I need to isolate the vibrations I feel when cruising 55 and up or spinning 3500 and up. I feels like a U-joint problem I once had, but I've never experienced an engine assembly being out of balance. When I let the clutch in doing 55-60, the vibration diminshed, but did not disappear. Tonight, I'll rev the engine in neutral to see if it comes on. I've checked the balancer and can feel no weights as in the externally balanced 454. ( this is a 396 ).

Any other tricks you fellas know to isolate the problem?

i had some vibration problems similar to yours a few years back in my 67 ss. turned out to be the rear control arm bushings check them out . hope this helps. happy motoring

Gene,
I had a similar problem once. Mine was a axle bearing going out. It wouldn't start to vibrate until about 45 mph's.
Here are some other things to check..
Drive shaft not balanced right, maybe one of your tires isn't balanced right???
Just about anything in the powertrain could be the culprit. Also check the rear suspension like Kevin said. What about the tranny mount or motor mounts??? maybe one is on the way out??
good luck and let us know

All the bushings in the car are new. I did have a gaping hole in the floor for a while ( rugs were out for some shifter work ) and I noticed the tranny moved around quite a bit. I'll start there and the drive shaft. But I should have been more specific. It seems to be an rpm related vibration, not just a general vibration.

[This message has been edited by Gene Chas (edited 07-12-99).]

Be very careful Gene, I just put my Th350 back in with my old driveshaft, and got a very bad rattle also. Soon it was happening at lower speeds, and finally, the driveshaft FELL OUT of my 67. Check it all again, maybe just a balancing problem.

DJ
67 El Camino

There is a small vibration from the engine itself ( could be flywheel clutch etc. ) but it is much worse when under power. I suspect its the shaft or rear tranny mount. I'll let Denny's here in Buffalo spin it and see what's up.

DJ I had a 75 Nova with a stout SBC in which I literally sheered off the locating pins on the leafs. My pads used to move all around. Until I machined up a replacement spacer, I used to travel around with a spare U-joint, straps and the 7/16 ( I think ) wrench. And guess what, I used em. El sucko grosso.

[This message has been edited by Gene Chas (edited 07-13-99).]

Hey guys I have some simelar experiances that may help...I have a 68 and I just rebuilt the whole suspension with new bushings, ball joints, control arms, springs/shocks, ECT. I had the driveshaft rebuilt and balanced. I also had all 4 wheels balanced and new rotors and disks. THe rear end is still untouched but is questionable now. I have a vibration from 45-55mph and always had before suspension work but now it is stronger. I think it may be in the engine becouse When i take it out of gear or downshift at that speed it goes away.It runs about 1900 RPM at that speed in top gear. Try taking it out of gear at the speed which it does it or downshift to put the engine in a different rev range.

mcortese, that's exactly the drill I'm going to run on the way home from work today. Thanks. BTW when you downshift, you're picking up engine R's so if it's the motor it shouldn't go away. I'd concentrate on the axle. I hope mine isn't the same deal. I've got 3.73's to go in place of 3.31's but I didn't want to have to rebuild the thing.

[This message has been edited by Gene Chas (edited 07-13-99).]

gene here are some not so commons I heard of.
bent fan blade,loose or wobbling harmonic bal.pilot bushing.bent tranny input shaft,bad tranny output shaft bearing,ring and pinion not set up correctly,do you feel it in the shifter?.hope this helps . 67rat
member #199
could be pinion angle.

Well I dropped the shaft after work and was fully expecting to see a bad U-joint. No luck. They felt good. I regreased them and it did take care of some of the problem.

Since I've put a little over 500 miles on the 396 I decided to spin her a bit. In neutral the motor seems smooth at 5000. Phew. I thought I had a balance problem. Key since I want to wheel the 396 for a good buck.

After the drive shaft was replace I snugged up the tranny mount and took her out. For the first time I let her run to 6000+ before grabbing 2nd. No crazy vibrations but I do have a header pipe snugged up against the frame in front.

67RAT, I do feel it through the shifter handle. I just wondering if spending the last 15 years driving family cruisers is caused me to become too "comfortable". Maybe you should come up to Buffalo and wring my girl out and see what you think!

I want to square this all away. The L88 is about 1 month away.

BTW, I've decided to leave the SS396 emblems on the car. They don't need to know I'm running a tripower 427!

Anyway, greasing up the U joints seemed to help.

OK after reading all these I have to drop in with a problem of mine. I get a nasty vibe up around 90-100MPH @4500rpm. Still haven't figured it out for sure, It's not the tires they are balanced just fine and it feels like its in the drivetrain somewhere. I'm going to yank the driveshaft to have the balancing checked. One thing after reading a post here about the balancer wobbling, it sure looks like mine does, It's not loose I'm sure of that. The only problem with pointing at that as the cause is I took the car out and wraped it out in 2nd and it was smooth. Soon my drive train may be all new again as I'am looking hard for a 12bolt and might build a new TH350 just for fun.

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JT
71 SS 350 soon to be Vortec 355 then a 454
www.angelfire.com/co/KellyMotorsports (http://www.angelfire.com/co/KellyMotorsports)




[This message has been edited by L6571SS (edited 07-15-99).]

---stupid p.o.s. computer posts twice---

[This message has been edited by L6571SS (edited 07-15-99).]

JT,

Yeah I drove her into work today and passed a group of cars on the thruway and , there it is again, at about 75 or so. Definitely feels like a out of round, out of balance condition coming from my ass end. Made an appointment Monday AM at the speed shop afiliated with Denny's Driveshaft to see if they can figure this one out. My yoke looked fine, but something's vibrating. I can't imagine why a factory balanced driveshaft would suddenly go bad.

