Trans temp issues
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Lead Driver
Joined: Mar 2000
Posts: 9,359
Likes: 1
From: Hampstead, NC
Trans temp issues
I have been having some trans temp issues lately, especially when it is <20 degrees outside.
To start with, the trans was rebuilt last year, has about 14,000 miles on it. It is a good, HD rebuild with a 3 disc converter and full Tugger kit. I also have a Tru Cool cooler in conjunction with the factory cooler. It will get up to 150+ just driving empty down the highway. It does take 30+ miles to get that warm though. I saw 185 today after plowing, let it sit and idle for 15 minutes and the temp was back down under 120.
These problems didn't start until it got below 30 degrees, otherwise it ran about 110 even on the hottest summer days unless I was towing, then it never got above 150.
Could this be the bypass isn't opening and allowing fluid to circulate through the coolers?
Any and all opinions are welcome.
To start with, the trans was rebuilt last year, has about 14,000 miles on it. It is a good, HD rebuild with a 3 disc converter and full Tugger kit. I also have a Tru Cool cooler in conjunction with the factory cooler. It will get up to 150+ just driving empty down the highway. It does take 30+ miles to get that warm though. I saw 185 today after plowing, let it sit and idle for 15 minutes and the temp was back down under 120.
These problems didn't start until it got below 30 degrees, otherwise it ran about 110 even on the hottest summer days unless I was towing, then it never got above 150.
Could this be the bypass isn't opening and allowing fluid to circulate through the coolers?
Any and all opinions are welcome.
Fleet Owner
Joined: Mar 2007
Posts: 28,281
Likes: 6
From: BLT, MN
I have been having some trans temp issues lately, especially when it is <20 degrees outside.
To start with, the trans was rebuilt last year, has about 14,000 miles on it. It is a good, HD rebuild with a 3 disc converter and full Tugger kit. I also have a Tru Cool cooler in conjunction with the factory cooler. It will get up to 150+ just driving empty down the highway. It does take 30+ miles to get that warm though. I saw 185 today after plowing, let it sit and idle for 15 minutes and the temp was back down under 120.
These problems didn't start until it got below 30 degrees, otherwise it ran about 110 even on the hottest summer days unless I was towing, then it never got above 150.
Could this be the bypass isn't opening and allowing fluid to circulate through the coolers?
Any and all opinions are welcome.
To start with, the trans was rebuilt last year, has about 14,000 miles on it. It is a good, HD rebuild with a 3 disc converter and full Tugger kit. I also have a Tru Cool cooler in conjunction with the factory cooler. It will get up to 150+ just driving empty down the highway. It does take 30+ miles to get that warm though. I saw 185 today after plowing, let it sit and idle for 15 minutes and the temp was back down under 120.
These problems didn't start until it got below 30 degrees, otherwise it ran about 110 even on the hottest summer days unless I was towing, then it never got above 150.
Could this be the bypass isn't opening and allowing fluid to circulate through the coolers?
Any and all opinions are welcome.
Cargo Master
Joined: Jun 2003
Posts: 3,292
Likes: 6
From: Ardenvoir, Washington
This increase in temp might be normal.. see the following info for the bypass valve..
1999-2003 Ford 4R100 Transmission Cooler Bypass Valve
1999-2003 Ford 4R100 Transmission Cooler Bypass Valve
Cargo Master
Joined: Jun 2010
Posts: 2,771
Likes: 3
From: Louisiana
After reading the trouble shooting sec. on the by pass hopefully it is as simple as a bad by pass valve or blocked cooler. These instructions seem very helpful in diagnosing your prob. and you can get it fixed without having to go into the tranny. Wish you luck and let us know what you find.
David
David
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Lead Driver
Joined: Mar 2000
Posts: 9,359
Likes: 1
From: Hampstead, NC
Thanks for the link Clint.
That's what I was thinking too Bob, today was the first day I'd seen the temps rise above 150 degrees.
I should add, the fluid level is perfect and it is still nice and clean. I did get under the truck and check the cooler lines, one was warm and the other was cold. Which was which, I can't tell you, I forgot to check. I'll look into that more tomorrow.
The temp is being read from the port on the driver side of the trans too.
I was just reading up on that cooler bypass test on Dieselsite, looks like I'll have to do a flow test here soon. Hope that is all it is............
That's what I was thinking too Bob, today was the first day I'd seen the temps rise above 150 degrees.
I should add, the fluid level is perfect and it is still nice and clean. I did get under the truck and check the cooler lines, one was warm and the other was cold. Which was which, I can't tell you, I forgot to check. I'll look into that more tomorrow.
