Home » Public Forums » GMCnet » Re: [GMCnet] Checking THM425 Fluid Level
| Re: [GMCnet] Checking THM425 Fluid Level [message #289906] |
Tue, 03 November 2015 21:40  |
fbhtxak
Messages: 191
Registered: April 2006
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For Ken Henderson:
I am consulting you for myself and others who may share my frustration in
checking the THM425 fluid level with the OEM dipstick immediately after
changing fluid and filter..
IIRC, you recently advised to remove the vacuum modulator and fill until the
fluid flows from the VM connection.
1. Is that after starting the engine (cold), cycling through the selector
positions from/to "park" and then shutting down the engine?
2. How did you determine that the THM425 is properly filled (cold?) when
fluid flows from the VM connection? Correlation with the dipstick when you
finally got a readable level?
In the past, I have waited several hours to get a readable level after the
initial fill. I then estimate the volume required to bring the level to the
"cold" mark. I then wait another several hours to see if I got it right.
There has to be a better way than the way I have done it for 25 years.
'Appreciate your guidance...
Fred Hudspeth
1978 Royale (TZE "last four"... 1335) - Tyler, TX
1982 Airstream Excella (motorhome) - Cooper Landing, Alaska
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| Re: [GMCnet] Checking THM425 Fluid Level [message #289908 is a reply to message #289906] |
Tue, 03 November 2015 22:22  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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You need to check it by the stick while it is running at idle and warm. If you are checking by removing the modulator, you need to check it IMMEDIATELY AFTER turning off the engine. If you wait too long, the torque converter can leak down and cause you to read too high.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Checking THM425 Fluid Level [message #289912 is a reply to message #289908] |
Tue, 03 November 2015 23:06 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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The way I have always checked my trans level is look in the shop manual you will find a chart that shows where the level should be for a given fluid temperature. This way you won't be over filled when the fluid is hot.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Checking THM425 Fluid Level [message #289913 is a reply to message #289908] |
Wed, 04 November 2015 00:28 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Ken is very correct.
Some will tell you that the convertor does not leak down, but they do.
On Tue, Nov 3, 2015 at 8:22 PM, Ken Burton wrote:
> You need to check it by the stick while it is running at idle and warm.
> If you are checking by removing the modulator, you need to check it
> IMMEDIATELY AFTER turning off the engine. If you wait too long, the
> torque converter can leak down and cause you to read too high.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Checking THM425 Fluid Level [message #289917 is a reply to message #289913] |
Wed, 04 November 2015 04:26 |
Mr ERFisher
Messages: 7117
Registered: August 2005
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This is mannys trick
Read here
http://gmcmotorhome.info/transmission.html#DIP
On Tuesday, November 3, 2015, Jim Kanomata wrote:
> Ken is very correct.
> Some will tell you that the convertor does not leak down, but they do.
>
> On Tue, Nov 3, 2015 at 8:22 PM, Ken Burton > wrote:
>
>> You need to check it by the stick while it is running at idle and warm.
>> If you are checking by removing the modulator, you need to check it
>> IMMEDIATELY AFTER turning off the engine. If you wait too long, the
>> torque converter can leak down and cause you to read too high.
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Fremont,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Checking THM425 Fluid Level [message #289953 is a reply to message #289906] |
Wed, 04 November 2015 19:04 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Fred,
Here's something I've sent in a couple of times.
There is one problem with the procedure below, if your body is too "THICK" when lying on the ground you're not going to be able to
get under the GMC to access the modulator and you'll have to put it up on 4 jack stands making sure it is level.
Regards,
Rob
-----Original Message-----
From: Robert Mueller [mailto:robmueller@iinet.net.au]
Sent: Sunday, November 09, 2014 8:57 AM
To: 'gmclist@temp.gmcnet.org'
Subject: RE: [GMCnet] Calibrating Transmission Fluid Level
G'day,
Back in February I published this Manny Trovao has reviewed this procedure and "blessed" it.
