TH400 Transmission using Fluid...but where is it going??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

southplainsag02 · 05-04-2011, 09:14 PM

I just recently purchased a 72C10. I believe it has the TH400 Transmission. When I pulled away from the place of purchase I added a quart of transmission fluid. I drove it at most 10 miles and it has been parked for 2 weeks while I tinker with it. Tonight I had to put in another quart to get the fluid to the correct level. There are no visual signs of leaks on my garage floor. Is this leaking around the transmission and then collecting dirt or what?

gcburdic · 05-04-2011, 09:16 PM

wonder if the torque converter is full??...has the tranny been recently rebuilt???

hugger6933 · 05-04-2011, 09:30 PM

could the vaccum modulator be the culprit? when they go bad the diaphram leaks and fluid is sucked into the intake manifold then burned by the engine. pull the vac. hose off see if it is wet in there or really soft and squishy. jim

dave2953 · 05-04-2011, 09:31 PM

Possibly leaking from the transmission cooler into the cooling system?

southplainsag02 · 05-04-2011, 09:41 PM

Quote:

Originally Posted by gcburdic

wonder if the torque converter is full??...has the tranny been recently rebuilt???

The tranny has not been rebuilt for a long time. I will check the vacuum lines and see if that is it. There seems to be a lot of oil soaked dirt all around the transmission that could be soaking it up. Where would leaks form on a transmission except for around the pan?

hugger6933 · 05-04-2011, 09:46 PM

front seal ,rear seal ,around the dipstick[thats a bigge] speedo housing extension housing and of course the overflow in the top [breather]

Tim R · 05-04-2011, 10:46 PM

Check the vaccuum modulator on the pass side probably diaphram busted sucking the fluid into the motor .It does it so slow it doesnt smoke but sucks the fluid out of the trans

Gobbles · 05-05-2011, 12:03 AM

Mine leaks out the tach cable, like a sieve mind you.

eightbanger · 05-05-2011, 06:16 AM

Just putting this out there,...you did check the fluid level on hot idle? it may not really have needed the top up.

MARKDTN · 05-05-2011, 07:13 AM

Quote:

Originally Posted by hugger6933

could the vaccum modulator be the culprit? when they go bad the diaphram leaks and fluid is sucked into the intake manifold then burned by the engine. pull the vac. hose off see if it is wet in there or really soft and squishy. jim

That's where I would start too.

ubtripn · 05-05-2011, 08:32 AM

I would check your radiator. I lost one 700R4 this way as stated above, the heat exchanger can go and mix the fluid, you keep pouring in tranny fluid and it disappears. If it's your heat exchanger your antifreeze/coolant will look like a brown/pinkish milkshake.

**leddzepp** · 05-05-2011, 10:52 AM

Quote:

Originally Posted by eightbanger

Just putting this out there,...you did check the fluid level on hot idle? it may not really have needed the top up.

this is also my first question.

the truck is running and warmed up when you are checking the fluid, right?
Posted via Mobile Device

southplainsag02 · 05-05-2011, 09:37 PM

The truck is definately warmed up and running. I will check the heat coolant when I get back and also look at the other things you guys mentioned. Thanks for all the help!

05-04-2011, 09:14 PM	#1
southplainsag02 Registered User Join Date: Apr 2011 Location: Idalou, TX Posts: 20	TH400 Transmission using Fluid...but where is it going??? I just recently purchased a 72C10. I believe it has the TH400 Transmission. When I pulled away from the place of purchase I added a quart of transmission fluid. I drove it at most 10 miles and it has been parked for 2 weeks while I tinker with it. Tonight I had to put in another quart to get the fluid to the correct level. There are no visual signs of leaks on my garage floor. Is this leaking around the transmission and then collecting dirt or what?

05-04-2011, 09:16 PM	#2
gcburdic Restoration Virgin! Join Date: Jan 2008 Location: Huntersville, NC Posts: 8,298	Re: TH400 Transmission using Fluid...but where is it going??? wonder if the torque converter is full??...has the tranny been recently rebuilt??? __________________ Geoff with a G 1968 Chevy C10 SWB The Mistress 1972 Custom Deluxe C20 Suburban A Suburban Named Isabella 1966 Ford Mustang Mama's High School Graduation Present

05-04-2011, 09:30 PM	#3
hugger6933 Registered User Join Date: Oct 2008 Location: Marianna Arkansas Posts: 7,261	Re: TH400 Transmission using Fluid...but where is it going??? could the vaccum modulator be the culprit? when they go bad the diaphram leaks and fluid is sucked into the intake manifold then burned by the engine. pull the vac. hose off see if it is wet in there or really soft and squishy. jim

05-04-2011, 09:31 PM	#4
dave2953 Dave's not here, man Join Date: Jun 2004 Location: Winder, Georgia Posts: 2,000	Re: TH400 Transmission using Fluid...but where is it going??? Possibly leaking from the transmission cooler into the cooling system? __________________ - 2014 VW Jetta - 2015 VW Jetta - 1966 Ford F-250 Last edited by dave2953; 05-04-2011 at 09:39 PM.

05-04-2011, 09:46 PM	#6
hugger6933 Registered User Join Date: Oct 2008 Location: Marianna Arkansas Posts: 7,261	Re: TH400 Transmission using Fluid...but where is it going??? front seal ,rear seal ,around the dipstick[thats a bigge] speedo housing extension housing and of course the overflow in the top [breather]

05-04-2011, 10:46 PM	#7
Tim R Registered User Join Date: Jan 2009 Location: bmt,tx Posts: 127	Re: TH400 Transmission using Fluid...but where is it going??? Check the vaccuum modulator on the pass side probably diaphram busted sucking the fluid into the motor .It does it so slow it doesnt smoke but sucks the fluid out of the trans

05-05-2011, 12:03 AM	#8
Gobbles Registered User Join Date: Sep 2010 Location: British Columbia Posts: 484	Re: TH400 Transmission using Fluid...but where is it going??? Mine leaks out the tach cable, like a sieve mind you. __________________ Trevor "You already said spite"

05-05-2011, 06:16 AM	#9
eightbanger 454 MAKES IT ROAR Join Date: Jan 2008 Location: Essex, U.K Posts: 2,701	Re: TH400 Transmission using Fluid...but where is it going??? Just putting this out there,...you did check the fluid level on hot idle? it may not really have needed the top up. __________________ Nigel. An American living in a British body. 1971 Chevy Cheyenne 10 454 "In a time of universal deceit, telling the truth becomes a revolutionary act." - George Orwell "When injustice becomes law, resistance becomes duty" - Thomas Jefferson No more pain. 03.12.60 -- 12.28.10 http://www.youtube.com/Eightbanger

05-05-2011, 08:32 AM	#11
ubtripn Registered User Join Date: Apr 2010 Location: Boise, ID Posts: 1,280	Re: TH400 Transmission using Fluid...but where is it going??? I would check your radiator. I lost one 700R4 this way as stated above, the heat exchanger can go and mix the fluid, you keep pouring in tranny fluid and it disappears. If it's your heat exchanger your antifreeze/coolant will look like a brown/pinkish milkshake.

05-05-2011, 09:37 PM	#13
southplainsag02 Registered User Join Date: Apr 2011 Location: Idalou, TX Posts: 20	Re: TH400 Transmission using Fluid...but where is it going??? The truck is definately warmed up and running. I will check the heat coolant when I get back and also look at the other things you guys mentioned. Thanks for all the help!

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