42RLE No Overdrive: No 4th Gear Diagnosis and the Real Fix

42RLE No Overdrive: No 4th Gear Diagnosis and the Real Fix

42RLE No Overdrive: No 4th Gear Diagnosis and the Real Fix

You are cruising at 60 mph and the tach is sitting where it should be at 45. The trans pulls fine through first, second and third, but fourth never shows up. Maybe the OD light is flashing, maybe there are no codes at all. This is one of the most common complaints on the Chrysler 42RLE, and it shows up across the whole family that used it: Jeep Wrangler TJ and JK, Liberty, Nitro, Dodge Dakota, Durango, Charger, Magnum and Chrysler 300 with the rear-drive four-speed.

The good news is that "no 4th gear" is one of the most diagnosable failures on this unit, because of how the 42RLE builds fourth. You do not have to guess. Follow the clutch chart, read the volumes, then put a gauge on it.

What fourth gear actually needs

Per the Chrysler factory service manual "Elements In Use At Each Position Of Selector Lever" chart for the 42RLE, every forward gear is made by combining exactly two clutches - one input clutch and one holding clutch:

  • First: Underdrive clutch + Low/Reverse clutch
  • Second: Underdrive clutch + 2/4 clutch
  • Third (Direct): Underdrive clutch + Overdrive clutch
  • Fourth (Overdrive): Overdrive clutch + 2/4 clutch

Read that fourth-gear line again, because it is the whole diagnosis. Fourth gear is the only gear that uses the overdrive clutch and the 2/4 clutch at the same time, with the underdrive clutch fully released. That gives you a free process of elimination:

  • Second gear is good, third gear is good, only fourth is missing. Both the OD clutch and the 2/4 clutch can hold on their own at lower torque, but one of them slips when it has to carry fourth alone. Marginal clutch pack, not a dead one.
  • No third and no fourth. Suspect the overdrive clutch circuit - it is the common element.
  • No second and no fourth. Suspect the 2/4 clutch circuit - it is the common element.

The factory manual makes the same point plainly: road testing can identify which unit slips, but not why, because almost any condition can be caused by leaking hydraulic circuits or sticking valves. So confirm the gear pattern first, then chase pressure.

Step 1: fluid, then codes, then volumes

Check fluid level and condition before anything else, and check it warm. The 42RLE is an ATF+4 transmission - the factory manual calls for Mopar ATF+4 and nothing else. Burnt-smelling fluid with dark friction material floating in it tells you where this is heading before you ever pull a code.

Then scan it and read the clutch volume indexes. CVI is the 42RLE's built-in wear gauge, and most people skip it. Per ATRA's technical write-up on the subject, CVI is the measurement of the physical amount of fluid required to fill a clutch and stroke its piston, and one CVI equals 1/64 of a cubic inch of fluid. The TCM calculates it from input and output speed sensor data every time the clutch applies. As the friction material wears, the volume needed to apply that clutch goes up.

Acceptable 42RLE ranges are Low/Reverse 35-83, 2/4 20-77, Overdrive 48-150 and Underdrive 24-70. An overdrive or 2/4 number climbing out the top of its range is worn friction material, and it is the cheapest confirmation you will ever get.

One caution on this unit specifically: the OD clutch volume updates during the 2-3 upshift and is known to read well below its minimum, sometimes as low as zero. If the shifts are otherwise clean, a low OD CVI by itself is not the fault. It is the high side you care about.

Step 2: put a gauge on it

Pressure testing is where this diagnosis gets settled. Get the fluid to operating temperature - the factory procedure specifies 150 to 200 degrees F - raise the vehicle so the wheels can turn, and hook up the taps. The factory specs that matter here:

  • Overdrive clutch tap, selector in Drive with OD off, 20 mph: should read 74 to 95 psi. Then bring it to 30 mph in second - overdrive clutch pressure should now be less than 5 psi.
  • 2/4 clutch tap, selector in Drive with OD on, 30 mph in fourth: should read 75 to 95 psi.
  • Underdrive clutch tap, Drive with OD on, 40 mph in fourth: should be below 5 psi - fourth does not use the underdrive clutch.
  • Reverse and low/reverse tap, brake held at 1500 rpm: 165 to 235 psi.
  • TCC on: 60 to 90 psi. TCC off: less than 5 psi.

How to read the results, straight from the manual: if proper line pressure shows up in any one test, the pump and pressure regulator are working. Low pressure in every position points to a bad pump, a clogged filter, or a stuck pressure regulator valve. Pressures that fall outside a single circuit's spec indicate a leak in that clutch circuit. And two specific tells worth memorizing - if overdrive clutch pressure is greater than 5 psi when it should be exhausted in second, that indicates a worn reaction shaft seal ring or a defective solenoid assembly. If underdrive clutch pressure is greater than 5 psi in fourth, the solenoid/pressure switch assembly or the controller is the cause.

If the unit is already out and apart, air check it. Apply air to the 2/4 clutch retainer feed hole and watch the 2/4 piston move rearward; apply air to the overdrive apply passage and watch the push/pull piston move forward. Both must return when the air is released. A large volume of escaping air means seals, not solenoids.

Step 3: the fix

Sort the outcome into one of four buckets.

Burnt overdrive or 2/4 frictions. High CVI plus in-spec apply pressure plus burnt fluid equals worn clutch material. There is no shortcut here - the clutch packs come out. A 42RLE high-energy friction clutch kit is the targeted repair if the rest of the unit measures clean, but if the fluid is burnt the debris is already everywhere, and the honest call is a full teardown with a 42RLE master rebuild kit so the frictions, steels, seals, gaskets and bushings all go back fresh together.

