Chevy HHR
Transmission Problems

HHR Transmissions

Almost every automatic HHR uses the 4T45E, the same transmission GM put behind the Ecotec in the Cobalt, Malibu, G6 and Saturn Ion. Confirm it with the MN5 code on the service parts label. The manual cars use Getrag five-speeds, which have their own short list of habits covered below.

Why HHRs Run Hotter Than Cobalts

Here is the part most generic guides miss. The HHR weighs a few hundred pounds more than a Cobalt, has a taller and less aerodynamic body, and the Panel models were bought by florists, couriers and parts stores who loaded them to the roof and drove them in stop-and-go traffic all day. The 4T45E is cooled through a small cooler in the radiator tank, and GM called its fluid fill lifetime. Put those together and you get a lot of HHR transmissions with cooked fluid at 100,000 miles.

Heat is what turns the cheap electrical problems below into expensive mechanical ones. If you work an HHR hard, an auxiliary transmission cooler and a fluid change every 30,000 miles is the single best thing you can do for it.

Problem 1: Stuck in Third (Failsafe)

An HHR that suddenly pulls away from stops in third gear, will not upshift or downshift, and has the check engine light on is in failsafe. The TCM has lost trust in a sensor or solenoid circuit and locked the transmission into a fixed gear to protect it. Speed sensor codes (P0715, P0720) and shift solenoid codes (P0751, P0756) are the usual causes, and corroded connectors at the case are common on cars that saw salted roads.

On a unit with clean fluid and only electrical codes, the transmission is usually fine. Replace the full set with our 4T40E/4T45E solenoid kit once the pan is down. Doing one solenoid at a time on a high-mileage HHR is how you end up dropping the pan three times.

Problem 2: Harsh Shifts and P0748

Hard, banging shifts at every gear change usually mean the pressure control solenoid has failed and line pressure is stuck at maximum, often with a P0748 or P1811. The opposite, mushy shifts that slip, points at a pressure control solenoid stuck low, a tired pump, or low fluid. A line pressure gauge sorts them out in minutes. If the shifts are good when cold and get worse as the fluid heats up, the valve body bores are worn and leaking pressure. For 2007-up HHRs, our remanufactured 4T45E valve body is the fix. Match your casting number first.

Problem 3: No Reverse or a Slipping 2-3

Hard-part failure on the 4T45E usually shows as a loss of reverse while the forward gears still drive, or a flare on the 2-3 shift. The reverse clutch and the 2-4 band are the weak points, and both burn up faster in a hot transmission. Drop the pan. If you find friction material and the fluid smells burnt, it is a rebuild. Our 4T40E/4T45E master rebuild kit covers the frictions, steels and seals. Flush or replace the cooler when you put it back together, or the debris left in the cooler will finish off the new parts.

Problem 4: Converter Shudder

A light shudder at 40 to 55 mph under gentle throttle, like driving over rumble strips that are not there, is torque converter clutch shudder. Tap the brake while it happens. If it stops when the converter unlocks, that confirms it. Fresh Dexron VI often fixes mild cases because the old fluid has lost its friction modifiers. If it comes back within a few thousand miles, the converter clutch lining is worn and the converter needs replacing.

Manual Transmissions: F23 and F35

The Getrag F23 five-speed in standard HHRs is generally durable, but it has two habits. First, the shifter cable ends and their bushings wear or break, which leaves the shifter sloppy or unable to find a gear. It feels like a transmission failure and is actually a cheap cable or bushing. Second, high-mileage units develop bearing whine that rises with road speed and goes quiet with the clutch pedal down. Fresh fluid of the correct type helps notchy shifts, and the wrong fluid causes them.

The SS uses the stronger F35, which holds up well when driven sensibly. Repeated hard launches on the turbo cars wear the synchros and the clutch quickly, so a grinding shift on an SS usually has a hard-driving history behind it.

Fluid and Service

The 4T45E takes Dexron VI. Change it with the filter every 40,000 to 50,000 miles in normal use, and closer to 30,000 on a working Panel. We stock ACDelco Dexron VI by the gallon and the 4T40E/4T45E filter and pan gasket kit. Check the level with the engine running at operating temperature.

Repair Costs

Bottom line: most HHR transmission complaints start as a $100 to $300 electrical problem. The ones that become $2,500 problems are the ones that kept getting driven hot.

FAQ

What transmission is in a Chevy HHR?

Automatic HHRs use the 4T45E four-speed. Manual cars use the Getrag F23 five-speed, and the SS turbo uses the Getrag F35.

Why is my HHR stuck in third gear?

That is the 4T45E failsafe mode, triggered by a speed sensor, shift solenoid or wiring fault. Read the codes before assuming the transmission has failed.

Why does my HHR manual shifter feel loose or not go into gear?

The F23 shifter cable ends and bushings commonly wear or break. Check them before suspecting the transmission.

How often should I change HHR transmission fluid?

Every 40,000 to 50,000 miles with Dexron VI, or about every 30,000 miles on a Panel or any HHR that works hard.