Question, I got an 89 suburban that had a 400 turbo mated to a NP241. The previous owner replaced the 400 with a 700R. He said he beefed it up with all the good parts and I think, cant get ahold of him, he said he replaced the output shaft, believe he said it came out of an asto van or some type of van. He did say that was done though because it was a stronge output shaft. He didnt say it was because of the spline count. Im thinking of putting a 205 doubler in it and I was wondering if the output shaft on the 700R4 would mate up to the 205. I would have to pull the transfer case now to count the splines and didnt realy want to do that until I was ready to put the 205 in. I dont believe he changed anything on the transfer case so whatever the previous 400 spline count was Im guessing is the same as what the 700R4 currently has in it.

the TH400 had a different spline count than the 700r. If the PO change the output shaft on the 400 to mate with the same tcase that was on the 700, which would be my guess, then you should be fine throwing the 700 back in it

if you do need an output shaft or anyother questions you may try these guys: https://www.wittrans.com/Default.aspx? . I ordered an output shaft for a 400 a built for a guy to mate it to his tcase that was currently mated to a 700 and it was only like $70.00

I think he is saying the opposite. Took out the th400 and replaced it with a 700r4 and replaced the output shaft in the 700 (27 spline) for the 400 equal shaft (32 spline)

what a way to go backwards.

what a way to go backwards.

someone did that to a truck i bought. i couldnt figure out why when i swapped to a different 400 why the heck the 208 wasnt going on.

Backwards hell, lower 1st gear and overdrive. You can build the 700r4 to take a lot of HP and abuse, just takes money and the right parts. Been stomping on mine with a built 502, about 550 hp and 600 ft lbs. Ive broke everything but the tranny and the transfer case. I think im on borrowed time with the 241 though and would like to do the 205 doubler thats why I asked. Im guessing then without looking that he changed the spline count on the 700r4, im hoping anyway then the 205 will bolt up, guess ill just have to pull it and check.

700r4s can be built to withstand a lot of abuse, it just costs a little more then a 350 or 400.

Whichever shaft it has in it you just need to find a 203 (for the doubler you mentioned) that was behind the a 350 or 400 depending on what shaft is in the 700. Much easier then swapping out an output shaft on the tranny.