4L80-E Archives - Transmission Digest
GM 400, 4L80-E Case Saver Retainers

Protect case lugs from blowout with the only intermediate clutch retaining ring case saver that allows the intermediate band to be retained. Only the Sonnax case saver retainers support the intermediate clutch retaining ring, yet are thin enough to allow the intermediate band to be installed, allowing case lug protection in all applications. · Fits

GM 4L80/85-E 2-3 Accumulator Spring

This new Sonnax 2-3 accumulator spring (p/n 34931-01) for GM 4L80/85-E units is a direct replacement spring that has been stress relieved and shot-peened for increased durability compared to factory springs.

Hydraulic Fundamentals: AFL/Solenoid Modulator Valves

Knowing your transmission’s hydraulic circuit — and solenoid circuits in particular — can be very helpful when identifying the underlying cause.

Don’t Assume; Be Systematic with Diagnosis

Like many of you, this time of year I am usually asked to assemble a variety of items and gifts for my family members. In light of these requests, I have spent a significant amount of time analyzing why we waste so much time assembling, disassembling and re-assembling items out of an unwillingness to simply read the instructions. Often this process results in leftover spare parts and frustration.

Blame it on Missing Harness Retaining Clips

The subject vehicle that was fitted with one of our remanufactured transmissions six months prior showed up at one of our repair locations recently, with the customer concern of an intermittent bumpy 1-2 shift, and a low-power lugging sensation along with a CEL on. While performing our initial evaluation, we found a P1860 code stored in history, but not current. During the road test the truck was working well with no clear signs of what set the DTC, but after several minutes of driving it started to act up. The TCC was applying right on top of the 1-2 shift, but according to the scan-tool data, was not being commanded on by the ECU.

Understanding 4L80-E Overdrive Clutch Failure

Wintertime typically equals a parking lot full of snowplow trucks. Sometimes they represent repeat business — of the bad kind — but most of the time, new work.

Multiple Issues Demonstrate Need for Thorough Diagnosis

Our story begins with a 1995 Chevrolet K1500 with a 6.5-liter diesel and a 4L80 E transmission that was brought into our shop by one of our wholesale customers. The customer had replaced the transmission in this vehicle with one of our remanufactured units. After the installation, the customer said the check engine light came on and the vehicle was setting multiple transmission codes, and that when the truck was going around a left-hand turn the transmission would neutralize.

Salvaging Late-Model 4L80-E Stators

As if having another wave of cracking pistons was not bad enough, the problems with the second-generation stators were even worse. The first issue rebuilders noticed was excessive wear in the stator housing where the roller-clutch inner race contacts the housing. On some converters, the inner race would wear its way out through the stator housing and into the impeller hub. This was especially problematic because – unlike in the first generation – the impeller side of the stator was not a removable stator cap.

History Repeats Itself

Most torque-converter rebuilders routinely deal with the undersize pilots on GM 298mm converters. It is common either to build up the pilot by welding and then re-machine, or to sleeve the pilot area. The issue is so widespread that the repair is a requirement on the OE remanufactured-converter process.

Diagnosing the Elusive No Reverse with the 4L80-E

Diagnosing a shift concern can be easy, as long as you understand some basic techniques to help get to the root of the problem. A reliable and orderly diagnostic approach is splitting the circuits. Splitting the circuits means separating and analyzing the hydraulic, electrical and mechanical issues that could create the problem. Let’s follow through the flow of diagnosis in this one together. Make sure you have the following on hand: a line-pressure-test spec sheet with test-port locations, and a clutch and band chart to help eliminate other areas that may be associated with the problem shift.

More Torque-Converter Forensics

Try to imagine the difficult job tech-line technicians have. They are asked to decipher bits and pieces of information that may not be accurate and then come up with the correct answer. The information the technicians collected for the following two scenarios seemed to be as different as night and day. The information even originated in different countries. The amazing thing about these different complaints and symptoms was that they all had the same root cause.

Do You Speak My Language?

The local transmission shop, in an effort to eliminate a code 68, replaced the input- and output-speed sensors, 2-3 solenoid and the transmission-range pressure switch (later you will see why). It also replaced the internal harness and external connector because they where “old and fitted loose.” When the problem persisted, the local transmission shop sent the vehicle to us.