Cool down my ytrans
Senior User
Joined: Nov 2014
Posts: 436
Likes: 0
mines a L99...OTW here. OP, Shake-N-Bake had a tthread about a year ago where he removed the radiator to have it cleaned out. He couldn't believe how caked it was, between fins...has before/after pics. Clearly, you can see, right thru the darn thing, after the fact....something to think about
I'm getting schooled here.
Tuned
Joined: Oct 2012
Posts: 391
Likes: 8
Check the operation of the fluid cooler bypass valve. If it's failing it will direct hot fluid back into the trans. Or the bypass is doing it's job correctly due to a partially clogged trans cooler. Read up on Mark K.'s trans fluid flush and cooler flow rate instruction.
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
Personally I'd be fine with just the 6.0 cooler and monitor my temps when backing up or driving at very slow speed (which isn't that often for me). If you find that your temps get higher than you'd like then purchase a new radiator and plumb in the lines and you should be good.
I've been running just the air cooler on my '99 since day one. I upgraded the air cooler when I upgraded my trans around 144k miles and have been good ever since. Odometer is just over 340k now. My heaviest trailer (5th wheel) was around 16k lbs most days and my trans fluid temps have been well managed at all times. I would keep an eye on the temp gauge when backing up but it never got above 190 degrees so I didn't worry too much about it.
Post Fiend
Joined: Sep 2003
Posts: 6,096
Likes: 26
From: Mesa AZ
My wife's truck has all items described above. 2000 model year, F250, helper spring, OTW cooler, 7 Pin trailer plug etc....
Molon Labe
Joined: Dec 2006
Posts: 5,272
Likes: 1
From: Alaska
I don't think so. My buddies 01 dually has the OTW cooler but no tow package. No helper leafs on the rear which I thought was strange on a dually.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,725
Likes: 2,651
From: SE Florida
All 1999 and the first half of 2000 Superduty trucks left the factory with only an air to oil cooler. Many trucks later had the radiator replaced with one that had a cooler. There was a TSB that addressed overheating transmissions, and the fix was to add a radiator cooler. It worked.
Mid year 2000 Ford reintroduced the radiator cooler along with the air to oil cooler.
No 4R100 ever had a thermostat from the factory. There is NOTHING that bypasses the coolers until the trans warms up. That's not how it works no matter how many times you read that on the 'net. It's simply not true.
The radiator cooler is a very effective cooler. It is especially effective at low speed, high load conditions. One example of where the radiator cooler would be extremely effective would be snow plowing.
Mid year 2000 Ford reintroduced the radiator cooler along with the air to oil cooler.
No 4R100 ever had a thermostat from the factory. There is NOTHING that bypasses the coolers until the trans warms up. That's not how it works no matter how many times you read that on the 'net. It's simply not true.
The radiator cooler is a very effective cooler. It is especially effective at low speed, high load conditions. One example of where the radiator cooler would be extremely effective would be snow plowing.
Tuned
Joined: Oct 2012
Posts: 391
Likes: 8
Here's the the instruction on the 4R100 fluid flush. Within it you will see how to check if your (pressure activated) trans cooler bypass valve is activating for any reason.
https://www.ford-trucks.com/articles/changing-atf-fluid-in-a-e4od-and-4r100-transmission/
Start there. If the bypass is activating it's because the check valve in the bypass line is faulty (which is common) or your trans cooling system is clogged. Both scenarios will cause your transmission to run hot. If the bypass is fine move on to the next possible culprit.
https://www.ford-trucks.com/articles/changing-atf-fluid-in-a-e4od-and-4r100-transmission/
Start there. If the bypass is activating it's because the check valve in the bypass line is faulty (which is common) or your trans cooling system is clogged. Both scenarios will cause your transmission to run hot. If the bypass is fine move on to the next possible culprit.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
Tuned
Joined: Oct 2012
Posts: 391
Likes: 8
Here's the the instruction on the 4R100 fluid flush. Within it you will see how to check if your (pressure activated) trans cooler bypass valve is activating for any reason.
https://www.ford-trucks.com/articles...-transmission/
Start there. If the bypass is activating it's because the check valve in the bypass line is faulty (which is common) or your trans cooling system is clogged. Both scenarios will cause your transmission to run hot. If the bypass is fine move on to the next possible culprit.
https://www.ford-trucks.com/articles...-transmission/
Start there. If the bypass is activating it's because the check valve in the bypass line is faulty (which is common) or your trans cooling system is clogged. Both scenarios will cause your transmission to run hot. If the bypass is fine move on to the next possible culprit.
Tuned
Joined: Oct 2012
Posts: 391
Likes: 8
Maybe I missed it, have you mentioned if your torque converter is in lockup while plowing? Can you control TC lock with trans command? What speed do you normally plow at? An unlocked TC under load will produce massive trans heat over time.
Your '99 may be controlled differently, but on my '02 the TC lockup solenoid is controlled according to transmission speed (along with several other factors) and not speedometer speed. Assuming your '99 is controlled the same way, running 35's with stock gearing will bump TC lock to a higher GPS vehicle speed even with a recalibrated speedometer.
Assuming you are plowing under the speed of TC lock and trans command won't get the job done, consider a manual TC lock switch.
One last thing is the manual lock should only be used in 2nd gear or higher. From my research on the 4R100 there is not enough pump pressure to manually lock the converter in 1st gear. Hope my rambling help ya a little.
Your '99 may be controlled differently, but on my '02 the TC lockup solenoid is controlled according to transmission speed (along with several other factors) and not speedometer speed. Assuming your '99 is controlled the same way, running 35's with stock gearing will bump TC lock to a higher GPS vehicle speed even with a recalibrated speedometer.
Assuming you are plowing under the speed of TC lock and trans command won't get the job done, consider a manual TC lock switch.
One last thing is the manual lock should only be used in 2nd gear or higher. From my research on the 4R100 there is not enough pump pressure to manually lock the converter in 1st gear. Hope my rambling help ya a little.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,725
Likes: 2,651
From: SE Florida
Your '99 may be controlled differently, but on my '02 the TC lockup solenoid is controlled according to transmission speed (along with several other factors) and not speedometer speed. Assuming your '99 is controlled the same way, running 35's with stock gearing will bump TC lock to a higher GPS vehicle speed even with a recalibrated speedometer.
Mine shows a different result. You can lock the converter in ANY gear as long as the engine RPM is greater than 1300 RPM. Below that the pump doesn't have enough output to maintain lockup.
Tuned
Joined: Oct 2012
Posts: 391
Likes: 8
The lockup is controlled by rear axle rotational speed on ALL years of the 4R100.
Mine shows a different result. You can lock the converter in ANY gear as long as the engine RPM is greater than 1300 RPM. Below that the pump doesn't have enough output to maintain lockup.
Mine shows a different result. You can lock the converter in ANY gear as long as the engine RPM is greater than 1300 RPM. Below that the pump doesn't have enough output to maintain lockup.