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72 HO TA · 05-11-2002, 08:46 PM

hi..I have a 70 ram air III eng in a 70TA...manual trans.. When in rev it up,i get a vibration,like it's out of balance. Do all 400 balance the same? are there different front balancers? also this car has solid aluminum body mounts..maybe some of it is being transmited that way...could a clutch assembly be badly out of balance?...help...

72 HO TA · 05-11-2002, 08:46 PM

hi..I have a 70 ram air III eng in a 70TA...manual trans.. When in rev it up,i get a vibration,like it's out of balance. Do all 400 balance the same? are there different front balancers? also this car has solid aluminum body mounts..maybe some of it is being transmited that way...could a clutch assembly be badly out of balance?...help...

johnta1 · 05-11-2002, 10:27 PM

First need some more info.

Did this happen after a rebuild or did it just start all of a sudden?

Was a clutch just put in?

Most stock 400's would be balanced about the same.

There could be a lot of reasons for the vibration.
Clutch misaligned,
broken damper,
loose clutch,
loose pulleys,
something wrong internally,
etc.

72 HO TA · 05-11-2002, 10:33 PM

Well...i just bought this car this week..drove it home 450 miles...it has a richmond 5 speed,and yes,a recent clutch,according to the former owner. I looked at the mounts front and trans..they look ok. The vibration dampener seems to be good,doesn't look like the rubber has slipped {i hate when that happens...lol}...also...i can feel a vibration in the clutch pedal when depressed lightly...when the car is on a lift,the vibration seems less....

johnta1 · 05-11-2002, 11:20 PM

Is the vibration there even in neutral?

Was the previous owner anxious to sell this car? [img]tongue.gif[/img]

Could be the tranny to bellhousing might be mis-aligned.

ta406pont · 05-12-2002, 09:16 AM

There are two different style flywheels as well all pre 1976 engines are externally balanced,and 76 & up were internally balanced all you need to do is look underneath and see if there's a piece of the flywheel cut out if so than it's externally balanced.
Just an idea to look at.
Hope this help's Robb...

72 HO TA · 05-12-2002, 03:12 PM

there is some vibration in neutral,but not as pronunced...I'm not sure of the yr orign of the block...it says 400 on the side,but i can't find any codes where they should be,maybe it's a service block...

Tim Swain · 05-12-2002, 08:22 PM

Recently I had some vibration, all kinds of things went through my head. Turned out to be a lose driveshaft.

72 HO TA · 05-12-2002, 08:32 PM

found the engine code...has the 1970 ram air III block and heads...so i don't think it's the wrong eng for the car...but maybe the flyweel or clutch is out of balance..

LenCaverly · 05-12-2002, 09:46 PM

What kind of clutch does it have some center force clutches have been known to go out of balance.To further narrow down your search take your car out on the highway and get it to the speed it vibrates most at, throw the clutch in and kill the motor, that will tell you if its from the transmission back, then put it in low gear and run it up to the same rpm and see if you still have it,and again in neutral at the same rpm , that will help you to isolate whether its forward or behind the transmission.I,m not sure about flywheels but I always thought pontiac flywheels were zero balanced and would look elsewhere first. keep in mind that solid mounts will amplify any vibration.
Len

72 HO TA · 05-12-2002, 10:31 PM

Len...it has a centerforce dual friction clutch..The former owner noticed a increase in vibration after the clutch was installed..i've heard that these clutches have weights that can stick and throw off the balance..True???

LenCaverly · 05-13-2002, 10:49 AM

Yup
Len

TTS · 05-13-2002, 09:56 PM

Possibly a 350 crankshaft?

72 HO TA · 05-14-2002, 07:32 AM

i removed the trans and clutch last nite..looked like the weights were off center,but maybe they center when it runs..but also the pilot bearing is worn....that might let it vibrate...

Rocky Rotella · 05-14-2002, 10:29 AM

You may want to take the pressure plate and the flywheel to a machine shop have have them spun balanced. My machine shop removed the weights and bolted the PP to the flywheel and found that the PP was way off and I'd have had a horrible vibration. They marked the PP and the flywheel, reinstalled the weights and I put it together. Smooth as can be!

Rocky Rotella · 05-14-2002, 10:31 AM

One other thing, if the pilot bearing is badly worn, that may be an indication of a different problem.

The weights being off center should not affect the vibration as they're centifugal. They'll move wear they need to. Now if they're stuck off-center, you're found a problem.

Half-Inch Stud · 05-14-2002, 10:43 AM

Sure, all of the above.

Flywheel/pressure plate/fork/throwout is the likely culprit.

Then I'd figure on the sausage driveshaft if you say it vibes on the highway.

Engine power balance is possible if would also note an occasional exhaust burp or backfire in front of the mufflers....happened to me. A brand new shorted sparkplug (properly gapped) caused a dead cylinder.

Good luck.

H.I.

TTS · 05-14-2002, 09:26 PM

H.I. We call that a miss around here.

Half-Inch Stud · 05-15-2002, 12:49 PM

TTS,

OK....but I though anything was called a miss in New Oleans

Hehehe

H.I. Stud

72 HO TA · 05-17-2002, 12:04 AM

ok..thanks guys for the info..i replaced the flywheel with a Hays steel and put in a roller pilot bearing and Poof...no vibrations..run smooth now...by the way,my richmond 5 speed is a super way to go. great acceleration and 20 mpg on the freeway...

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