8L45 Governor Pressure Solenoid 2015, new and ready to install. Fits the 8L45. Ships fast from the USA.
This listing carries an old title, but the part is a new Sonnax 154740-29K pressure regulator and O-ringed shuttle valve kit for every GM 8L45 and 8L90 built from 2015 on. The 8L45 and 8L90 have no governor; line pressure is set by a pressure regulator valve in the valve body, and when that bore wears the Colorado, Canyon, Camaro, CTS, ATS, Silverado, Sierra, Tahoe or Yukon starts shifting harsh, burning clutches or running hot. If you are chasing line pressure that is too high, too low, or wandering between the two, this is the repair aimed at the cause.
The pressure regulator valve meters pump output into line pressure. A variable force solenoid sends a throttle-based signal to one end of the valve, and a shuttle valve sitting in a sleeve feeds balance pressure to the other. Sonnax found two wear points. Signal oil leaks past a worn inboard port at the solenoid end, so the valve cannot respond and can sit in the low-pressure position. The shuttle valve also oscillates constantly, wearing its sleeve until balance pressure exhausts and line pressure falls off. The opposite failure is just as real: Sonnax measured over 415 psi on units that should peak near 315 psi, enough to crack the valve body casting or shatter a drum when a worn regulator lineup is paired with a blow-off spring calibrated too high.
The kit answers both. The regulator valve signal spool is 200 percent longer than original, so it rides in unworn bore, and the critical shuttle spool is 30 percent longer. The valves are hardcoat anodized aluminum, the sleeve is billet aluminum, and the O-ringed sleeve seals against a worn casting. It installs as a drop-in, with no reaming.
A line pressure gauge tells you more than any code. Compare actual pressure to what the TCM is commanding; a reading that will not follow the command, or one well above about 315 psi, points at this lineup. Fluid comes first on an 8L45, so make sure the unit has DEXRON HP at the right level. A no-move or no-pressure condition is a separate problem, often pump priming or a pressure regulator assembled backward; our 8L90 and 8L45 pump failure guide sorts those out, and the valve body symptoms and testing guide covers bore wear.
Sonnax lists 154740-29K for all 8L45 and 8L90 units from 2015 on, which is broader than the 2015 in our title. That covers the 8L45 in Colorado, Canyon and Cadillac ATS, CTS and CT4 applications and the 8L90 in full-size trucks, SUVs, Camaro and Corvette. See our 8L90/8L45 collection for the rest of the family. If you are unsure which unit you have, send us the year and VIN.
The valve body has to come out, so plan this with any valve body service. Note the orientation of every piece in the original regulator bore before you pull it; a backward regulator is a known cause of no-pressure complaints. Lube the O-rings and drop the new valves and sleeve in per the Sonnax instructions. Sonnax recommends replacing the regulator lineup and line pressure blow-off spring on every 8L45 or 8L90 valve body rebuild and pairing this kit with its 154740-18 relief spring to keep peak pressure in the 300 to 315 psi range. If the casting is already cracked, replace it with an 8L45 valve body. Fit a new filter and steel pan gasket, refill with DEXRON HP (GM lists a 7.4 quart fluid change), set level hot and run the adaptive relearn.
| Fits | 8L45 2015 |
| Part type | Governor Pressure Solenoid |
| Condition | New |
| Brand | OEM |
| Reference | 154740 |
| Ships | From the USA |
| Warranty | 1-year |
No. The 8L45 and 8L90 have no governor. This is a Sonnax 154740-29K pressure regulator and O-ringed shuttle valve kit, the valve body parts that control line pressure in these transmissions.
Yes. Sonnax lists 154740-29K for all 8L45 and 8L90 transmissions from 2015 on.
High or low line pressure caused by a worn regulator bore at the solenoid signal port and a worn shuttle valve sleeve. That shows up as harsh or soft shifts, burnt clutches, low cooler and lube flow, and overheating.
No. It is a drop-in kit. The longer valve spools ride in unworn portions of the bore and the O-ringed sleeve seals against wear in the casting.
Sonnax recommends replacing the line pressure blow-off spring at the same time, using its 154740-18 relief spring, plus a new filter and pan gasket and fresh DEXRON HP.
Put a gauge on it and compare to the commanded value. Sonnax says these units should peak around 315 psi; field units with worn lineups have shown over 415 psi.
