727 issue

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Zwap

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Overhauled a -72 727 a couple of years ago because my -66 727 didn't shift like I want, anyhow this weekend I decide to shift gearbox to the overhauled 727.
I bought an used converter to fit the "newer" 727 splines.

Got it all together and filled it up with aboul 7 qts but when I start it up a could hear a metallic sound like as there was something that hit something, double check the flexplate bolts but they where tight and right torqued.
Start it up again and let it warm up in N and then I got it thru all gears and filled it up to right oil level, still some metallic sound, but when i rise the rpm to about 1.100 rpm it disapear to come back at idle.
Drove it slowly around the block and it shifts like a dream.
Back to the garage and still a metallic sound at idle and as I can hear it's coming from around the converter.
Rev it up to about 2.500 rpm in N and P and I can notice a small vibration that wasn't there before I changed the gearbox.

There is a little thought that the converter that I bought has external weights that my others converters don't have, could the cause the vibrations and cause that something is hitting something?
Any other thoughts?
 
Do you know if it is a lock up converter ?
 
Was going to ask if your used conv was for an externally balanced setup (w/weights). Just out of curiously, did the conv seat properly?
 
I now realize that I got the wrong converter, the one i put on is for externally balanced setup with weights, mine -66 383 is internal balanced.
The question now is if i just can remove the weights or if i must change converter?
 
The weight(s) should be plug welded on . Drill the plug weld but be careful not to go too far as to pierce the converter . Try it , if it works, you are golden . If not, you may have to pull the tranny . F.I.Y., most 383's are neutral balanced , therefore require a neutral balanced torque converter .
 
If it's put together that makes it hard to get something in there but I'd think a small die grinder should get in there. Just be careful like scampman said and don't go through the converter shell
 
I manage to remove the weights an the vibrations is completely gone and the transmission and converter works perfect but the noise is still there in some low rmp, it sounds like the starter ring is hitting something, I've let the engine run on idle and looked without the inspection cover, the starter ring seems not to wooble and I can't se it hitting the starter.
The starter is a brand new mini starter.
Any suggestions?
 
Look very closely at the flexplate. Could be cracked in the "leg" portion.
 


This is not my car but I found a video on You Tube that sounds just like mine.

I will check the flexplate.
 
Also, the dust sheild could be hitting the convertor bolts! I put my 360/727 into my car with headers and all. Set the car on the ground and spun the motor over and got rewarded with an awful sound. So I get to jack it back up remove the starter and bend the sheild out.
 
Possibl the bolts used for the converter have too tall of a head, and hitting the back of the block. Do you have the plate that goes behind the starter installed? That could be hitting. Did you drive it without the lower shield on it? Every time i run one with an aftermarket converter, they hit, and make that sound.
 
For SURE check out the dust shield, as it's just way to common for the bolt heads to hit it.
What I do to verify it (as if I didn't know what it sounds like already:D) is to push on the cover a little with something (not your hand) with the engine running.
It'll get obvious if it's the converter bolts hitting it.
The reason I say don't push it with your hand because I have seen a bolt catch the edge of the shield and turn it halfway inside out with the motor running.
You wouldn't want your hand next to that if it happened.
 
Removed the starter dust shield and found scratch marks at the end of the shield, put it all together without the shield and the noise is gone.
I don't like to drive around without the shield so I have to fix that but It's far more easier than changing the converter.
Thanks all!!
 
Did you use the factory type "thin head" torque converter bolts or standard 1/4" bolts? Standard bolts will almost always scrape/hit the dust cover
 
I use the factory thin head bolts and the bolts didn't hit the shield if I rotate the converter but when the engine was running I guess the shield began to vibrate and hit the bolts, that's my only theory.
 
Last edited:
Zwap said:
I use the factory thin head bolts and the bolts didn't hit the shield if I rotate the converter but when the engine was running I guess the shield began to vibrate and hit the bolts, that's my only theory.
Click to expand...
I've seen them do that. Sometimes they can be contrary buggers
 
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