Brunt trans oil - Diesel Forum -
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 5 (permalink) Old 07-19-2019, 01:32 AM Thread Starter
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Brunt trans oil

please bear with me if I get a a bit rambly here.
I bought a 2002 f350 that a farmer type had bought with a bad transmission as a project and installed a used trans in.

When I started driving it the light on the shift lever started flashing because the Transmission was over heating, thinking it was the bypass tube I took the truck a to Amco trans shop to have the tranny flushed and bypass the bypass.
when the mechanic tried to flush the transmission he found the the oil to water cooler was plugged so he put a filter on and bypassed the OTW cooler.
I have a spare rad here at home so I can change that out but what I need an opinion on is the transmission ruined. Any idea what kind of life would be left in it?
The mechanic at Amco advised me to just replace it but it still drives and shifts fine.

I do have a spare manual trans but really dont want to swap it out right now.

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post #2 of 5 (permalink) Old 07-19-2019, 09:44 AM
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If it is shifting fine, don't replace it. Get the bypass installed again - that's what saved your transmission when the OTW cooler plugged. Many people are under the misconception that the bypass is some sort of temperature regulator - it's not. It's a spring loaded ball that allows ATF to flow around the coolers should a blockage occur. Without it, the rear of the transmission starves for fluid and burns up almost instantly.

Swap the radiator - get the OTW cooler back in place. Replace your bypass line. Drop your pan at your next oil change and inspect the magnet and check the fluid condition. It takes 8 quarts to refill after a drop and drain. Then, start doing that every third oil change to keep an eye on the transmission.
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post #3 of 5 (permalink) Old 07-20-2019, 10:32 AM
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If all fails, don't do the standard swap. Replace the auto. The standard swap takes a whole lot of parts and a re flashed CPU in the truck. Not a cheap deal unless you have a donor truck. I want a standard in mine. The auto cant handle the power. I procrastinated on a complete swap kit for 1500 beans, used of course, but it sold before I got there. Never seen one since, and parting it together at the wrecker was about 3k, so pretty mad at myself for missing that one. Stick with the auto, get the HD if you have to redo it.

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post #4 of 5 (permalink) Old 07-21-2019, 12:34 AM Thread Starter
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I do have a parts truck to do the swap.
For now I am going to swap the rad, do a transmission oil change and see how it works out.
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post #5 of 5 (permalink) Old 07-21-2019, 09:14 PM
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Although not a Ford I have a Chevy Express 3500 that had black, burnt fluid at 30K. I flushed it all out, added a cooler and have swapped out 8 quarts every few years since that time. 10 years later I am now at 114K with no issues. I am sure the first 30K was accelerated wear on the clutches but after that with the fresh fluid and large cooler I would guess that it is wearing less than the average loaded 3500, I know guys that didn't do anything to theirs and lost trannys early. like 70K.

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