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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => LT/LS Swaps => Topic started by: nighthawker5 on June 10, 2016, 09:56:12 PM

Title: 4l80E to a NP208
Post by: nighthawker5 on June 10, 2016, 09:56:12 PM
Hello,

This is my first post to this forum.  Here's my story.  I have an 86 K20 LWB that had a 350 4bbl and a th400 with a NP208 transfer case.  I am swapping a 6.0L LQ4 and a rebuilt 4L80E into it.  My dilemma is with the transmission and the transfer case.  I know the bolt patterns are the same but the adapter on the transfer case won't bolt up because the Transmission mount bolts hit the transmission pan.  Does anyone know where I can find the correct adapter?  I've looked and there are hundreds out there and I'm not sure which one fits.  Heres a pic
Title: Re: 4l80E to a NP208
Post by: 1967KaiserM715 on June 11, 2016, 10:08:57 PM
Any one from a 90's Chevy that had the 4l80e should work, I'm fairly positive that all the transfer cases had the same bolt pattern, at least the Borg Warner I had did, and it was the heavy duty one


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Title: Re: 4l80E to a NP208
Post by: nighthawker5 on June 11, 2016, 10:12:16 PM
Thank you very much.  That's will get me in the right direction


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Title: Re: 4l80E to a NP208
Post by: Irish_Alley on June 11, 2016, 10:19:17 PM
is this a 208 off a th400? never did that much research on the 208 only the 205. i know you cant just take the th400 adapter and slap it on the 4l80 for the 205. think its the same problem.
Title: Re: 4l80E to a NP208
Post by: nighthawker5 on June 11, 2016, 10:37:07 PM
Yeah it's the 208 off the 400.  The bolt patterns match it's just too short


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Title: Re: 4l80E to a NP208
Post by: frotosride on June 12, 2016, 07:04:22 AM
https://www.novak-adapt.com/catalog/adapters/transmission-to-transfer-case/4l80e-to/kit-4l83/

Scroll down to the last item listed. It is the 4l83-c kit and made to adapt all the NP cases to the 4l80e. This is my plan when I get to that point!
Title: Re: 4l80E to a NP208
Post by: hatzie on June 12, 2016, 10:37:14 AM
I assume you didn't get the 15724745 1999-2007 4L80E to New Venture transfer case adapter with the tranny.  The yard goons seem to like to pull the adapter and pitch it in the smelter or evilbay em.
Pick one up from Amazon and try it for fit.  I'd be willing to bet this will take care of your problem.  If it doesn't fit return it.
 
The TH400 and 4L80E have the same 32 spline output shaft so that shouldn't be an issue.
Title: Re: 4l80E to a NP208
Post by: nighthawker5 on June 12, 2016, 10:47:38 AM
Thank you very much.  That should clear up the issue


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Title: Re: 4l80E to a NP208
Post by: hatzie on June 12, 2016, 03:22:05 PM
Thank you very much.  That should clear up the issue


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The only mild problem is where the 88up LH drop vs 87 down RH drop puts the transfer case bottom.  You can get clocking rings to fix this...  if it's an issue.

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Title: Re: 4l80E to a NP208
Post by: Irish_Alley on June 12, 2016, 03:37:22 PM
are you sure its the adapter hitting and not the output shaft is too long and stopping on the input shaft of the transfer case?

this should work if it is inface the the shafts hitting each other
http://www.cutthroat4x4.com/catalog/product_info.php?products_id=122
Title: Re: 4l80E to a NP208
Post by: nighthawker5 on June 12, 2016, 03:40:35 PM
Right now it's definitely the adapter.  I might get the new adapter on and get it in another 1/4" only to find the output shaft is too long too. 


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Title: Re: 4l80E to a NP208
Post by: hatzie on June 13, 2016, 12:18:23 PM
If the output shaft is a little long that's not the end of the world.   The 1999-2007 T800 chassis used LH drop and the squarebodies are RH drop.  When you swap sides like that the transfer case may hang too high or too low...  For some reason I got away with it on my NV4500 when I bolted on the military surplus NP208C.  You'll probably want to re-clock the transfer case for ground clearance and you'll need 7/8" - 15/16" for the Novak clocking ring.
Title: Re: 4l80E to a NP208
Post by: nighthawker5 on June 13, 2016, 12:21:17 PM
If i do that do i need to do anything with the front differential or driveshaft?
Title: Re: 4l80E to a NP208
Post by: hatzie on June 13, 2016, 02:21:31 PM
If i do that do i need to do anything with the front differential or driveshaft?
If you raise it to near the original position nothing.

I did forget to mention one of the 6 bolts is asymmetric.  The clocking ring can give you back the 6th bolt.

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Title: Re: 4l80E to a NP208
Post by: nighthawker5 on December 27, 2016, 09:21:44 AM
I assume you didn't get the 15724745 1999-2007 4L80E to New Venture transfer case adapter with the tranny.  The yard goons seem to like to pull the adapter and pitch it in the smelter or evilbay em.
Pick one up from Amazon and try it for fit.  I'd be willing to bet this will take care of your problem.  If it doesn't fit return it.
 
The TH400 and 4L80E have the same 32 spline output shaft so that shouldn't be an issue.

This fixed it.  Ordered it from Amazon and put it right on with sealant.  Evertyhing bolted up like it should.  Thank you
Title: Re: 4l80E to a NP208
Post by: 2011laramie on January 22, 2017, 09:55:54 PM
Would an adapter from a np241 have worked instead of the 208 adapter? Thought i read somewhere that the pads were in a different spot off to the side, so it wont hit the pan.

So with the LS swap with a 4l80e being longer than the turbo 400. If you use the "insert name brand" ls swap brackets that can adjust the ls 2.5" forward in the engine bay, would this account for the longer transmission and allow the transfercase to be in Stock location?

Ive read so many different things about 4l80e to 205 or 208 im confused. would like a definite answer about what i need to buy or do.
Title: Re: 4l80E to a NP208
Post by: hatzie on January 24, 2017, 05:14:24 AM
The adapter part number is for the NP261/263.  By 1999 the NP208 and NP241 were no longer in use and the NP26x was LH drop.  All of the round pattern 1980's and beyond NP208 NP241 NP261 NP263 etc use the same bolt pattern.  It's just a matter of getting the correct LH/RH side drop transfer-case for your chassis with the correct input spline count to mate with your transmission output shaft. 
The older NP205 is where it gets mildly exciting because there were at least two different bolt patterns.   I didn't study the NP205 that much because I wasn't going to use one...

The length issue is just a matter of moving the transmission/transfer-case crossmember on the frame rails and shortening/lengthening the driveshafts. 
If you move the engine forward the needed amount the driveshafts should be OK and maybe even the crossmember.  The trade-off is where that places your fan and accessory drive parts in relation to the radiator and fan shroud.