Most of the vehicles we are working on have computer-controlled transmissions, so we will be bringing you the latest types of checks to help in diagnosing the vehicles’ transmission problems.
The 4L60-E and 4L80-E transmissions used in General Motors C/K trucks can be stuck in fail-safe. One of the causes could be a blown fuse but the replacement fuse also blows. We have a check procedure and the common cause for that problem.
Sometimes scan tools can give incorrect information on GM THM 4T80-E units with diagnostic trouble code P056 stored. You should access the codes through the onboard diagnostic system on Cadillacs.
Mazdas equipped with the R4A-EL transmission may exhibit normal 1-2 and 2-3 upshifts but no 4th gear. The cause could be a faulty or misadjusted inhibitor switch, a faulty theft-deterrent system or a grounded wire harness leading to the inhibitor-signal fuse.
Nissan Maximas equipped with the RE4FO2A may have only a 1-2 shift and the reverse lamps do not illuminate. The cause may be that the connector for the auxiliary air-control valve has been switched with the inhibitor-switch connector.
No forward engagement in a Ford E4OD may occur because the plastic-caged low roller clutch was installed incorrectly.
An A4LD in Ford light trucks may require shift-lever PRNDL adjustment because the cable-assembly locking tab is not fully seated.
If you have a Chrysler A-604 with a broken tapered snap ring in the underdrive/overdrive reaction plate, be sure you install the late-type snap ring.
We have corrections for bind-up or 2nd-gear starts on KM-177, and a pump-gear change on KM 175.
In Ford Probe 4EAT and Mazda G4A-EL units, a
4-2-3-1 shift pattern after rebuild may be caused by reversed shift solenoids.
We also have the procedure for FIPL (fuel-injection pump lever) sensor adjustments on the Ford E4OD.
This month’s Tech/Talk covers a variety of complaints and fixes, leading off with a Saturn that moves forward in all gear selections. The problem is caused by a mismatch of the manual valve and manual-valve link.
A missing rubber-coated sleeve in the overdrive-servo assembly of a 4R70W may result in burned forward clutches.
Torque-converter discoloration in a 4T60-E may be caused by a melted plastic spring retainer in the to-cooler fitting.
A weak or collapsed 4th-apply piston return spring in 4L60 and 4L60-E units may be the cause of burned 2-4 bands.
We also have information on a Subaru Justy ECVT that has no ratio change from low.
Mismatching manual valve to case in G4A-EL units will result in either no reverse or movement in neutral. Mismatching reverse and forward drums will cause stacked shifts.
A complaint of no movement in any range on a Subaru RE4-style transmission may be caused by an incorrectly installed lockup-control valve and spring.
Shift-solenoid and lockup-solenoid wires that are connected backward on Mazda MPV R4A-EL units will produce a 1-3 upshift in Drive.
Some overdrive planetary gearset changes that were made in 1995 Chrysler A518 models can create service concerns. We have covered those changes from the previous-design straight-cut (spur) gears to the 15° helical-cut gears.
In the middle of the 1997 model year, GM changed the transaxle case, channel plate and check-ball locations on the THM 4T40-E. Those changes are noted along with the illustrations.
In some instances, the Park/Neutral position switch on General Motors 4L60-E cannot be removed. Related problems may occur, such as the dash indicator showing either an improper shift or no shift, or no back-up-light operation.
A speed-sensor-harness repair kit now is available for General Motors 4L80-E and 4L80-EHD. Part numbers are included.
The location of the rear lube seal and orifice on General Motors 4L80-E and 4L80-EHD is still a problem for many technicians. We have illustrated this location.
Premature failure of the 3-4 clutch in General Motors 4L60 and 4L60-E units usually is associated with vehicles used for police, taxi or other heavy-duty service.
No upshift from first gear after overhaul of a Chrysler A500SE (42RE) may be caused by excessive wear on the overdrive-piston support where the low-reverse drum rides.
After rebuild, some Chrysler 42RE vehicles may have a 1-2 upshift shuttle that may lead to an incorrect diagnosis as a valve-body problem.
The checkball locations are similar in Chrysler 42RE and 47RE transmissions, but we have illustrated some differences. None of the individual parts will interchange with those of previous design levels.
Chrysler A500/A518 with no 3-4 shift before or after overhaul may not have the right computer for the vehicle.
