Question about 1994 Chevrolet K1500

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4L60E slipping and not locking up

Hello, I have a 94 Chevrolet 1500 (4X4 – 5.7 liter) with the 4L60E tranny. I had the tranny rebuilt a couple months ago. At the time, I had the upgrades done (servo, 3-4 clutch pack) to minimize the normal problems the 4L60E has been known to have. However, none of the electrical components were replaced. So, they are from my previous tranny that had 200,000+ miles on it.

A couple weeks ago, while driving at 75 mph on the freeway, the tranny instantly began to slip. As I slowed down, I found that 3rd gear was also slipping. After reaching slower speeds (against my desire at the time), I found that manual 1st and 2nd were fine. After getting off the freeway, I played with it and found that I could shift from manual 1 to manual 2 with no slippage whatsoever. I also found that occasionally I could accelerate to 45-50 mph (with the throttle under even pressure) in manual 2 and then I could shift into overdrive and the tranny would operate normally. This was occasionally. Most of the time, no matter what I shifted into from manual 2 it would simply slip (allowing the truck to accelerate to a max speed of 55 mph at 3500 rpm).

The tranny is under warranty. But, I’ve had limited success in getting an appointment to have it looked at. So, I’m forced to forge ahead on my own. I have driven the truck very little since the tranny failure. But, I have noticed that the times I have driven it the problem has gotten worse. In fact, this morning manual 1 and 2 were also slipping badly and my top speed was 25mph in all gears.

In talking to the guy that rebuilt the tranny, he suspected that the problem was electrical (this was based on the problem being intermittent).

Any ideas of what electrical component could cause the described problem? Thanks in advance for your input.

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  • Chris Hall
    Chris Hall Dec 31, 2008

    Followed your instructions and it did not change anything.

  • Chris Hall
    Chris Hall Dec 31, 2008

    I have no "check engine" codes. Also, I have a Genysis ECM scanner and get no codes (this unit connects under the dash, not directly to the tranny).

  • Chris Hall
    Chris Hall Jan 02, 2009

    Ok. Took it for a short drive. The tranny has gotten much worse and now will not lock up in any gear. Still no codes.


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Very well could be taht the Computer is not recieving the Shift codes Correctly. Just for an Easy Solution, Remove the ECM Fuse from the Fuse panel for 2 or 3 Minutes to Reset the Computer and let me know what you get.

Posted on Dec 31, 2008

  • 1 more comment 
  • Travis Humphries
    Travis Humphries Dec 31, 2008

    Ok. The next step would be to find a Scanner that you can hook up and get Trouble codes with. Not Cheap But, Cheaper than a 95.00 and Hour Mechanic. Can find out a LOT with Trouble Codes.

  • Travis Humphries
    Travis Humphries Dec 31, 2008

    When you pulled the ECM Fuse it Erased all the Error Codes. Can you Drive it for a Min and get Fresh codes? Just up and down the Drive would be Enough.

  • Travis Humphries
    Travis Humphries Jan 02, 2009

    Ok, This is Definately a Mechanical Problem in the Transmission Since you have tried all other options. The guy who rebuilt it needs to give an Explanation of the Parts used and Dianose or Fix what ever is Incorrect. Sorry I could not Help ya More!


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