Knock in Bellhousing? - Team Camaro Tech
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post #1 of 9 (permalink) Old Feb 26th, 06, 06:13 PM Thread Starter
Join Date: Nov 2005
Posts: 45
Knock in Bellhousing?

I was getting on the accelerator a couple weeks back. I didn't push it too hard through 2nd and 3rd but I noticed when I let off the gas that a knock loud knock had developed with the engine RPM. I did hit a pot hole under hard accleration. I first thought that I had shreaded a bearing but I didn't notice any change in the oil pressure. I have been thinking that it's somewhere in the motor but I had it up on a ramp this weekend and it really sounded like the noise was coming from the bellhousing. I noticed the noise varied when the clutch was engaged or disengaged once but I have been unable to get it to repeat that. Now it sounds the same either way. The noise is louder sometimes and at a lower volume at others. I used the old wooded dowel trick and it was loud in the bellhousing and tranny. It's hard to get it on the motor from underneath the car. Anyway, I just had the old 4 spd switched out for a new TKO 600. When they replaced it they had to replace the ring gear on the flywheel and the starter becuase it was eating the gear away. They also had to replace the clutch disc because tranny oil had leaked onto it from the prior tranny. With all that work happening just recently and knowing that the motor is brand new and was rebuilt professionally, I really want to rule out anything in the motor.

My question is this. Is there anything in the bellhousing that could knock with the RPM of the motor? Is there anyway to verify without dropping the tranny? I have read of the flexplate cracking and causing a knock but it's always followed by talk of tightening the torque converter. Can the flywheel crack and cause a knock that increases with the rpms? I've checked for dent's in the oil pan too so I don't think it's the oil pickup on a counterweight. And I should mention that they motor runs exactly the same as it did prior to the knock appearing which is damn good!
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post #2 of 9 (permalink) Old Feb 26th, 06, 07:23 PM
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Re: Knock in Bellhousing?

I have had the springs come out of clutch disk before that made a sound similar to what you have described.May be able to pull dust cover to see if any are laying in bottom of bell housing or any metal shavings inside.

Last edited by smokin 67 rs; Feb 26th, 06 at 07:29 PM. Reason: Added more text
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post #3 of 9 (permalink) Old Feb 26th, 06, 08:34 PM
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Re: Knock in Bellhousing?

Agree with Smokin.

I bought a 69 once,..guy said it had a "loud engine knock caused by a bad main bearing". After I got the car home, started it, the noise seemed to be coming from the tranny. Pulled the inspection cover off, and out fell a twisted up starter shim.

Engine was fine.

Last edited by Straight-line-69; Feb 27th, 06 at 02:53 PM.
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post #4 of 9 (permalink) Old Feb 27th, 06, 09:53 AM Thread Starter
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Re: Knock in Bellhousing?

Man o man do I hope it's behind the motor and not the motor itself. Like I said, the motor is brand new. It would be a crying shame if something broke in there. I will take the plate off tonight or tomorrow to see if I can see anything. Would the knocking noise still increase with the RPM if a bolt is loose? Would the knocking be that loud? It was sort of loud while the car was idling when I was looking around. I killed it, started it back up, and it was really loud but then it got quieter to where it was barely noticable. When it was at it loudest was when I noticed the difference in the sound when the clutch was engaged/disengaged. I will give an update when I take the cover off. I'll start it up without the cover too. Maybe it will help me pen point the noise.

Anybody else have any other ideas?
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post #5 of 9 (permalink) Old Feb 27th, 06, 04:40 PM
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Re: Knock in Bellhousing?

Check the bolts on your flywheel, they can get loose and make that type of sound


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post #6 of 9 (permalink) Old Feb 28th, 06, 03:00 PM Thread Starter
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Re: Knock in Bellhousing?

I took the cover off the bellhousing and could not really see anything abnormal. I had someone turn the motor over a bit while I was under there too. I do think that the guys that did the tranny swap and replaced the starter, ring gear and clutch disc did not torque the flywheel bolts and that this is the problem. I am towing it to a relatives house and he will help me find and fix the problem whether its in the motor or bellhousing. Good to have an uncle that races cars for a living. Thanks for the advice.
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post #7 of 9 (permalink) Old Feb 28th, 06, 03:47 PM
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Re: Knock in Bellhousing?

i had a similar noise one time with my 4 speed, turned out to be the milodon diamond stripper windage tray was broken and hitting the crankshaft.

67 RS marina blue, 406 ,M20 4spd, 9". car has been in my family since new!

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post #8 of 9 (permalink) Old Mar 14th, 06, 10:35 AM Thread Starter
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Posts: 45
Re: Knock in Bellhousing?

So get this. I haul the car from Houston to Baton Rouge to have my uncle help me pull the tranny and belhousing and fix the knocking noise. I get it there and after about 15 mintues if messing with it, he found the problem. I mentioned earlier that I just had the tranny replaced and that they also replaced the ring gear, clutch disc, and the starter. The dipwads that did this work for me put the spring on in the wrong direction that goes from the clutch fork to the frame. So instead of the throw out bearing pulling away from everyhing, it was pulling it towards which was causing it to partially engage. Hence the knocking. I guess the good news is, it didn't cost me more than a few hundred in gas but what a pain in the arse to do all that and know that I could have fixed it by myself, in my garage, in less than one minute.
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post #9 of 9 (permalink) Old Mar 14th, 06, 11:20 AM
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Re: Knock in Bellhousing?

Isn't that the way it always goes. I had an engine quit once, had all electrical working but couldn't figure out why the car just quit while I was driving it. Messed with it for a while and couldn't find anything. Then just happened to brush a wire on the coil and notice that it had come loose. Tightened it up and away we go, no problems after that.

Dave, 69 Coupe, 383, Q-jet, Thorley headers, 350 turbo, P.S., P.B. console gauges, Tilt wheel, Black with green pearl paint, Black and White Houndstooth interior.
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