Dead 4x4, and/or dead 4L60?

[idatahoe]

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!

 

[stutaeng]

Unfortunately, we don't have a (4L60e) transmission guru here, so I will try my best to offer advice:

1. Start with the basics. Fluid levels okay? ATF and Tcase. Tcase are known to have fluid loss through the pump rub issue. Not uncommon for guys that just bought one of these truck to check and Tcase is dry.

2. Has the transmission ever been serviced? You mentioned you just bought the truck, so I'm guessing you don't know on this?

3. Check for codes. Many times you will have CEL codes being thrown if you have a mechanical issue. Try to get a mid-tier scanner that will also scan U-codes (for the transfer case). Also, these scanners will show live datastream, and you can see if parameter are showing up like turbine speed sensor RPM. Maybe you can determine where the powerflow is loss by doing so.

4. Good idea to check driveshaft. Chock the wheels for safety.

 

[99Sierra2500]

Had some grinding going into park.

This sounds like the transfer case. Not an expert though.

 

[idatahoe]

Thank you for your replies!

I checked and neither driveshaft is turning under throttle, in gear.

It does roll though, so we were able to get it pushed back down the driveway.

I'll try to get it into the shop to check further. I think the next thing is the transfer case. Is there a way to manually put it into gear? I think there's a motor that controls the gear selection that I can take out. I can at least test its functionality. Although because there's no lights on the switches, I am not sure it would move for me.

I have a basic OBD-II reader, but that's it. I should see what it says, though have very little experience diagnosing with codes.

Is there a way to convert an electric kit transfer case to a manual shift? It may not be worthwhile, but it seems preferable to me.

 

[ORVietVet]

Nick @NickTransmissions is out of Vegas and is on GMT400 and Tahoe/Yukon Forum and is the guru. You can reach out to him at those forums or at a web site.

 

[stutaeng]

Yes, you can covert to the manual shift (floor shift) Tcase, but you have do some rewiring. There's videos out there that show you how to do it.

I think the NP241 ( the third digit "1" indicates it's a floor shift unit) is the one that fits?

 

[INW-Iron-Steel]

Yes, you can covert to the manual shift (floor shift) Tcase, but you have do some rewiring. There's videos out there that show you how to do it.

I think the NP241 ( the third digit "1" indicates it's a floor shift unit) is the one that fits?

NP261LD is the floor shift for the 1500 GMT800s. The 241 was used on the GMT400s, although I am sure you could make a 241 work

 

[INW-Iron-Steel]

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 checked and neither driveshaft is turning under throttle, in gear.

It does roll though, so we were able to get it pushed back down the driveway.

Quick check for you. Can you roll the vehicle with the transmission in park? If so, it is likely a T-case issue. It could be stuck in neutral or between gears. Have you tried to shift it again? I would put the transmission in neutral with the engine idling (parking brake on of course) and try to shift the case to neutral, and then to 2H.

The clunk/grind going into park isn't much to worry about if the transfer case is the issue. With no output to the wheels, the output shaft would still be spinning. It would be like shifting into park while driving down the road. I bet if you shifted the transmission into neutral and turned the engine off first, and then shifted to park, it wouldn't grind.

 

[idatahoe]

Thank you all for your replies!

I can definitely reach out to @NickTransmissions. I think I need to get this in the stop to do some basic diagnosis first.

I was doing some more reading on manual shift transfer cases. It sounds like the NP241C should work. I read about the 261 and someone said it has issues with the oil pump wearing through the case -- not sure if that's true or not. Still not sure if I want to swap the transfer case at all, but very disappointed if the transfer case indeed did randomly get into neutral and can't be put back. Worse than not having 4WD!

It's hard to roll the vehicle as there's a bit of a hill and a fair bit of snow. I actually had to move the Tahoe out of the way this morning and had to use the tractor to give it a nudge down the hill.

Will do some more clearing in the shop, then drag it back up the hill and into the shop. I think while I drag it, I can test park.

I'll test putting the transfer case in neutral and then 2 high with the transmission in neutral, and the engine running. There's no lights on the dash though, so not sure if anything happens when I press those buttons.

 

[idatahoe]

I managed to get it into the shop. What a pain!






It does roll in park quite well. It also appears that the transfer case is in 4x4... When I rotate one driveshaft, the other rotates as well...

I find that a bit perplexing. I was expecting the transfer case to be in neutral.



Is this the motor that selects the gear the transfer case should be in?



