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27 spline TH400???

Stephen said:
I broke a 27 spl conversion shaft in my K5 a couple years ago. It worked hard for a few years but ended up in 2 pieces in a crappy spot to recover the truck from.

Given a choice of taking a 400 apart or taking a 205 apart, the 205 wins every day, the 205 is just way easier.

Cost wise, to convert a 205 to 32 spline runs $190 for the conversion kit and typically $60-70 to machine it.

Not sure you can take a trans apart and re-seal it for a lot less than that, definitely not if you're paying for labor.

Strength wise, not only is the 27 spline shaft smaller but conversion shafts are often weaker by construction than a factory shaft.

You also have to consider potential adapter issues, a 400/205 adapter housing isn't going to work with a 27 spl. input gear in the 205 so you have to use a 6 hole to 4 hole adapter on the back of the TH400 and then use a 350/205 adapter housing and drivesleeve.
Compare this to using a 32 spl output that plugs directly into the input gear of the 205 and a single adapter, overall a more robust system.

That said, if you have a 27 spl. shaft keeping it may work for you but I wouldn't spend money to go backward with it, especially if you have an application where you really need the strength of the TH400.
Click to expand...

Yeah maybe I should start looking harder for th400 np205

I found a lomax for 1k, I may get, I figure after I sell my working th350 and np205 I would only have about 500 into it.

I do have to convert my 400 either way though because it's a 2wd tranny.
 
After talking considering the options on my particular set up, I will be going with the 32 spline short T400 output, and change the 203 input as well. I just feel more secure in knowing that with a strong BB up front, I have the bigger parts in the combo. I don't really want to take this thing apart again, and have to replace more parts later.
 
76zimmer said:
After talking considering the options on my particular set up, I will be going with the 32 spline short T400 output, and change the 203 input as well. I just feel more secure in knowing that with a strong BB up front, I have the bigger parts in the combo. I don't really want to take this thing apart again, and have to replace more parts later.
Click to expand...

Wise decision i think. :thumb:
 
76zimmer said:
After talking considering the options on my particular set up, I will be going with the 32 spline short T400 output, and change the 203 input as well. I just feel more secure in knowing that with a strong BB up front, I have the bigger parts in the combo. I don't really want to take this thing apart again, and have to replace more parts later.
Click to expand...

Do you still have the 27 spline output shaft?

I'll run it :D
 
T400 output to 203/T350 to 203 comparison
I decided with my Fresh Big Block, going in the truck and having a T400, I wanted all the strength through the transfer case system I could get. I don't want to have to take this bitch apart, once I get it together.

I think you can guess which is which.


HPIM1579.jpg
 
So after all this, it seems my T400 already has the short 32 spline output in it.
It does have the 4" adapter between the trans and the round pattern 205. So how odd is this?
the output I took out is the same as the output ORD sent me????
 
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