Checking Valve Bodies With a Homemade Hydraulic Test Stand - Transmission Digest

Checking Valve Bodies With a Homemade Hydraulic Test Stand

There are several ways to check valve bodies for wear: wet air tests, wiggle tests, deflection measurements, vacuum gauges or the hydraulic test stand, the last of which is the focus of this article. In our shop I needed to be able to measure the leakage accurately and record the findings before and after the repair, and be able to print the results on paper to hand to my customers.
Checking Valve Bodies With a Homemade Hydraulic Test Stand

TASC Force Tips

Author: Rick Hoffman

TASC Force Tips

  • Author: Rick Hoffman

There are several ways to check valve bodies for wear: wet air tests, wiggle tests, deflection measurements, vacuum gauges or the hydraulic test stand, the last of which is the focus of this article. In our shop I needed to be able to measure the leakage accurately and record the findings before and after the repair, and be able to print the results on paper to hand to my customers.

I’ve been using a Zoom Technologies AMI hydraulic-circuit analyzer for the past two years on all transmissions before and after any repairs. This machine will find very small leaks in any circuit. But it lacks the ability to record and print the results. The hoses and operating valve are too clumsy to use on valve bodies. So it was time to modify the machine.

A trip to the hardware store yielded all the fittings, adapters and plastic tubing I needed to set up the following test procedures. I installed a tee fitting in the main feed line and attached a short piece of tubing to the fitting and installed a Sonnaflow™ in the line (see Figure 1). I connected a 6-inch piece of line to the Sonnaflow™ and attached a rubber-tipped blowgun to it. Then I connected the Sonnaflow™ to my Snap-On Vantage graphing meter (see Figure 2). The Sonnaflow will monitor oil flow accurately down to 0.5 milliliter per minute, so the Vantage obtains the best resolution in the graphing mode set at 50 Hz or less and the 1-second interval.

I can now read and record the flow in hertz. The flow is any leakage past a valve spool, which is isolated by the test plate. I can freeze and save the screen on the Vantage, which can be downloaded to the computer and printed for the customer.

Once this was done, I started to set a standard to check for leakage. Free flow on my machine is 2.5 Hz. A good tight circuit will read 0.4 Hz. Any circuit that flows more than 1.0 Hz is in need of a repair. Whether replacing a boost valve and sleeve or reaming a bore for an oversize valve, I can check before and after the repair to verify a fix.

An example is the 4T60-E TCC apply valve. Leakage at the largest spool will cause a no-lockup condition, even if the scan tool says TCC enable yes but the valve is not stroked. Leakage at the other lands can cause no lockup when hot, DTC 740, torque-converter shudder and burn-up of lockup plate. After repair of this complaint, a modified/closed solenoid can be installed. Pressure is applied to the TCC-signal passage and you can watch the valve stroke.

In AXODE, AODE, AX4N and CD4E units, converter shudder and reduced cooler flow can be traced to worn bypass/TCC control-valve lineups. This can be easily checked for wear by isolating and checking for leakage. Figure 3 shows a bypass clutch-control sleeve and plunger valve being tested for leakage. This bore is showing a 1.5-Hz leak. I replaced the sleeve and plunger assembly and rechecked the leakage. This unit came in with overheated planets.

In the 4L60-E, wear at the TCC regulator and the isolator valve can cause DTC 1870 codes and on later-model units can cause unit failure. This can be checked easily by isolating the circuit and checking for leakage. In 1991-94 units, isolator-valve wear will exhaust second-gear oil (see Figure 4). The TCC solenoid in the pump will not receive sufficient converter-clutch-signal oil and will create a no-lockup condition. In 1993-97 PWM units, isolator wear will exhaust AFL PWM boost pressure (see Figure 5), causing slipping converter clutch and failure of the 3-4 clutch.

Figure 6 shows a 4L60-E TCC regulator valve being tested. This bore is showing a 1.85-Hz leakage. After removing the valve train, I reamed the valve body and installed a Sonnax TCC regulator-valve kit. Leakage was checked again and the circuit now showed minimal leakage. This valve-body bore is now properly repaired. Pinning this valve will not correct leakage.

