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727 leak


Well-Known Member
Local time
7:26 PM
Jul 31, 2008
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AZ Desert
Above the pan is dry but the pan gasket is wet and trans oil dripping off some of the pan bolts. Is it just a pan gasket or are there any pan bolts into the fluid or all blind holes?
If its dry above the pan rail for sure, for sure, its the pan gasket or pan rail. Most leaks are never the gasket thats been replaced two or three times. It ends up being the reverse servo pivot shaft o-ring, shift shaft seal, or dipstick o-ring.
Spray it down with brakeleen. Dry is all off. Puff some baby powder on the potential leak points above the pan rail. Watch for it to get damp. Won't take long. Check dipstick tube, kickdown lever seal, shift lever seal, cooler line fittings, rear band anchor pin (directly above the pan gasket), tailshaft gasket, neutral safety switch. All of these will weep down to the pan and run around the gasket. The pan bolt holes that do go through will do so externally. Not in a fluid area. The rest are blind holes.
No pan bolts go into liquid
On my’84 w150, the normally dry(!) 727 developed a leak a couple weeks ago and it was leaking through the neutral safety switch.
I'll look above the pan again but with only 6000 miles since the build it looked clean and dry. Every thing is tight in a big block A-body

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Somebody said clean trans then pull talcum powder on suspect areas. It will show where leak is where wetness starts.

The somebody was @dvw I believe.
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Like pnora said check the servo pivot shaft. It's on the rearward side of the transmission a hair's width above the pan rail. When it leaks it make it look like the pan gasket is leaking. The O ring on that shaft, inside the tranny, needs to be changed. I can get a picture tomorrow if you want me to.
I found a new place for cable shift (push button) 727's to leak. A friend just had me freshen up his 1965 transmission. He specifically wanted me to look at the rear band anchor pin, because he was noticing a leak near the back of the oil pan. To pull this pin to put a new "O" ring deal on it, the tailshaft housing needs to come off. There is one long housing bolt that doubles as the PARK lever pivot pin. The shaft of this bolt is exposed to transmission fluid, while the other ones are dry. The factory puts a fibre washer under the head of this bolt as a gasket. If this bolt is loose, or fibre gasket is damaged or missing, fluid can leak here. When I reassembled the transmission, I wiped a little black RTV sealer on the new seal on the band anchor pin, and banged it back in place. I also dabbed some RTV sealer on both sides of the washer on the long tailshaft bolt before I tightened it up.
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