# 2000 Chevy 2500HD 6.0 4x4 Tranny Problem



## chamonixvt (Dec 16, 2009)

Hoping someone can point me in the right direction on how to trouble shoot a tranny problem. 

Transmission would not shift out of first gear which led me to believe it was in need of a rebuild/replacement. So, purchased a used tranny through a friend who owns a body shop, got it installed, new filter & fluid, and it still has the same problem, it won't shift out of first gear. My buddy at the body shop is telling me it is an electrical problem 

Before potentially spending a lot of money with a tranny mechanic trying to figure out what is wrong, I thought I'd see if anyone out there might have an idea or suggestion or experience?

In the end, I'm likely heading to a tranny mechanic but I thought I'd give this a try.....

Thanks


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## B&B (Nov 4, 2006)

Very likely an electrical issue, especially considering you changed the entire trans.

When a 4L80E gets stuck in first only it's usually do to a broken/damaged wire to either the input or output speed sensor, or a bad sensor if you swapped them from the old trans. Need to check the wires with an OHM meter and the sensors too. Your trans shop can do these checks for you for minimal cost.


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## chamonixvt (Dec 16, 2009)

thanks for pointing me in the right direction. In the course of tracking down this problem we came across the neutral safety switch which had two of the connections melted. Could this be the cause of the tranny not shifting or do we need to continue searching? We have not put in the new switch yet, just got it today from the dealer.

Any help would be appreciated.


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## B&B (Nov 4, 2006)

chamonixvt;922572 said:


> thanks for pointing me in the right direction. In the course of tracking down this problem we came across the neutral safety switch which had two of the connections melted. Could this be the cause of the tranny not shifting or do we need to continue searching?
> 
> Any help would be appreciated.


Melted connectors? As in from excessive heat?


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## chamonixvt (Dec 16, 2009)

appears to be the case - excessive heat that is..


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## chamonixvt (Dec 16, 2009)

if it is from excessive heat, any idea what could have caused this? I'm at a loss.


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## 2COR517 (Oct 23, 2008)

Are the connectors melted, or does it look there is glue type stuff all over them? Can you post a pic?


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## chamonixvt (Dec 16, 2009)

My buddy and I both agree, melted as they are disfigured. Will try and post a pic tomorrow.

Like the quote about change in your post - quite accurate.


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## B&B (Nov 4, 2006)

If they're actually melted then replace the connectors along with the switch. Connectors can be purchased as pigtails from the dealer. Not inexpensive, but available.


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## chamonixvt (Dec 16, 2009)

Got the switch and connectors from the dealer just haven't had a chance to work on it as my buddy who has the skills works for a ski resort in their maintenance shop - planning on replacing today. I'm just an extra set of hands and a source of information through this site - which has been extremely helpful and saved a fair amount of time.

Do you think this is the cause of the shifting problem? Also, any idea how these could have melted?


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## GLSCPE (Dec 22, 2006)

LOL this is such an issue with these trucks!! I have replaced Neutral Safety Switches twice in three years on my Duramax/Allison. They get trashed, and start throwing range shift inhibited errors, and wont drop into any gear. When they work they are great, but it is a common problem!


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## B&B (Nov 4, 2006)

chamonixvt;923693 said:


> Got the switch and connectors from the dealer just haven't had a chance to work on it as my buddy who has the skills works for a ski resort in their maintenance shop - planning on replacing today. I'm just an extra set of hands and a source of information through this site - which has been extremely helpful and saved a fair amount of time.
> 
> Do you think this is the cause of the shifting problem? Also, any idea how these could have melted?


Excessive resistance in the connectors due to corrosion on the connectors or the switch itself are a contributor. Tapping in extra reverse lights into the stock reverse light circuit without using a relay to carry the extra load is the #1 killer.


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## Sydenstricker Landscaping (Dec 17, 2006)

B&B;924405 said:


> Excessive resistance in the connectors due to corrosion on the connectors or the switch itself are a contributor. Tapping in extra reverse lights into the stock reverse light circuit without using a relay to carry the extra load is the #1 killer.


Shyt better get mine on a separate wire harness with a switch then, lol


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## 2COR517 (Oct 23, 2008)

You won't be LOLing when you price those pigtails :laughing:

Nothing wrong with using the reverse lights for the "switch" just use a relay and pickup power from the trailer charge wire.


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