10 GEARS October/November 2013

This is a problem that goes like this:

“I built this 5R55E unit two months ago and it came back bind-ing up in reverse and manual low. I’ve got it apart on the bench and don’t see anything wrong. Everything air checks good. Help!”

This is a very common problem and is usually centered around the ser-vos. This problem has been with us since the A4LD and has continued on through the 4R44E, 5R55E, and into the 5R55W, S and N models.

Hydraulic or Mechanical?Any time you’re dealing with a

bind up, your first step should always be to determine whether the problem is hydraulic or mechanical.

In most of these cases, the problem is mechanical and caused by the servo delaminating and getting stuck in the bore (Figure 1). Of course you need to make sure you check the parking pawl isn’t being engaged by some misalign-ment issue first.

Here’s a quick test to figure out

what’s causing the bind up. Put the vehicle on a lift.

• Loosen both band adjusting bolt locknuts.

• Have a person in the vehicle start the engine, hold the brakes on, and put the transmission into gear.

• Slowly release the brake pedal until the transmission binds up.

• Check to see if one of the band adjustment bolts is tight.

The tight bolt is the adjustment for the band that’s being applied and is causing the bindup. The second part of the test is to turn the engine off. If the bolt adjustment goes lose, you have a hydraulic problem. If it stays tight, look at the delaminating servo as the failure, this is usually the problem.

STREET SMART

by Mike Brownmembers.atra.com

Bound by the Bond!

Figure 1

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12 GEARS October/November 2013

When the servo seals become delaminated it can roll over, causing it to bind in the case. As you can see in the photo, the damaged to the piston causes it to bind in the bore, holding the band on.

If you’ve determined the problem is cause by something hydraulic then look for a problem in the valve body. Begin by examining the gaskets for damage or blowouts. This could have been caused by high line pressure, or warping in the valve body or transmis-sion case. Use a straightedge to make sure the valve body and transmission case are flat.

One last tidbit: we often see a wrong gear start diagnosed as a bind up. The most common problem is the EPC plug (figure 2). Check the EPC

plug for wear. Some technicians like to turn the EPC adjustment in to raise pressure which if overdone could cause wrong gear starts.

What happens is the 1-2 (4R55E) or 2-3 (5R55E) shift valve plug becomes loose due to wear. This allows EPC pressure to flow past the end plug and stroke the shift valve, causing wrong gear starts.

I know it sounds like a lot of work, but take the valve body com-pletely apart. Don’t just pick the valves; make sure no valves are sticking.

Anytime you’re working with an aluminum valve body, it’s very impor-tant to torque it correctly. Overtorquing the valve body bolts can pinch a valve and prevent it from moving freely.

Then, after you remove it, there won’t appear to be anything wrong.

So before you pull the transmis-sion and disassemble it for a bind on this unit, take the time to think about what can be causing the problem… or, more appropriately, what’s not causing it. Sometimes a couple simple tests can save you a lot of time and money.

And that’s not just smart… that’s street smart!

Bound by the Bond!

Figure 2

EPC Plug

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