TRANSMISSION DIPSTICK CALIBRATION
You will need the following items to perform this procedure:
1) Three ton jack stands - 2 ea.
2) Rags
3) Oil drain pan
4) Tool capable of removing existing marks on transmission dipstick
5) Tool capable of remarking transmission dipstick
6) Half inch (1/2") socket, extension, and ratchet to remove / reinstall modulator retainer
7) Transmission fluid
Comments:
1) Before you start this procedure look at the passenger side of the transmission and locate the modulator (Ref: Parts Book 78Z -
TRANSMISSION - Pg. 17-2 Key 6 Modulator.
2) You need to do the checking fairly quickly after stopping when the engine and transmission are HOT and the torque convertor is
full.
Procedure:
1) Park your GMC on a level surface
2) Set the parking brake
3) Set the suspension system to TRAVEL
4) Start the engine and allow coach to reach TRAVEL height
5) Depress the brake pedal
6) Cycle the transmission lever through all the positions back and forth several times slowly
7) Return the transmission to PARK
8) Leave the engine running and check the fluid level of the transmission
9) The fluid level should be at the "COLD" line if not slowly and carefully fill the transmission to that level DO NOT OVERFILL IT!
10) Get back in the coach and drive it long enough for the engine and transmission to come to normal operating temperature
11) Park the GMC on a level surface
12) Put the transmission in Park and set the parking brake
13) With the engine running check the fluid level of the transmission; if it's not on the HOT mark continue as below
14) Shut the engine off and place jack stands under the frame so that if a torsion bar were to fail you won't get crushed
15) Be careful from this point onwards not to burn yourself on the HOT exhaust pipes or with HOT transmission fluid
16) Place a drain pan under the modulator on the passenger side of the transmission
17) Remove the rubber vacuum line
18) Remove the bolt that holds the modulator retainer to the transmission using the half inch socket, extension, and ratchet
19) Remove the modulator (be careful it will be HOT)
20) Allow fluid to drain into the pan until it just starts to drip (be careful, the fluid will be HOT!)
21) If fluid does not drip out add it slowly until it does
22) Re-install the modulator, hose, and retaining screw
23) Remove the drain pan and jack stands
24) Get back in the GMC, start the engine and drive the GMC until the engine and transmission are at normal operating temperature
25) Park the GMC on a level surface
26) Set the hand brake and put the transmission in Park
27) Check the level on the dipstick, it should be at the "HOT" mark; if not note where it is
28) Remove the existing "HOT" mark on the dipstick and mark it at the correct level
29) Allow the transmission to cool overnight
30) Start the engine the next day and cycle the transmission lever through all the positions back and forth several times slowly
31) Check the level on the dipstick, it should be at or near the "COLD" mark; if not note where it is
32) Remove the existing "COLD" mark on the dipstick and mark it at the correct level
If I missed anything or what I've written isn't clear PLEASE let me know.
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of Fred Hudspeth
Sent: Wednesday, November 04, 2015 2:41 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Checking THM425 Fluid Level
For Ken Henderson:
I am consulting you for myself and others who may share my frustration in
checking the THM425 fluid level with the OEM dipstick immediately after
changing fluid and filter..
IIRC, you recently advised to remove the vacuum modulator and fill until the
fluid flows from the VM connection.
1. Is that after starting the engine (cold), cycling through the selector
positions from/to "park" and then shutting down the engine?
2. How did you determine that the THM425 is properly filled (cold?) when
fluid flows from the VM connection? Correlation with the dipstick when you
finally got a readable level?
In the past, I have waited several hours to get a readable level after the
initial fill. I then estimate the volume required to bring the level to the
"cold" mark. I then wait another several hours to see if I got it right.
There has to be a better way than the way I have done it for 25 years.
'Appreciate your guidance...
Fred Hudspeth
1978 Royale (TZE "last four"... 1335) - Tyler, TX
1982 Airstream Excella (motorhome) - Cooper Landing, Alaska
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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