Saturday, February 04, 2012 Detailed Auto Topics
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Checking automatic transmission fluid is quite simple and straight forward, right? Well not really. Like so many things today, something that should be simple has become quite complex. The following is meant to serve as a guide to help simplify the process.

Procedures vary from one vehicle to another but certain things remain constant

  1. The vehicle must be at normal operating temperature. This requires at least ten minutes of driving.
  2. The vehicle has to be on a level surface.
  3. Before checking, start the vehicle and move the shifter slowly through all gears.
  4. Most vehicles are checked in Park, with the engine running and parking brake set.
  5. On vehicles with a dipstick, both sides of the stick should be read and the LOWEST reading is correct.
  6. If there is fluid on the stick, then a void, then more fluid, the LOWEST reading is correct.
  7. Check the reading at least twice, wiping the dipstick clean between readings.

Read both sides of the stick,  and watch for air gaps; this is full

Both sides of the dipstick read full.  This is an accurate reading, assuming above conditions are met.

transmission fluid is full on one side and low on the other, the low reading is the correct one

One side of the stick reads full, this is from splash.  The lower reading is the actual fluid level, assuming above conditions are observed.

transmission fluid below the gap is the correct reading

The lowest solid reading on the stick is the correct level.  The reading above the air gap is from splash and is not accurate.

Many automatic transmissions today no longer have a dipstick

The trend, by vehicle makers, appears to be eliminating automatic transmission dipsticks.  Special checking and filling procedures are often required.   The Ford Explorer 5R55(W, S and N) are common examples. Some require special tools and methods we cannot go into here. The following illustrations are for Ford and may be typical of others.

5R55 series fluid is checked by removing the small plug

In the bottom of the pan are two hex shaped nuts. The larger is the drain plug. The smaller, in the center of the larger, is the check and fill plug. When the small plug is removed, with the vehicle level and fully warmed, fluid will drip from the opening.

Inside view of the 5R55 series drain/check/fill plugs shows how it works

If the fluid is low, the small internally raised tube, will prevent if from coming out.  The proper amount will slowly drip and too much fluid will run out. A special tool is used to fill such a unit. Also be extremely careful when removing any external bolts. Some bolts appear to be fill plugs, but actually secure components within the transmission. Though they may look like a fill plug, removing them can create problems that may only be corrected by disassembling the transmission.

Installing only the proper fluid is as important as the checking procedure. There are dozens of transmission fluids on the market today. Using the improper fluid can cause shifting concerns, void a transmission's warranty and possibly damage the transmission.

You can always trust AGCO Automotive to check and service your transmission properly.  The right procedures, the right parts, professionally done, that's the AGCO way.



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