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TH400 and T-Case Opinions Needed!!!!

bulldog327

bulldog327

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Hey Guys,

I need some opinions from you guys. My K5 build is coming along pretty well right now and i had some questions about my set-up. I have a Dana 60 and 14 Bolt that is going to be driven by a 468 (500HP, 600 ft lbs of tq)and possibly a TH400. The TH400 i have is 2wd and i was wanting to put a NP205 behind it, but i also have two good running NP208's in the garage. What would you guys do? I am kinda on a budget, but don't want the 208 to shatter either.

A)TH400/NP205

B)TH400/NP208

What will it take to make the TH400 4WD?

Thanks in advance!

Brent
 
Here is what I know from some reading, but not personal experience.
1. TH400 2wd has a tail housing and long output shaft.
2. TH400 4wd has a short output shaft and now tail housing.
to convert between the two you will have to swap the output shafts.
N.B. the out put shafts for the NP205 is different from the output of the NP208.
It might be easier to get a TH400 that is set up for which ever application you are looking for, rather than convert one transmission over. Unless you know a transmission guy who can help you out.
As far as the 208 shattering...I really do not know.
I hope this helps
cheers Matt
 
It depends, if you have a short tailshaft TH400 it will bolt right up to a 400 version NP205 with the correct adaptor. But it will have to be the older figure 8 205. Also, the trans case won't have the bolts for the aluminum converter cover/trans brace if that matters to you. If you can find the correct 205 go for it, if not, just run the 208, but the 208 has to be the correct one for that trans you have as well.
 
If you have a 400 with a bolt on yoke, it's the same as a 4wd that had the 8 track adapter and short input 205. I can't remember bout the long input 205/adapter....
 
TH400/205. Realistically speaking the 208 will not be up to the duty with that much torque from your BB. Do it right the first time and go 205. THe first time the 208 breaks you'll regret not going 205, AND you'll have the additional cost of doing it all over and switching to 205. If the 208 breaks somewhere on a trail or far from home, expect more costs and hassles. With a 205 you'll never have an ounce of doubt that it will break on you. If you need lower gearing than 2:1 low, you can always get the LowMax 3:1 NP205 conversion for $1000. The 208 will be the weak link in your drivetrain - I wouldn't even consider a 208 with your BB.
 
What are you building the truck for? Are you going to use it for mud or pulling? If your building a street truck and just running a mud bog or 2 then the 208 should do ok. It all depends on what your plans for the truck are. The 205 would be the better of the 2 though.
 
Thanks Guys,

That was alot of help. I am building the truck for strictly trail riding and mudding. If i post pics of the TH400 could you tell me what model i have??

Thanks Again!
 
Take the 2wd tail cone off and post up a measurement of how much tailshaft sticks out beyond the body of the trans. This is the easiest way to determine what you have and can do with it.
 
If weight is an issue and mudding/trail riding the 208 will be fine. I am running 400/208 with a little more power and without breakage. Oh did bust one in a hill-n-hole but will not attempt that again. But then it may depend on which adapter you already have.
 
Hey Guys,

Thanks so much for your help. I figured out that i have a short shaft TH400 and from what i can see i should be able to get a TH400 to NP205 adapter and it will work. Is this all i would need? It looks like i could take the tailshaft off and put the adapter on and install the 205. I found one on ebay for $175.00 is that the going rate or should i keep shopping?

Thanks Again,

Brent
 
Just make sure that the adapter & 205 are pre '85 so the adapter is the tall design and the face of the 205 has the figure 8 bolt pattern (a round bolt pattern is '85+).
 
Make sure you use the two brace bars going from transmission inspection cover to the motor mounts. It will help prevent stress and cracking of your TH400 case. I know of people who didn't re-use them and ended up cracking their trans case. Alot of work to fix and so easy to prevent.

See picture in post #54 and #77 here:
http://coloradok5.com/forums/showthread.php?t=139806&highlight=transmission+brace&page=6
You can fab it up easily enough with steel rod and some plate if need be, thats what I had to do after I misplaced mine when doing a BB swap.
 
sweetk30 said:
had a fig 8 th400 adaptor for sale and just sold it shipped for 150 .

day late :doah:

pic of tail shaft id's
Click to expand...


That helps alot. Mine is the threaded 2wd shaft. Will it still work fine??

Sorry for so many questions i'm just trying to do this right the first time.

Thanks so much guys!
 
I've done the exact same conversion, take the tail cone and yoke off and you're good to go. Again, use the pre '85 np205 set up.
 
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