I currently have a 99 2dr Tahoe already swapped with a 4l80e and the autotrac transfercase. I wanna install a NP149 for its AWD. I know that there’s a custom 32 spline input shaft being built out there but I came across GM part number 12386258. It’s a 32 spline input shaft made for the NP246. Does anyone know iOS interchangeable with the NP149 from a SS

 

Dont quote me but i think Ive heard that the transfer case from the NNBS AWD trucks like the Denali's and the Escalades, bolts right up to the 4L80.
In other words the AWD transfer case from the 6L80, dont quote me though.

I was thinking of this same thing yesterday, since im looking to build an AWD OBS next.

 

Seems like only the np149 will work being it ises a Viscous coupling to split the power 68% 32%. When it senses slip it can divide the power either front or back up to 100%. All other transfer cases use the ABS system to work. The NP149 only camenwith 4l60e’s in Sierra Denali C3 and Silverado SS. The only way to get it to work with an4l80 is to change the input shaft on transfer case to 32 spline or change output on 4l80 to much weaker 4l60 size which defeats the purpose of having a 4l80. After reading seems like ONLY option is custom input shaft

 

Yeah im aware of the input shaft method, as I've built an SS with a 4L80 before.
Ive also seen a few AWD trucks built around town, who swear they have a 6L80 TC on a 4L80 trans, as the 6L80 TC is 32 spline as well. I didnt know the 6L80 TC worked off the ABS system, guess you learn something new everyday.
Good luck buddy

 

the nnbs awd transfer case (bw4485) bolts up to a 4l80 with a 4l80 tcase adapter. same spline. there is no viscous coupling in it though so it acts like an open differential.
when i had mine apart the planetaries are stamped "40/60" it's all mechanical. the ABS/stabilitrack is used to control wheel spin - worthless if youre trying to race with it since it you can tune out most of the TM that gets pulled but it still wants to apply the brake to the spinning wheel. pulling the ABS fuse will keep it from applying brake.

never used one but id imagine the np149 would be a much better transfer case to use, im not particularly attached to my nnbs case it just hasnt died, I have thrown a lot of weight over the front, adjustable coilovers, when it starts becoming the limiting factor ill do something with it

 

The NVG 149 is the ticket. Or NP149 depending. I even bought a spare for my truck just in case. It’s a great Tcase.

 

How much HP are you running. Do you get front wheel spin when nailing it at the line?

 

when I get wheel spin it’s all 4, never had just the front spin. As far as hp, never Had it on a dyno but based on mph and weight I am around 900-950 to the wheels.

 

What front differential are you running. I have a 9.25 2500 front diff in my obs currently. I also jus picked up a awd front diff from a 2002 Denali. If I keep my 2500 diff do I just leave it locked in 4wd with the NP149 case or should i swap it out for the awd diff. Is the awd 8.25 diff strong enough Only looking for 700hp

 

I have the stock front diff that was in my Denali.