Hi guys.
I have an urgent question about my datsun.
This is going to be a long forum but I must post it to get answers to this problem of mine.
This problem I have experienced before but it was before I knew of datsun1200.com.
Last night me and a friend went out for a drink or 2.
We went home and got next to a Mitsubishi Pajero Turbo Diesel at the traffic light.
DO NOT TAKE ON A PAJERO WITH A STANDARD DATSUN 1200.
He kicked my butt.
He must juuuuust wait until I get my electric dizzy in.

Ok.To get to the problem.
When my car gets to 5500rpm it gets a strange vibration from the front asif I am driving on a gravel road.At 5800rpm it goes away.BUT. Then there is a vibrasion or movement on the gearlever asif the gearbox main shaft is oval or something.I only rev to 6000rpm due to this stuff happening.
After I dropped off my friend at home.
I drove around and did this test 2 times to get my facts 100% correct for this forum.
Again.It feels asif I am driving on a gravel road from 5500rpm to 5800rpm and then it goes away and that strange vibration comes through the gearlever.
This little engines can rev to 6700rpm.
Why the hell is it doing this asif it is at its end?It is however still pulling strong at these revs.Not asif valvebounce or anything is happening.It also makes alot of noise at these revs.Is it normal?
What I can mention is that my flywheel was heavy skimmed due to hotspots.
This is because an idiot mechanic put in a A14 utility clutch and it grabbed wrong.
I used a other mechanic who put in a correct clutchkit.
He said he needed to skim or cut the flywheel alot due to burned spots on the flywheel.
My question: Is it possible that the flywheel is out of balance and causing this vibration?
Someone else here in south africa said that he revved to 8000rpm his standard A12 only with a 288 cam and gasflow and ported head and 32/36 carb.
Please help me.I know I will not abuse my datsun to 6700rpm, but hell.It must not complain like this only at 5500 to 6000rpm if it can rev to 6700rpm.
Thanks.

Are you sure that you've not lost a tailshaft balance?

One of my Universal joints wore out once, and man!, it felt like I was going on a graded gravel road.

The specific nature of the vibration between 5500-5700 or whatever, makes me think this is a balance issue. Maybe the lower revs harmonics aren't as obvious.

Chris

im with dattodude, i was thinking tailshaft, or maybe flywheel, i wonder if you could get it to do the same thing with the clutch disengaged, that way you could tell if it was flywheel or further back past the clutch??

good idea...

1. Get up to speed/revs
2. Depress the clutch (maintain the revs to the vibration region) Don't over rev.
3. See if the vibration continues.

It'd be interesting to see if it's revs..or speed related.

Chris

it sounds like a balance problem I had similer problem after replacing a clutch turned out to be a bad clutch plate
Bob

Hi guys.
Thanks for the replies.
Here is more information.
My driveshaft was little bend when my clutch was replaced.
The good mechanic I used to do the correct clutch replacement took the driveshaft to an engineering place.
He said he stood with them when they bend it straight and balanced it again.
It is definately not speed related.
Only revs related.
If I do it in 1st and second gear it does the same thing in both gears.
In second gear at 6000rpm I get 100km/h.
My universal joints are also brand new.It was replaced and fully greased a year ago.
Has not too much miles on them.
Can it be the flywheel being out of balance?

you say its a standard 1200? and it can rev 6700? ok... maybe my car is screwed! I cant get nearly that fast in second gear & im pretty damn sure the car's never revved that hard in its life

Loose flywheel

Sounds like as loose flywheel to me.
Another thing to check is the bolts that hold on the alternator bracket and also the front crankshaft pulley. My old A14 had a habbit of breaking these only because of 8000rpm plus gearshifts. The sound was quite loud and rev related.
Andrew

Astro boy.

Its not totally a standard 1200.
Its a 1200GX.Standard GX engine.
They can rev to 6700 but max power is at 6400.
And yes, I can get 6000rpm in 1st,second and third gear.
Third gear just takes a while, but it pulls all the way to 6000 never stopping or showing that it cannot go anymore.
It is just this vibration that I need to sort out. My max power of 83hp is at 6400rpm.
I must get 6400rpm if it can go to 6400.
My flywheel was torqued by the guy.
If the flywheel is'nt loose, can it be that it is out of balance?

I thought of something else.
That sound I talked about at 5500 to 5700rpm.
Can it be the timing chain being worn and rattling at that high revs?
Thanks for all the replies.