| posted on 7/11/22 at 12:29 PM |
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15mm spacer at the diff flange?
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MikeR
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| posted on 7/11/22 at 12:57 PM |
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I've thought about this a few times, it's a bodge & I don't know anyone to make one plus I'll need to source longer bolts.
Figured a extended prop wouldn't be that much more expensive (didn't expect the size of quote from Dave Mac but I'll pay if it needs
doing).
Just taking the prop out today got me thinking that the 15mm I'm adding isn't that much. It's not a mega power 16v engine. It's it
needed?
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MikeR
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| posted on 7/11/22 at 01:07 PM |
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Thought I should add, it's to a Sierra diff so I'm not expecting any movement on the prop.
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dmac
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| posted on 7/11/22 at 01:54 PM |
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So you've got over 75% of the recommended engagement, since you are running an IRS and there is not going to be any sliding in use to reduce it
still further, are you running more than 75% of the rated power? If not then you should be fine.
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gremlin1234
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| posted on 7/11/22 at 06:03 PM |
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quote:
Originally posted by dmac
15mm spacer at the diff flange?
or 7.5mm each end.
or
if you needed to add a reverse.(usually just motorcycle engines) then the answer would be very easy.
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MikeR
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| posted on 7/11/22 at 06:18 PM |
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You can't do a spacer on the type 9 gearbox end. The gearbox bellhousing is hard up against the bulkhead so I can't move it back 
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theconrodkid
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| posted on 7/11/22 at 07:22 PM |
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quote:
Originally posted by MikeR
Thought I should add, it's to a Sierra diff so I'm not expecting any movement on the prop.
having a sierra diff changes my thoughts on the subject, should be fine then.
who cares who wins
pass the pork pies
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