I am having problems with my E4OD transmission not shifting on my 1990 F150. While on a short trip two months ago my ignition module went out. At the same time the transmission started not shifting. If I start out in drive it remaind in overdrive regardless of whether I push the OD button or not. Also, I don't hava 1st gear any more and if I want any geag besides overdrive, I have to manually shift it int 1st or second manually. When I do I get 2nd ok and I can shift it into drive and it will go into OD and I can drive it. I think it is an electrical problem. Could it be a shift solenoid and if so, where would I locate it? Any help would be appreciated sinct my tranny guy and a local (and recommended) mechanic can not find the problem.

 

Welcome to the site

I can help by mentioning this thread will be moved to the 87-96 Truck or the Transmission forum

 

Hey,DS
I'll pass on what I know ,maybe it'll help.The solenoids are in a pack w/valvebodies,left side of pan. The harness is on left back corner above pan rail.You should ceck out the range switch on drivers side-where the shifter cable connects.It's a variable resistor switch that tells the PCM which gear you've selected.If you can't find the res. values for each gear I can look them up.

 

Thanks, that is where I will start looking. My 3 service manuals don't mention any variable resistor but it makes sense. I hope it is as simple as that.

Dana

 

There isn't a variable resistor. There is a Transmission Range Sensor, which has internal resistors. Different resistors are in the circuit when the shifter is moved to different positions.

Usually when these start to fail a resistor gets intermittent. It won't show up in a check, because it only happens while the truck is driving and causing the sensor to vibrate. It also may only happen once every few hundred miles. Any water in the connector or sensor is real bad news.

These sensors are almost impossible to troubleshoot. If a problem is suspected, and I think yours is suspect, replace it.

 

Casey,
Have you noticed that the holes that mount the switch are slotted?There is a variable resistor inside-you have to read the switch w/an ohm meter and adj. to prop. value.

Dana,
W/the tranny in park you're looking for 3770-4607 ohms.In 1st,78-95 ohms.Pins 2&3,wire colors GY/R and LB/Y
When I replaced mine I think it cost about $100.00 for the switch.

 

Brainsshop,

Have you ever opened up a TRS? I have.

Where is this variable resistor hiding? I've had several of them apart, and there are several discrete resistors, but no variable resistor. The adjusting slots are to align the contacts for each resistor so that the proper resistor is read when the shifter is in each position.

 

Yea Casey,
Sounds good-it's been about 3 yrs since I replaced mine.Didn't remember feeling "dents" or spaces between readings at each pos.But did remember having to adj. it.

And btw it's BRIANSSHOP

 

Sorry about the typo! I did mean to type BRIANSSHOP.

You won't feel any detents between spaces. There is a copper strip that makes contact with the wiper. The copper is etched away between spaces so that there is no electrical contact, but no feel to it.