transmission pan seal leak after fluid change, twice!!!

[swedenboy]

hello everyone,
I have my tahoe 2022 ,5.3 L , has only 59000KM on it, got my transmission oil changed in last service ,
everything was amazing within city, but when hit highway above 120Km/hr , the transmission seal leaked and oil started dipping
i towed back to the dealership, they replaced the seal and oil,
everything was amazing within city, but when hit highway above 120Km/hr , the transmission seal leaked and oil started dipping AGAIN.

anyone faced problem, or knows what could be the problem,

i dont wana repeat the same process again with no results.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in your truck's generation will chime in.

 

[jfoj]

In theory the trans pan gasket is reusable, however, I would not reuse it if over 2-3 years old. The OEM pan is only slightly thicker than a beer or soda can, easy to bend, warp, distort. The key to a good seal is use brake cleaner to clean the pan, gasket and transmission gasket surface. Any oil will compromise the seal and a bad trans pan also is a problem. I would recommend installing a PPE pan with a drain plug. The PPE pan is a solid cast pan with a strong, flat gasket surface that will not distort or bend. Then get all oil off gasket and mating surfaces.

 

[jerry455]

Ireused mine when I did a filter and fluid swap. No problems. It was at least 3 years old.

 

[Kpwweb]

How difficult was the exhaust to drop? I did it on my 2016, but the stids are different on the 2021 and much harder to reach. Any hints?

Ireused mine when I did a filter and fluid swap. No problems. It was at least 3 years old.

 

[jfoj]

How difficult was the exhaust to drop? I did it on my 2016, but the stids are different on the 2021 and much harder to reach. Any hints?

On my 2024 I needed to remove the driver side O2 sensor in order to reach one of the exhaust manifold studs.

Overall it was not too difficult, as I recall I used 3/8" drive deep socket of the correct size, cannot recall exactly but it may have been 14 or 15mm?? and a number of wobble extensions. I did use a 1/2" female to 3/8" male adapter and a 1/2" breaker bar to actually "crack" the nuts loose on the studs. Then used a LOT of anti seize on the studs before putting the nuts back on.

 

[jerry455]

Whe I did mine, I did not drop the pipe. I unbolted the trans mounted, raised the back of the engine and pried down the rear of the exhaust. There was a video somewhere that I saw it done. There is barely enogh room to wiggle the pan out.

 

[jfoj]

Unbolting the trans mount and raising the trans may work for the stock pan, but not sure this will give enough room to install an aftermarket pan. I was aware of that option however just decided to have space to get after market pan in without a fight. The benefit of the aftermarket pan is the drain so more frequent fluid drains can be performed easily.

My plan is a trans pan drain and fill every 12-16k miles and leave filter alone.

 

[tom3]

On the OP's problem I wonder if it's the front pump seal leaking at higher speed and pressures? I ran into this with my 700r trans after a filter/lube change. I guess tightening the pan bolts distorted the case just enough to make it start leaking. After changing the pan gasket again it really let go.

 

[jfoj]

More likely if the pan gasket is not leaking the shop overfilled the transmission fluid. A bit hard to do, but I am always surprised what some people are capable of!

 

[jerry455]

I am putting the PPE pan on in another month or so, waiting for better weather. I may have to drop the exhaust this time, but I am going to do the same, fluid and filter with better pan and then yearly fluid changes. I need to look at the "top" plug to see how much room there is between the trans tunnel and trans. It is the same thread size as "fill" plug. I wonder if a 90* fitting would fit. Then I can run a hose to a convenient spot under hood for a fill point. That would make life easier.

 

[jfoj]

Do not over think this transmission fill method. First off both GM and Ford have it all WRONG. WTH were they thinking requiring the fluid to be at 175F"+??? This is a SERIOUS burn and possible fire hazard if the hot fluid hits the hot exhaust, especially while you are under the vehicle. Crazy liability problem waiting to happen. They did not fill the transmissions during assembly at 175F!! A safe procedure/design with the fluid at 100F could have been developed. This is the way the German manufacturers have done it for years, along with the bottom pan fill with the standpipe, this is a genius way to check and fill a transmission once you understand how and why it works. The 10L1000 has something similar, but not the 10L80/10L90's. Kind of wish PPE or someone would have added the standpipe feature to their trans pans, not sure but it my be able to be added after the fact if there is enough meat to drill and tap a hole in an area where there is no obstructions, but the side fill works fine.

News flash, if you do not remove the valve body the cooling loop does not drain!!!! So no need to get the fluid up to 175F+. Get the fluid to 100F and you will be safe and can set a the fluid level correctly. If you remove the valve body, you are likely removing/bypassing the cooling loop anyway, so the same holds true, 100F and set the level with the engine running. No problems, safe temperature, no burns, no fire hazard. BTW, if you break torque the transmission to raise the temperature and you are no patient, you can easily overheat the torque converter and possibly cause permanent seal damage!!

Just use the side fill and a fluid pump of some sort, very easy, fill until it starts to drain with engine off, loosely install fill plug, use Keyfob to remote start engine (hood needs to be closed!), pull plug, fill until it starts to drain, watch fluid temp or use the palm of your hand on the trans pan to get an idea that the fluid is warmed up a bit. You can keep your palm on the trans pan at 100F. The pull plug and either allow to drain, or top off and allow to drain to a trickle and install fill plug. Drive a few days and recheck. Make sure fluid is not too hot. You can perform the fill with the front up on ramps, but ideally vehicle should be level, but this will not be a big issue.

 

[DontTaseMeBro]

Ireused mine when I did a filter and fluid swap. No problems. It was at least 3 years old.

Same.