I have a 4.2 v6 1997 ford f150 pickup. I am having problems with the transmission..I need to know where the fuse for the transmission is located. The transmission will shift into first and second but not into third or fourth.I was told it could be a fuse causing this. can someone please help me..

SOURCE: f150 transmission neutralizes when shifts to overdrive

I have that exact same truck and transmission and My Transmission did the exact same thing about a year ago and there was some kind of snap ring inside the transmission that broke. I originally thought it had to be an electirical problem because the truck shifted fine until OD or if i turned OD off. The 4r70w is a light transmission and i would suggest you have a shift kit put in and they make a heavier kit to beef it up.. Sorry its probably not the new you were looking for.

SOURCE: Transmission is not shifting into third gear. I

Generally, if a transmission shop has told you that you do not need a new transmission, you do not need a new transmission. Let them replace the shift solenoid (they won't have to remove the transmission to do this, just the pan, fluid and filter) and tell them to use the Sonnax Heavy Duty 2-3 Shift valve as well (this can be done without removing the transmission too).
Then if it doesn't shift, you will need a complete rebuilt. Tell them you want a new torque converter, a hardened input shaft, a 29-element Borg-Warner input sprag, The Beast sun shell, a new reverse drum, an extra wide Carbon Fiber power band, a Sonnax .490" Boost valve, a Sonnax cast-aluminum pinless forward accumulator, the Sonnax "Super Hold" 1-2 and 3-4 servos, all Alto Red Eagle frictions and full-thickness Kolene steels, as a minimum over a stock rebuild. 4L60E's are weak and die at about 100,000-150,000 miles, sooner if you tow regularly. This build will cost you about 500 bucks more than a stock rebuild, but you will then have a bullet-proof transmission.

SOURCE: my transmission slips going through second gear if

this problem is a common failure associated with your shift solenoinds inside your tranny. of course a shop is not gonna tell you this because by the time you wanna get it repaired it is usually too late and have already cause damage to your clutch pack and internal parts, thats the main reason why a shop wont mess with just replacing your shift solenoid (aka valve bodie)

SOURCE: 1991 Chev 1500 pickup, 5L,

Vacuum Modulator -(THM 400 only) REMOVAL & INSTALLATION NOTE: This applies to the THM 400 only.

1. Raise and support the front end on jackstands.
2. Disconnect the vacuum line at the modulator.
3. Remove the screw and retaining clamp. Fig. 1: Vacuum modulator on the THM400
   
   
4. Remove the modulator. Be careful, some fluid may run out. To install:
   
5. Install the modulator.
6. Install the vacuum line. Be careful not to kink the vacuum line during installation. Replace any lost fluid.

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The Governor is used in newer transmissions:

HYDRAULIC CONTROL SYSTEM The hydraulic pressure used to operate the servos comes from the main transmission oil pump. This fluid is channeled to the various servos through the shift valves. There is generally a manual shift valve which is operated by the transmission selector lever and an automatic shift valve for each automatic upshift the transmission provides. NOTE: Many new transmissions are electronically controlled. On these models, electrical solenoids are used to better control the hydraulic fluid. Usually, the solenoids are regulated by an electronic control module. There are two pressures which affect the operation of these valves. One is the governor pressure which is effected by vehicle speed. The other is the modulator pressure which is effected by intake manifold vacuum or throttle position. Governor pressure rises with an increase in vehicle speed, and modulator pressure rises as the throttle is opened wider. By responding to these two pressures, the shift valves cause the upshift points to be delayed with increased throttle opening to make the best use of the engine's power output. Most transmissions also make use of an auxiliary circuit for downshifting. This circuit may be actuated by the throttle linkage the vacuum line which actuates the modulator, by a cable or by a solenoid. It applies pressure to a special downshift surface on the shift valve or valves. The transmission modulator also governs the line pressure, used to actuate the servos. In this way, the clutches and bands will be actuated with a force matching the torque output of the engine.
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At any rate, if the auto transmission shifts roughly, try to have it flushed out and refilled with new transmission fluid for $100 or so.

If this doesn't solve the problem, the transmission will have to be rebuilt to original specifications, or replaced with a transmission that doesn't have this problem (used or another rebuilt).