Transmissions 101: The 68RFE Valve Body

Transmissions 101: The 68RFE Valve Body

Nathaniel ValentinAugust 25, 20202 comments

                The 68RFE Transmission’s Valve Body is inundated with problems, with nearly every component of it being prone to extreme failure. This is the part of the transmission that controls where all of the fluid travels to, to apply certain clutch packs and henceforth activate gears. For example, when you move your shift lever from park, to reverse, an oil circuit is opened by the manual valve in this valve body (which is connected to the shift lever) that directs oil to the L/R clutch pack, and the reverse clutch pack, putting the transmission in reverse.

68RFE Check Ball Locations

                The 68RFE has changed multiple times in it’s lifespan, and the lineage is as follows:

Gen 1 - 2007.5 to 2010 (7 Check Balls, known as the most problematic 68RFE’s. The Valve Bodies and Pumps are made of incredibly soft metal and have a fraction the lifespan. White Solenoid Pack.)

Gen 2 - 2011 to 2018 (5 Check Balls, Grey Solenoid Pack, but can be replaced with White.)

Gen 3 - 2019+ (Blue Solenoid Pack, can ONLY be replaced with Blue OEM Solenoid Pack)

                The accumulator pistons are the part of the valve body that absorbs the shock that would otherwise be applied to directly to a clutch pack. You can think of these as a shock absorber for a gear shift. Without accumulation in place, every gear would bang very aggressively and clutch application timing would be poor. The 68RFE Transmission’s accumulator pistons are dismally low quality; made of low quality plastic. They have 2 seals that are extremely loose and allow an extreme and unsafe amount of venting. Accumulator pistons are supposed to leak, they’re a controlled vent, but the factory pistons vent excessively which forces the clutch to suffer from less apply pressure. The solution to this is a quality, billet aluminum set of pistons with added seals of tighter tolerance, endorsing quality shift timing and behavior as well as predictable driving dynamics and increased torque capacity.

68RFE Valve Body Accumulator Piston

                The 68RFE Valve Body accumulator backing plate is the component that bolts to the valve body and holds the accumulation pistons in place. The pistons have springs between them and the plate, creating the “shock absorber” dynamic. In analogical comparison to a motor, this would be like a girdle. It’s designed to bolt somewhere and never move. Unfortunately, it is unable to do this efficiently. It often blows off from flexion due to being an incredibly weak and soft metal; a child could bend it by hand effortlessly. Increased line pressure from TCM tuning or pressure boxes only proliferate this failure. The solution is a steel, high quality backing plate that simply won’t fail. The issue here is not design, it’s part quality.

68RFE Valve Body Failed Accumulator Plate

                One of the less talked about subjects is the solenoid switch valve, often in acronym format as SSV. This is the biggest crossleak in the 68RFE Transmission, and infamously, is the one that causes most overdrive failures and P0871 codes. In short, this valve is very coarse in nature and causes bore wear quickly. When this happens, they will cause oil to leak out of overdrive when it’s needed most, decreasing torque capacity and catalyzing a catastrophic failure of the overdrive clutch pack. The solution here is to machine this bore in totality, replacing it with an upgraded valve designed not to fail.

68RFE Valve Body Solenoid Switch Valve

                In association with this, is the solenoid pack itself. The solenoid pack is the “box” of electronics that bolts to the valve body and controls the activation of clutches inside the transmission in conjunction with the TCM’s adaptive shift logic using “Boolean” style logic and logic gates in the internal pressure manifold of the solenoid pack to comply with TCM issued commands. Simply put, it’s the electronic part of the valve body with the solenoids, it fails a lot over time, replace it with a brand new OEM unit every rebuild, do not use an aftermarket solenoid pack! They are far more prone to failure. Solenoid packs with a “Black” rubber weather ring around them are aftermarket.

68RFE Solenoid Pack

                A further failure is the separator plate itself. The separator plate is the component that functions as a gasket the upper and lower half of the valve body assembly. This would be like a head gasket in the motor, it is a steel plate with holes laser cut into it to perpetuate oil circuitry in the valve body. The failure here is two-fold; firstly, that the separator plate is too thin and just simply leaks, and secondarily, that the oil circuitry is just not efficient and an updated design is a critical opportunity to enhance how this transmission behaves. Aftermarket plates should also be thicker as the thickness of this plate is not nearly as fussy as a head gasket job. (PTV clearance, etc.) Below pictured is a "bonded" style aftermarket separator plate.

68RFE Valve Body Bonded Separator Plate

                Yet another failure to the 68RFE Valve Body is the L/R switch valve, the L/R switch valve is a small valve the size of a pea that controls the application of the L/R clutch pack when directed by the L/R oil solenoid. This valve rarely fails, but when it does, it either crossleaks immensely causing potential P0736 (Incorrect gear ratio reverse) or P0731 (Incorrect gear ratio first gear) codes. The solution here is a precision machined aluminum valve that features cleaning lands to prevent bore wear over time.

                Lastly, and not least, the transfer plate of the transmission is the lower half of the valve body. It simply directs oil about the valve body in a convoluted fashion. There are two problems with this plate, both design and quality. The design is inefficient because it endorses limitation to potential line pressure capabilities by forcing oil directly to the PRV bore of the pump for relief. The quality concern is that this is the softest metal used anywhere in the 68RFE Transmission. It is incredibly soft and will flex aggressively over time. The solution here is to precision machine this plate to perfection on either a mill or laptable and modify the oil circuitry by hand to create a relief before the PRV bore enabling higher pressure without modifying the pump. Optimally, aftermarket plates like our’s often come with modifications pre-made and are manufactured from high quality billet materials that are design to be totalitarian and life-long solutions that never fail. These are called “Billet Channel Plates” and are critical. Pictured below is a billet style channel plate.

68RFE Billet Channel Plate

                To conclude, the 68RFE Valve Body is undeniably the largest failure point in the entire unit. Above, we’ve assessed why this occurs from a technical perspective and presented informative data and content to educate our consumers on the failures and solutions needed to modify and upgrade a quality 68RFE Transmission. For further education, we encourage you to call us and talk to an expert.

See more 68RFE Valve Body information here:

https://nextgendiesel.com/collections/valve-bodies

Comments (2)

John A Walsh on October 05, 2020

68rfe transmission 2008.6.7 4×4.it only had first and second gear.

John A Walsh on October 05, 2020

68rfe transmission 2008.6.7 4×4.it only had first and second gear.

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