TH400/205 swap questions

[hi pinion]

Ok, i have some qusetions.

My 74 i just got has a 350/350/203 setup right now.

Its got a 4 inch lift on it right now.

Desert Rat replaced the shafts on the truck both front and rear, it has Off Road Design shafts on it, brand new...........



My qestion is this, if i do the 400/205 install, what do i have to modify?The crossmember? The shafts? Is the 400/205 LONGER than the 350/203 in it now? Also, could i technically find some shafts off of a truck the already HAD a 400/205 in it and make that work easy?

Whats involved? Also, are all the th400 trannys the same in length/cases? I thought i read some of the th400s were shorter than others ,, or mabey it was the 205 i was thinking about.

Anyways,,,,yeah

 

[dyeager535]

Only thing I know about is the TH400's. The length is all the same when talking about the case. Since the adapter on a 4wd is what places the crossmember on the frame, not sure if GM was smart and made the TH400/TH350 length the same with the crossmember in regards to crossmember location, or if they were different.

 

[Desert Rat]

The NP203 is longer than the NP205 (http://www.offroaddesign.com/Transfer%20Case%20ID%20Guide.htm). The TH400 case and the TH350 case are very similar in length. If you swap in the TH400/NP205 combo, it is likely that the crossmember will have to move, but not a huge amount. This will result in the driveshafts (made by Bayshore Truck in Livermore, not ORD ) will need to be modified. However, they are new and it shouldn't cost a lot to have a local driveshaft company shorten or lengthen them for you. Or, you can find someone with a TH350/NP203 setup around and sell them to them since they are brand new and then go HAD. I wouldn't use used shafts from another truck with the TH400. I would just have new ones made or modify the ones you have. The easiest way to make the change is to support the engine, drop the tranny and TC. Swap in the TH400 and install the NP205, bolt the crossmember to the bottom of the NP205, jack it up against the frame, mark the frame, drill new holes, and install the crossmember. Then take measurements on the length from the TC outputs to the diffs and see if you can use the existing shafts. If not, modify them or sell them and go new.

 

[BranndonC]

i'm no help since i went straight to a doubler, never just a 400/205, and my 205 is a slip yolk, so my shaft from my 241 worked for it

 

[sweetk30]

case length from bell to end of case where tail adaptor bolts on

th350= 21 5/8
th400= 24 5/16
th700= 23 3/8
4l60 to 95= 23 3/8
4l60 96-up= 21 3/4
4l80= 26 even

 

[hi pinion]

case length from bell to end of case where tail adaptor bolts on

th350= 21 5/8
th400= 24 5/16
th700= 23 3/8
4l60 to 95= 23 3/8
4l60 96-up= 21 3/4
4l80= 26 even

Thanks!!!

 

[sweetk30]

no problem. just poped over to tci and grabed the specs for ya.

 

[BizeeB65]

You still have those shafts? Is the rear shaft stock length? Has it been lengthened for the lift? I am looking for a lengthened rear driveshaft for a NP203 to 12B with 6" lift. Interested in selling?