Converter drain back / 727 leak

[Malicious]

My 727 has been leaking quite a bit since getting the car all together and running, and I think I have found what the issue is now, looking for some feed back on it...

Seems like the toque converter is draining when not in use, so the pan over fills and oil comes out of the dipstick hole. I've attempted to reseal it better but the issue is the drain back.

Ever time I start it up the trans will slip a little until the converter fills up then its fine.

It will do it with whats seams as little down time as a couple of days. I drive it on weekends only, so every first start it I'm putting it in neutral and getting the revs up a bit to make sure its good to go before leaving. That and the oil patch are a pain in the butt.

Anyone have any suggestions?!?

Converter is a 2600 Holeshot (new), the trans is a new Hughes, has a trans cooler mounted up front with soft lines, engine is fairly hot, but low comp so more 'warm'. I did put a quart in the converter before assembly as well.

 

[AR67GTX]

Wishing you good luck. This is where I'm at on my converter drain down issue (and whinny planetary).

 

[1967coronet440]

Same issue here....

 

[khryslerkid]

I had the same problem on my 2003 Ram.

Drained a pint out and just remember to start in neutral if it has sat for awhile. Just a temporary fix.

I'm wondering if the trans cooler sitting too high would cause an overflow situation?

 

[lewtot184]

nature of a 727. rick allison at A&A trans told me that some shift kits can contribute to drain back. both of mine do it, so i just start in neutral after sitting a few days or weeks.

 

[Forklift]

Had the same problem ordered a Hughes Performance 727 locking stick for big blocks part # HP1235A it has a rubber sleeve that goes into the tube hole first with a stop on top. Them install tube this does a great job to seal up the dipstick hole.

 

[not so famous bob]

View attachment 390861 Had the same problem ordered a Hughes Performance 727 locking stick for big blocks part # HP1235A it has a rubber sleeve that goes into the tube hole first with a stop on top. Them install tube this does a great job to seal up the dipstick hole.

the factory had a comment about the convertors draining in the ram trans., said it`s not unusual, if yours does , let it idle upon start up in gear till it starts moving. it lets the convertor fill up. mine has always done it, no problem. my 505 - 727, barracuda always gets warmed up before moving anyway, no problem.

 

[Greg Ducato]

There are one way valves designed to help with this problem that plumb into the cooler return line. These are called "anti drainback" valves and can be purchased at most transmission parts suppliers. The return line on the 727 is the rear line and the flow is towards the case.

 

[AR67GTX]

Curious as to the principal of how these anti-drain valves work on the cooler lines.

 

[Greg Ducato]

There is a spring and ball in the valve that only allows fluid to pass under pressure. When the car is sitting and not running there is not enough pressure in the line to overcome the spring thus keeping fluid from flowing past the ball and seat.

 

[Dan]

I was told many years ago by a trans guy that a loose fit on a bushing in the pump is the the culprit. I've owned my Satellite for 35 yrs. and it has always leaked back, even after a rebuild. I just start it up and pull it into neutral for a few seconds to fill the converter. I don't know if the bushing was replaced when rebuilt.

 

[customusclegarage]

I run a deep pan half qt low and have trans cooler line fitting facing up with a trap bent in the return line. Like the drain under the kitchen sink ,stopped all mine from draining

 

[AR67GTX]

There is a spring and ball in the valve that only allows fluid to pass under pressure. When the car is sitting and not running there is not enough pressure in the line to overcome the spring thus keeping fluid from flowing past the ball and seat.

If the leakdown is from the converter draining back into the transmission body through the converter seals/bushing and raising the fluid level in the unit until it finds a leaky dipstick tube or throttle shaft seal - I'm not seeing how a valve in the return line from the radiator/cooler is preventing that or otherwise keeping the level down. Not trying to argue or be a smart aleck but just not understanding the principal

 

[Greg Ducato]

The converter drains into the cooler circuit, through the return line and back to the trans

 

[AR67GTX]

The converter drains into the cooler circuit, through the return line and back to the trans

I guess that makes sense if it can drain in that direction. I've also heard they can drain back through the converter control valve in the valve body so I guess there are a couple of possible drain paths. I'm suspecting mine was draining due to the TQ hub and bushing wear as it has definitely gotten worse over the last few thousand miles. I can see the hub/bushing wearing that quickly but can't see anything taking place in a valve body that would happen that fast (unless it was sticking maybe).

 

[Moparsmitty]

The 47RE TF in my 01 Ram has always done this and it's typical. I've gotten so used to it that I don't even notice it anymore. When I start it up cold and shift into reverse it takes a few seconds for the converter to fill and off I go. The older 727s don't seem to do this as much but I've seen a few that do. Like Lewtot said, some shift kits contribute to drainback but it's not worth tearing into an otherwise good trans.

 

[dvw]

Trans fluid level will always end up an inch or more above the pan after sitting awhile. Really the only area that tends to seep is the pump seal depending on the condition of the converter snout. Dipstick tube , shaft and selector seal, low band pin, pressure tap plugs, front kick down pin plug tailshaft gasket , tailshaft span ring cover, speedo O-ring and cable sea are all resealable in the car. Not that tough and cheap.
Doug

 

[Malicious]

THanks for the thoughts all, at this stage I think all my seals are good except the distick, so I'll definitely look into that Hughes dipstick tube. I've alwasy been a little sus on the braided one I have anyway.

The converter drains into the cooler circuit, through the return line and back to the trans

Greg, will this put additional stress on the pump seal? Just thinking that its easier to seal up the pan and low seals than pulling the trans to replace the pump seal...

 

[Richard Cranium]

Starting it up in neutral engages the pump, so when you finally do shift it into gear, it moves.

 

[Greg Ducato]

THanks for the thoughts all, at this stage I think all my seals are good except the distick, so I'll definitely look into that Hughes dipstick tube. I've alwasy been a little sus on the braided one I have anyway.



Greg, will this put additional stress on the pump seal? Just thinking that its easier to seal up the pan and low seals than pulling the trans to replace the pump seal...

No, it will not put any additional strain on the pump seal