4R70W Issues
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Freshman User
Joined: Jan 2008
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From: Dartmouh, Nova Scotia
4R70W Issues
Hi everyone.
My brother in law has a 2003 F-150 King Ranch, 5.4L 4X4 with a 4R70W. Truck used to work great, but he decided to go mud bogging with it, had to get it towed home (not the first time for this truck, lucky for him I'm a mechanic and own a F-350) Serpentine belt tensioner self destructed. SO I've been busy over the last two weeks cleaning/changing fluids/adjusting/freeing things up on it for him. It was working fine up until recently. Now hes complaining that as he's driving along on trips longer than an hour, at around 45-55 mph his truck will start to shudder, then it will downshift or the t/c unlocks. He thinks its the tranny itself. He has a cel on in the dash. The truck was VERY full of mud after the trip, he pressure washed the engine (and probably all the electrical) I made sure to clean out the intake and maf and repleaced the air filter. I read in other posts that a bad coil pack could cause some shuddering, but no one mentions a downshift issue. Hope someone ahs some idears for me. Thanks in advance.
My brother in law has a 2003 F-150 King Ranch, 5.4L 4X4 with a 4R70W. Truck used to work great, but he decided to go mud bogging with it, had to get it towed home (not the first time for this truck, lucky for him I'm a mechanic and own a F-350) Serpentine belt tensioner self destructed. SO I've been busy over the last two weeks cleaning/changing fluids/adjusting/freeing things up on it for him. It was working fine up until recently. Now hes complaining that as he's driving along on trips longer than an hour, at around 45-55 mph his truck will start to shudder, then it will downshift or the t/c unlocks. He thinks its the tranny itself. He has a cel on in the dash. The truck was VERY full of mud after the trip, he pressure washed the engine (and probably all the electrical) I made sure to clean out the intake and maf and repleaced the air filter. I read in other posts that a bad coil pack could cause some shuddering, but no one mentions a downshift issue. Hope someone ahs some idears for me. Thanks in advance.
Lead Driver
Joined: Sep 2006
Posts: 7,907
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Again, the tell tale sign is the miss between 45 and 60 mph.
It's one coil with low output.
There is a lengthy explaination that discribes the cause and effect of this condition that does not set a code because it's not a hard fault.
Find the one and you find the miss..
Good luck.
It's one coil with low output.
There is a lengthy explaination that discribes the cause and effect of this condition that does not set a code because it's not a hard fault.
Find the one and you find the miss..
Good luck.
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