Dead 4x4, and/or dead 4L60?

idatahoe · Apr 17, 2026

Hi everyone,

It's been a while. Finally getting ready to do the swap. Picked up a 27 spline NP241C and pulled the studs from the original transfer case to put on the "new" case. One stud was an absolute bear, but all made it over.

I have a few questions before I proceed.

I'd like to have a working speedometer/odometer. I assume the transfer case output is used for that? The GMT800 connector is on the left, the GMT400 connector on the right. GMT400 connector is larger. Assuming this is my speedometer wiring, does anyone know of someone selling adapters, or where I could get pigtail to put this together? Unfortunately, I don't have any wiring harness parts.

I'm not concerned about the 4x4 actuation because I plan on using a cable setup for that.

What is this port with the red cover for? A breather?

What is the red marked and blue marked line? Blue marked one looks like maybe 3/16" or 1/4" hose.

I am assuming one is a breather, but confused at why I'm seeing two. Not sure what I should do here.

It looks like someone was in this NP241C before. Ideally I would go through it, but I'm starting to run out of time and am hoping for the best.

Thank you!

stutaeng · Apr 17, 2026

1. Yeah, just steal one of those connectors and cut/splice into your wiring.

2. Yes, that's a breather. I think it routes and terminates near the transmission top of the bellhousing. There's another breather for the transmission as well.

3. The red is the breather, looks like. Isn't the blue the cable for the transmission shifter? Doesn't that come from the floorboard?

5202500HD · May 10, 2026

idatahoe said:
Hi everyone,

I'll start in the past, before the question of the present.

2001 Tahoe, 4x4, 5.3. 181k miles or so. Visually good condition, inside and out.

A few weeks ago, I was coasting down a hill in neutral. Came up to the top of the hill, and tried to switch into drive at around 30 or 35mph. Accidentally put it into reverse, which immediately stalled the motor, so I put it back in neutral and coasted to a shop. Very stupid mistake! I'm used to transmissions that block you out of reverse.

Yesterday, my wife tried to drive it up our driveway with a good bit of snow on the ground. Transfer case had been working quite well, in auto mode, 4WD high, and 2WD (we've had the Tahoe for about a month and haven't tested everything yet.) 4WD lights were not working when she started it. She easily made it up to the (fairly long) driveway and lost power about 20 feet from the road. She tried to get 4WD to engage, but no lights on the buttons, and eventually a "service 4WD" message popped up. She said there was some grinding when shifting (it has always shifted perfectly.)

I made it back home, started it, and found absolutely no wheel spin. Shifted fine, but no output in any gear, forward, or reverse. Could not shift the transfercase. Had some grinding going into park.

I initially assumed that the 4L60 was blown, but one shop I talked to said that the output shaft must be spinning for parking to grind. Now I'm not so sure.

Some possibilities that come to mind:

4x4 is unrelated and differential blew.
Transmission is blown.
Transfer case is blown or in neutral.

Obviously, I need to check if the driveshaft(s) are turning, but I figured I'd start this thread and see if anyone can offer any insights.

Thank you!

I'm curious as to why you were coasting down a hill in the first place. Was there an issue? As a general rule you should not coast an automatic transmission while driving to avoid pump stress and failure and lack of transmission lubrication. Id stop doing that. From what it sounds like you only have a T-Case issue likely associated with an actuator/solenoid or similar electrical issue. Anyways there's a few good shops in the Fruitland/Ontario area on either side of the Snake.

idatahoe · May 30, 2026

Thank you for your replies!

You're right about that one cable going to the transmission... Not sure how I got that confused.

As far as coasting goes, it was just for mileage reasons. But it sounds like it was a bad idea. I didn't realize coasting in neutral, in an automatic, could cause issues even just from the pump.

I'm actually quite a ways north of Fruitland/Ontario.

--

Got the swap done! Well, most of it anyway. There's a clearance issue with that red-covered breather and a bracket that I didn't forsee. Breather tube barely fits on and is pretty pinched.

I found a connector and wired it up. In testing, I had the speedometer working. After taping it all up, I must've had a bad connection and it's no longer working.

Still needs a shifter assembly, the front actuator sorted, and front driveshaft. At least I can drive it now (in the summer, anyway.)

AuroraGirl · May 30, 2026

idatahoe said:
Thank you for your replies!

You're right about that one cable going to the transmission... Not sure how I got that confused.

As far as coasting goes, it was just for mileage reasons. But it sounds like it was a bad idea. I didn't realize coasting in neutral, in an automatic, could cause issues even just from the pump.

I'm actually quite a ways north of Fruitland/Ontario.

--

Got the swap done! Well, most of it anyway. There's a clearance issue with that red-covered breather and a bracket that I didn't forsee. Breather tube barely fits on and is pretty pinched.

I found a connector and wired it up. In testing, I had the speedometer working. After taping it all up, I must've had a bad connection and it's no longer working.

Still needs a shifter assembly, the front actuator sorted, and front driveshaft. At least I can drive it now (in the summer, anyway.)

The trans pump should still run in neutral but the rpm’s might drop too far and thus be insufficient lube potentially , but I’d be more worried about the increase in gas used and also lack of ability to stab the gas to avoid something, you’d have to drop into gear and wait for a potentially longer than normal shift to occur then you’d get power. Before that happened you may have the engine rpm sink, then when it kicks in you aggressively lunge more than you expected

Dead 4x4, and/or dead 4L60?

idatahoe

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stutaeng

Well-Known Member

5202500HD

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idatahoe

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AuroraGirl

Well-Known Member

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