O/T Pickup shot craps

NEKS · May 7, 2019

Took some cattle to the sale barn with gooseneck trailer. Its a 92 6.5 diesel with a 4L80-E tranmission. It would shift throught the other gears alrght. It would not move in low range. Just like you put the park brake on. Hauled some today and now I have low range again, but no reverse. What is going on here. Didn't seem to slip or nothing.

MSM · May 7, 2019

Probably the shift solenoids in the valve body. Might get by replacing the valve body but it is doubtful. It usually messes up the clutch packs

Sprint 6 · May 8, 2019

You have a mechanical internal issue. A 4L80E will have 3rd and reverse without any electrical input. No reverse means mechanical failure. I'll have to find my 4L80E manual to give you a likely area.

SVcummins · May 8, 2019

I have a service manual on cd for a sick five you can have if you tell me where to ship it provided that I can find it

Dune Country · May 8, 2019

what kind of front hubs do you have?
is low range a automatic 4x4 lockup?
if so might be a problem in the front pumpkin.

Glenn/Mn · May 8, 2019

Before you get side tracked checking other things mentioned, with the truck cool double check for tranny oil in the plastic radiator overflow tank, if you see some there, the tranny cooler inside the radiator had failed and any amount of moisture in the tranny means you need a rebuild, there is a update available if it has not been done already, the 4l80e is said to be bullet proof it is just lacking another set of gears since the national speed limit was raised to 70 from 55

Glenn/Mn · May 8, 2019

Before you get side tracked checking other things mentioned, with the truck cool double check for tranny oil in the plastic radiator overflow tank, if you see some there, the tranny cooler inside the radiator had failed and any amount of moisture in the tranny means you need a rebuild, there is a update available if it has not been done already, the 4l80e is said to be bullet proof it is just lacking another set of gears since the national speed limit was raised to 70 from 55

4play · May 8, 2019

When you said it was locked in the "L" position, did it take off in 1st gear in the others positions (O/D, D, 2 ). Also since you have low-1st gear back, check to see if you have engine braking after you let off the throttle. Basically shift to L, speed up to 10-15mph and let off the throttle, does the eng rpm drop to idle, or does it slowly decrease with speed.

Basically the only difference between 1st gear and manually selected 1st is the application of the rear band (low/rev band) this band is applied to allow engine braking. This band is also applied for Reverse gear. This problem is one of the more common failure areas for this transmission

O/T Pickup shot craps

NEKS

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MSM

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Sprint 6

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SVcummins

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Dune Country

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Glenn/Mn

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Glenn/Mn

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4play

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