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4L80E to 205

Gunwalls_Buckthorne

Gunwalls_Buckthorne

American
Joined
May 19, 2020
Member Number
254
Messages
92
Considering a swap from:

454/465/205 out of my 87 Chevy V30 to:

6.0/4l80e/205

I know there are a million ways to skin a cat. What flavor 4l80e should I be in the lookout for to get the 205 to bolt up? I’d need to confirm but I’m fairly certain the case I’ve got is the round pattern with 32 spline female input.

Also, it’s a work truck and not a serious wheeler. I don’t necessarily need a 205. Any other t cases I should consider? Passenger drop.

Goals are the have a little more pep in her step, auto trans (tow haul a plus!) and occasional, oh dang I’m stuck type 4x4.

Thanks in advance!
 
The 4L80E needs two speed sensors; in and out. For '91, they modified the 205 to have a true electronic VSS.

So what you can do is build the 4L80E to have both speed sensors (like a 2wd does) or find some way to make the signal off the 205.

You would also use the 91-only 4L80E to 205 adapter, or use the late Th400 version that preceded it with a few thou' shaved off the pilot diameter. Either one has the boss for the 205 shifter.

Edit: An 88-91 K5/Burb NP241 could be substituted using the more common adapter. Similar for the 208 that preceded it. Same business with the VSS for the 4L80E's sake.
 
This is all good info. When starting with the 4l80e, it sounds like a 4x4 version with a speed sensor added is the move?
 
Gunwalls_Buckthorne said:
This is all good info. When starting with the 4l80e, it sounds like a 4x4 version with a speed sensor added is the move?
Click to expand...

25 years ago i helped my co-worker source the 91 np205 and he did the machining on a th400 adapter.

Today - if overhauling the trans anyway - ya, think I'd scope out the sensor ordeal.

Screenshot_20240402-190804-385.png
 
total newb said:
Th400 adapters dont work without the spacer becae the mou t wont clear the trans pan
Click to expand...
I believe youre thinking of a different length adapter. The th400/205 one from say a '90 crewcab; all it needs it a pilot 'adjustment'. Otherwise its identical to a 4L80E adapter.
 
Just notch out the 4l80 4x4 adapter and cut down or install the short input. I used a 2wd 4l80 in my builds for the output speed sensor
 
If you use a 2wd 4l80, put the 4x4 housing on the back cut down the main shaft you get the VSS in the trans.

Or just be badass and put a reverse manual valve body in it and fuck the stupid VSS shit.
 
Mattygwheeler said:
Just notch out the 4l80 4x4 adapter and cut down or install the short input. I used a 2wd 4l80 in my builds for the output speed sensor
Click to expand...

Winchested said:
If you use a 2wd 4l80, put the 4x4 housing on the back cut down the main shaft you get the VSS in the trans.

Or just be badass and put a reverse manual valve body in it and fuck the stupid VSS shit.
Click to expand...
I believe you are saying the same thing, 2wd trans with 4x4 rear housing. Then trim the output shaft of the trans.

Would I need to notch the 4x4 tail housing on the transmission to clear transfer case shift rails?
 
Gunwalls_Buckthorne said:
I believe you are saying the same thing, 2wd trans with 4x4 rear housing. Then trim the output shaft of the trans.

Would I need to notch the 4x4 tail housing on the transmission to clear transfer case shift rails?
Click to expand...

No clue, I've got a doubler. And a 4x4 4l80 sitting on my floor for when the clunky nv4500 dies. Just plan on doing the reverse manual.
 
Ok so I am running the Late LS 4l80e with a ford NP205 t-case.

I used a 2wd transmission and cut down the output shaft spline length around 2-1/2".

I swapped in a 32 spline GM input shaft into t-case. I went with a twin stick cable shifter.

Now to mate the trans and t-case together I used the GM Genuine Parts 15724744 Transfer Case Adapter. This a symetrical 6 bolt pattern and is fairly short so the t-case doesn't hang way off the back and make the rear driveshaft short. To achieve the 6 bolt pattern I got a Ford NP205 clocking ring. Clocking Ring NP205 Round Mount Pattern Transfer Case Ford Down GM UP | eBay

Now I used 3 of the bolt holes to clock the t-case a little bit and 3 to clock it more and it resulted in the same as GM 6 bolt pattern. I then notched the GM adapter for the shift lever to clear. Slid them together fully measured the gap between then. That's the amount of the output shaft on transmission I cut off. Also when running a 2wd 4l80e there is a small expansion type plug on back of the transmission that has a small hole so oil can get in and on the slip yoke to keep it lubricated, with 4x4 you don't need that so I sourced a new solid expansion plug.



I don't have any photos of this currently since it is installed in my truck but it worked easily and didn't require any costly adapters that usually result in t-case further back on truck and making rear shaft shorter.

Photo here is similar to how I got bolt pattern to match. I don't remember if this is the exact locations on these but they use all thread so I was able to see what holes lined up and threaded the all thread from the back side. I had to ream a few of the holes a little bit with a burr to get it to slide on easily. This also resulted the the bottom of the t-case being flat with the trans pan surface so I was able to make a straight tube for trans crossmember. I also did another on back of t-case to help support it all.
205 clocking ring.jpg


 
u2slow said:
I believe youre thinking of a different length adapter. The th400/205 one from say a '90 crewcab; all it needs it a pilot 'adjustment'. Otherwise its identical to a 4L80E adapter.
Click to expand...
Mine was a 89 th400/205 oe setup.
Whent to install my 4x4 4l80 and run into 3 issues.

Shaft length, easy enough to cut
Pilot, can be milled obviously
Mount hits pan, must be pushed back.

Nwf space resolves all 3 issues with zero machining
 
total newb said:
Mine was a 89 th400/205 oe setup.
Whent to install my 4x4 4l80 and run into 3 issues.

Shaft length, easy enough to cut
Pilot, can be milled obviously
Mount hits pan, must be pushed back.

Nwf space resolves all 3 issues with zero machining
Click to expand...

This thread says theres 5/8" difference between the 4L80E and th400 adapters... That must be my mixup

www.pirate4x4.com

4l80e to NP205- again

www.pirate4x4.com www.pirate4x4.com
 
I used a factory adapter with the NWF spacer. Then just had a local shop install a tone ring and VSS in the back position. Computer is happy and speedo uses the factory cable drive.

Note the ECM reads double the speed in lo range but it works fine with no faults or quirks.

If you try to use a factory output VSS on the 205 you will need to arrange the ECM to see a low range input signal which will require a micro switch on the shifter. You will also need to program the gear ratio so we it differs from any of the factory chain drive cases. Then you also need to figure out how to make the speedo work on top of this.

All doable
 
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