Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-19-2018, 02:02 PM   #1
Rivet Master
 
WayneG's Avatar
 
1984 27' Airstream 270
Scotia , New York
Join Date: Oct 2012
Posts: 1,082
Two TH400 questions

After I installed the new aluminum radiator, I noticed on the first trip the transmission fluid temp made it up to 300 deg. F.

The blue line is the transmission fluid line temperature and the top line is 300 Deg. F.

To avoid huge images here, I only put up thumbnails of the charts.
Full size charts are at this link:
http://theouterlimits.ws/projects/ai...tml#Trans-temp


It was mentioned that it could be transmission slippage causing the heat.


The first chart was the uphill run with 2K pounds in tow. The second is downhill without the 2K in tow.
The charts are ordered from highest speed to lowest. The black lines are the average RPMs from the red lines and the blue lines are the speed at that RPM.


The RPMs are definitely 250 to 300 higher under load in the first chart compared to the second chart.

Questions:
What is the normal transmission fluid temperature under load?
How much slippage is normal on a TH400 transmission under these conditions?
__________________
Do not take life too seriously.
You will never get out of it alive.
WayneG is offline   Reply With Quote
Old 05-19-2018, 10:49 PM   #2
Rivet Master
 
cmadmaxman's Avatar

 
1991 35' Airstream 350
Columbia , Tennessee
Join Date: Apr 2006
Posts: 925
Images: 40
Reposted From TCI Website

There's More To Coolers Than You Think:It's no secret that heat kills automatic transmissions. And in high-performance street-strip applications, the problem is especially acute. Small diameter torque converters coupled with stop-and-go traffic greatly increase the heat level in an automatic transmission. In most cases, the extra performance heat under the hood can have the same effect as heavy loads, trailer towing and desert conditions.

How hot is too hot? The ideal operating temperature for automatic transmission fluid is between 175 and 225° F. At approximately 240° F, important additives in the ATF begin to cook. The result is the formation of varnish inside the transmission. At approximately 260° F, internal transmission seals (which are typically manufactured from a polyacrylate material) begin to harden. The end results are leaks, both internal and external, simply because the seals lose their elasticity. At approximately 295° F, transmission clutch plates begin to slip because the oil is breaking down further. At approximately 315° F, seals and clutches effectively burn out. Carbon forms in the oil and for all intents and purposes, the transmission is junk. Just for your information, a typical transmission will die within 2000 miles if subjected to 300° F+ heat.

I have a deep pan on the TH475 with a temperature sending unit that reads the pan oil temp. I try to keep under the 225 deg. Unless long grades it stays under 200 deg. I also have a big trans cooler and also use the radiator cooling coil first then the separate cooler second. Also have larger lines from the transmission to the radiators.
__________________
Chris & Brenda....................cMADMAXman
AIR Member 12654
1991 350LE "Zephyr"
1982 310 MoHo (Sold! New home, NYC.)
Many Years ago, 1972 Argosy 24' trailer
Toad, 2001 Chevy Tracker 4x4
cmadmaxman is offline   Reply With Quote
Old 05-20-2018, 01:31 AM   #3
Rivet Master
 
WayneG's Avatar
 
1984 27' Airstream 270
Scotia , New York
Join Date: Oct 2012
Posts: 1,082
Thanks, that info has me be a bit more worried.
Maybe it is time to have someone take a look inside the transmission and maybe put in a new converter?
Looking back on other runs the transmission fluid did get high but seldom over 250.
My lines are 5/16 I wonder if 3/8 would be better for cooling if the new cooler is not good enough?

When I installed the cooler, I caught some of the fluid and noticed it was not the bright red like out of the bottle, more of a faded red with a bit of cloudiness. I saved a sample for Blackstone Labs.

Looking back through my records, a PO had replaced the transmission about 20K miles/ 20 years ago

Quote:
7/16/1998 84732 Replace transmission with rebuilt #401-23HDM by Shift Dynamics $1,737.00 $898.40
$2,560.23 Ritter Precision Automotive Gunnison, CO
__________________
Do not take life too seriously.
You will never get out of it alive.
WayneG is offline   Reply With Quote
Old 05-20-2018, 09:51 PM   #4
Rivet Master
 
cmadmaxman's Avatar

 
1991 35' Airstream 350
Columbia , Tennessee
Join Date: Apr 2006
Posts: 925
Images: 40
I also use Mobile 1 ATF. I have switched the lines to AN-8, witch is a 7/16 ID stainless braided line similar to PROFLEX HOSE. The deep pan is cast aluminum with fins on the bottom to add extra help to the cooling.
__________________
Chris & Brenda....................cMADMAXman
AIR Member 12654
1991 350LE "Zephyr"
1982 310 MoHo (Sold! New home, NYC.)
Many Years ago, 1972 Argosy 24' trailer
Toad, 2001 Chevy Tracker 4x4
cmadmaxman is offline   Reply With Quote
Old 05-21-2018, 01:27 AM   #5
Rivet Master
 
WayneG's Avatar
 
1984 27' Airstream 270
Scotia , New York
Join Date: Oct 2012
Posts: 1,082
Mine has the deep steel pan, over 2" high. I am going to do another test run up the same hill today. I wont be loaded heavy, but it will be closer to 80F outside. I will be monitoring Transmission fluid temperature in and out of the transmission.


I started looking into what may be the best transmission fluid of the TH400, and according to may opinions, modern Dexron VI is not the best for our older gear.
They recommend either finding Dexron III or Type F fluid.
The claim is that the newer fluid does not give enough "grip" on the plates.
Any thoughts on this?
__________________
Do not take life too seriously.
You will never get out of it alive.
WayneG is offline   Reply With Quote
Old 05-22-2018, 12:01 AM   #6
Rivet Master
 
cmadmaxman's Avatar

 
1991 35' Airstream 350
Columbia , Tennessee
Join Date: Apr 2006
Posts: 925
Images: 40
I have run Mobile atf for over 10 years on our 310. This was also in the time frame that I was trying to get the temps. down on the trans. In the over 10 year time frame, have not had any problems with any slip for trans issues. Take a look at a Mobile 1 site. I have run this in all my cars with no problems so far.
__________________
Chris & Brenda....................cMADMAXman
AIR Member 12654
1991 350LE "Zephyr"
1982 310 MoHo (Sold! New home, NYC.)
Many Years ago, 1972 Argosy 24' trailer
Toad, 2001 Chevy Tracker 4x4
cmadmaxman is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
1976 Cpe.de Ville Tow Car 500c.i.V8/TH400 Trans. Cheetah Airstream Classifieds 0 12-08-2014 10:32 PM
TH400/3L80E Conversion marydixon555 Airstream Motorhome Forums 3 07-07-2012 09:51 PM
Non-Automatic Transmission - TH400 Warbs Mechanics Corner - Engines, Transmission & More... 11 02-12-2011 10:27 PM
Filling a new TH400 transmission with fluid bkahler Mechanics Corner - Engines, Transmission & More... 16 01-15-2009 03:26 PM
TH400 blowing ATF @dipstick TomW Mechanics Corner - Engines, Transmission & More... 7 01-11-2009 04:54 PM


Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.



All times are GMT -6. The time now is 11:49 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.