Propshaft Query

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Old and Slow
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Propshaft Query

Post by Old and Slow » Mon Aug 19, 2019 4:22 pm

A bit of backlash in the crown wheel/pinion?
Jack up one wheel and see if there's a lot of play between the wheel and the prop shaft?
Put some STP in the diff and see if the noise lessens?
If it isn't very loud then I'd guess it isn't something to worry about, but someone with more experience & knowledge might be along shortly to tell you more.


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Propshaft Query

Post by mark rudder » Wed Aug 21, 2019 10:27 am

If the noise changes with slight changes of load at cruising speeds I'd guess the diff.
From what I've read It's fairly standard, mine does it.


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Propshaft Query

Post by IanC » Wed Aug 21, 2019 12:31 pm

Hi, Thanks guys for the suggestions. I had already fretted about it being the diff, but there's little play detectable when trying old and slow's technique. Also the noise seems to be coming from the front, not from the back as in the many noisy diffed scimitars I've owned in the past. When I lift my foot off the accelerator the noise continues, going down in pitch as the car slows. I see from the invoices that came with the car that some MolySlip has been put in the axle so it seems likely that the PO was chasing this problem too!


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Propshaft Query

Post by AJL Electronics » Wed Aug 21, 2019 2:12 pm

Steel timing gear?


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Propshaft Query

Post by philhoward » Wed Aug 21, 2019 2:39 pm

Soggy engine mount letting the exhaust touch the chassis on deceleration?


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Propshaft Query

Post by Oldconn » Wed Aug 21, 2019 3:19 pm

I would guess its coming from the differential.You probably need to renew the input bearing and reset the meshing. Not an easy job, I'm sorry to say.


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Propshaft Query

Post by Oldconn » Wed Aug 21, 2019 3:21 pm

P.S: Fiurst of all check the big nut holding the input flange . It should be tight. If not, you may just get away with re-torquing it.


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Propshaft Query

Post by scimjim » Wed Aug 21, 2019 5:22 pm

Sounds like the gearbox to me - maybe input shaft bearing?


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Propshaft Query

Post by IanC » Wed Aug 21, 2019 6:59 pm

Thanks guys for the constructive suggestions. In no particular order:
Engine mounts - these are new, but just yesterday I was underneath checking out this very point, I can't see any evidence of the exhaust touching.
Diff - The 'big nut' has been off recently to do the pinion oil seal and done up right so I hope that's not the problem.
Gearbox - I hope not, it was out recently for a torque converter repair and some seals, and pronounced to be good by the repairer.
Steel timing wheel - yes it's got one, and it fits in with the 'middle to front' apparent source of the noise, and the 'tram-like' whine.
That last suggestion looks promising!


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Propshaft Query

Post by scimjim » Wed Aug 21, 2019 7:10 pm

Steel timing wheel noise is obvious and not a “droning on over-run”.


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SECURE DRY STORAGE FOR YOUR SCIMITAR

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Propshaft Query

Post by Dennis Nicholas » Thu Aug 22, 2019 7:52 am

The bearing in the belt tensioning pulley can make a noise when worn...varies with engine speed, but will not vary with drive/overrun.


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Propshaft Query

Post by IanC » Thu Aug 22, 2019 8:45 am

Hi, thanks for that, but I think it's unlikely to be the source anyway since the cover, pulley etc came as a new unit with the 'box of bits' that constituted the engine.


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Propshaft Query

Post by gtcse8 » Thu Aug 22, 2019 8:47 am

Ian check that the gearbox is no where near the stiffener plate that is bolted forwards of the Rear GB mounting.

I have chases all sorts of noises over the years and a few have been due to this plate either being bent, or soggy rear mountings allowing the two to touch.

This plate sometimes have spacers between them to lower it and they may have been left out.

I can`t explain what the plate is there for as nothing is mounted to it. :roll:


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Propshaft Query

Post by scimjim » Thu Aug 22, 2019 9:26 am

I always assumed it was there to protect the clutch slave cylinder - but autos have it too :D


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SECURE DRY STORAGE FOR YOUR SCIMITAR

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Propshaft Query

Post by gtcse8 » Thu Aug 22, 2019 9:33 am

Correct Jim

It has a large cutout that wouldn`t protect a lot.

It`s listed as " CROSS CHANNEL/CROSSBRACE, SUMP ", but its behind the engine :?:


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