This equipment is not a valve-body machine, but it does allow the operator to quickly and accurately test valve bodies for wear before and after any repairs. This will reduce comebacks and increase the quality of your shop’s work.

Another method of testing substitutes a vacuum pump for the hydraulic pump. A good vacuum pump such as an air-conditioning evacuation pump or an air-over-vacuum motor can isolate oil loss past a spool. Using a plate similar to the one mentioned, fitted with a tee to the pump and vacuum gauge, you can “gap”-test the circuit. In theory, this is no different from the hydraulic test described, except for the absence of pressure and mess. The lack of vacuum pulled at the valve-to-bore clearance is similar to vacuum tests on piston rings and valve seats. The great part of this test is the relatively low cost of equipment and identification without disassembly. A negative of vacuum testing is the inability to test Teflon seals, since they require fluid to lift them.

If you have a vacuum source that pulls to 30 inches in one second or less, a rule of thumb for very good or normal tolerance is 26 inches and above. A reading of 22-24 inches means the valve body is marginal and will have signs of polish or scoring. If the test results are 20 inches or less, it must be fixed.

Rick Hoffman is the owner of Custom Transmissions in Bethel, Ohio. The TASC Force (Technical Automotive Specialties Committee) is a group of recognized industry technical specialists, transmission rebuilders and Sonnax Industries Inc. technicians.

You May Also Like

Trying to Stop the Wheel Hop on Ford Edge with 6F50 Transmission

The 2014 Ford Edge SEL with a 3.5L engine (figure 1) and a 6F50 transmission can also be equipped with an AWD system. This would include a Power Transfer Unit (PTU) attached to the transmission with a rear driveshaft going to the Read Differential Unit (RDU). The RDU comprises a differential assembly along with a

The 2014 Ford Edge SEL with a 3.5L engine (figure 1) and a 6F50 transmission can also be equipped with an AWD system. This would include a Power Transfer Unit (PTU) attached to the transmission with a rear driveshaft going to the Read Differential Unit (RDU). The RDU comprises a differential assembly along with a viscous coupling assembly controlled by an Active Torque Control (ATC) coupling solenoid. The system is designed to monitor vehicle conditions continuously and seamlessly adjust torque distribution between the front and rear wheels. When it is functioning correctly, there should be no perception of this taking place when launching or driving the vehicle. 

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.  Related Articles –

ab60
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 – TASC Force Tips: Hydraulics Fundamentals: Check Valves – Shift Pointers: Mazda Sensitive to Pressure – Transmission Testing & Repairs:

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

Other Posts
GM 9T series: Critical wear areas, vacuum test locations

Sonnax has provided the following guide on critical wear areas and vacuum test locations for the GM 9T series of transmissions. Technicians working on these models should find this guide helpful. Related Articles – Shift Pointers: Sometimes, a repair needs a little more push – Less is more with cordless work lights – Are cell

TASC-Tip-1400
The torque converter can of worms: Lockup and aftermarket programming

Lockup torque converters have been around now for some time. They came into production around the time when fuel mileage demands were put into effect by the government, and the auto manufacturers needed to do something to better connect the fluid coupling (torque converter) of the automatic transmission to the motor. By doing this, OEMs

tascfeature-1400
Watch out for high pressure in GM 8L45, 8L90 valve bodies

Hey now! Oh boy, do I have a fun failure to share with you and warn you about today! Related Articles – The powertrain aftermarket: Growing and global – 6R80 whirring noise: TCC slip or engine surge? – The Subaru mystery burn Have you encountered a crack in the worm tracks in your GM 8L45

Shift of the shaft: Diagnosing Chrysler 48RE manual shaft issues

The TorqueFlite transmission has been around since mid-to-late 1950s. There have been many changes surrounding the manual shaft and rooster comb through the years. This transmission shaft controls the position of the manual valve that directs oil for the gear ranges, but it also is used for a Reverse light control as well as Park/Neutral