Trans temp curiosity

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Feb 9, 2021 | 09:11 PM

tfunk88

Thread Starter

Fleet Mechanic

Joined: May 2010

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From: West by God Virginyuh

Trans temp curiosity

So, I find the following info interesting for some reason.

When I start my truck in the morning after it’s been sitting in the cold air, let’s say my trans temp is approx 50 degrees on my monitor. On the dash gauge it will be just below normal operating range. At about 100 degrees it is in the normal operating temp according to the dash gauge. I drive along and get everything fully up to temp. Sweet.

I get to work and shut down the truck. And let’s say an hour or so later I go out and start it up, and the trans temp has only gone down to 120 degrees. The dash gauge will actually have the needle farther away from the normal range than it was at 50 degrees. Anyone know why that is?

Feb 10, 2021 | 01:55 PM

FiveOJester

Fleet Mechanic

Joined: Sep 2006

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From: Fresno, CA

I've never been able to figure out how the logic for that gauge actually works. It almost seems like it wants to always start at "cold" when you restart the truck.

My 13 Ecoboost was the same way with the weird "warmup". It would show normal around 100F and wouldn't move above middle until 230F. Ask me how I know? I was seeing temps around 240F on long/hot pulls towing until I put in a larger tranny cooler.

Feb 10, 2021 | 01:58 PM

bismic

Fleet Owner

Joined: Nov 2003

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Some added detail from Ford (came up a long time ago - in the early 6.0L days):

The panel gauge will show the temp as fully warmed up at 50 *F. Between 100-220F the needle will remain in the same position on the gauge. At 230F it will move up slightly to the middle of the normal range. At 250F it will move to Yellow. The gauge moves to red at 280. This is supported on page 36 of the OBDII Theory and Operations manual. The tow/haul light will flash at 275.

Feb 10, 2021 | 02:51 PM

tfunk88

Thread Starter

Fleet Mechanic

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From: West by God Virginyuh

Interesting...I watched it today to see what specific temp it first nudged into the normal range. At 60 it was right at the bottom of the normal range. By 100 it was in the middle of the normal range, stayed there like the description you gave while the trans warmed fully to 160. Then when I started the truck after work it was at 118 and slightly below the bottom of the normal range, by 130 degrees was back into the normal range 🤷‍♂️

Feb 13, 2021 | 12:11 PM

HT32BSX115

Logistics Pro

Joined: Feb 2005

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From: Upper Left Coast

You have to understand it's not really a "gage". It's an analog indicator

Feb 13, 2021 | 02:53 PM

tfunk88

Thread Starter

Fleet Mechanic

Joined: May 2010

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From: West by God Virginyuh

Yep, I get that, I was just wondering why it was inconsistent in its inaccuracy

Like, if when I start it up at 50 and it’s in the “normal” range at 60, in the middle at 100, if I start it up later and it’s at 120 why isn’t it in the middle?

Feb 14, 2021 | 09:37 AM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,734

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From: SE Florida

My guess, and it's only a guess, is that it is programmed to start low and rise up during operation because that is what people expect a gauge to do. While the dash people were required to put the gauge in the dash, their overriding concern was to head off customer complaints. So they made the "gauge" operate in the manner that they thought would generate the least customer complaints. And it still works as well as a light, i.e. it shows when the trans is overheated.