Automatic Trans Diagnostic Flow Chart Needed

[dave]

Here’s the scoop: I’m in a trans class and my teacher is an idiot. Q: Does anyone out there have a good general flowchart of what to do when an A/T comes in for diagnosis and/or repair?

I have found this one for kia transmissions; however, the chart simply resolves to either “replace transmission” or “call kia tech line” which are cop-out options. I need something that directs me to apply problems, stuck valve, torque converter problem, burnt clutches, hardware failure, leaking seals or bad valve body gasket for example. Hopefully there is something out there the would incorporate using bi-directional communication to actuate some of the various transmission components.

This is what I got, but it is definitely not the best:

Attachments:

• transflow.jpg

Topic

[John B Kobberstad]

A good scanner could probably do it. My Snap On MT2500 allows me to do testing on my 1990 Caravan A604 transmission.

[SpawnedX]

That chart is absolutely worthless and makes everything so much more difficult than it has to be.

You should look up the Operation Table in the service manual for the transmission you are working on. Makes life so much more simple.

Here is one for the Subaru 4EAT Phase 2:

How does it work?

O = Engaged Component

Gray Boxes = Subset of gears for the current selector position.

Let’s say 2nd and 4th do not work. Let’s look at what we know 2nd and 4th only share one component, the 2-4 brake. Boom, done. But the chart can also confirm this for us.

4th uses the 2-4 brake and high clutch. 3rd uses the high clutch and low clutch. Does 3rd work? Then the high clutch must work. 2-4 brake is all that is left to be the problem.

2nd uses the low clutch. 3rd uses the high clutch and low clutch. We already know 3rd works. The low clutch must work. 2-4 brake is all that is left to be the problem.

—

Next step? Is it an internal mechanical failure or does it have to do with the electronics behind the solenoid, or the solenoid itself? Find the hydraulic passage for the 2-4 brake, take your blow gun, blow air in it.

Did you hear it clunk when you put air to it? Did it clunk back when you removed the air? Yes? Issue lies with the solenoid or the electrical / control unit in charge of triggering it.

Didn’t clunk? Internal mechanical issue. Overhaul time.

—

It’s really that simple, lol.

Torque converter locking up? Does it intermittently feel like you just drove over a rumble strip? TC is locking up.

Remember, always start with the two most basic steps, verify condition and complete visual inspection for broken components, such as the cable, and dirty or low fluid (or none).

I hope this is somewhat helpful.

[dave]

This is probably the best explanation of how to approach auto trans repairt that I have been taught thus far 🙂 It seems a lot of diagnostics can be done while the trans is on the vehicle w/ the pan dropped. 🙂

Thank you very much :side:

[Author]

Replies