727 issue

Zwap

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?
 
DITCH THE CONVERTER WEIGHTS!! They will seriously damage your engine. Either remove them from the converter, or change the converter. If you're running a 1966 engine, it almost certainly has a forged crankshaft with internal balancing weights on it. Torque converters with balancing weights are meant for cast iron crank shafts which were introduced in the 1970s. The harmonic balancers likewise are incompatible between these iterations of engines. The present "small vibration" will become a LARGE VIBRATION if this isn't remedied in short order. I'm facing a very similar nasty issue myself, having a 1977 727 and a nearly destroyed old 1966 one still in service on my Newport. Tempting as it is, I WON'T go cheap or lazy on this matter.
 
OK, thanks!!!
Is ok just to remove them? In that case I maybe not have to remove the entire transmission and save alot of work.
 
Last edited:
twostick said:
They are just spot welded to the converter. Some careful hammer and chisel work will get it/them off.

Kevin
Click to expand...
The weights can be a bastard trying to get off without damaging the torque converter.
I have found this way the easiest and safest.

PicsArt_09-25-09.07.09.jpg
 
I had That same problem happen to me 25 years ago . As the others have said you must remove the weights. After that you should be good to go. I still have that transmission in my car today and it works great .
 
Manage to remove the weights that was welded in the middle of the weights.
Guess what, vibrations and metallic sound is GONE!!

Thanks everyone!!!
 
Last edited:
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?
 
This is not my car but I found a video on You Tube that sounds just like mine.

Any suggestions what tha could be?
 
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.
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 slightly, that's my only theory.

Another thing, I adjusted the KD linkage exactly by the book (service manual and several instructions) but my shift point at WOT is way to high, about 4.500rpm, I guess I have to shorten the linkage at the carb a turn or two to get a lower shift point?
 
Zwap said:
Another thing, I adjusted the KD linkage exactly by the book (service manual and several instructions) but my shift point at WOT is way to high, about 4.500rpm, I guess I have to shorten the linkage at the carb a turn or two to get a lower shift point?
Click to expand...
That's how I would like it... you can lift briefly to induce an earlier shift... don't go lighter if everything else feels good, you will reduce line pressure and may hurt clutches by slippage.

You should be able to tweak the shield at the scratch marks... a few hundredths of an inch is all you need.
 
Aha, I thought it should be much lower, then I leave it as it is.
Thanks!!
 
You may have to "adjust" shield. If it is just one bolt hitting the flexplate might have bent a touch with weight on there, it may pry back a bit with a bar, but be cautious.
 
Kickdown linkage should not affect WOT shift points. That's the governor that does that. KD adjustment will affect the part-throttle shift points. At 70mph, it should downshift to "2" at WOT and then upshift a little later. Once in "2", you can then manually move the shift lever from "D" to "2", carefully. Then upshift at about 85-90mph (2.76 rear axle ratio/H78-14 tire size equivalent).

On my '66 Newport 383-2, I actually added two more turns to the KD linkage "pre-load" adjustment with no problems. It raised the part-throttle shift points such that less throttle was needed to accelerate with traffic. Kept the lower gears a little bit longer, but not too much longer. Feels better to drive, too! Used "gear" rather than "torque converter". Didn't need to manually shift it to keep up with traffic! Better when the trans does it by itself.

Take a small black "cable tie" and put it at the back of the slot in the KD rod, wrapping in around the rod at that point. Slide it to the back of the slot. Then drive the car. This will effectively add pre-load to the linkage adjustment without physically readjusting the linkage. If the shift points are raised slightly, in normal driving, the car should feel better. I used that trick on my '80 Newport 360 and it worked well.

With 2.76 gears, I aim to have the minimum-throttle 2-3 upshift occur at about 28mph, which result in it being in "high gear" with the engine at 1000rpm. With a 3.23 gear, 25mph. This makes the torque converter "more solid" rather than "slipping" (NOT clutches slipping!), but the converter making up for the upshift speed 2-3 being too low. You'll feel the difference.

The '72 trans should also have part-throttle kickdown, whereas the '66 trans did not.

CBODY67
 
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