Humvee 4L80e ATF 3 or 6, can ATF 6 cause leaks?

[Hummer Guy]

From the information I gathered, both of these fluids can be used in the 4l80e but GM recommends the ATF 6, I heard that the ATF 6 is a thinner fluid which can give it a better chance of leaking, which is why I'm asking this question. This is at least my 4th time having a leak with the ATF 6 after changing the gasket and trying to use a gasket maker one of the time. Each time I change the gasket, it last for about 3 weeks and then the leak comes back and then get bigger over time. The first time I tried an RTV and a aftermarket gasket, this lasted about a month and leaked (didn't know this RTV wasn't made for ATF till now), next I tried the aftermarket gasket itself and it leaked in about a week or 2, after that, I tried RTV itself, that leaked in a few days, and then now I got a new transmission pan plus an original 4l80e gasket from AC Delco. This lasted about 3 or 4 weeks and then started to leak. This is really starting to get irritating, is it something with the ATF 6 fluid that eats up the gasket over time?

My next plan is to try an actual transmission sealant that's made for ATF fluids.

 

[Mogman]

Get the reusable gasket and do not use sealer, AND torque the bolts to the proper spec, this problem is why I try to always use a cast pan, the gasket surface is much more stable. (read stays flat unlike a steel pan)
I do not think the DEX VI is any more likely to leak out of a properly installed gasket surface but more likely to leak out of a seal.
Surface prep is very important

 

[Mogman]

The torque is only 100-120 inch pounds, that is a max 10 foot pounds.
Unfortunately if the tin pans get over torqued they will likely always have problems.

 

[Hummer Guy]

Get the reusable gasket and do not use sealer, AND torque the bolts to the proper spec, this problem is why I try to always use a cast pan, the gasket surface is much more stable. (read stays flat unlike a steel pan)
I do not think the DEX VI is any more likely to leak out of a properly installed gasket surface but more likely to leak out of a seal.
Surface prep is very important

One thing that came to my mind, why would it stay sealed for a few weeks and then leak afterwards, seems like it'll start leaking soon as I put the pan on or the day after if the pan had got bent or wasn't torque completely to 10 Ibs foot Ibs

 

[Mainsail]

When I changed the two filters in my Grand Cherokee I (for a change) read the directions on the RTV; said to let it cure X hours before exposing it to the ATF. That meant I had to leave the pan empty and roll the jeep off the ramps, then leave it overnight. After refilling it the next morning - no leaks. Major pain in the butt too, but that's what the manufacturer said, and they know a wee bit more than I do about the product.

I agree with the above about the steel pans- once some gorilla fisted mechanic that measures torque by the amount of smoke that comes out from around the bolts, the pans gets deformed around the bolt holes. If it won't seal with the OEM gasket, replace the pan. Also, make sure the mating surface on the transmission is clean.

EDIT to add: Is it leaking when it's parked level? Often there won't be any leak evident after you install the pan because the fluid level is below the sealing surface. Later, when parked on a slope, or accelerating/braking, the fluid finds a leaky spot on the front or rear of the pan/trans mating surface, and leaks there.

 

[Hummer Guy]

When I changed the two filters in my Grand Cherokee I (for a change) read the directions on the RTV; said to let it cure X hours before exposing it to the ATF. That meant I had to leave the pan empty and roll the jeep off the ramps, then leave it overnight. After refilling it the next morning - no leaks. Major pain in the butt too, but that's what the manufacturer said, and they know a wee bit more than I do about the product.

I agree with the above about the steel pans- once some gorilla fisted mechanic that measures torque by the amount of smoke that comes out from around the bolts, the pans gets deformed around the bolt holes. If it won't seal with the OEM gasket, replace the pan. Also, make sure the mating surface on the transmission is clean.

EDIT to add: Is it leaking when it's parked level? Often there won't be any leak evident after you install the pan because the fluid level is below the sealing surface. Later, when parked on a slope, or accelerating/braking, the fluid finds a leaky spot on the front or rear of the pan/trans mating surface, and leaks there.

Its leaking while parked on level surface. I drove it for about 100 miles without any leaks, it didn't start leaking till around 3 days of being parked