2002 Avalanche Transmission + Problems





The 2002 Chevrolet Avalanche came with two automatic transmissions.  It had no manual transmission option.  The standard transmission for these trucks was the 4L60E.  The heavy duty transmission option was the 4L80E.  They are both four speed overdrive transmissions.  Most of these trucks are going to have the 4L60E since that was the transmission that came behind the 5.3.

 

Identifying Which Transmission is in Your 2002 Avalanche

It is very easy to determine which transmission is in you 2002 Avalanche.  Utilizing GM’s RPO codes is a huge time saver.  Open the glove compartment.  You’ll see a little sticker in there that’s a little bit larger than a credit card.  You’re going to be looking for one of these two alpha numeric codes in there:

  • M30-4L60E
  • MN8– 4L80E

Here’s a full list of RPO codes by year, in case you were wondering what any of the other numbers and letters meant.

RPO Codes Avalanche Fan Club

 

If the transmission is out of the truck and you’re trying to determine what make or model it came from, or even if you’re looking at the right transmission, go ahead and check out the in depth transmission identification articles on this site.  Start with the 4L60E.  They are a lot more common.

4L60E Identification

4L80E Identification



2002 Chevy Avalanche Transmission Problems

This section on Chevrolet Avalanche transmission problems is broken into two sections.  The first is common more top level troubleshooting.  The second will be slightly more technical.  If you are having trouble now, stick with the first section.  If you would like to troubleshoot from a transmission specific article check these out:

4L60E Transmission Problems

4L80E Transmission Problems

No Reverse

In the event that the truck refuses to move, it can be a few different problems.  The first would be that the clutches that engage reverse have simply worn out.  It could also be something to do with the valve body.  It could either be full of crud and not functioning properly.

Shudder from 1’st to Second Gear

If your avalanche is experiencing a shudder when going from first to second, particularly under load, you may have an issue with the 1-2 accumulator.  Take a look and make sure the piston isn’t broken or the spring isn’t cracked.

Harsh Shift

When it feels like the transmission is shifting a lot harsher than normal, it is often an issue with the throttle position sensor.  The transmission will shift harder when it’s under heavier throttle.  When it can’t tell how far you’ve pressed the throttle, it’ll default to harsher shifts as a way of protecting itself from wear and tear until you can have it looked at.  This is a common transmission problem with the 02 Avalanche.

Not Moving in Any Gear

If you find that your 2002 Avalanche just isn’t going anywhere, the first thing to do is make sure that it’s not low on transmission fluid.  Has it been behaving oddly before it finally stopped working at all?  That’s a pretty good indication.

It could also be that the linkage is broken.  You’ll usually be able to tell this because the gear shifter will move a little too freely.

Another good possibility is that the driveshaft fell out and you didn’t notice.  This not moving in any gear section is presented in a most likely to least likely order.  It’s not going to hurt to duck down and look anyway.

The torque converter bolts could have sheered or come out too, but this is only likely if you’ve replaced the transmission and didn’t use OE bolts and loctite.

More on this:  Automatic Transmission Wont Go in Gear

Second and Third Gear Only

Another common transmission problem to the 2002 Chevy Avalanche is when it goes into limp mode.  Limp mode is nothing more than the transmission trying to save itself from mortal danger.  It usually occurs if it’s not getting a signal from the PCM.  But there are many other issues that cause it as well.

The first thing to do is get under the truck and see if the wiring harness is plugged in.  If it is go ahead and look to see if the harness is plugged in.  It’s on the passenger side and plugs into the transmission right above the pan.  It is about the size of a vacuum hose where it meets the transmission.

More on this:  Limp Mode Causes and Solutions

2002 Avalanche Transmission Problems

This plugin is where the wiring harness meets the transmission.

 

What type of transmission fluid does a 2002 Avalanche use?

The 2002 Avalanche uses Dexron Mercon, which supersedes all factory Mercon fills for GM vehicles.




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