2wd 400 trans changed to 4x4

[bigben129]

is this a possible switch?  where would i find the parts?  also the trans adapter to the transfercase?  lots of questions and you guys with more experience and know how let me know if I am  biting off more than i can chew?
got a solid 1984 2wd for a steal and want to do some modification.  i have 3/4 ton running gear and would like to swap it underneath.
ideas and options appreciated.

if ya need more details i can provide whatever you want.  if it is numbers off trans    someone will have to tell me where to look.  LOL

[nvrenuf]

What is needed to be done on the th400 will depend on the current tailshaft. Take the 2wd tail cone off, measuring from the back of the case, how much tailshaft sticks out?

Next, do you already have a t-case you want to use?

[Blazin]

You will need the output shaft from a 4 wheel drive transmission. This is the last piece to come out of the trans, and the first to go back in. So you might as well rebuild it while you have it torn down. As far as the adaptor you will need the one that mates the transfer case you use, either an NP 205, or NP 208 to a TH 400. The 205 is a much stronger case. If your only planning light off road use, or snow driving the 208 will work fine with up to 35" tires.
As far as the input shaft on the transfer case you will need a transfer case from another TH 400, or a 79 / 80 or newer SM465. Its been a while but if I remember correct they are 32 spline.

Or you could find a divorced NP 205, and use your transmission just the way it is with a jack shaft between the trans., and transfer case.

Do you have the front rear spring hangers from the 4x4 chassis? You will also need the cross member that goes underneath the motor from the 4x4 chassis to suport the motor after you remove the 2 wheel drive front end.

You will need to cut the floor center hump out and install a 4x4 hump, or run a body lift.

[nvrenuf]

Hold it, you don't necessarily need to change the tailshaft - again, it depends on what you already have. A lot of 2wd 400's have a shaft that sticks out of the case 4". These versions will readily accept a 32 spline 205 & adapter from a pre '85 truck, these are also referred to as a tall, figure "8" style adapter and the t-case uses a short 32 pline input.

Iirc, the 208's will use a 4wd only tailshaft so he should not have the right version trans for this.

Also, the 32 spline 205 from a 4spd started in '85. Anything '84 and older will be 10 spline.

Starting in '85, ALL 205's are 32 spline using a long input shaft which requires a short, round style adapter and a4wd only tailshaft.

It gets even deeper but the simple answer is that your 2wd 400 will most likely accept a 205 (with adapter) from an '84 or older th400 application (3/4 or 1 ton).

[Sartobuilt]

(quote from above) It gets even deeper but the simple answer is that your 2wd 400 will most likely accept a 205 (with adapter) from an '84 or older th400 application (3/4 or 1 ton).

This is what i remember, I had to change my tailshaft to convert to a 208 then changed it back to the 2wd shaft when i put in a 205.
Of coarse check with a tape measure to be sure.