jkade72

iTrader: (23)

I just got done with a LQ9 swap in a 86 k5 using a th400 and a np241 and now my buddy has bought a LQ4/4L80E for his suburban. I have not done a 80E swap and I am unclear about the VSS issues. His suburban has a np208 with a cable for the speedo. What are we gonna have to do to make the computer shift the trans correctly? I didn't have this problem with my swap since I used a th400 but I assume the 80E is going to need to sense 4low as well? Thanks for any help!!!

Bo185

Get a NP241 pass drop with a VSS from a 89-91 3/4ton burbin' with 32 spline input. Or get the 27spline and convert to 32. The VSS is in the transfer case on 4x4 applications. He'll have to provide a ground to a pin in the PCM for when its in 4low so the PCM knows its in 4low. (can't remember pin number off top of my head).

jkade72

iTrader: (23)

Thanks, that is what I did in my k5. I had to change the input to a 32 spline to mate to my th400 of course I didn't really need the vss but I always here they run better when they sense movement. I was thinking only the 91's had the vss on the t-case?

jkade72

iTrader: (23)

Would the dakota digital pulse generator work to feed the pcm and make the 4l80e shift correct?

mwgasman

I swapped a 4l80e into my '87 blazer. I was exceedingly lucky to find a '91 np241 passenger side drop 32 spline input in my local U Pull It. I also got the cluster from the same truck so i dont have any need for the cable driven speedo.

I was unable to find a good solution to convert the cable speedo to a 40 pulse per revolution signal that the pcm/transmission requires.

The only problem i had is that the trans i used didnt have the reluctor ring on the output shaft. Because of that my trans goes in to limp mode if im in 4lo. I am getting vehicle/output shaft speed from the transfer case speed sensor. If my trans had the ring, then the pcm would get the shaft speeds from the trans and the transfer case would only send vehicle speed to the speedo. Unfortunately my situation is a bit different from LS swaps because my engine is a TBI454.

jkade72

iTrader: (23)

Thanks for the info, he bought a np241 this morning so we are going that route. I still have to figure out how to let the pcm know it is in 4low, might have to use a toggle switch?

Thanks, Kade

Bo185

That's the easiest way or you could mount a switch on the transfer case shift lever as well so it will contact it in 4low.

mwgasman

The passenger side drop cases dont have the 3 position switch on the internal shift mechanism cam like the drivers side drop ones do. Like bo said, the easiest will be to put a contact switch on the external shifter mechanism.

tlape4965

Did you guys have success with the install? I put a 454 tbi with a 4l80e in a 1990 suburban with a np241c. I'm having the some issues with the vss. My speedo works but the tranny is stuck in limp mode.