F SUPER DUTY trans problem
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F SUPER DUTY trans problem
I recently bought a 1991 F SUPERDUTY with a 460 and an E4OD. The truck has about 100K miles on it. When I bought it the guy told me he had some work done to the transmission because it wasn't shifting right. I have the invoice for the work. The invoice says they tore it down found nothing wrong internally, ended up replacing the main computer, an ECT sensor and the NLPS switch, blaming the problem on a bad NLPS switch.
After driving the truck for awhile, anywhere from 30-60 minutes. The trans seems to go into "limp mode". If I stop and let it sit for a couple hours it works fine again, but only for a short time. Any thoughts to the cause of the problem? I don't know what a NLPS switch is or why it would have caused a problem before.. I was thinking maybe it needs a solenoid body?
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After driving the truck for awhile, anywhere from 30-60 minutes. The trans seems to go into "limp mode". If I stop and let it sit for a couple hours it works fine again, but only for a short time. Any thoughts to the cause of the problem? I don't know what a NLPS switch is or why it would have caused a problem before.. I was thinking maybe it needs a solenoid body?
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Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
There's no such thing as NLPS. There is MLPS, Manual Lever Position Sensor. It's the sensor on the driver's side of the transmission where the shifter cable attaches. It tells the PCM where the shifter handle is.
What do you mean by limp mode?
What do you mean by limp mode?
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The trans will shift really hard and late, and overdrive won't work. I was told that is called limp mode. I read the codes today and I am getting 628. So I'm guessing its time for a converter? The truck only has 115,000 miles on it, and the trans fluid looks great. I would think that a slipping converter would burn the fluid? The speedo bounces at lower speeds, below 40mph. So I replaced the VSS thinking it was the root of both problems. Changing the sensor didn't fix the bouncing speedo or code 628. Is there anything but the converter that would cause code 628? Maybe a solenoid?
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,725
Likes: 2,651
From: SE Florida
A solenoid won't cause a 628. That code means something is slipping in the transmission. It could be the trans or the torque converter clutch, usually it's the torque converter clutch.
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Sounds like I will be installing a TC... What is a good brand and model? and where can I get one?
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I am looking at getting either a TCI converter or a Huges Performance converter. The TCI has a stall of 1200rpm and the Huges has a stall speed of 1800rpm. Any thoughts on the different stall speeds or manufacture? The truck has a 7.5L and an 11' service body
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