ODD rod knock sound.....

mrvette

mrvette

Phantom of the Opera
Joined
Mar 24, 2008
Messages
15,194
Location
NE Florida
'72 vert, 200 4r auto, '89 truck 4 bolt 355, L98 heads, Injection, closed loop/headers serp drive, electric fans 336 rear,

I have a very strange problem, I already replaced the mufflers on the car, because if I pounded my fist into the left rear muff, it rattled but good, and that's what I thought it was.....so 100 bux later, two new tight stainless muffs in place, and I even bought new sleeves to wrap/patch the two pipes just after the headers...they are solid now....

When pulling in the garage, and hit the brakes, the engine sounds like a rod knock, but it's not, under no other circumstances does the car make that sound....it's equal from both sides of the car, it's not the brakes, i'ts not the differential, car drives normal, no brake pulling or other issues....

If I coast the car down hill going any decent speed, hit the brakes with engine in neutral...no noise....put car in gear, uphill or down hill or on level ground, hit brakes and no noise, UNTIL just before car comes to a stop, those last few feet sounds like pinging/rod knock.....car comes to a stop and the knock disappears, in gear or out.....pull it into gear with car stopped and no knock ease forward, no knock, go to stop and the knock is back...

frigging weirdest symptom I have ever had....

I just jacked the front WAY in the air, and inspected the converter/flex plate with a good flashlight up there and even prying around it seems solid as hell...

I jacked up the rear, spinning wheels in the air, no go...no sound...

WTF???:shocking::hissyfit:

Oh, I have had no lockup on the converter for some time now, down to maybe that O ring on the shaft, or the converter itself, so there something going on with the converter, but that knock?? it would think it would be much more rapid or even louder if it was the converter at speed, being unlocked especially....

front balancer/belts all LOOK fine....

:banghead::hissyfit:
 
Check to make sure you have no loose bolts in the steering or arms. That last bit of pressure right before you stop may be stressing something up front.
 
SmokinBBC said:
Check to make sure you have no loose bolts in the steering or arms. That last bit of pressure right before you stop may be stressing something up front.
Click to expand...

Car stops straight, no pulling, steering tight....I kinds wondering about brake pads....

anyone??:crutches: they are kinda thin, not down to rivets, rotors are good and smooth...:suspicious:

but if it was the brakes, why not do it on a downhill coast?? it ONLY does it in forward gear at the end of the stop, maybe1-2 mph, the speedo even on zero it's so slo....
 
Reason I mention steering is that I had a very similar problem. Idler arm bolts were loose and the braket banged against the frame when coming to a stop.

I know you have R&P, so just thinking.
 
is there much of an apron on you garage with a height differetntial from the driveway? maybe the suspension is getting loaded as you pull into the garage and you are hearing it "unload"
 
bobs77vet said:
is there much of an apron on you garage with a height differetntial from the driveway? maybe the suspension is getting loaded as you pull into the garage and you are hearing it "unload"
Click to expand...

NOPE, on the slab edging forward, REALLY hear it off the block walls....

does it in the street too, but ONLY when in forward gear, not neutral or reverse.....:goodnight:
 
it may just be reflective noises that are always going on......i hear them when i go to the driveup window at the bank and the curbing and brick walls give a different sound perspective. the car is the same you just hear it differently
 
bobs77vet said:
it may just be reflective noises that are always going on......i hear them when i go to the driveup window at the bank and the curbing and brick walls give a different sound perspective. the car is the same you just hear it differently
Click to expand...

OH, sure, but what is this 'rod knock' sound? it's NOT normal, and didn't used to be there....only in the last couple months....I hear it easing up on traffic to a stop, I hear it going uphill or downhill but ONLY in gear...

:sweat::hissyfit:
 
Do yoy feel the knock? Almost sounds like your lockup is engaging. Did you wire the brake release switch properly?

Sent from my GT-I9000 using Tapatalk
 
Twin_Turbo said:
Do yoy feel the knock? Almost sounds like your lickup us engaging. Did you wire the brake release switch properly?

Sent from my GT-I9000 using Tapatalk
Click to expand...

NO feel to it what so EVER, nothing, not steering not brakes, not vibration even, just sounds like a freeking ROD knock...like one hell of a ping on acceleration because of too much timing/too lo octane....

I even dropped the timing back this morning, just in case...but it's the 20 years old standard TPI speed density system with L98 cam in there....I dropped timing back to 6* methinks 8-10 is more normal....and readjusted the idle....

no real change, engine don't pull as hard now, but knocking persists, and stops when car is totally still....

why ME Lord? WTF did I do???eh?? damnit!!@#@!!:hissyfit:
 
Does the knock relate to vehicle speed or rpm?

Weird fricken prob indeed

Got a way to shoot a vid?

Sent from my GT-I9000 using Tapatalk
 
Maybe it's the hydrobooster :)

In gear, engine lugs down, with booster more load on p.st. pump.....

Sent from my GT-I9000 using Tapatalk
 
Twin_Turbo said:
Does the knock relate to vehicle speed or rpm?

Weird fricken prob indeed

Got a way to shoot a vid?

Sent from my GT-I9000 using Tapatalk
Click to expand...

Twin_Turbo said:
Maybe it's the hydrobooster :)

In gear, engine lugs down, with booster more load on p.st. pump.....

Sent from my GT-I9000 using Tapatalk
Click to expand...

I wish I could do a vid....but all I got is a still cam....got a cphone, but dunno how to do any vids off it....no clue, never needed...
engine at idle stays same ~650-700 rpm HB feels same coasting downhill for a ways in neutral, I have maybe 500' to coast and reach maybe 10 mph...hit the brakes and no sound, no matter how hard or soft on the pedal...

engine mounts....hummm. causing the exhaust to clank against the cross support....but engine don't turn backwards in reverse, so why not backing up the hill?? and hitting brakes? :hissyfit:




nutty, I know full well, otherwise I not be asking....guaranfuckingTEE I WILL find this MFer and when I do, it will be posted, but I getting sorta to end of solutions...
 
Knock, or a "crack."

My list?:

Check a arm shaft bolts.

Tranny yoke to spline

U-joints

Pinion gear slop

Cracked spring pocket

Maybe cracked rad support.

Something else stupid like that/these items.
 
big2bird said:
Knock, or a "crack."

My list?:

Check a arm shaft bolts. Not a single knock, a high rate of speed knock

Tranny yoke to spline OR U joints?? why not in reverse??

U-joints on the drive shaft, is my next exploration...maybe tmrw after a couple cups of coffee.....

Pinion gear slop forward or rear I would have to hear some whine...nothing and no clunks either.....

Cracked spring pocket UP FRONT??

Maybe cracked rad support. it's new to the car and a few years ago it was out, and fine....but it IS a replacement ...electric fans and I can't see how

Something else stupid like that/these items.
Click to expand...

OH, believe ME, it's STUPID..... :crap::confused:
 
My way of diagnostic testing, keep driving it until soemthing breaks. About 10 years ago i had a noise on the vette that sounded like a rod knock but some other times it didn't.

Kept driving it and it finally threw the rod through the side of the pan on route 3 about 6 miles from the house. And it kept running good enough to get me home. The dude following me a bit closely on route 3 put his wipers on a few seconds after it blew. At least i got a good laugh out of it.
 
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