42RLE master transmission rebuild kit - frictions, steels, seals and gaskets for Jeep and Dodge four-speed
Shop 42RLE rebuild kits for the Jeep and Dodge four-speed →

Electrical / solenoid side. Underdrive pressure that will not exhaust in fourth, or overdrive pressure that will not exhaust in second, can be the solenoid and pressure switch assembly rather than a clutch. That assembly is also the usual suspect behind the shift-solenoid and switch codes this unit throws, so if your CVIs are clean and only the electrical behavior is wrong, start with a 42RLE shift solenoid pack. We covered that failure in detail in 42RLE solenoid pack symptoms, codes and the real fix.

Reaction shaft seal rings. Overdrive pressure bleeding where it should be exhausted is the classic sign. These are internal, so it is a teardown - which is another argument for doing the clutches at the same time.

Pressure regulator bore wear. Sonnax documents that wear in the 42RLE pressure regulator bore shows up in two different ways depending on location: wear at the inner bore causes high line pressure, harsh shifting and erratic converter apply pressure, while wear at the spring end of the bore lets line pressure exhaust, giving low line pressure, soft shifts and burnt clutches. That second pattern is exactly how a good clutch pack gets cooked. If you rebuild the unit without addressing a worn PR bore, you will burn the new frictions too.

Note that the correct PR repair depends on which valve body you have. Per Sonnax, beginning in 2007 the 42RLE went to electronic variable line pressure (VLP) control - identified from outside the case by an extra 5-pin or 6-pin connector next to the range sensor connector, feeding a pressure sensor and a pressure solenoid that let the TCM trim line pressure to load. Earlier 42RLE units were fixed line pressure. Sonnax lists the oversized pressure regulator valve 92835-29 for VLP units and 92835-24 for non-VLP. Identify before you order.

Replace while you are in there

If the pan is down or the unit is out, these go back new. It is cheap insurance against doing the job twice:

  • Filter and pan gasket - always, and mandatory if there is friction material in the pan
  • Overdrive clutch hub bushing - Sonnax lists this bushing against planetary failure, shaft breakage and bushing wear, and notes two late-style sizes (0.937 in. and 0.941 in. housing bore), so measure before ordering
  • Input clutch hub bushing - Sonnax lists 92003-01K against premature underdrive clutch failure
  • Pump bushing - Sonnax lists 12502-01 against pump seal leakage, pump noise, loss of prime, low pump volume, low cooler flow, TCC codes and switch codes
  • Reaction shaft support seal rings, while the unit is open
  • Torque converter, if the fluid was burnt - it holds debris no flush reliably removes

Clutch pack clearance specs from the factory manual, for setup: Overdrive clutch (no select) 0.042-0.128 in., Two/Four clutch (no select) 0.030-0.104 in., Underdrive clutch (select reaction plate) 0.037-0.059 in., Low/Reverse clutch (select reaction plate) 0.033-0.063 in., Reverse clutch (select snap ring) 0.035-0.054 in.

Torque specs you will need: oil pan-to-case 20 N·m (14.5 ft-lb), valve body-to-case 12 N·m (105 in-lb), solenoid/pressure switch assembly-to-valve body 5.5 N·m (50 in-lb), valve body-to-transfer plate 5 N·m (45 in-lb), oil pump-to-case 30 N·m (265 in-lb), converter-to-driveplate 88 N·m (65 ft-lb), cooler line fitting 47.5 N·m (35 ft-lb).

Refill quantities per the factory procedure: 3 quarts of ATF+4 if you only changed fluid and filter, 5 quarts if the unit was fully overhauled or the converter was replaced or drained - then bring it to level warm, on the dipstick, shifting through the ranges first.

What this costs you in effort

A solenoid and pressure switch assembly is the easy end of this job - pan down, filter out, assembly swapped, refill. Most DIYers with a lift or good stands can do it in an afternoon, and a shop will typically book it in the two-to-three hour range. Valve body work sits a step above that. A full teardown for burnt overdrive or 2/4 clutches is a different animal: the transmission comes out, and between removal, rebuild and reinstall you are realistically looking at a full day or more of shop labor plus the parts. That gap is exactly why the diagnosis above is worth doing carefully - reading CVIs and putting a gauge on the taps takes an hour and tells you which of those two jobs you are actually buying.

FAQ

Can a 42RLE lose only fourth gear and still drive fine otherwise? Yes, and it is common. Fourth is the only gear that combines the overdrive clutch and the 2/4 clutch with the underdrive clutch released, so a pack that is worn but not dead can still hold in second and third and let go in fourth.

Will a fluid and filter change bring back overdrive? Only if low or badly degraded fluid was the reason line pressure was down. If the fluid is burnt and the CVIs are high, the friction material is already gone and fresh fluid will not restore it. Change it, but do not expect it to be the repair.

Do I need to know whether mine is a VLP unit before ordering parts? For valve body and pressure regulator parts, yes. Per Sonnax, 2007-and-later units use electronic variable line pressure and are identified by an extra 5- or 6-pin connector next to the range sensor connector on the case. The pressure regulator valve part number differs between VLP and non-VLP units.

Browse the full transmission rebuild kits selection to match parts to your build, and if the symptom is limp mode rather than a missing fourth, start with 42RLE limp mode and stuck in second gear instead.

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