And after reading all your posts, I come back to 67RATs " ring and pinion not set up right". The prior owner of the car swapped out the 488's for 3.31's. If the quality of work on that job is as bad as everything else I've had to redo, maybe that's it. Hey RAT, would you feel this at higher axles revs only? Guess I'll be putting in the 3.73's I got from Wally sooner rather than later.

[This message has been edited by Gene Chas (edited 07-15-99).]

Mine feels like it's in the floorboards and its more of a vvvvoomm....vvvvoomm... sound with shaking. That at first it made me think it was the engine out of balance. I'll see what happens too when I put the new 355 in it. I've had the axle rebuilt twice now and the sound has remained the same (I blew up my Auburn pro-posi shesh you think one of those could handle a stock 350).

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JT
71 SS 350 soon to be Vortec 355 then a 454
www.angelfire.com/co/KellyMotorsports (http://www.angelfire.com/co/KellyMotorsports)

gene
I once had a nova that the faster I went the more more IT would vibrate.IT would start at about 45 mph.IF you rode in the back of the car it would seem louder.you could feel it more through the floor and butt than the steering.the car had 355s installed by (god only knows)Ihad a chevy dealer redo the rear and It was gone.they said the pinion depth and carrier shimming were way off.Im not saying this is whats up with yours,but ya never know.I hate thing like this,they will drive ya crazy.and then someones in the car with ya and they say so slyly(WHATS THAT NOISE,MAN)and Im like if I knew I would fix it.hey maybe the drive shaft dude will fix ya up,well good luck finding the gremlin.
67rat member #199

67Rat, I'm hoping for 7's at 90+ with the L88 in the 1/8th. My luck it'll friggin blow right at the traps. If it's noticeable at 70, it's gotta be wicked at 90. I gotta feeling about this one. I think it's your Nova problem all over again. I'm bringing my 3.73's and 12-bolt gasket with me to my Monday am app't. Not only does it do it at higher axle rpms, but when you're putting power through it like runnin' through the gears. Pinheads. Probably didn't set up the gears right. Up shot is that my speedo is off and the 3.73's should bring it real close to being right.

[This message has been edited by Gene Chas (edited 07-16-99).]

Had a Monte with a 10 blt posi 373s,auto trans. I put my foot into the pedal to get it up to 55 to 60 mph it would be fine. But, as soon as I took my foot off the pedal to coast the rear would vibrate. I thought it was strange but continued to drive. few days later when pulling away at a stop sign , I only made it about 3 feet when I heard a pop and the tach shot up around 4000. after the tow home I pulled the rear cover and out came the kibbles and bits. there was about 4 or 5 teeth left on the ring gear, the spiders were shattered, the pinion was not as bad but, trashed. But the only clue I had was the deceleration vibration. Just something else for you to check on while driving.

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–Joe454–
"67 Malibu"

Joe, yeah I'm thinking it's there. I hope it's not Muncie bearings. I can get it to vibrate while holding 4000rpm or so in first, and then at higher speeds. But I ran the engine up to 5000 with the tranny in neutral and clutch out ( engaged ). Would a tranny bearing problem occur whether there's load ot not?

Anyway, have an app't with a race shop today to see if their guru can isolate it. I really hope it's the 12 bolt gears 'cause I do have a new set of 3.73's I'd like installed. What a PITA.

The answer gentlemen : clutch/flywheel ass'y thats out of balance. Not severely according to the race shop guru, but I guess I'm just a "sensitive" guy. No matter, the L88 has a balanced flywheel and I trust that a new CenterForce dual friction is pretty close as well.

Anyway, I was given the OK to flog it.

OK GUYS......Ya ready for a new twist??? I did exactly what everyone else does...and that is to check out the drive train, of course, right? Well if your viration happens at cruising speed and will come and go with the touch of the throttle yet not noticable at idle, I hate to say it but, you may have a valve train problem?!? If your lifters are weak they may be bleading down while at a constant rpm giving you that "harmonic vibration". Does it have a ticking noise? Also if the valve springs are old they won't be able to keep up with the rest of the valve train creating a whole new problem. When this happened to me I started with balancing the tires. I new it wasn't in the drive train because it happend before I replaced the tranny & rearend. I had driveline balanced and installed a new SFI flex plate and new torque converter. Yet I kept getting those weird vibrations. There was no smoke or oil consumption but a leakdown test proved the problem was in the valve train.
Hope Ya find your gremlins.
Dale

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are we talking internal or external balanced engines? i have a vibration in my 454 that at 4000 rpm or so vibrates the review mirror so much you can't see behind you. doesn't seem to be an engine problem or at least not noticeable in netural (4sp). my gear shifter does rattle pretty loud at the same point so i suppected a throw out bbearing. with these ex balanced motors can you just change the fly wheel or harmonic balancer? are they balanced seperately or is the engine balanced all at once? i don't think this applies in my case, just interested. my car is a real frankenstein 68 this, 69 that!! it's a wonder this pretty mother runs as well as it does. john

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John, my 396 is internal, but the vibration problem lies with the clutch/flywheel ass'y. It would seem, logically, that with an externally balanced 454, the clutch/flywheel and balancer are even more critical. In fact, the first piece of advice I got was " make sure it's not a 454 balancer, you never know", and I didn't feel any weights on the inside surface of the balancer. So might I suggest you double check the same. I'll have my old clutch flywheel balanced to to see if was the problem.

Of course, the first ride with an already broken in 427 ( read, I can spin it!) and new clutch/flywheel, should tell me too.

I've had many people say that bad balance will tear an engine up pretty quickly. Espcially the way I like to hear them sing.

Dale, wild little problem there. I can say with certainty is not the valvetrain. It's all fresh, quiet, and held by polylocks on Harlan Sharps.

[This message has been edited by Gene Chas (edited 07-23-99).]