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Discussion Starter #1
Hi all,

I have a 63 with a freshly rebuilt L6 and a freshly rebuilt powerglide, by fresh I mean the car has less than 50 miles on it since the rebuild. Everything was running well on it except for a bit of a carb. problem so I picked up a rebuilt carb and took it to a mechanic to install and adjust etc. On my way home with the newly installed carb. I noticed that the car is all of a sudden making a clunking sound when I am coming to a stop, also sort of jolts the car a bit. I called the mechanic and he took the car back and readjusted the carb but the car is still clunking, he said sounded like it was something in the drivetrain. Any ideas on what on going on with my baby??? Man- just when I thought everything was going so good:confused:
 

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Loose bolts at the torque converter/flywheel?
 

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Maybe, I torqued them myself but things have a way of loosening up. I have been meaning to go through and recheck all of the bolts but thought to wait a little while longer, perhaps that was a bad idea. Ack- I am a total newbie. I'll see of I can get at them to check, can't remember if they are easily accessible or not, I am thinking not.
 

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what kind of clunk & jolt are you referring to ? the "seat of the pants feel" is important. can you determine if it's drivetrain or a suspension issue ?

what's the history of the car... fresh engine & trans but what about brakes, front end, u joints, leaf bushings etc...

jack it up, stand it on all 4 corners and give everything a good looking over. BE SAFE !!! the stuff needs a good firm shaking to see if it's tight or loose so don't pull the car down on yourself. grab a wheel and man handle it. see if anything feels loose. do it on all wheels. grab steering linkage and shake it. it should twist because it all has ball joints but rotating/twisting is different from shaking ;)

check idler arm bushings & bracket also... remember. ya have ta man handle this stuff and also remember to be safe ;)


let us know what ya find...
 

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Discussion Starter #5
No way it is suspension. It is bigger than that, the jolt seems to be from the tranny shifting down I believe. And when it does so it makes an audible sound. It does sort of do it when I put the car in drive too I guess. It does not really do it any other time though so accelerating is fine, but then I have not taken it over 30 mph since this started going down.


The car has new leaf springs, bushings, shackles, u- joints, and shocks. Yes- I experienced another kind of clunking a while back so I went through it then and replaced everything. The car has two broken leaf springs when I bought it- jeesh. That is all better now though:)
 

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OK, you've narrowed it down a little (hoping so)

with the car in park, on stands, grab front of driveshaft and trans and give the joint a shake. maybe a bad u joint ? at pinion, rotate driveshaft as much as possible, clockwise & counterclockwise to check ring & pinion play.

not trying to eliminate trans but it's a fresh rebuild so i'm assuming it's OK.

not looking at the car either so maybe my suggestions don't fit the situation... just tryin' ta help ;)
 

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Discussion Starter #8
I had a loose wheel on my other car a while back and this does not seem at all similar. It made a noise all right but definitely not the same as the my nova is currently making and it is not a constant clunking. Still I just put brand new tires on it so I'll check all the bolts anyhow and tighten any that need it.

The u-joints are also brand spankin' new, did them when I was doing the rebuild, but I'll take your advice and check it- would not be the first time that a new part I used was no good. I'll also check the steering linkage but honestly the steering seems fine to me. The steering wheel does not shake or turn when the car misbehaves.

It only clunks once when I am braking to come to a stop and seems like the rpm's drop off right after the noise-jolt combo. It is not a constant or continuous noise/jolt but does do it once every time I am coming to a stop. When I accelerate it does not do it, nor does it do it when I am just cruising.
When I put the car into drive or reverse it also jumps a little- I think the jolt is much the same- sort of a quick jump then everything is fine- does that makes sense?:yes::no:
 

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No way it is suspension. It is bigger than that, the jolt seems to be from the tranny shifting down I believe. And when it does so it makes an audible sound. It does sort of do it when I put the car in drive too I guess. It does not really do it any other time though so accelerating is fine,
Road tested a 66 Biscayne with my Dad back in the day(283-Powerglide)
If I remember right , a vacuum hose was disconnected, giving it a harder shift going up 1-2 , and a bang when it was going back to first coming to a stop 2-1.

Just a thought.
 

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run up to 30mph then pull it down a gear and see if it makes the noise if it does keep doing it until your sure its the trans. then take it back to the rebuilder...
From what I read it sounds like its trans related.
 

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Transmission mount, leaf spring bushing, Control arm bolt, just throwing some suggested things I would check. The idle drop is puzzling unless you have more than one problem going on. Hope it's a cheap and easy fix for you...
 

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Discussion Starter #13
mmmm- yes the vacuum hose had been purposefully blocked with the old carb as it had a constant vacuum I believe. I did not even check to see if that has been reconnected to the new carb or if he left it blocked. The car did not jump with the old carb when stopping though and it had been blocked then, it did jump though when going from park to drive or reverse ever since the rebuild. Thought it might just be the tranny getting settled but Ha what do I know:rolleyes: I also thought it might have been cased by the carb running too rich. So that may be worth looking into as a possible cause. Any ideas what may have caused the constant vacuum? Is it something that the new carb should have fixed or are there other causes I may need to investigate?

As for the rpm's I have no gauge so I am not really sure they are dropping just seems like it drops but could simply be the car shifting down. So that may be a non issue and just me being overly sensitive to how the car is driving now. I have been a bit worried about it but I think that should be a given seeing as to how much time and $ I have into her since the rebuild. I really tried to do everything the right way but being my first time and all I am a bit paranoid I managed to screw it up still.
 

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If your talking about the vacuum to the trans module I think its to manifold vacuum(constant) I never had a glide so I don't even know if they run a module.:D
 

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Since the problem started after the mechanic installed the new car, I'd start with things that he might have removed. It's been awhile since I worked on a PG but Kick down linkage and vacuum modulator hose come to mind that can cause an abrupt hard shift. Since it sounds like there's a metallic audible component, you should do a complete diagnostic check of the drive line for looseness. If the problem is the trans is shifting harder, the jolt may be revealing a loose part.
 

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Discussion Starter #17
Thanks for the info guys:)

I have not been able to find anything wrong with it. Just dropped it off at the place that did the rebuild on the tranny for me. I am hoping he might be able to figure out what is going on with it. At this point though it does not look to hopeful. He had a look at it and can not seem to locate the problem either but is thinking it might just be the carb is not working as it should. He'll be going over it again tomorrow a little more thoroughly so fingers crossed that he might be able to unravel the mystery.
 

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I know this has been sorta eliminated but my nephews car was missing a strut rod bushing when he got it and it clunked real good when you put on the brakes
 

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Did you purchase a carb for an automatic transmission?

If so maybe they got it wrong and you have one for a manual transmission. I had the manual one on my 194/glide and it did cause a hard downshift.

If I am correct ( someone correct me if I am wrong) I believe the carb for the glide receives full vacuum from under the throttle plate and the one for the manual receives vacuum from above the throttle plate.

I had the one for the manual transmission on the car for about a year because it did not hesitate from a stop. The hard down shift was noticeable most of the time. The one I had for the glide did hesitate so eventually I put the throttle body from the glide carb on the top part from the manual carb. I no longer have the hard down shift and the car does not hesitate:yes:

Maybe some one who knows the best way to tell the difference between the two carbs will see this and help.

EarlyIIs
 

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Discussion Starter #20
Wow- I think you figured it out my friend. I am going to check on the carb- could very well be I got a manual one- I guess I did not even know there was a difference. It sounds like exactly what my car is doing too and there is literally nothing that seems wrong at all with the linkages, hookups etc. Yes I think that is it!!!:yes:

I'll check it out first thing tomorrow.

Thanks!
 
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