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Help with TH400 to Ford NP205

Doberman Racing

Backyard Fabricator
Joined
Jun 12, 2020
Member Number
1974
Messages
21
Loc
New Jersey
I have a TH400 that I was told is out of an H1. It has a 2.5" stick out 32 spline output shaft. My front axle is a Superduty 35 spline D60 so I'm needing a driverside drop tcase.

I'm in the middle of build a cage/backhalf chassis, 2" rogue fab die, swapping from leafs to king coilovers, front and rear stretch, 6.0 swap, seats, harnesses, etc so my wallet has been used an abused these last three weeks collecting parts and buying tools.

I'm trying to keep this as budget friendly as I can :lmao:

Considering last night was the first time I've ever even seen a picture of an Np205 I stayed up late and did some reading.

From what I gather is the Ford NP205 (married) is a 31 spline input shaft. Some GM np205 cases used a 32 spline input shaft along with a bigger bearing. The Ford 31 spline case
​​uses the same size bearing as the GM 32 spline input case.

GM also has 10 and 27 spline inputs but they are of no use to me.

The Ford also has 32 spline fixed yoke outputs vs GM 205s which can have either a fixed or slip yoke.

The Ford NP205 uses a 6 bolt pattern and GM is 8 bolt until they went to 6 bolt like on the Ford. The NP 208 which came mated to TH400 from the factory also uses the same 6 bolt pattern.

If I swap the GM 32 spline input into the Ford NP205 case I can use the factory TH400/NP208 adapter? Is there a more economical solution?

Is there anything I'm understanding wrong about these cases?

My build is running 37s, 5.38 gears in the axles, and I plan on stepping up to 42s asap.
​​​​​​
With a stock 6.0, th400, is the 2:1 low going to be enough for 42s?

​​​​​​Should I stop being a bitch and pony up to build a 203/205 doubler or does that put me in used atlas territory?

​​​​
 

nyebrosfab

Member
Joined
May 20, 2020
Member Number
430
Messages
9
NWF Ecobox, get a junkyard 6 pinion planentary gear setup from a Chevy NP241. Then you'll have a range box and adaptor to the Ford tcase all in one package for about $1000.
 

slowlygettingthere

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May 26, 2020
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1455
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cousinfuckingbama
This is basically what I did to bolt my ford 205 to bolt to back of my chevy nv 4500. The NWF ecobox I mean. I just used the 241 that came with the 4500 for the planetary. The NWF ecobox mounted to the 205 is within an inch or so of being the same length as the stock 241.
 
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total newb

senior jerk ass
Joined
May 19, 2020
Member Number
283
Messages
1,609
Loc
trinity center ca
While yes the 6bolt patterns are the same, the clocking is different.

Youll want the 32 SHORT input.

Get trans in place.
Order input
Strip 205
Place empty case on trans and mark adapter and case together.

Drill new bolt pattern into case as you see fit.

Reassemble 205 with gm in put.



I found a master 205 gasket kit $30 from cobra trans in florida
 

HYDRODYNAMIC

Rock Stacker
Joined
May 20, 2020
Member Number
545
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760
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Lost in the forest
Im right in the middle of putting my ecobox together. Make sure you put the annular ring gear in the right direction, don't accidentally flip it and don't ask how I know.
Yes you will need more gearing. Do it now so you have the correct axle gears for both speed and crawling.
The 241 I got had the wrong input, it was for a 700R4 so I got a 32 spline input gear off ebay.
 

slowlygettingthere

Well-known member
Joined
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Member Number
1455
Messages
195
Loc
cousinfuckingbama
Im right in the middle of putting my ecobox together. Make sure you put the annular ring gear in the right direction, don't accidentally flip it and don't ask how I know.
Yes you will need more gearing. Do it now so you have the correct axle gears for both speed and crawling.
The 241 I got had the wrong input, it was for a 700R4 so I got a 32 spline input gear off ebay.


It's been a year or 2 since i put mine together so I can't remember for sure. Doesn't it have a lip on it?
 

HYDRODYNAMIC

Rock Stacker
Joined
May 20, 2020
Member Number
545
Messages
760
Loc
Lost in the forest
It's been a year or 2 since i put mine together so I can't remember for sure. Doesn't it have a lip on it?

Yes there is a groove that goes in first. As the gear is pressed in, the splines cut into the case the shavings fill in the groove so they don’t pile and get jammed up when you get to the bottom when it seats flat. It also keeps the shavings from getting into the case and oil.
 
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