LT1's a knockin'

[Bobabooie]

I'm now a semi-proud owner of two 4th gen f-bodies. I bought a 97 Trans Am yesterday that has a "knock" in the engine. The car has been sitting for a couple of years since he didn't feel like messing with it so I think I got a pretty good deal on it even if it needs some engine work. I'm just curious as to where to look first. The guy said that it still ran so he started it up so I could hear it. At idle it has a steady knock that sounded more like it was coming from the rear of the engine or the torque converter. He brought it up off of idle to about 1300 rpm's and the knock all but disapeared. Any thoughts? Maybe better oil pressure was quieting it down?

[koolrayz]

Loose torque converter bolts, cracked or broken flywheel, Loose bolts at the flywheel to crank. Best way to look is to pull the starter and see if you can move the converter, is there play between the converter and the flywheel? Same thing moving the flywheel? if the converter bolts came loose you may get away with tightening them up but the flywheel is cracked alot of the time IMHO

[Bobabooie]

Thanks for the info Ray! How much play are we talking about? Should the flexplate not move at all? I'm new to this auto trans deal. The only auto's I've had were trucks and they weren't around long enough to have issues.

[koolrayz]

The flexplate should not move at all without the converter and the crank moving , NO play at all

[Bobabooie]

Awesome! I've got my fingers crossed that it's that simple of a fix. Now to find time to work on it.

[0rion]

what color is it? I've seen a silver LT1 T/A twice in the last week or so. Is that you? I saw it today by the Krogers on main with the tops out. I couldn't see who was driving it.

[Bobabooie]

It's black and I haven't fixed it so I'm not driving it yet. Plus it's going to need wheels and tires since it is using the doughnut. The previous owner took the wheel off and "lost" it. How you loose a 17" wheel I'm not sure but the remaining c5 wheels need to go anyway.

[Bobabooie]

Just thought I would update this thread since it has been so long. I opened up the inspection plate to discover the flexplate was broken. The entire center of it was broken out but wouldn't come apart. I dropped the transmission and replaced the flexplate. While dropping the tranny, the wiring harness that runs along the drivers side of the bellhousing got tugged with the transmission and broke the oil pressure sending unit in two. I replaced the sending unit but now I'm getting lower than normal oil pressure readings but no longer have any knock to speak of. When the car starts, it reads about 38 psi at idle on the gauge but when fully warmed up it reads 0-5 psi. but makes NO noises at all. I'm planning on putting in a mechanical gauge just to double check the reading because I can't see how this engine could run so smooth with 0-5 psi of oil pressure. A GM tech told me good luck with getting a "good" sending unit since they are known to be defective and that the only way an LT1 could have that crappy of oil pressure is if the main bearings were shot. I know I can take the "new" sender back for a replacement but would hate to have to keep doing this. Should I just call GM and buy one from a dealership?

[Zeppelin]

That or just find an LT1 bird in a junkyard and grab the sending unit off it. Most likely it was working when the car was wrecked. A new dealership one would be preferred for sure, if the price wasn't stupid.

[Bobabooie]

Tried a mechanical gauge this weekend and confirmed the crappy oil pressure. I also found that the K-member is slightly bent so looks like the k-member and engine need to come out to check the bearings and oil pump. Just figure it will be easier with it out of the car. Can it be done without a cherry picker? I have 3- floor jacks, jack stands and furniture dollies. Any advice would be great!