I assume this connects/disconnects one of the front axles?

 

[Cadillacmak]

Your transfer case for sure. No holes in it and fluid is good? Disconnect your battery, turn you key on and lights on. Wait 10 seconds and then turn your lights and key off and reconnect your battery and place the t-case in 4low with the transmission in neutral. If that works, go back to 4high and cycle through to 2x4.

If this doesn't work, check your t-case module with a scanner and your t-case encoder motor.

You can pull the encoder motor off the side on the tcase and shift manual, if that doesnt work you have an internal fail in the T-case.

 

[INW-Iron-Steel]

No holes in it and fluid is good?

My first thought, LOL

OP mentioned his wife said there was "grinding with shifting"... I'm thinking it was probably more than a little grinding.

 

[Cadillacmak]

My first thought, LOL

OP mentioned his wife said there was "grinding with shifting"... I'm thinking it was probably more than a little grinding.

Those dang pumps like to cut their way out, and as soon as its dry, it all over.

 

[idatahoe]

Your transfer case for sure. No holes in it and fluid is good? Disconnect your battery, turn you key on and lights on. Wait 10 seconds and then turn your lights and key off and reconnect your battery and place the t-case in 4low with the transmission in neutral. If that works, go back to 4high and cycle through to 2x4.

If this doesn't work, check your t-case module with a scanner and your t-case encoder motor.

You can pull the encoder motor off the side on the tcase and shift manual, if that doesnt work you have an internal fail in the T-case.

I disconnected the battery, waited, and tried to shift the transfer case. No luck, still no lights for the transfer case shifting buttons. I checked the 4WD fuse and it was fine.

Drained the transfer case fluid. It definitely needed replacing, but no signs of catastrophic failure. Same with the transmission.

Pulled the front driveshaft and encoder motor. Was able to shift it, but it didn't always want to go into neutral. And sometimes in neutral, it would make a weird noise when spinning the input shaft, but not every time.

Tested drive with the encoder motor out and shifting the transfer case. Very happy that the transmission seems to be fine.

So the transfer case module, and/or motor is out and suspect. But the transfer case itself acted funny and I don't know if it shifted itself, or if the electronics did. Either way, I have little confidence given that it was able to pop into neutral on its own.

I think I'm going to pursue a NP241C swap. This could have failed anywhere, all so we could have a button instead of a lever! (And maybe a couple more cupholders?) Thankfully, it failed at the top of the driveway. NP241C shouldn't wear a hole in itself, either.

I appreciate everyone's help so far!

Does anyone have more detailed swap instructions than this post? https://www.gmfullsize.com/posts/3226090/

It seems fairly straightforward at first glance.

 

[stutaeng]

Good to hear that.

Lawrence Tolman did a similar swap on the K2500 GMT400 suburban he had briefly on his channel. I think it should be very close to your swap and he shows the electronics portion as well:

 

[INW-Iron-Steel]

I think I'm going to pursue a NP241C swap. This could have failed anywhere, all so we could have a button instead of a lever! (And maybe a couple more cupholders?) Thankfully, it failed at the top of the driveway. NP241C shouldn't wear a hole in itself, either.

I appreciate everyone's help so far!

Does anyone have more detailed swap instructions than this post? https://www.gmfullsize.com/posts/3226090/

It seems fairly straightforward at first glance.

Fully support the manual T-case endeavor. I have never owned a 4x4 without manual shift for the exact reason above. I went full manual in my 93 with a posi-lok. Anyway, a few notes:

-The pump rub issue has been addressed and fixed (with case saver and upgraded case options) if you did find a nice used 261 you wanted to use.

-Make sure to get a NP241C from a GMT400 (88-98 truck, 92-99 suburban) with a 700r4 or 4l60. One from a 4l80 or 5 speed truck will have a different input shaft. The "v" suburban cases are different if I am remembering correctly.

-Wiring and a driveshaft will be your biggest obstacles. The case will go in, but you will need to reconfigure the wiring so the actuator on the front axle knows when to engage. The 241 also has a different front output when compared to the 246. Either a flat flange or yoke for u-joint. You will need a new front driveshaft.

-NP241 are not without their flaws. Most notably, the snap ring on the rear output shaft. I would recommend either the upgraded snap ring or the snap ring eliminator.

Good luck on the swap!

