4r70w tranny swap , 50 miles later, I lost O/D .
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Junior Member
Joined: Jun 2022
Posts: 2
4r70w tranny swap , 50 miles later, I lost O/D .
In need of some educated, straight to the point advice . Ive spent countless hours reading forums and I feel more lost now then before .
My son has a 01 F150 2wd 4.2 V6 with a 4r70w.
He bought it used and we pieced it together to get it rolling . Since day one the O/D never engaged . He'd start the truck , hit the O/D button and run 4000 RPM everywhere he went for the past year.
He just graduated high school and got some gifted cash from family and decided to spend it fixing the ol truck.
We pulled a tranny out of a 95 mustang 3.8l with 89,000 miles on her .
As mentioned , I've got more time in reading then I do in labor at this point .
We pulled his tranny out and started swapping parts .
- hardwired electronics to circuit board electronics
-The shift arm from a car to a truck - The Tailshaft from mustang to f150
- The slip yolk from mustang to F-150
- The 9 pin bulkhead to a 7 pin bulkhead
I believe that's it , everything from the prior F-150
tranny that wasn't the same on the mustang tranny we just swapped the parts .
Everything but the Torque Converter. My son managed to strip and round off 3 of the 4 nuts on the flex plate . Was originally going to use the Torque Converter that came with the new tranny , but after reading , I got the impression that I should keep the old Torque Converter on there anyways .
So that's what we did , drained and refilled the original torque converter and put in the new tranny.
Everything was working beautifully.
For the first time since he's owned that truck it went down the road , shifted through every gear and did so running 1000 - 1500 rpms like a normal truck .
50 miles later , we now have the same exact issue as the original transmission.
Hit the gas , shifts to 2nd , accelerates and right when it's suppose to hit 3rd , it goes into neutral.
Hit the O/D button , she downshifts and keeps on trucking @ 4000 rpm .
Have I ruined the new / used tranny ?
Should I have switched that torque converter or bought a new one ?
I got one code , can't remember the exact number but I'm pretty sure it said Speed Sensor Circuit Malfunction or something close to that .
Anybody got a straight forward answer for me ?
My son has a 01 F150 2wd 4.2 V6 with a 4r70w.
He bought it used and we pieced it together to get it rolling . Since day one the O/D never engaged . He'd start the truck , hit the O/D button and run 4000 RPM everywhere he went for the past year.
He just graduated high school and got some gifted cash from family and decided to spend it fixing the ol truck.
We pulled a tranny out of a 95 mustang 3.8l with 89,000 miles on her .
As mentioned , I've got more time in reading then I do in labor at this point .
We pulled his tranny out and started swapping parts .
- hardwired electronics to circuit board electronics
-The shift arm from a car to a truck - The Tailshaft from mustang to f150
- The slip yolk from mustang to F-150
- The 9 pin bulkhead to a 7 pin bulkhead
I believe that's it , everything from the prior F-150
tranny that wasn't the same on the mustang tranny we just swapped the parts .
Everything but the Torque Converter. My son managed to strip and round off 3 of the 4 nuts on the flex plate . Was originally going to use the Torque Converter that came with the new tranny , but after reading , I got the impression that I should keep the old Torque Converter on there anyways .
So that's what we did , drained and refilled the original torque converter and put in the new tranny.
Everything was working beautifully.
For the first time since he's owned that truck it went down the road , shifted through every gear and did so running 1000 - 1500 rpms like a normal truck .
50 miles later , we now have the same exact issue as the original transmission.
Hit the gas , shifts to 2nd , accelerates and right when it's suppose to hit 3rd , it goes into neutral.
Hit the O/D button , she downshifts and keeps on trucking @ 4000 rpm .
Have I ruined the new / used tranny ?
Should I have switched that torque converter or bought a new one ?
I got one code , can't remember the exact number but I'm pretty sure it said Speed Sensor Circuit Malfunction or something close to that .
Anybody got a straight forward answer for me ?
Junior Member
Joined: Jun 2022
Posts: 1
I don't have any answers for you but I can say that I am in a similar boat. My truck can't seem to make it past 2nd gear either and my thought is that it is the torque converter but of course, the local transmission shop told me I need a complete rebuild or new transmission. I have been considering just ordering a remanufactured 4r70 for the truck since you can get one for 2k shipped like this one, https://reman-transmission.com/trans...es/?code=4R70W, and then try and swap it in myself. However, if this can be fixed by just replacing the TC then I might try that myself
Senior Member
Joined: Jun 2010
Posts: 16,609
I believe the torque converter only transfers power from the engine to the transmission. If it doesn't operate the oil pump in the pump body of the trans you would have no trans power.
If we lose a particular gear but have other gears it can't be the converter.
There is something going on with either signals the trans is receiving or a component is not functioning correctly.
It is rare for a trans to have an internal problem and the replacement to have the same problem,,, unless they were both at the same stage of failure.
There comes a time when you have to bite the bullet and do what needs to be done and that is to have someone with the knowledge and equipment to diagnose the problem.
There is always that part of the problem that if you need to open up the trans, you might as well do the entire job while it is apart.
It doesn't make good sense to open up a trans with unknown miles and use to anticipate replacing one part when other parts are approaching the end of their life.
If we lose a particular gear but have other gears it can't be the converter.
There is something going on with either signals the trans is receiving or a component is not functioning correctly.
It is rare for a trans to have an internal problem and the replacement to have the same problem,,, unless they were both at the same stage of failure.
There comes a time when you have to bite the bullet and do what needs to be done and that is to have someone with the knowledge and equipment to diagnose the problem.
There is always that part of the problem that if you need to open up the trans, you might as well do the entire job while it is apart.
It doesn't make good sense to open up a trans with unknown miles and use to anticipate replacing one part when other parts are approaching the end of their life.
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