Strange Noise from a 727, Have NO Idea...

[70DusterBob]

I have only about 14,000 miles on this rebuilt tranny, it sits behind a 1975 360, it is an 83 model. I have been hard on it a lot, but don't drag race it. I was on the floor with a heavy passenger, a full tank of gas and a bunch of tools in the trunk when I suddenly hear a knocking. It was not, is not a rod knock, much too shallow and not consistent with a rod knock. So I backed out of it, pulled into the garage, in park, revved it to about 2500 RPM and heard a rattling/shimmering type noise. Parked it for a number of months. Took it to a garage to today when my flex plate came in, which was the consensus at the time, and the flex plate is okay, it was not cracked or broken. So what is it? It still moves the car, though I only drove it in the parking lot of the garage, forward and reverse work fine, but it makes a mild rattle noise, not loud, you can barely hear it over the exhaust. I have no clue!

Any ideas?

 

[TrailBeast]

Dust cover getting touched by a converter bolt.
Loose starter touching the flywheel.
Cracked converter snout

Does the noise speed up and slow down with RPM changes?

 

[70DusterBob]

Dust cover getting touched by a converter bolt.
Loose starter touching the flywheel.
Cracked converter snout

Does the noise speed up and slow down with RPM changes?

How could the snout/TC mount cylinder crack? Too much torque to convert with too much weight to move? I must have had 750-800 lbs including me, the passenger, a full tank, and the tools in the car when I nailed it.

I haven't noticed if the noise speeds up or down with RPM, I can check tomorrow. I have to get it towed back from the shop. I'm thinkin' torque converter too, but the starter is tight, no dust cover, checked all the flywheel and TC bolts, all tight. Maybe something came off the road and got into the dust cover/converter area? I know 727's are strong, very strong, and it seems unlikely that the tranny is bad, but they want $200 to pull it, $200 to put it back in, plus it will need all new fluid since the ATF in there is Dextron V, so that's $500 to "see" if there is a problem with the converter, or what the problem is w/o tearing apart the tranny.

I'm thinking it may be best to just get another transmission and have them pull this old one and put another one in. I have a friend who can swap me a tranny for something else. Does this sound like the best move considering they have to pull the tranny and swap the fluid either way? PLUS rebuild the one that is in there if there is a broken part in there if I don't get that tranny from my friend.

 

[TrailBeast]

How could the snout/TC mount cylinder crack? Too much torque to convert with too much weight to move? I must have had 750-800 lbs including me, the passenger, a full tank, and the tools in the car when I nailed it.
Not necessarily to much torque, but snouts do crack and make rattling noises.

I haven't noticed if the noise speeds up or down with RPM, I can check tomorrow.
This is important to know trying to diag a problem over the net.
Otherwise it's just a huge guessing game.
I have to get it towed back from the shop. I'm thinkin' torque converter too, but the starter is tight, no dust cover, checked all the flywheel and TC bolts, all tight. Maybe something came off the road and got into the dust cover/converter area? This happens
I know 727's are strong, very strong, and it seems unlikely that the tranny is bad, but they want $200 to pull it, $200 to put it back in, plus it will need all new fluid since the ATF in there is Dextron V, so that's $500 to "see" if there is a problem with the converter, or what the problem is w/o tearing apart the tranny.

I'm thinking it may be best to just get another transmission and have them pull this old one and put another one in. I have a friend who can swap me a tranny for something else. Does this sound like the best move considering they have to pull the tranny and swap the fluid either way? PLUS rebuild the one that is in there if there is a broken part in there if I don't get that tranny from my friend.

You could very well end up with worse problems doing this without knowing what's up with either one.
You should take a little bit of time to nail this down before you do anything drastic.
Find out if it's RPM related.

 

[70DusterBob]

You could very well end up with worse problems doing this without knowing what's up with either one.
You should take a little bit of time to nail this down before you do anything drastic.
Find out if it's RPM related.

You are brilliant. I think you are right. I should find out what is causing the problem before I pull this one and get another one to put in. I was planning on changing out the TC when I change tranny's but it would be best if I could find out what caused or is the problem with this one... Excellent! Of course I may have to pull this one to find out, but if I make sure my garage has room to store the car while I go get the other tranny, it would be best... Thanks!!! I will try to see if it is RPM related either tomorrow or after I take it to a different garage. The mechanic said you can hear it better inside the car than outside, maybe because there is less exhaust noise inside, not sure. But he was under it and still said that.

 

[TrailBeast]

You are brilliant. I think you are right. I should find out what is causing the problem before I pull this one and get another one to put in. I was planning on changing out the TC when I change tranny's but it would be best if I could find out what caused or is the problem with this one... Excellent! Of course I may have to pull this one to find out, but if I make sure my garage has room to store the car while I go get the other tranny, it would be best... Thanks!!! I will try to see if it is RPM related either tomorrow or after I take it to a different garage. The mechanic said you can hear it better inside the car than outside, maybe because there is less exhaust noise inside, not sure. But he was under it and still said that.

Not brilliant, just done a lot with little money to throw away.
If you are confident it's the trans you could/should pull the pan and see if there is any indication of what might be going on.
Your sure it's not an exhaust leak?

 

[SGBARRACUDA]

You sure the noise isn't coming from the engine?

 

[70DusterBob]

You sure the noise isn't coming from the engine?

Rather if not totally certain it isn't the engine. How could I figure out if it was to be totally certain? I'm thinkin' its the TC cracked at the flange. But it never hurts to be sure as one can be.

It is a stock TC btw, and I'm pushing about 400 or a little over that HP through it.

 

[Leadfoot]

so that's $500 to "see" if there is a problem

Yep!!! Along with the fun, glory, and the enjoyment of multiple cuts on our fingers, that's one of the main reasons we all learn to work on our own cars.

 

[70DusterBob]

You got that right!!!