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Hello. I just purchased a 2008 Impala that is leaking tranny fluid from various locations. I replaced both cooler lines and fittings at the transmission, new gasket and filter kit, and a new fill tube seal/grommet. I still have a leak that appears to be coming from above and it's collecting on the pan gasket, making it appear as if the pan gasket is leaking. I checked the vent and it is open and working fine. I checked both axle seals and looked at torque seal through the inspection plate. All are dry. I put vehicle on the lift while running and wheels spinning, and no leak. It only leaks while driving/under load, with tranny at operating temperature. It runs down from somewhere, collects on the pan, and the aluminum frame behind the pan, and blows back on the converter, and most of the way back on the underneath of car. I can't tell where else the fluid may be leaking from and I'm wondering what other leaks are common on these transmissions? Thanks.
 

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First off
Welcome to the forum.

It almost sounds as if it's been over filled. Perhaps when you did the service on it you may have put too much in? I know the owner manual ( or someplace I read it ) says that after its HOT it must sit for a couple minutes under idle to check for the proper level.

Other than what you have replaced and repaired already, and it's not leaking from the main gasket that goes between the outer portion of the transmission not really sure where it can come from.
 
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Thanks for the welcome. The thought of overfilling crossed my mind. I have wondered whether or not the dipstick is accurate. When I first got the car, there was no fluid at all showing on the dipstick with a warm transmission at idle. It took approx 5 quarts to bring it to proper level according to the dipstick. I may have overfilled it at this point. I wasn't expecting to use 5 quarts just to top it off. It was after this that I dropped the pan, changed the filter and gasket. It took approx 7 quarts to refill, according to the dipstick. Does 7 quarts sound like the right amount to put in after a pan drain and filter change? I don't have an owners manual. The last thing I did was replace the fill tube grommet, as it appeared to be coming from there. When I had the fill tube out, I looked in there with a mirror, and the fluid level was right at the top of the fill tube hole. When I pushed the new rubber grommet in, fluid pushed out, so it appears to be full--maybe too full. Currently, I'm still getting significant dripping to the point of blowing back on the exhaust while driving, however, the dipstick is showing that I need approximately 1/2 quart just to get me into the crosshatch, or 1 quart to get me to the top end of operating range. With engine shut off and tranny cold, fluid level shows over full, near the bend in the dipstick. If I am overfull, the dipstick is not reflecting that. Guess I just drive it and keep and eye on things. Thanks for the reply, and any more tips relative to this update, are welcome. Thanks again!
 

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Guess I just drive it and keep and eye on things. Thanks for the reply, and any more tips relative to this update, are welcome. Thanks again!
I would personally NOT 'just drive it' under these conditions... maybe try to score a year-appropriate fill tube and dipstick off of eBay (from a reputable seller, of course) or an automotive website?

By the way... if you're an Amazon user, you can add your vehicle to your Amazon Garage and find year- and model-appropriate replacement parts. That's how I got replacement headlamps for my 2005 Impala for $90.

Edit:
Your Garage: Automotive: Amazon.com


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You'll have a fire if it's blowing out on the exhaust.
Common automatic transmission leak points are the pan gasket, cooler lines, input seal, and output seals. The 4T65E has an end cover on the LH end of the transmission too. As long as you're using the original gaskets the pan and side cover usually don't leak. If it's coming out around the dipstick tube with a new seal it's probably overfilled.

The original AC Delco GM 24206182 steel core 4T65E pan gasket is right around $30. It's reusable multiple times and it doesn't leak. I hope you or the previous owner didn't put it in the bin. The gaskets that come with the strainer, what you're calling a filter, should be put directly in the trash bin. They will not seal like the OEM gasket.

Transmission fluid levels aren't checked like motor oil... with the engine off. They need to be checked with the fluid warmed up in PARK with the engine running. The dipstick usually says how it should be done.

If you have it overfilled it'll aerate the fluid and cause other issues.

Did you replace refrigerator magnet that GM originally installed in the pan on your 4T65E with high temp magnets following the instructions in GM TSB 08-07-30-040C?

Did you check it with the engine running, in PARK, and the transmission up to temp?

Did you use Dexron VI? If you used fluid claiming to be Dexron III or some other transmission fluid you need to get it out of that transmission ASAP and refill with Dexron VI.
Dexron VI is Dexron VI... It doesn't have to be GM AC Delco branded Dexron VI as long as the bottle says Dexron VI and not "Dexron VI compatible". WalMart Supertech Dexron VI is fine. Draining, re-filling, running the engine til the trans is hot and draining again... twice... should dilute the remaining Dexron III, on the third fill with Dexron VI, to the point that it won't hurt much.
 

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It took approx 7 quarts to refill, according to the dipstick. Does 7 quarts sound like the right amount to put in after a pan drain and filter change?
This sounds right. I believe I put around 7.5 quarts in after I dropped the pan and did the filter on my transmission. If you put that amount in and the dipstick shows that as being correct, sounds like that is good to go. Like others said, must check level with fluid hot, and vehicle running.
 

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Hello I just joined the group I have an 08 impala ls and yesterday I saw transmission fluid leaking which started yest I have 210,000 miles on it and I was wondering does it mean The trans is blowing and also started slipping today
 

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Have you checked the atf level/condition? Check fluid level idling in Park and warmed up. Pan, cooling lines or dipstick tube (if vent is plugged) are common culprits.
 
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