 

[AuroraGirl]

Fully support the manual T-case endeavor. I have never owned a 4x4 without manual shift for the exact reason above. I went full manual in my 93 with a posi-lok. Anyway, a few notes:

-The pump rub issue has been addressed and fixed (with case saver and upgraded case options) if you did find a nice used 261 you wanted to use.

-Make sure to get a NP241C from a GMT400 (88-98 truck, 92-99 suburban) with a 700r4 or 4l60. One from a 4l80 or 5 speed truck will have a different input shaft. The "v" suburban cases are different if I am remembering correctly.

-Wiring and a driveshaft will be your biggest obstacles. The case will go in, but you will need to reconfigure the wiring so the actuator on the front axle knows when to engage. The 241 also has a different front output when compared to the 246. Either a flat flange or yoke for u-joint. You will need a new front driveshaft.

-NP241 are not without their flaws. Most notably, the snap ring on the rear output shaft. I would recommend either the upgraded snap ring or the snap ring eliminator.

Good luck on the swap!

np241 from a V suburban or blazer would be the WRONG drop. Which can be reclocked, but i bet there is other differences too maybe

The tcase the OP has is also always spinning the front output, so the fact they both spin is not strange

 

[idatahoe]

Thank you all for your replies! Looks like I can't do multi-quote on here...

Re: The video. That was helpful. I do think with the posi-lock, even wiring isn't even a concern. And most of the time if I'm using 4-low, I'll just want first gear anyway.

About the 261 vs 241, would you recommend a 261 or 241? It does seem like upgrading the case is more involved than just a snap ring.

Speaking of the output shaft snap ring upgrades, I'm not quite sure what to get. I can't find "Gilly's Transfer Case Savers" available anywhere.

I do see upgraded snaprings here: https://www.oregonperformancetransmission.com/product/SUP-K067.html

And this split bearing retainer here: https://www.oregonperformancetransmission.com/product/SNX-100420-02K.html

Does sound like a fairly common failure (if there's any failure) so probably something I should address while I have it on the bench.

I'll need to count my splines to double check, but I think 27 is the number I need to get. As for the driveshaft, I assume they are identical between Tahoe, Suburban, and K1500 trucks?

The only wiring I need to get right is for the speed sensor for the speedometer, right?

np241 from a V suburban or blazer would be the WRONG drop. Which can be reclocked, but i bet there is other differences too maybe

The tcase the OP has is also always spinning the front output, so the fact they both spin is not strange

I didn't realize that these t-cases were always engaged. At first we were confused because we only found 3 positions on the transfer case and expected 4. But it seems like it's low, high, and neutral. I guess the front axle disconnect is what's able to give you 2-high.

I recall your username on some Excursion forums when deciding between a Suburban, Tahoe, Excursion, or Expedition. Are you happy that you switched into the Chevy realm?

 

[stutaeng]

Yes, 4L60e = 27 spline output shaft

4L80e = 32 spline output shaft

 

[AuroraGirl]

Thank you all for your replies! Looks like I can't do multi-quote on here...

Re: The video. That was helpful. I do think with the posi-lock, even wiring isn't even a concern. And most of the time if I'm using 4-low, I'll just want first gear anyway.

About the 261 vs 241, would you recommend a 261 or 241? It does seem like upgrading the case is more involved than just a snap ring.

Speaking of the output shaft snap ring upgrades, I'm not quite sure what to get. I can't find "Gilly's Transfer Case Savers" available anywhere.

I do see upgraded snaprings here: https://www.oregonperformancetransmission.com/product/SUP-K067.html

And this split bearing retainer here: https://www.oregonperformancetransmission.com/product/SNX-100420-02K.html

Does sound like a fairly common failure (if there's any failure) so probably something I should address while I have it on the bench.

I'll need to count my splines to double check, but I think 27 is the number I need to get. As for the driveshaft, I assume they are identical between Tahoe, Suburban, and K1500 trucks?

The only wiring I need to get right is for the speed sensor for the speedometer, right?



I didn't realize that these t-cases were always engaged. At first we were confused because we only found 3 positions on the transfer case and expected 4. But it seems like it's low, high, and neutral. I guess the front axle disconnect is what's able to give you 2-high.

I recall your username on some Excursion forums when deciding between a Suburban, Tahoe, Excursion, or Expedition. Are you happy that you switched into the Chevy realm?

Wait. I misremembered. Spinning the front shaft is only done because of the axle. It’s not driven normally , I apologize. If you had the wheels off the ground and the shafts both spun, the Tcase was engaged