We also have center-gearbox differences on General Motors 4L80-E/4L80-EHD center-lube transmissions. Notice that none of the parts listed will interchange with any previous-design-level parts, and none of the previous-design-level parts can be used in the units with center-lube design.
In This Issue
Chrysler A518 (46RH) and 46RE: Broken Front Planetary Carrier
Saturn: Erratic Shift Pattern After Rebuild or After Reprogramming PCM
Ford/Mazda CD4E/LA4A-EL: Continuous Front-Seal Leak or Seal Blowout
Honda/Acura: Grade Logic Control
With all the updates on transmissions and transaxles, the interchange of parts is not as easy as it was in the past. So this month’s tech information will help in the identification of these parts and in transmission/transaxle identification.
The information on General Motors 4T60-E covers the identification of the channel plates on models that have no manual low, plus information on the parts affected: inside detent lever, channel plate and 2nd-start switch.
The new-design 1-2 roller clutch on the THM 4T60-E has created parts changes, along with inter-changeability and retrofit concerns.
In a Ford AXODE (AX4S) that slips on the 2-3 shift or has no 2-3 shift, the cause may be mismachining of the direct-/intermediate-clutch cylinder or an out-of-round clutch cylinder.
The new input-clutch retainer on Chrysler 41TE and 42LE units changed snap-ring thicknesses, and the reaction plate was modified.
Chrysler A500/42RE series transmissions may have no reverse or a bind-up on the 3-4 shift because of a mismatch of the overdrive-/direct-clutch housings, depending on engine size and transmission model.
We have preliminary information on BMWs equipped with the ZF-5HP-18.
In Chrysler rear-drive vehicles with premature planetary failure, the one-way checkball may have been installed incorrectly.
Chronic internal leaks in Honda/Acura vehicles cause premature clutch failure, poor shift quality and shift hunting.
A continuous front-seal leak in a CD4E may be due to the installation of an incorrect torque converter.
In a GM 4L80-E/4L80-EHD with trouble code 68 in overdrive or trouble code 39 in Drive 3, the cause can be mechanical. The units also have new-design fourth- and overrun-clutch steel plates.
The oil-pump driveshaft in Ford AXOD/AXODE may be the culprit in no movement in forward or Reverse, or no converter-clutch apply at any speed.
We also have updated electrical diagnosis and cautions on 1991-1992 Ford AXODE.
Chrysler 41TE has a change in the overdrive/underdrive reaction plate, as well as a change in the 2-4 low/reverse reaction plate.
In a Honda M24A, no reverse after overhaul may be caused by the bore plug that retains the servo control valve having been installed backward.
Valve-body screens for GM 4L30-E units now are available individually from Isuzu. We list the part numbers for those screens.
This month, we start off with some complaints on Ford 4R44E/4R55E/5R55E units. Delayed engagements and/or slipping may be caused by a missing extension housing lube orifice plug. Insufficient oil to the forward-clutch circuit can cause delayed forward engagement on 4R44E/4R55E units, and no forward engagement in the overdrive range may be because a bore plug in the valve body was installed backward.
A lack of clutch capacity for the overdrive clutch in a Ford E4OD may cause premature failure of the overdrive clutch.
We also have some information on Ford E4ODs with missed shifts that scan tools reveal as “No Codes Present.”
Defective thermostats can cause no converter-clutch applications on Honda Civics and Accords.
After TCM replacement on GM diesels, no 3-4 shift or TCC occurs and a code 88 is stored. We explain what caused the code to be set.
GM has made some changes in the PCM on 4L80-E transmissions to eliminate one of the causes of no upshift from first gear.
The malfunction indicator lamp illuminated and DTC P0503 stored on a 4T80-E transaxle may be caused by movement of the final-drive internal ring gear relative to the transaxle case.
In a Chrysler 42RE, a buzzing noise in Reverse may be caused by either a partially clogged main filter or the pressure-regulator valve.
A cracked forward piston or reverse/forward and coast-clutch drum can cause premature coast-clutch failure on GF4A-EL units.
GF4A-EL transaxles with codes 6, 25 and 55 that place the unit in failsafe may require replacement of the PCM.
We also have diagnostic-connector locations and code-retrieval information on GF4A-EL units.