727 always leaking

[justavillain]

I have a 727 that is always leaking out the front. I had the trans rebuilt by a quality shop and it runs fine but after I park it, it always leaks. not a ton but enough to make the shop floor slippery. I check the fluid level all the time and it doesn't really seem to go down. its getting close to race season and that is worrying me a bit on tech inspection

With it being a new build can it still be the front seal? or would the vent leak that bad?

 

[khryslerkid]

The seal could have been damaged when the torque converter was installed. Then it could not be a quality seal. Several things could account for a leaking seal. The vent could leak if it's over filled. Check when warm and in neutral. Converter drain back could be a problem also over filling the trans.

 

[Mopars & Missiles]

Dipstick tube O'ring leaking??


Shift lever seal leaking??

 

[w.Hudson]

The pipe plug for the front band lever pin is in the bellhousing also. It could be leaking also.

Loose or just needing some sealant on it.

Check the dipstick O-ring. It could leak and run down the case and look like the fluid is coming out of the bell housing

 

[pnora]

I have a 727 that is always leaking out the front. I had the trans rebuilt by a quality shop and it runs fine but after I park it, it always leaks. not a ton but enough to make the shop floor slippery. I check the fluid level all the time and it doesn't really seem to go down. its getting close to race season and that is worrying me a bit on tech inspection

With it being a new build can it still be the front seal? or would the vent leak that bad?

You need to spend some time locating the leak. Dry it off well and keep looking. Asking here is going to give you all the could Be's.

 

[justavillain]

I didn't see any leaks around the dipstick. there is no leak at the shift linkage. I don't see any fluid on the tq converter or flex plate.

 

[RemCharger]

Do you have a locking dipstick? Seems like mine started doing that once I put one in. It's coming out the vent.

 

[pnora]

I didn't see any leaks around the dipstick. there is no leak at the shift linkage. I don't see any fluid on the tq converter or flex plate.

You are not looking hard enough. Post some pics and maybe someone can see something.

 

[justavillain]

I have an inspection cam I might be able to sneak it up by the main seal. I'll hit it with some brake clean and run it a little in the barn to see if I can find a fresh drip.

 

[Pistol Pete]

Hose that trans down real well with Brakeleen and after it dries, put little pieces of paper towel all around the pan, dipstick tube, shift lever etc. Check it periodically and wherever the leak is originating from will be readily apparent by the red paper towel.

 

[68 Sport Satellite]

I thought it was common knowledge that all 727's leak after sitting from converter drain back? I asked this same question before and that's the answer I got.

 

[dadsbee]

I thought it was common knowledge that all 727's leak after sitting from converter drain back? I asked this same question before and that's the answer I got.

Even after drain back and the unit is then "overfilled" there is no reason for it to be leaking on the floor! Rear band pivot pin...

 

[dvw]

The trans needs to be thoroughly cleaned and dried. Then puff some baby power all around and above the pan rail. where does it get damp? Is it really coming out of the bell housing? Or is it leaking elsewhere and running off the bell? If it's coming out of the bell. Not many possibilities; Pump seal, Pump O-ring/gasket, worn converter hub, fluid being pushed out the vent, cracked converter. My race trans has been out for service a few times in the last 5 years. Never changed the pump seal during that time. I build a bunch of these. Most often leaks in the bell are converter related. As a side note. A racecar should have the vent relocated to the rear of the case with a catch can.
Doug

 

[Runcharger]

Clean and verify. Shift selector seal is another common leak spot. Any leak can be repaired but ATF is really thin and travels well so the most important part is verifying where it is leaking.

 

[Rick62]

If a 727 isn't leaking it's empty.

 

[icetech]

for dipstick i went with this after my stock one gave me issues.. It's a pain in the *** to get in but i have not had a drop leak. (put the grommet in the trans case first)

https://www.amazon.com/gp/product/B009Q7A3L4?ie=UTF8&psc=1

 

[justavillain]

The trans needs to be thoroughly cleaned and dried. Then puff some baby power all around and above the pan rail. where does it get damp? Is it really coming out of the bell housing? Or is it leaking elsewhere and running off the bell? If it's coming out of the bell. Not many possibilities; Pump seal, Pump O-ring/gasket, worn converter hub, fluid being pushed out the vent, cracked converter. My race trans has been out for service a few times in the last 5 years. Never changed the pump seal during that time. I build a bunch of these. Most often leaks in the bell are converter related. As a side note. A racecar should have the vent relocated to the rear of the case with a catch can.
Doug

that is a good idea on the baby powder. I will attempt to clean it and puff it. the leak is always seen at the leading edge of the bell housing and rolls back about 2" and then drips. I never thought of relocating the vent. I will look into that also.

 

[dvw]

This is the best spot. You have to be careful to keep the location forward of the gasket suface. I tap it for 1/8" pipe. That way fluid doesn't sling from the output shaft rotation. You can do it in the tail shaft. Just make sure the catch can is up on the firewall so it drains back. In the first location I've even run the catch can below the trans. Never saw more than an ounce of so in the can.
Doug

 

[Rebelrouser]

727 leaks when sitting, shift shaft lever seal, and dip stick O-ring most common. A front seal seldom leaks when sitting. the pipe plug that hold the band lever can leak but pretty rare. Most common is a pump bolt loose, each bolt has a sealing washer on it and I have seen them back off sometimes. And the O-ring around the pump seldom leaks unless the seal is old and shrinks from time. Also, rare but I have seen it, is the weld where they connect the two converter halves. I used to have a fixture that I could pressurize the converter out of the car to find those leaks, but it got away from me.

 

[Don Frelier]

Very unlikely but perhaps worth mentioning.
I have a good friend that had his out 3 times due to a front leak.
He finally determined he had a thin spot in the casting that developed into a pin hole near the front pump.
Very difficult to find.