Trans stop-leak

[scrounge]

My '99 1500 with a 318 and a 46re has had a trans fluid leak since I bought it. It's dripping from the bell housing, which I'm interpreting as that gasket. The trans was reportedly rebuilt during the 2nd owner's tenure, at least 15 years ago. It otherwise performs like it should, so I'd just been adding fluid as needed, usually 2 quarts per month. (I've changed the fluid and filter twice, also replacing the gasket both times.)

ATF+4 ain't cheap, and its price keeps rising. Earlier this year, I happened across good recommendations for this:

https://www.amazon.com/ATP-AT-205-Re-Seal-Stops-Bottle/dp/B000NVW1LM

I bought a container and added it, and the fluid stopped leaking -- for several months. But the leak recently returned, so I'm wondering if this stuff needs to be added every so-many thousands of miles (or every few months). I have a can of this:

https://www.walmart.com/ip/CRC-K-W-...smission-Slip-Stop-Leak-Fix-15-fl-oz/16767860

I have half a mind to add it. The other half wonders if doing so might gum up works that need to be free for the transmission to function properly. The right thing to do would be to have the gasket replaced, but that will be expensive and time-consuming, and trans shops might insist that I spend more money to replace everything, even though most of it doesn't need replacing. Time and money are current problems for me.

So, if anyone has any experience with these additives, good or bad, please share.

 

[Spike95]

Do not keep adding stop leak products. If one dose didn’t fix it, then it will just have to be fixed properly. Too much of that stuff can definitely turn into a nasty mess that will cost you more money in the long run.

If you have a 46re that has gone 15 years since it’s last rebuild, then count your lucky stars. If you do have a shop tear into it, I would recommend just having it rebuilt instead of trying to do piecemeal repairs… but I guess that depends on how long you plan to keep it.

 

[scrounge]

Well, one dose DID fix it, but only temporarily. After thinking about it, my guess is that the seal rotted through in another spot.

But you're probably right about adding more of the stuff. This is a $1200 truck, bought for helping clear out an estate, and while I'd like to keep it running as long as possible, the $ for such an expensive repair might better go toward another vehicle with fewer miles and problems. Should have mentioned at the start, this one now has 387K miles on it.

The trans doesn't seem to have any problems other than the leak. It shifts when it should, and each shift takes only a split second. Just replacing the seal might help the trans last another 100K miles or more without problems.

 

[Sherman Bird]

My '99 1500 with a 318 and a 46re has had a trans fluid leak since I bought it. It's dripping from the bell housing, which I'm interpreting as that gasket. The trans was reportedly rebuilt during the 2nd owner's tenure, at least 15 years ago. It otherwise performs like it should, so I'd just been adding fluid as needed, usually 2 quarts per month. (I've changed the fluid and filter twice, also replacing the gasket both times.)

ATF+4 ain't cheap, and its price keeps rising. Earlier this year, I happened across good recommendations for this:

https://www.amazon.com/ATP-AT-205-Re-Seal-Stops-Bottle/dp/B000NVW1LM

I bought a container and added it, and the fluid stopped leaking -- for several months. But the leak recently returned, so I'm wondering if this stuff needs to be added every so-many thousands of miles (or every few months). I have a can of this:

https://www.walmart.com/ip/CRC-K-W-...smission-Slip-Stop-Leak-Fix-15-fl-oz/16767860

I have half a mind to add it. The other half wonders if doing so might gum up works that need to be free for the transmission to function properly. The right thing to do would be to have the gasket replaced, but that will be expensive and time-consuming, and trans shops might insist that I spend more money to replace everything, even though most of it doesn't need replacing. Time and money are current problems for me.

So, if anyone has any experience with these additives, good or bad, please share.

That additive (ATP 205) is a harmless polymer that won't "gum up" your trans, when mixed with petroleum based fluids. The fact is, it only effectively works on, say, the front pump o-ring, but not the gasket, but it is not going to harm your trans, engine, or p/s. Problem is, modern fluids are largely synthetic, so, to stop the leak, you'll have to find old fashioned +4 fluid of the old school variety. You can find it. Why not just have it fixed properly in the first place? Stop leak is a bandaid for something that needs surgery.

 

[Burla]

The number one mistake when someone rebuilds the transmission is using the old rear main seal instead of using a new one, and last time I checked over 20 years ago it would be 600 dollars to fix, don't even want to know what it is today. Stop leaks can swell seals, but over time that can make the situation worse, and at some point you may need to fix the seal. This product you are using is indeed a plasticizer, meaning it will interact with the seal not just clog it up or slow it with viscosity.

My advice, keep putting in atf, maybe go a little thicker. If you change to lucas trans fix, maybe use is in three doses, as it leaks add another third. It is a thickner, not too bad but I wouldnt want my transmission fluid too thick. ATF 4 is about 7 viscosity, rfe is 12-14 quarts? Lucas visc is 48, so if you use lucas against 10 quarts of transmision fluid it would boost visc only by 3, and that number goes down with every quart over ten quarts, so it is fairly safe to use as a thickner.

Stop Leaks are something more to use when a guy is trying to sell his car or truck as opposed to a legit strategy, most of them that is. You mix an old seal with something that swells seals, you are asking for that seal to fail. Might be too late anyhow, but I wouldn't go adding more plasticizer.

 

[scrounge]

Thanks for the informative replies. I found a local mechanic who quoted me a bit over $500 to replace the pump and the rear main seal. But he's popular, and booked about 2 weeks in advance, so I made an appointment. Meanwhile, ATF+4 was on sale at NAPA last month, so I stocked up on it.

 

[Sherman Bird]

Thanks for the informative replies. I found a local mechanic who quoted me a bit over $500 to replace the pump and the rear main seal. But he's popular, and booked about 2 weeks in advance, so I made an appointment. Meanwhile, ATF+4 was on sale at NAPA last month, so I stocked up on it.

"My Old Plymouth Ain't Running"!

 

[Theck4291]

I personally haven't ever had luck with the stop leak stuff. I just finished rebuilding a 545RFE myself and wasn't too bad of a job in my downtime, and about to start on a 46RE.