Tranny failure prep
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Senior User
Joined: Mar 2007
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Tranny failure prep
Just did a 300 mile travel trailer tow with a friend who's GM 1/2 ton burned up a tranny. Bad luck for him, but it was fun to help him out with my Ford. 
Anyhow, it got me thinking about an upcoming tow to Florida in Sept. totaling 3200 miles. My '01 X was manufactured during the 'Mechanical Diode' time frame so I'm just waiting for the tranny to fail. Side question - is there an easy way to learn if this has already happened and been repaired?
I'd like to do everything I can to ensure I'm ready for a tranny failure should it happen while on the road. What would you all recommend to someone who has to repair the diode problem? I don't want to tear the tranny out on speculation. But I would like to have all my ducks in a row so that the decisions are made now, calmly, rather than during the fray.
Anyhow, it got me thinking about an upcoming tow to Florida in Sept. totaling 3200 miles. My '01 X was manufactured during the 'Mechanical Diode' time frame so I'm just waiting for the tranny to fail. Side question - is there an easy way to learn if this has already happened and been repaired?
I'd like to do everything I can to ensure I'm ready for a tranny failure should it happen while on the road. What would you all recommend to someone who has to repair the diode problem? I don't want to tear the tranny out on speculation. But I would like to have all my ducks in a row so that the decisions are made now, calmly, rather than during the fray.
Elder User
Joined: Dec 2005
Posts: 520
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From: Marietta, GA
post your vin and someone can run an Oasis report to see what work was done at the dealer, or you can go to the dealer and have them give you the oasis. that's the only way I know to tell about the tranny...but I'm not that familiar with the diode problem other than reading here a little bit. I'm sure others will add to what I've said. good luck
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Senior User
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OASIS report on vin please: !FMNU43S81EA62275.
As far as what is wrong with the '01 tranny: for several months of the '01 production year (I can't remember which months but it spanned the end of calendar year 00 thru the beginning of calendar year 01) they changed the design of something inside the tranny from an "electroic diode" to a "mechanical diode".
I have no idea what the component does, I just know that they are failure prone - and when they fail, the tranny will only use 2nd gear.
I had more detail on this that I had learned on this site, so I'm sure a search for "mechanical diode" will yield the info I no longer remember.
As far as what is wrong with the '01 tranny: for several months of the '01 production year (I can't remember which months but it spanned the end of calendar year 00 thru the beginning of calendar year 01) they changed the design of something inside the tranny from an "electroic diode" to a "mechanical diode".
I have no idea what the component does, I just know that they are failure prone - and when they fail, the tranny will only use 2nd gear.
I had more detail on this that I had learned on this site, so I'm sure a search for "mechanical diode" will yield the info I no longer remember.
Lead Driver
Joined: Jan 2006
Posts: 7,308
Likes: 250
From: Hartford, WI
In my 2001 4R100, Ford used a Mechanical Diode which has failed in my truck from what I was told. What is this and what has Factory Tech done to eliminate it happening again?
The 2001 Models built for August 2000 to March 2001 are the ones with a mechanical diode, all other models have a 34 element sprag from the factory. All Monster Boxes, irregardless of year are built with the 45 element sprag assembly. A mechanical diode is one form of a one way clutch. When the E4OD came out in 1989, it had a sprag one way clutch on the top of the direct drum, and it worked great for 12 years. So Ford in 2001 changed it to the mechanical diode, which didn't work great and after literally 8 days, they realized it was not going to work. The only problem was that all the tooling for the original sprag was destroyed already and it took Ford 6 months to get new machines to go back to the way that they always were. The units built during those 6 months are the diode units. The diode has a different clutch plate pattern, different direct drum and an integral race. To replace one with a sprag, you need to replace all these parts.
The 2001 Models built for August 2000 to March 2001 are the ones with a mechanical diode, all other models have a 34 element sprag from the factory. All Monster Boxes, irregardless of year are built with the 45 element sprag assembly. A mechanical diode is one form of a one way clutch. When the E4OD came out in 1989, it had a sprag one way clutch on the top of the direct drum, and it worked great for 12 years. So Ford in 2001 changed it to the mechanical diode, which didn't work great and after literally 8 days, they realized it was not going to work. The only problem was that all the tooling for the original sprag was destroyed already and it took Ford 6 months to get new machines to go back to the way that they always were. The units built during those 6 months are the diode units. The diode has a different clutch plate pattern, different direct drum and an integral race. To replace one with a sprag, you need to replace all these parts.
