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Discussion Starter · #1 ·
Hello all, I really enjoy this site for all it's good information and help.
I have a 2003 f350 6.0. the transmission was rebuilt a year ago and has been working great. I have had this happen a couple times while towing recently. When in tow mode the transmission will downshift coming to a start extremely hard. First time this happened I thought the transmission exploded. Now I was pulling a trailer load of hay at the time that weighed probably 12,000 libs or so. I called the shop that did the rebuild and he said it could be a sensor or a error code. His shop is 200 miles away and I thought I would see if it was something I could take care of instead of spending the money on fuel.
Thank for any help!
 

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When in tow mode the transmission will downshift coming to a start extremely hard. First time this happened I thought the transmission exploded. Now I was pulling a trailer load of hay at the time that weighed probably 12,000 libs
can you elaborate ?

is this a down shift slam that is so hard your teeth rattle ?
if so it is a overlap from a delayed release and is kinda common .. mine does this and I don't use tow haul because of it
 

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Discussion Starter · #3 ·
Yes it is a teeth rattling slam. I only use the tow mode when pulling a heavy load. I just don't want to damage anything.
Thanks for the help. It is much appreciated!
 

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i was told it could be a slow solenoid,what happens is you are in two gears at the same time for a fraction of a second and the trans is locked , this was an issue for ford even with good parts and they had to work hard on the programming to keep this at a minimum
, I bought a used solenoid pack to try and replace the one responsible for the downshifts
I have not installed it yet
 

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Sticky shift valve -- may be deformed plastic or fine metal particles in the magnetic core

just another point for the case of the little bypass filter -- those small particles that the little filter cleans out are one of the causes of sticking shift solenoids
 
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mine has done this since I bought my ford reman .. I don't even use TH anymore
when the frod reman chit the bed under 15,000 miles I had a local rebuild it ( I was out of town for a funeral )
when I got it back it still had the slam downshift ( quite spectacular while towing)
i never pursued it and now 2 years later I am fixing to drop the pan and swap the solenoid body and cross my fingers
 
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