241c or stay with the np203

[riessecup1]

I am new to the forums so if there is this info already out there please just link me to it. I have a 79 k10 with a 5.3L (LM7) with a 99 computer. it currently has a th350 trans and a np203 transfer case. I bought it like this but I want to put a 4L60e in it so I can drive 70 mph comfortably. I plan on redoing everything I am just starting here. So my question is which transferase would be best for a true daily driver. My goal for this truck is to be my daily driver and be able to go a few hours away without worry. I also plan on towing and I'm not sure if either of the transfer cases are ideal for this. thank you for the help!

 

[Bextreme04]

I am new to the forums so if there is this info already out there please just link me to it. I have a 79 k10 with a 5.3L (LM7) with a 99 computer. it currently has a th350 trans and a np203 transfer case. I bought it like this but I want to put a 4L60e in it so I can drive 70 mph comfortably. I plan on redoing everything I am just starting here. So my question is which transferase would be best for a true daily driver. My goal for this truck is to be my daily driver and be able to go a few hours away without worry. I also plan on towing and I'm not sure if either of the transfer cases are ideal for this. thank you for the help!

The problem is going to be finding a 241c with a passenger side drop. The most likely candidate for you, and the easiest to find, will be a NP208 from an automatic trans equipped 85-90 K10. They are all round pattern and will bolt right up to a 4L60. The 0411 from the 99 will run a 4L60 no problem as long as the tuner that switched it to work with the TH350 didn't mess anything up. It probably came from a 4L60 equipped truck to begin with and the tuner just selected non-electronic automatic trans in the tune and disabled any auto trans DTC's.

You will need to find a way to get a VSS signal. There are a few options out there, but the walters one is pretty reasonably priced and simple to do.
https://www.walterseandp.com/product-page/np208-electronic-vss-conversion-kit-r2

 

[legend57]

The only complaint I've heard about the NP203 is the shifter. While they are full-time 4x4, you can easily convert to part time and then add locking hubs. That's what I did. I swapped from a TH350 to a 700R4, but kept the NP203. The one thing you need to do is space the shifter forward since the 700R4/4L60 transmission is ~2.5" longer than the TH350. I did this by using the t-case shifter bracket from a TH400. While rebuilding the t-case shifter, I just swapped in the longer bracket and it all bolts up and looks stock. I did a write up on rebuilding the t-case shifter. It really is pretty easy. I went the extra mile and cerakoted all the parts to make sure they don't corrode and gives a little extra lubricity.

 

[Tonimus]

I beat the hell out of my NP203. And the only "issue" I ever had was shifting. She was sometimes stubborn to shift if you were already stuck. Sometimes I'd have to push on the t-case shifter and bump the trans back into drive. Always clunked in to place.

 

[riessecup1]

I beat the hell out of my NP203. And the only "issue" I ever had was shifting. She was sometimes stubborn to shift if you were already stuck. Sometimes I'd have to push on the t-case shifter and bump the trans back into drive. Always clunked in to place.

Mine is the same way. That’s why I came here to see if rebuilding it was worth it or if switching to a different transfer case would be better for the money.

 

[legend57]

Key things to look for if the NP203 shifter is giving you a hard time:

#1: Check alignment of shifter rods. The whole shifter can bend and get out of alignment or things just wear. There is a GM procedure for realigning the rods. Just search on the forum.
#2: Excessively dirty: Commonly, people would lather the shifter in grease, but that would just collect dirt over time and really jam things up. In this case, the shifter needs to be disassembled, cleaned, and reassembled.
#3: Improper assembly: If a PO tried to fix the shifter and reassembled it wrong, it may still kind of work, but will be a PIA to operate. It is easy to fowl up the assembly.
#4: Worn parts: During disassembly, fully inspect the parts for wear. Excessive wear will prevent the detents from working properly. In this case, you'll need to find another shifter for parts.

Cleaning and reassembling is pretty easy. Just take your time and make sure it all goes back together correctly.

 

[riessecup1]

The problem is going to be finding a 241c with a passenger side drop. The most likely candidate for you, and the easiest to find, will be a NP208 from an automatic trans equipped 85-90 K10. They are all round pattern and will bolt right up to a 4L60. The 0411 from the 99 will run a 4L60 no problem as long as the tuner that switched it to work with the TH350 didn't mess anything up. It probably came from a 4L60 equipped truck to begin with and the tuner just selected non-electronic automatic trans in the tune and disabled any auto trans DTC's.

You will need to find a way to get a VSS signal. There are a few options out there, but the walters one is pretty reasonably priced and simple to do.
https://www.walterseandp.com/product-page/np208-electronic-vss-conversion-kit-r2

I could be wrong but as far as I know the 4L60 has two different output shafts. A 27 spline and a 33 spline, do you know which one I should search for?

 

[Tonimus]

Mine is the same way. That’s why I came here to see if rebuilding it was worth it or if switching to a different transfer case would be better for the money.

Never rebuilt mine. Put 50k miles on it that way when I had it.

