leaking th400 - Page 2

richie 2 · 08-09-2020, 07:47 AM

thankyou everyone for your help! ive have the fluid level to the dipstick full mark, WITH the deep pan on...did not remark the full mark...2 3/4" deep pan.

Mark Ugrich · 08-09-2020, 09:49 AM

Fluid level cold should be at “add 1 pint” ATF will expand as it heats up.

richie 2 · 08-09-2020, 10:01 AM

1 1/2" ...full mark to dipstick end.

Mark Ugrich · 08-09-2020, 10:11 AM

Are you using the oem dipstick and tube or an aftermarket ? Even with a deep pan I believe the fluid level should be below the pan rail. If it’s an aftermarket dipstick try draining the pan so the oil level shows about 1/4 up the dipstick cold. Then go for a test drive heat cycle the trans and recheck to see if the oil level is at full when hot.

richie 2 · 08-09-2020, 10:46 AM

we originally had a fancy milodon unit. i thought it was the leak source, went back to the factory piece. will get it sorted out and go back to fancy...

Adger Smith · 08-09-2020, 10:58 AM

You just need Flex Seal

richie 2 · 08-10-2020, 01:48 PM

pan manufacturer says fill to the factory full mark...WTF... the flex seal idea is sounding better adger...

Mark Ruset · 08-10-2020, 02:34 PM

Before you start throwing parts at the transmission you really need to locate the source of the leak. My days as a GM tech when I had a complaint of a transmission leak, I cleaned the entire surface areas with brake clean and then used air to make sure it was completely dry. Next I used spray tracing powder and sprayed the entire area., in a short time you should be able to see the powder turning a pinkish color at the source of the leak. It may be as simple as transmission fluid leaking around the front pump cover bolts that would make it look like a pan rail leak.

Mark Ugrich · 08-10-2020, 03:11 PM

Quote:

Originally Posted by richie 2

pan manufacturer says fill to the factory full mark...WTF... the flex seal idea is sounding better adger...

I’d say the manufacturer is wrong. In 40 years as a tech, I’ve never started a trans with the level at the full mark.

richie 2 · 08-10-2020, 08:35 PM

with the pan off, dipstick in, the full mark is higher than the trans/pan surface. the modulator valve bore is right there too....sure seems to be seeping out there. the valve and o/ring fit feels sloppy. measured it all up and installed theres not much crush on the o/ring, .020" roughly...

08-09-2020, 07:47 AM	#11
richie 2 Senior Member Join Date: Feb 2009 Posts: 916 Likes: 319 Liked 155 Times in 71 Posts	Re: leaking th400 thankyou everyone for your help! ive have the fluid level to the dipstick full mark, WITH the deep pan on...did not remark the full mark...2 3/4" deep pan. Last edited by richie 2; 08-09-2020 at 09:08 AM.

08-09-2020, 09:49 AM	#12
Mark Ugrich Member Join Date: May 2011 Location: Auburndale,Florida Posts: 201 Likes: 20 Liked 57 Times in 32 Posts	Re: leaking th400 Fluid level cold should be at “add 1 pint” ATF will expand as it heats up.

08-09-2020, 10:01 AM	#13
richie 2 Senior Member Join Date: Feb 2009 Posts: 916 Likes: 319 Liked 155 Times in 71 Posts	Re: leaking th400 1 1/2" ...full mark to dipstick end.

08-09-2020, 10:11 AM	#14
Mark Ugrich Member Join Date: May 2011 Location: Auburndale,Florida Posts: 201 Likes: 20 Liked 57 Times in 32 Posts	Re: leaking th400 Are you using the oem dipstick and tube or an aftermarket ? Even with a deep pan I believe the fluid level should be below the pan rail. If it’s an aftermarket dipstick try draining the pan so the oil level shows about 1/4 up the dipstick cold. Then go for a test drive heat cycle the trans and recheck to see if the oil level is at full when hot.

08-09-2020, 10:46 AM	#15
richie 2 Senior Member Join Date: Feb 2009 Posts: 916 Likes: 319 Liked 155 Times in 71 Posts	Re: leaking th400 we originally had a fancy milodon unit. i thought it was the leak source, went back to the factory piece. will get it sorted out and go back to fancy...

08-09-2020, 10:58 AM	#16
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,348 Likes: 434 Liked 676 Times in 260 Posts	Re: leaking th400 You just need Flex Seal __________________ Adger Smith (Former SS)

08-10-2020, 01:48 PM	#17
richie 2 Senior Member Join Date: Feb 2009 Posts: 916 Likes: 319 Liked 155 Times in 71 Posts	Re: leaking th400 pan manufacturer says fill to the factory full mark...WTF... the flex seal idea is sounding better adger...

08-10-2020, 02:34 PM	#18
Mark Ruset Member Join Date: May 2006 Location: Southwest Florida Posts: 250 Likes: 23 Liked 34 Times in 24 Posts	Re: leaking th400 Before you start throwing parts at the transmission you really need to locate the source of the leak. My days as a GM tech when I had a complaint of a transmission leak, I cleaned the entire surface areas with brake clean and then used air to make sure it was completely dry. Next I used spray tracing powder and sprayed the entire area., in a short time you should be able to see the powder turning a pinkish color at the source of the leak. It may be as simple as transmission fluid leaking around the front pump cover bolts that would make it look like a pan rail leak. __________________ Mark Ruset 2048 STK

08-10-2020, 08:35 PM	#20
richie 2 Senior Member Join Date: Feb 2009 Posts: 916 Likes: 319 Liked 155 Times in 71 Posts	Re: leaking th400 with the pan off, dipstick in, the full mark is higher than the trans/pan surface. the modulator valve bore is right there too....sure seems to be seeping out there. the valve and o/ring fit feels sloppy. measured it all up and installed theres not much crush on the o/ring, .020" roughly...