727 lip seal

Hi guy if I have a bad lip seal, what more problems will happen?

What’s going on with it is when the car is cold putting it in any gear feels spongy after it warms up. In neutral, Everything seems to work fine. I was told it was a lip seal. I’m not really sure what a lip seal is or what it does.

When I used steel lip seals my transbrake would sometimes not hold on the starting line. Changing to Teflon seals cured this problem but over time can wear a groove in the aluminum drum. Custom making a steel sleeve pressed onto the aluminum drum cured the problem. Thanks to Pro Trans.

A lip seal is just the type of seal design, not related to any particular function in the trans.

Depends what and where the “lip” seal is. A lip seal is a rubber seal design that allows for radical and axial movement without leakage.

Used in the pump to converter area, rear servo, front and rear clutch inner and outer seals locations

Just talked with a1. Who did the trans I guess it’s what happens when it’s been sitting too long. The converter drains back. It’s works fine after I drive it every day

Convertor drainback is one of the FREE FEATURES of the 727 ... You original question says it feels spongy AFTER it warms up ? That didn't make it sound like convertor drainback. Chrysler FINALLY did something to help combat this in the 48RE trans after mid 2003 I believe it was , they added a seat ring to the stator support and more seal surface in the convertor snout for the seal ring to seal against.

Anywho it takes roughly a minute, to a minute and a half, for the entire hyd. system in the trans to charge and the convertor to refill , I assume your trans has the upgrade manual valve , but anyway pop it into neutral after starting and sit for a couple minutes before trying to engage drive.

Those are usually referred to as seal rings , not lip seals ?

Especially since he stated he warmed it up in Neutral which will refill the converter almost instantaneous.

Actually that added seal isn’t to address drainback - it’s to add to converter capacity in lockup. The only thing Chrysler did to try and address drainback was to add the anti-draindown valve in the cooler line on rear wheel drive vehicles.

Thanks for that clarification , I thought I read in one of the diesel forums it was for drainback. I removed that anti drain valve out of my 2000 because to me it was a flow restriction.

Question unrelated to the op's issue since you know a lot more about these things ... would changing my 47RE front pump to the larger gear/rotor 48RE pump be beneficial? I don't have a 48RE snouted convertor in it so I'll leave that seal ring out.

You won’t see any benefit going to the 48 pump. Unless you have the 48 cooler lines and hauling a bunch of weight the extra flow won’t help anything.
You can only pump so much fluid to brought the smaller lines.

And if your 47 is behind a gas engine you don’t want to use the diesel pump.

And that doesn't fully prevent converter drainback, it's more to prevent the high-mounted cooler in the side tank of crossflow radiators from draining through the converter. This wasn't a problem when the cooler was mounted in the bottom tank of downflow radiators.

Drainback has existed since day one. It’s exacerbated by cooler placement and pump internal clearances.

It exists in cooler placement below the pump too - front wheel drive vehicles are prone to it as well.

Thanks, that'll save me a couple hundred bucks. But I'll look into the difference in the 48 lines and the factory cooler which I know is on the opposite side of the engine.

The 47 is behind a 24V 5.9 , a 98 , it will be making close to 500 at the rear wheels, I don't tow it a lot it's, mainly my daily driver. The trans right now is in my 2000 lawn ornament that's a rusty 4x4, I've bought a 2wd OD unit out of a gas rig that I'm going to swap the OD guts, extra clutches and such out of the 4x4 OD unit, into the 2wd unit and reseal the trans which has billet shafts and such already to put in my DD and swap the injectors/turbo and chip into it. I thought maybe the extra volume available via the 48 pump would be a positive, I'm going to also put the GPZ clutches in it and have my convertor freshened as the trans was last driven in 2011.

The extra flow isn’t a bad thing, it really comes down to how you plan to use it. We upped the max GVWR on the 48 so to make things live, some things got beefed up.


The other thing that had to be considered was the use of Jake brakes. That added seal helped clutch capacity while in lockup using the Jake.

That makes sense , especially with the Jake brake that the newer trucks have. When I was hotrodding the lawn ornament, and buillding transmissions for Diesel Transmission Technologies back in 02-3, Bill ( the owner) told be to find a 48RE valvebody to upgrade to but It was around the time I was getting out of it and I never followed up. I keep looking for a complete trans now but unless I get a good deal on a core just upgrading a few of the parts that I really need from the 48 my 47 is more than capable as it is. I doubt I'll ever tow more than 10k with it.

sorry to the op for straying off topic.