Double Trouble - Transmission Digest

Double Trouble

In today's world of automatic transmissions we see several different types of solenoids being used depending on the strategy the engineer chose to employ. There are the typical on/off solenoids that could be normally closed or normally open. And then there are PWM solenoids, normally applied or normally vented.

Double Trouble

Technically Speaking

Subject: Solenoid modulating valves
Units: 722.9, AS68RC, RE5R05A, 09D
Essential Reading: Rebuilder, Diagnostician, R & R
Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

Technically Speaking

  • Subject: Solenoid modulating valves
  • Units: 722.9, AS68RC, RE5R05A, 09D
  • Essential Reading: Rebuilder, Diagnostician, R & R
  • Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

In today’s world of automatic transmissions we see several different types of solenoids being used depending on the strategy the engineer chose to employ. There are the typical on/off solenoids that could be normally closed or normally open. And then there are PWM solenoids, normally applied or normally vented.

Some of these solenoids are fed with line pressure through an orifice so its flow rate is less than the exhaust rate. When the solenoid blocks the exhaust, pressure builds to stroke a valve. Other solenoids are fed un-orificed line pressure, which a PWM solenoid could used to directly control the application and release of a clutch.

Then there are solenoids that are supplied with regulated pressure from a modulating valve. The modulating valve typically is fed with line pressure, which it regulates down to a lower pressure to be used to feed the solenoid. In many ways, this modulator valve acts as an over-glorified orifice. The modulating valve controls the flow rate to the solenoid so that it is less than the exhaust rate. Should this valve be compromised in any way, it could either starve the solenoid of feed pressure or flood it with too much pressure.

In some instances, there are designs that require two modulating valves to sufficiently supply the increased number of solenoids being used. The 722.9, AS68RC and RE5R05A transmissions are several such examples. Another is the 09D transmission.

As you can see in Figure 1, solenoid modulating valve A supplies regulated pressure to the TCC, line-pressure and K1-clutch control solenoids.

Figure 2 shows how solenoid modulating valve B supplies the B1, K2, K3, N88 and N89 solenoids.

We all should know by now how modulating valves wear the bore they live in (Figure 3).

So with these types of transmissions using two modulating valves we now have “double trouble” on our hands with solenoid feed supply (Figure 4). With the 09D transmission, the most-common complaint seems to be harsh shifting during acceleration through a 4-5, 6-4 and/or 5-3 shift. In many instances bumpy coast downshifts occur as well – a telltale sign of modulating-valve bore-wear problems requiring reaming and new valves or a complete new valve body.

Just a thought – it seems to me that once a flow rate can be determined, a simple orifice feed can be the modified fix via a redesigned spacer plate or a bore-fit orifice.

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

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

10L80 and 10R80 pump gear differences

You may have seen an article in the August 2023 issue of Transmission Digest called “GM 10L80: A new kind of pump noise,” which goes over how the front cover housing in the 10L80 is fitted with a converter drive gear and idler gear. The idler gear drives the pump’s driven gear, and is press

Spotting different 68RFE designs through the years to avoid issues

The Chrysler 68RFE has had several changes through the years. Its four-speed predecessor began with a noisy solenoid pack identified by a black colored pass-through case connector (seen in Figure 1).  Related Articles – Going the extra mile: Proving your transmission repair suspicions – Diagnosing Ford 10R60, 10R80 and 10R140 series speed sensor issues – Jatco JF613E

Sometimes, you should sweat the small stuff

It’s a common phrase: There may have been a time when you worried about something, and someone who knew what you are going through said, “Hey, don’t sweat the small stuff.” Sometimes, this may be good advice. But other times, it may be wise to handle the small stuff before it becomes bigger “stuff.”  Related