4L80E

[DaveEh]

Howdy.

Have a 1997 LB 6.5 TD TWD(two wheel drive) and pull a 30' fifth wheel. Have approx 206000kms (129,000 miles) and the transmission is slow to shift into high OD. Takes about 1.6km or 1 mile before it shifts. All other shifts are fine. Had tranny flushed and repolace fluid with synthetic last summer. Once it has been drive for any distance then it does not have the same problem. Seems to be only the first drive of the day. When pulling the trailer this does not seem to happen as, I woulld think the tranny heats up quicker. If I were to let it idle for a few minutes before take off seems ok. Any suggestions. Thanks :eek:

[65turboman]

Hi. My 1995 6.5L and my 1999 5.7L gas trucks have both had this slight delay before shifting into over-drive with the 4L80E on the first cold start of the day. After a few minutes of warm up idle they shift in quickly, not sure what causes the delay.

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1995 Regular cab 2500

[rjschoolcraft]

It may not be that it is slow to shift into OD, but slow for the converter clutch to engage. The converter clutch will not engage until the oil temperature is over 130F (I think that's the number). Usually, you will feel the 1-2, 2-3 shift, then the lock-up clutch, then the 3-4 shift. When the tranny is cold, you should feel 1-2, 2-3, 3-4 then lock-up clutch once fluid temp is above 130F.

I only notice this when it is really cold with my truck, but it could just be differences in calibration of the sensors.

[dstoops]

This delayed cold T/C lockup sounds entirely normal. Mine has behaved that way since "day one" I believe the logic is that a cold engine may not be ready to "lug" that high final drive ratio.
Dean

[DaveEh]

Howdy.

Thanks to all. Maybe I am just concerned as the miles (kms) build up. Hope this is all that it is. Good luck to all.