E4OD/RABS Related Problem???
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E4OD/RABS Related Problem???
My '90 P/U will not engage into OD unless I apply full throttle, then as soon as it does go into OD, it kicks back down to 3rd. Weird, 
huh. Most trannies need you to lay off the throttle to go into OD. Anyway, RABS light comes on now also. Seem's to me it's something electrical more than mechanical in the tranny. Replaced the fluid and filter. You guys are some of the best, give your thoughts here. Thanks, Terry
huh. Most trannies need you to lay off the throttle to go into OD. Anyway, RABS light comes on now also. Seem's to me it's something electrical more than mechanical in the tranny. Replaced the fluid and filter. You guys are some of the best, give your thoughts here. Thanks, Terry
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From: Kindersley, Sask
Sensor
Sounds like problem with rear abs sensor in rear diff. either sensor not working right or wiring to sensor. The sensor mounts in top of diff and is a input for abs and quite often trans uses it as speed input. You can pull codes out of this system but it requires grounding out wire and counting abs light flashes of bulb in dash. And than going to shop manual and check what code means.
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I believe a 1990 truck has a separate VSS sender at the transmission. It wasn't until later model years and the advent of the LCD odometer that Ford conditioned the RABS differential speed sensor to generate the VSS signal.
Check that your brake lights are working correctly. If they are both burned out, or the brake light switch is always on, the RABS module will flash the RABS light once you get above something like 16 MPH. The BOO signal (brake on-off) is also an input to the computer, which it uses to disengage the torque converter clutch in the trans, amoung other things.
Problems with the brake lights or brake light switch could cause the pair of symptoms you are seeing. So could problems with chassis/battery ground.
Alternatively, you have two independent problems, and will have to diagnose both. There is good info on diagnosing the brake system at autozone.com
But problems with the brake light switch is a good possibility. Make sure the brake lights are off with your foot off the brake pedal. Make sure they both come on when you press on the pedal.
Check that your brake lights are working correctly. If they are both burned out, or the brake light switch is always on, the RABS module will flash the RABS light once you get above something like 16 MPH. The BOO signal (brake on-off) is also an input to the computer, which it uses to disengage the torque converter clutch in the trans, amoung other things.
Problems with the brake lights or brake light switch could cause the pair of symptoms you are seeing. So could problems with chassis/battery ground.
Alternatively, you have two independent problems, and will have to diagnose both. There is good info on diagnosing the brake system at autozone.com
But problems with the brake light switch is a good possibility. Make sure the brake lights are off with your foot off the brake pedal. Make sure they both come on when you press on the pedal.
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Originally Posted by fefarms
I believe a 1990 truck has a separate VSS sender at the transmission. It wasn't until later model years and the advent of the LCD odometer that Ford conditioned the RABS differential speed sensor to generate the VSS signal.
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Originally Posted by Jarrett T
Is there any vacuum controlling this tranny? I pretty sure not, but...
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From: Remsen, NY
Originally Posted by HardScrabble
There may be some overlap here, I think my '91 has no VSOM and no digital odometer. I am not sure about this.
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