Which Planet Are You On? - Transmission Digest

Which Planet Are You On?

As most rebuilders know, in 1997 the 4L80-E went to a center-gearbox lubrication system by relocating the cooler return line from the pump to the center support. As a result, many internal hard parts were redesigned to accommodate this new lubrication system, as illustrated in figures 1 through 5 taken from an ATSG bulletin.

Which Planet Are You On?

Technically Speaking

Subject: Redesign of internal parts to accommodate center-lube system
Unit: GM 4L80-E
Essential Reading: Rebuilder, Diagnostician
Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

Technically Speaking

  • Subject: Redesign of internal parts to accommodate center-lube system
  • Unit: GM 4L80-E
  • Essential Reading: Rebuilder, Diagnostician
  • Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

As most rebuilders know, in 1997 the 4L80-E went to a center-gearbox lubrication system by relocating the cooler return line from the pump to the center support. As a result, many internal hard parts were redesigned to accommodate this new lubrication system, as illustrated in figures 1 through 5 taken from an ATSG bulletin.

Then, in 1999, the planetary pinions for both front and rear carriers increased in thickness by 0.075 inch for increased durability (Figure 6). With the increased thickness of the pinion gears, the sun gear needed to be lifted by 0.041 inch so it could run centered in the thicker pinion gears.

A 0.041-inch shim added between the thrust bearing and the rear internal ring gear gave the sun gear the lift it needed (Figure 7). The sun-gear shaft also changed to make room for this 0.041-inch lift (Figure 8). So now there are three different sun-gear shafts, with the second design being in use for only the 1997 and 1998 center-lube design.

It is imperative that you understand these part changes so that you use the correct parts when servicing this transmission. One example of using incorrect parts that often comes up can produce a stalling or stumbling of the engine when the shifter is placed into overdrive or reverse. This occurs when a non-center-lube sun-gear shaft is used in a center-lube system. The sun-gear shafts used in 1997 and later center-lube transmissions have a shortened bushing journal compared with the earlier design. Using the earlier-design shaft with the longer bushing journal will cause a restriction in the oil-cooler/lube circuit, producing increased pressure in the converter and making the clutch drag.

Another situation that occurs frequently is incorrect interchange of parts between first-design (1997-98) and second-design (1999 and up) center-lube units. This will cause a variety of different incorrect gear-train stack-ups. One example is using a 1997-98 sun-gear shaft with 1999 and later parts. This will cause the sun-gear shaft’s bushing journal to protrude above the bushing by nearly 0.90 inch (Figure 9). If the opposite occurs (1999 sun-gear shaft with 1997-98 parts), the bushing journal is nearly flush (Figure 9). When all the correct parts are used, the bushing journal should protrude above the bushing by about 0.050 inch, also shown in Figure 9.

Similar problems can occur if an incorrect center support or rear planetary carrier is used. Figure 10 shows how to distinguish 1997-98 center-lube center supports from 1999 and later supports. As you will see, there is a difference in height of about 0.050 inch between the two. But when it comes to the rear planetary carrier, determining the correct use requires attention to a small but very important detail.

As mentioned at the beginning of this article, in 1999 the planetary pinions for both front and rear carriers increased in thickness by 0.075 inch for durability reasons. The original pinion-gear thickness is about 0.710 inch, which changed to 0.785 inch for 1999 and later carriers. The front carrier pinions can be easily measured with a micrometer for thickness verification. The rear carrier is a bit more difficult. The easiest way, as I said, is by observing a small but very important detail. By simply looking at the carrier design between the pinion gears (figures 11, 12 and 13) you can quickly see the differences between a typical 400 rear carrier, a 1991-98 4L80-E carrier and the 1999 and later rear carriers. With these side-by-side comparisons, the differences speak for themselves.

With all these subtle differences dimensionally, you can see how easy it is to use incorrect parts and the various possibilities in clearance problems they can produce. They could cause too much, or maybe not enough, gearbox space. So make sure you know which planet you are on and prevent yourself from being lost in space or outer (out of) space!

Many thanks to the good folks at Hardparts For Transmissions, who shared their knowledge and pictures of the carriers used in this article.

You May Also Like

Sherlock Holmes Approach to an AB60 No-Move Situation

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult.  Using scopes provides

ab60

The effectiveness in diagnosing automatic transmission malfunctions is an art form. Although there are similarities among the wide varieties of transmissions on the road, each transmission has its own peculiarities. Aside from having mechanical, hydraulic, and electrical hardware systems to contend with, software/programming issues and various vehicle platforms make diagnostics much more difficult. 

GM 6T40 Pump Identification Guide

The 6T40 was introduced in 2008 for General Motors front-wheel-drive cars in the Chevrolet Malibu and has gone through several changes throughout its three generations, specifically in the pump area. The 6T40 is closely related to the more lightweight 6T30 and the heavier duty 6T45 and 6T50. Generation one started phasing out during the 2012

Seeing the Forest AND the Trees

They say that the proverbial phrase “I couldn’t see the forest for the trees” means that a person or organization cannot see the big picture because it focuses too much on the details. Related Articles – 4L60E Harsh 1-2 Shift – TASC Force Tips: Diagnosing 8L45 & 8L90 Shift Complaints – TASC Force Tips: Hydraulics

The Manifold Pipeway

The Honda six-speed transmission has been on the bench of many specialty shops for one reason or another (figure 1). But, for those of you who have yet to lay your hands on one, mounted on the upper side of the unit is one of the largest, if not the largest solenoid and pressure switch

8L90 Vacuum Testing

Below are the diagrams for vacuum testing GM 8L90 transmissions. Note: OE valves are shown in rest position and should be tested in rest position unless otherwise indicated. Test locations are pointed to with an arrow. Springs are not shown for visual clarity. A low vacuum reading indicates wear. For specific vacuum test information, refer

Other Posts

American Powertrain adds GearStar automatic transmissions for Ford, Chevy, Mopar

American Powertrain announced that it has added GearStar automatic transmissions for Ford, Chevy, and Mopar. Transmissions include the 4L60E for SBC, BBC and early LT engines; the 4L65E for LS and late LT engines; SB and BB Mopar and Gen III engines; the 4L80E for LS engines; and late model LTs and the 4R70W for Ford small block engines.  Related Articles

The Subaru mystery burn

The Subaru TR580 transmission is known for having torque converter clutch solenoid failures. An example of this can be seen in Figures 1 (above) and 2 (below). Related Articles – The torque converter can of worms: Lockup and aftermarket programming – Shift Pointers: Where’s that fluid leak coming from? – Multitasking: Sorting out multiple issues

Tech-Speak-May-Figure-1-1400
Ford 8F24 mechanical diode failure

Mechanical diode failure in automatic transmissions is not uncommon. As far back as the AODE/4R70 shops have seen this type of failure. In April 2022 an article was published in Transmission Digest called, “The ins and outs of the Hydraulic Selectable One-Way Clutch (SOWC).” This article provided photos of the type of damage this style

Tech-Speak-April-Figure-1-1400
Sometimes, a diagnostic code is all you need

With ATSG having the opportunity to help shops solve problems, sometimes we get faced with some real doozies. A shop will call and give us a laundry list of DTCs, leaving us to think someone must have a bulkhead connector unplugged. We then go through the arduous task of deciding which codes prompted other codes