bent

Ok, so I got in my 96 lt4/hot cam 6sp to come home from work today. When I started the car I heard a little noise. Sounded almost like a belt squelch. As I continued home and listened to this new, disturbing sound, I was almost sure that one of the idler/tensioner pulleys was acting up. The noise seems to oscilate with engine rpm, and is very apparent when shifting. when I got home I popped the hood and gave a quick visual inspection of the belt and noticed the sound was definitely not coming from the front of the engine. A mechanics stethoscope revealed nothing coming from the engine/valve train and my ear tells me it is coming from the firewall area. the sound is also very obvious when laying on the floor. At idle it comes and goes, chirping and pinging occasionaly...pinging meaning more of a rattle no deep knock or anything like that. The car has 80k and has never made a noise like this before. It seems very loud as I can hear the sound reflecting off of traffic as I pass them.

trackman44

The flywheel teeth are grinding against the inside of the bell-housing. That's why you hear pinging and grinding noises. Have your mechanic check clearences between flywheel teeth and bell-housing. Also have him check thrust bearing play ( could be grinding against clutch fingers).

bent

I don't think that's it. There is no "grinding" i.e. flywheel teeth against anything. I mean, maybe, but I have been involved with mechanical type stuff for most of my life and I can pretty much imagine what that would sound like and this isn't that sound.

Besides, how could the flywheel all of a sudden start having clearance issues with the bellhousing?

Chatman

Never mind.

Livin the Dream

I had a similar problem on an S10 with a T5 manual transmission. On this it was the input shaft. Started out as a squeal then it would rake second gear even if I double clutched it. and as trackman says it could be something with the thrust (throwout) bearing in your clutch. Doe the sound go away when the clutch is engaged?

bent

nope. the sound is there engaged/disengaged. what kind of sounds does the dm flywheel make when it fails.....?

bent

guess I'll have to get out the jack stands and have a look

shop14

that sound your talking about is something i went through with my 95 lt1. chirping and sometimes sounding like a tick.took a while to figure out,turned out to be a bad lifter roller.the roller actually stopped spinning causing this weird chirping sound. i got lucky,no cam damage.
it always sounded like it was on the driver side rear.turned out to be on the passenger side front #6 piston exhaust side lifter. good luck

engle1147

Perhaps a dry/failing throw out bearing?

Does if make the same noise with the clutch depressed as when not?

wtn

I hate to say this, but the sound you describe is exactly what my '95 LT1 sounded like when the #8 rod bearing went. I hope I am wrong.

bent

eek ya'll are starting to scare me. I know that sound travels in weird ways in vehicles but I didn't hear anything at all that sounded out of place when using the stethoscope. I didn't probe the oil pan at all so I will do that and some other listening before I tear into anything. I am wondering now about the lifter problem.....when I changed the valve springs I found a wear mark on the rocker arm where it had gotten on top of the valve...not too bad as it was aligned when we pulled the valve covers. It would be much easier to pull the intake versus the tranny....

ineVETTEable

Pilot bearing??

I've had them cherp and squeek.

bent

I had a friend come over today and work the throttle while I crawled around under the car and the noise is definately coming from the top of motor. It really seems like it is going to be valve-train related. I am pulling the intake right now. stay tuned...

bent

update. intake pulled, valvetrain removed. didn't find any obvious damage. all rollers fuctioning smoothly. I will now commence in beating my head against the nearest wall.

Well I am a bit disapointed but I will go ahead and order a new set of lifters and reassemble everything. If the noise still exists, then I will have an excuse for a stroker.

I know it seems like I'm jumping the gun a bit but I have been planning this for a while. I will just order a golen engine instead of taking the time to do it myself. This car is my daily driver so I need as little down time as possible.

I know that it might be possible for this to be tranny related but I feel strongly that if it was then the noise would be very obvious while under the car and it isn't. While under there this afternoon I literally pressed my ear against the bell housing and heard nothing.

any ideas?

trackman44

The only thing i can think of is crank shaft or cam shaft end play is non existant thus chirping against end cap walls or main bearing walls. Same goes for cam bearings. Other possibility is exhaust leakage thru header flanges. I would give a sharp blow to the ends of the shafts with a rubber mallet to get your end play back.

bent

thanks for the reply. Your idea sounds reasonable. However, If I have to tear things down that far then the engine is coming out and not going back in. It is only 80,000 miles but has had little problems ever since I got it. If the new lifters don't fix the noise, then It's going to be stroker time. while everything is apart, I will replace clutch,flywheel, etc....maybe going as far as a new trans, The zf has a front seal leak, trouble going into 3rd sometimes, popping out of reverse, and I would be leary of putting a 520hp crate motor in front of it. If I hadn't already been planning all of this then I'm sure my actions would seem absolutly crazy. The only thing that has really changed is the timeframe in which I thought I had to work.