hi everyone.
need some help.
im still getting bad vibration after 80km/hr.
have had new suspension all round
have had all tyres balanced
wheel alignment is sweet
im running out of ideas. could it be that my tailshaft is unbalanced?

Could be the tailshaft mate. Could also be the half shafts (depending on your car you are talking about). Wheels may need balancing.

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1928 Model A CC Pickup

i personally would have your tyres re-balanced.... again
its so easy to lose weights or for the tyre to not even be balanced correctly

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Driving takes three abilities: Accelerating, braking, and turning.
More power only helps acceleration.
Lower weight helps all three.

try and replace the tailshaft uni's, then the halfshaft uni's...

tailshafts need balancing too... they have little stick on weights on them too.

i remember years ago having a tailshaft shortened AND balanced.

I agree with MyDato and Nick.
I would try bolting on some different drive shafts (the ones that connect to the diff), ie new, or from a mate. If that doesn't fix it, the tailshaft would be next. Then getting wheels balanced.

Also Checking for the tags that 03stiwrx was talking about to see if they are missing. Sometimes they do come off and when they do it's vibration time. Good for the missus, but not for you.
You can send the drive shafts and tailshaft to a local tailshaft manufacturer and get them to check the balance and the play in the uni's....

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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#SR20Datsun @SR20Datsun

When you say new suspension all around - how low is it?
Are the rear half shafts now running at a steep uphill angle towards the wheels?

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SR20DET 1971 Datsun Bluebird 1800SSS Coupe - 11.58 @ 122.40 MPH 18PSI GT2871R and PLMS NIStune
Historic 1971 Datsun 1600 Wagon - L series nostalgia
Historic 1967 Datsun 1000 Wagon - A series resto

another issue could be a bent output shaft on the gearbox, seen this before, but it was on a 230kw Silvia that regularly visited the drags (11.5 sec CA)

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http://www.healingchambers.com.au

I think the car in question is a 1200 ute

make sure your diff is bolted down to the leaf springs correctly,it may be sittting a little off centre,is there any backlash/play when load is applied to the drive line

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68 510 - soon to be restored into a replica 68sss
69 510 - current build - L20b turbo
91 GT turbo legacy
GET THAT DATSUN DIFFERENCE!