 

[riessecup1]

Key things to look for if the NP203 shifter is giving you a hard time:

#1: Check alignment of shifter rods. The whole shifter can bend and get out of alignment or things just wear. There is a GM procedure for realigning the rods. Just search on the forum.
#2: Excessively dirty: Commonly, people would lather the shifter in grease, but that would just collect dirt over time and really jam things up. In this case, the shifter needs to be disassembled, cleaned, and reassembled.
#3: Improper assembly: If a PO tried to fix the shifter and reassembled it wrong, it may still kind of work, but will be a PIA to operate. It is easy to fowl up the assembly.
#4: Worn parts: During disassembly, fully inspect the parts for wear. Excessive wear will prevent the detents from working properly. In this case, you'll need to find another shifter for parts.

Cleaning and reassembling is pretty easy. Just take your time and make sure it all goes back together correctly.

I did take the shifter out and clean it. I also did the drill bit trick do re align it but I think the transfer case needs rebuilt. This thing had lot of issues so i just want to fix it right the first time.

 

[AuroraGirl]

The problem is going to be finding a 241c with a passenger side drop. The most likely candidate for you, and the easiest to find, will be a NP208 from an automatic trans equipped 85-90 K10. They are all round pattern and will bolt right up to a 4L60. The 0411 from the 99 will run a 4L60 no problem as long as the tuner that switched it to work with the TH350 didn't mess anything up. It probably came from a 4L60 equipped truck to begin with and the tuner just selected non-electronic automatic trans in the tune and disabled any auto trans DTC's.

You will need to find a way to get a VSS signal. There are a few options out there, but the walters one is pretty reasonably priced and simple to do.
https://www.walterseandp.com/product-page/np208-electronic-vss-conversion-kit-r2

he would also have to make sure he has the TCC lockup to match , 99 should be aftere they went PWM but not sure if they had the ECCC (electronically controlled capacity clutch) yet. we dont know where he got his 4l60e from
Also, the shifter gate wont be for a 4 speed and the indicators may not line up, this can be swapped. a 700r4 indicator can be put on the k10

 

[CalSgt]

I could be wrong but as far as I know the 4L60 has two different output shafts. A 27 spline and a 33 spline, do you know which one I should search for?

Which ever one you can get a matching 208 for…

 

[riessecup1]

he would also have to make sure he has the TCC lockup to match , 99 should be aftere they went PWM but not sure if they had the ECCC (electronically controlled capacity clutch) yet. we dont know where he got his 4l60e from
Also, the shifter gate wont be for a 4 speed and the indicators may not line up, this can be swapped. a 700r4 indicator can be put on the k10

I have not purchased anything yet. I came here to make sure I get the right one the first time.

 

[Bextreme04]

he would also have to make sure he has the TCC lockup to match , 99 should be aftere they went PWM but not sure if they had the ECCC (electronically controlled capacity clutch) yet. we dont know where he got his 4l60e from
Also, the shifter gate wont be for a 4 speed and the indicators may not line up, this can be swapped. a 700r4 indicator can be put on the k10

No, all of the issues and changes were pre-97 where these were installed on 350's, 305's, and v6's. He will want to stay away any early 90's 4L60 as they were still working things out in those years. He'll know it's the right one because it will have the LS bellhousing on it with the additional top bolt.
https://www.ltxtech.com/forums/showthread.php?23419-4L60E-year-differences-and-interchanges

Any 4L60 that came from an LS will be compatible with the 0411 ECU he has from 99. It would probably be best from a functionality perspective to flash a fresh 2002 5.3/4L60 OS on it, but it will likely need retuning after that.

I could be wrong but as far as I know the 4L60 has two different output shafts. A 27 spline and a 33 spline, do you know which one I should search for?

I think you are getting confused. I have never seen a 4L60 that had anything other than a 27 spline output. The 700R4 and 4L60 can use the same input shaft, but the 700R4 pre-1987 had a 27-spline INPUT shaft where it interfaces to the torque converter. After 87, they switched to a 30-spline INPUT shaft. So a torque converter for a 700R4 and 4L60 are identical except for the spline count on the inside of the converter.

 

[riessecup1]

No, all of the issues and changes were pre-97 where these were installed on 350's, 305's, and v6's. He will want to stay away any early 90's 4L60 as they were still working things out in those years. He'll know it's the right one because it will have the LS bellhousing on it with the additional top bolt.
https://www.ltxtech.com/forums/showthread.php?23419-4L60E-year-differences-and-interchanges

Any 4L60 that came from an LS will be compatible with the 0411 ECU he has from 99. It would probably be best from a functionality perspective to flash a fresh 2002 5.3/4L60 OS on it, but it will likely need retuning after that.


I think you are getting confused. I have never seen a 4L60 that had anything other than a 27 spline output. The 700R4 and 4L60 can use the same input shaft, but the 700R4 pre-1987 had a 27-spline INPUT shaft where it interfaces to the torque converter. After 87, they switched to a 30-spline INPUT shaft. So a torque converter for a 700R4 and 4L60 are identical except for the spline count on the inside of the converter.

Thank you. I figured I read that wrong but I appreciate all the help. I will post what I end up buying in here. It Will probably be another month or so.