A/T - A4LD No 4th Gear TECHNICAL BULLETIN # 127

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Myrtle Lester
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1 1992 Ford Truck Explorer 4WD V L Copyright 2004, ALLDATA 8.30 Page 1 Technical Service Bulletin # ATRATB127 Date: A/T - A4LD No 4th Gear TECHNICAL BULLETIN # 127 DATE: Aug TRANSMISSION: A4LD SUBJECT: Late Or No Fourth Gear APPLICATION: Ford No 4th Gear here are several conditions which may create no 4th gear. Use the following step by step procedure to isolate the problem. TEP 1 MECHANICAL TEST: rive the vehicle on a lift at a speed which should make the transmission shift to 4th (at least 45 mph). Loosen the overdrive band lock-nut and try to urn the band adjustment bolt. he band adjustment bolt won't turn: he overdrive band is applied. You have a mechanical problem. e.g., broken O.D. planet, stripped sun gear splines etc. he band adjustment bolt turns easily: he overdrive band is not applied. Tighten the overdrive band, this should cause the drive wheels to increase in speed. This will confirm that echanically, the overdrive section of the transmission works. The following steps vary depending on whether the transmission has one or two solenoids. f the transmission has one solenoid, proceed with step 2. f the transmission has two solenoids, go to step 6. Single solenoid units will have two wires at the case connector. Two solenoid units will have three wires. Steps 2 Through 5 STEP 2 LINE PRESSURE TESTS: Road test and compare all pressures to chart. Use a hand vacuum pump to regulate vacuum during 10" and WOT tests. (Figure 1) MODULATOR TESTS: 1. Vacuum to modulator at idle warm, should be at least 16" at sea level. 2. Vacuum must drop below 2" on a quick WOT. If either of these specifications cannot be met, check for bad vacuum hoses, plugged ports, worn timing chains, or restricted intake or exhaust.

2 1992 Ford Truck Explorer 4WD V L Copyright 2004, ALLDATA 8.30 Page 2 3. Check modulator pin length, free valve movement (Figure 2) and be sure you do not have a C3 modulator installed. A4LD MODULATOR PIN LENGTH = 1.375" Average A4LD MODULATOR APPLICATION E5TZ-7A377-B Altitude Comp Ford Mercury E5TZ-7A377-C Standard 87 - on Mustang, Bronco, Ranger E4SZ-7A377-A Turbo Charged T-Bird E4SZ-7A377-B Altitude Comp T-Bird F0TZ-7A377-A Altitude Comp CI 90 - on Aero/Bronco/Ranger SERVO PRESSURE TEST: Drill and tap the overdrive servo. Line pressure should be present any time the engine is running. If not, check for a valve body gasket that's covering the ervo feed hole. TEP 3 GOVERNOR TESTS: line pressure must be checked first. Remove the extension housing, governor body and pan Blow air into the governor return passage. Figure 3. Check for leaks around the valve body, valve lugs, governor ring area etc. At the same time, check for a stuck 3-4 shift valve.

3 1992 Ford Truck Explorer 4WD V L Copyright 2004, ALLDATA 8.30 Page 3 As you apply and release air into the governor return passage, you should be able to feel the 3-4 shift valve tapping on the plug. If not your valve body may be too tight. Loosen and retighten the valve body bolts to 70 in. lbs and try it again. (This should be a rebuild procedure). N There is an untapped boss (Figure 2) for governor pressure cast into the right side of the case. It may be to your advantage to drill and tap this during rebuild for future use. TEP 4 CHECKBALL AND SEPARATOR PLATE I.D.:

4 1992 Ford Truck Explorer 4WD V L Copyright 2004, ALLDATA 8.30 Page 4 Make sure your checkballs and separator plate are correct for the model you're working on. See figures 4 and 5 for this. alve Body, Separator Plate and Check Ball Locations TEP 5 CASE AND VALVE BODY PREPARATION:. Cross-file case and valve body with a large single cut file. Block plane both surfaces with 240 or 320 emery cloth. Install 2 case to separator plate gaskets. Torque valve body starting from center out, in two steps, with the final torque at 70 in. lbs. Step 6 Quick Test the Transmission: STEP 6 QUICK TEST THE TRANSMISSION: Using a high impedance test light, probe the wire harness going to pin # 2, (the center wire) for 12V. (See Figure 6) If there's no power, you have an external electrical problem. Make sure the trans works by peeling some insulation from the wire, and using a 10 amp fused jumper wire supply 12V to the center wire, and check for 4th gear.

5 1992 Ford Truck Explorer 4WD V L Copyright 2004, ALLDATA 8.30 Page 5 If you have 12V at the center wire, probe the front wire at an idle in drive. The test light should light. If not, the solenoid is bad or mis-wired. If the light comes on, accelerate on the lift to 60 MPH with the engine at operating temperature. Light should go out. If your test light doesn't go out, the computer is not grounding the solenoid. Try jumping the front wire to ground. If the unit shifts 1,2,4, the transmission works. Areas to check outside the transmission include: If your test light goes out, your problem is inside the unit. Do the servo pressure test from Step 2. Also review Steps 4 and 5. Check for a bad solenoid. (Figure 7 shows you how). N Solenoid resistance is OHMS

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