Author Topic: Transmission emptying...  (Read 236 times)

Offline zieg85

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Transmission emptying...
« on: September 14, 2018, 11:07:36 PM »
I am planning on taking my TH400 out of my truck for replacement.  I would like to pump it dry before I remove it.  Does the fluid flow go to the bottom of the radiator cooler or the top connection into the radiator?
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Stewart G Griffin

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Re: Transmission emptying...
« Reply #1 on: September 15, 2018, 01:33:25 PM »
It may be well known by now, i recently did a TH-350 replacement.  The top outlet on the rad/top line goes back to the trans, the bottom line/bottom inlet on rad, fluid goes from trans TO the cooler.

i'd ASSume TH-400 is the same, but better double check to make sure.
« Last Edit: September 15, 2018, 03:55:42 PM by Stewart G Griffin »

Offline VileZambonie

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Re: Transmission emptying...
« Reply #2 on: September 15, 2018, 08:44:48 PM »
Cooler feed is irrelevant. You will need to drop the pan and filter and if you want to empty the trans you will need to remove the valve body. To empty a torque converter, you will need to drill out the torque converter and lay it on its axis. It will never pump itself dry, just like a human, even if you cut the carotid artery, it will never bleed dry. Transmissions are messy and never dry unless 100% disassembled.
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Offline zieg85

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Re: Transmission emptying...
« Reply #3 on: September 15, 2018, 09:50:20 PM »
Cooler feed is irrelevant. You will need to drop the pan and filter and if you want to empty the trans you will need to remove the valve body. To empty a torque converter, you will need to drill out the torque converter and lay it on its axis. It will never pump itself dry, just like a human, even if you cut the carotid artery, it will never bleed dry. Transmissions are messy and never dry unless 100% disassembled.

Was hoping to get the level low enough to be able to take the dipstick tube out.  Still working on ramps with a transmission jack and not enough clearance to get the trans out without the dipstick tube removal.  New concrete I really don't want to spill red stuff all over...


1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline Stewart G Griffin

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Re: Transmission emptying...
« Reply #4 on: September 16, 2018, 11:23:44 AM »
1) Cooler feed may be irrelevant in terms of just physical trans removal, but possibly important if flushing the cooler out----which you should do if installing a new trans.

2)  i didn't understand the last description clearly, but if you are still working on getting ramps, then i would recommend 4;  i only used two on the rear wheels..........and suffered.....
Get it as high as possible, safely.

3) What new trans are you using?   The reason why i ask is if you use the plugs from the new trans (assuming they come with them), this could help with leakage, but you probably already knew that. 

If not, as an example:
https://www.summitracing.com/parts/ati-973080

i don't think the TH-400 uses a kickdown cable? (this is what caused most of the mess with me)    So, if the dipstick hole can be plugged, this would be helpful in preventing spills.

What i did was go to harbour freight and get those cheap $3, 5'x7' tarps and laid them down under the truck.  They really don't affect how the trans jack rolls, especially on concrete.   If it gets soiled, who cares?  Just chuck it.   It's only $3.
 

Offline zieg85

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Re: Transmission emptying...
« Reply #5 on: September 16, 2018, 12:22:29 PM »
I have really heavy duty home built RV ramps that are higher than the standard orange ones.  My plans are to drive it up on the HD ones and jack up the rear with a floor jack and slide the other ones under the wheels.  Th400 replaced with a TH 400, both have the bolt on yolk so no mess there.  My trans jack is a nice one I bought 25 years ago, I forgot the brand but it works extremely well and has all the angle knobs.  I'll get er done.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline zieg85

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Re: Transmission emptying...
« Reply #6 on: September 16, 2018, 12:26:00 PM »
I also plan to chase a new quart of transmission fluid through the lines and radiator cooler before the new trans goes in using a 2 quart paint pressure pot and the right adapters to get it all hooked up well.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 4.56 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline VileZambonie

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Re: Transmission emptying...
« Reply #7 on: September 16, 2018, 12:43:51 PM »
Just drop the pan and filter and that will be plenty low enough for you to pop out the dipstick tube without making a mess. Buy a can of cooler flush instead.

As far as the cooler lines on these trucks, you can flush in either direction. There is no check valve or thermostat.
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