The temp is being read from the port on the driver side of the trans too.
I was just reading up on that cooler bypass test on Dieselsite, looks like I'll have to do a flow test here soon. Hope that is all it is............
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,696
Likes: 2,618
From: SE Florida
This increase in temp might be normal.. see the following info for the bypass valve..
1999-2003 Ford 4R100 Transmission Cooler Bypass Valve
1999-2003 Ford 4R100 Transmission Cooler Bypass Valve
The bypass valve is ONLY there to allow flow to the rear of the trans if the coolers are plugged. The bypass does NOT open to help the trans warm up faster.
You need two containers to run the flow test. Using one will give the wrong result.
Warm the trans, shut the engine off, remove the rear line and put it into one of the containers. Start the engine. Once the flow is steady, move the line to the second container for exactly 15 seconds, then back to the first container, and shut the engine off.
If there is at least a quart in the second container it passes.
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Lead Driver
Joined: Mar 2000
Posts: 9,359
Likes: 1
From: Hampstead, NC
So it's normal for the trans temps to climb like that??
Also, thanks for the info on the flow test Mark.
Another thing I should add (I was in a hurry when I posted last night). I drove about 85 miles yesterday towing a trailer (about 3K) and the temps climbed to 190 by the time I got to my destination. They were steady around 160 while traveling down the interstate but once I ventured off to 2 lane roads they climbed steadily to 190. Again, I let it sit and idle and they came back down to 110 or so. Now, on the way home, they stayed about the same as before (with 1K more on the trailer). That is, until I got in the driveway. The temp guage reached 200 degrees. That is the point I checked the fluid again(and the lines for temperature).
Also, thanks for the info on the flow test Mark.
Another thing I should add (I was in a hurry when I posted last night). I drove about 85 miles yesterday towing a trailer (about 3K) and the temps climbed to 190 by the time I got to my destination. They were steady around 160 while traveling down the interstate but once I ventured off to 2 lane roads they climbed steadily to 190. Again, I let it sit and idle and they came back down to 110 or so. Now, on the way home, they stayed about the same as before (with 1K more on the trailer). That is, until I got in the driveway. The temp guage reached 200 degrees. That is the point I checked the fluid again(and the lines for temperature).
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Posting Guru
Joined: Aug 2007
Posts: 1,317
Likes: 0
From: Auburn, Wa
I havent seen seen 200 on mine but I have seen 190, I was under the impression that it was part of the normal operating range. IIRC 220 is when its starting to get a bit hot and you should be resting it.
Lead Driver
Joined: Sep 2005
Posts: 9,399
Likes: 188
From: Norco,CA
Off the interstate were you going in stop and go. If the tork convertor doesn't stay locked up the temps will climb. On the interstate at speeds its locked. The extra weight of a trailer will cause them to climb at slow speeds and stop and go.
Senior User
Joined: Oct 2005
Posts: 309
Likes: 0
You're tilting at windmills there Quixote.
Those temps are really normal for the activities you're describing. I've run mile after mile pulling 15k at 190-200 (degrees not mph), only to see it climb when I hit towns and slow down to 30-35mph. TC unlocks, no forceful wind hitting the front end, then speed up, get over 40 or so, get some air flowing back through everything again, and its back to 190. No biggie.
But what do I know with only 257,000 on my orig stock tranny/truck.
Those temps are really normal for the activities you're describing. I've run mile after mile pulling 15k at 190-200 (degrees not mph), only to see it climb when I hit towns and slow down to 30-35mph. TC unlocks, no forceful wind hitting the front end, then speed up, get over 40 or so, get some air flowing back through everything again, and its back to 190. No biggie.
But what do I know with only 257,000 on my orig stock tranny/truck.
Mountain Pass
Joined: Sep 2009
Posts: 230
Likes: 1
From: Lower Mainland BC
FWIW when I first got my Evo I noticed that my trans temps were 150-160 F on the freeway and the highest was 175 F on a hot summer day climbing a pass with my camper on. The temp gauge on the dash stayed in the same place once warmed up so not very good info from it. To confirm my trans temps were in an acceptable range I asked a mechanic at a dealership where I was having a service done what the max acceptable temp should be for my Tans. He said 225 F. 
2002 F350 Lariat Crew LB 4X4, 7.3L, 4R100 , S&B intake, MBRP 4in, Edge Evo, Bilsteins, Pacbrake
2002 F350 Lariat Crew LB 4X4, 7.3L, 4R100 , S&B intake, MBRP 4in, Edge Evo, Bilsteins, Pacbrake
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