E4od Strange Behavior?
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E4od Strange Behavior?
Have a 1990 F150 4x4 inline 6 , 180,000 miles. E40D tranny was serviced about 3000 miles ago with new filter and full fluid change. Recently started doing something strange. When I let off the gas, the rpms drop to idle. Example: when doing 50mph in overdrive, and let off gas to slow down. Rpms drop to 800 and truck coasts down to about 35MPH then downshifts to 3rd and rpms come back up. Seems like the torque converter is unlocking. I read that the TC would normally unlock for a few seconds if you taped the brake. Thought maybe the brake was somehow being engaged and sending signal to unlock. Tried setting the cruise at 40MPH then running speed on up to 50 and letting off gas. TC unlocks and engine idles down until speed comes down to 40 then locks back up and runs steady. Since cruise did not disengage I assume brake signal not being sent.
Any ideas on what is causing the TC to unlock everytime I let off the throttle?
Is this a problem I should be worrying about?
Thanks Frank
Any ideas on what is causing the TC to unlock everytime I let off the throttle?
Is this a problem I should be worrying about?
Thanks Frank
Senior User
Joined: Feb 2004
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From: Washington
My first guess is the lock-up in the TC is wore out. You got pretty good mileage for a E40D. I never got more than 80,000 per re-build on my last one, of course I worked it pretty hard all of the time.
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Joined: Mar 2001
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From: So Cal
I was thinking about this as I drove home yesterday. Yes the TC lockup clutch may be disengaging, but the RPM should only drop a few hundred, maybe at most 500RPM I would guess. My 2004 Lincoln LS unlocks when you let off the gas while at freeway speed and drops maybe 200RPM. My old SS used to do similar. Used to drive me nuts watching the tach on my cars with lockups.
Now then, yours sounds like it is dropping a lot more than it should. I am assuming that at freeway speed your PRMs are normally between 1500 and 2000 RPM, which seems average from my last 3 or 4 auto trannies. So dropping to 800 sounds a bit much, unless your cruise speed is down around 1200 RPM or so.
I am guessing that your truck has not had a rebuild or new converter in a long time if ever. Could be your converter is just old and no longer has good coupling between the two or more sets of blades. Alternatively, your fluid pressures may have dropped to the point where your clutches are no longer engaging as tightly as they should.
I am not a tranny expert so these are my quasi educated guesses.
Good Luck,
Jim Henderson
Now then, yours sounds like it is dropping a lot more than it should. I am assuming that at freeway speed your PRMs are normally between 1500 and 2000 RPM, which seems average from my last 3 or 4 auto trannies. So dropping to 800 sounds a bit much, unless your cruise speed is down around 1200 RPM or so.
I am guessing that your truck has not had a rebuild or new converter in a long time if ever. Could be your converter is just old and no longer has good coupling between the two or more sets of blades. Alternatively, your fluid pressures may have dropped to the point where your clutches are no longer engaging as tightly as they should.
I am not a tranny expert so these are my quasi educated guesses.
Good Luck,
Jim Henderson
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Hey Guys
Thanks for your input. I was hoping someone would say " your ? sensor is going bad". Hope this tranny holds together for a while yet. It does drop a couple 100 rpms when I initially let off the gas, but then after a second or two it drops all the way to idle.
Thanks Frank
Thanks for your input. I was hoping someone would say " your ? sensor is going bad". Hope this tranny holds together for a while yet. It does drop a couple 100 rpms when I initially let off the gas, but then after a second or two it drops all the way to idle.
Thanks Frank
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