700r4 to np203...

Boonie Buster · Apr 6, 2008

So apparently there are two methods to this..

I currently have a 700r4 mated to a np231 (was mated to a np207 before). And am now thinking of taking the dual cases from the LUV project and putting them in the s-10. the cases are a np203/np205 mated behind a th350. I dont know much about the th350 it is mated to, but i know that i just had my 700r4 rebuild a little to replace some broken/worn gears/clutches.

Supposedly the tailshaft on a 700r4 is approx. 2" longer than that of a th350 requiring either a 2" spacer or a new tailshaft, I am thinking for the price a new tailshaft would be my best bet.

1. get a 2" spacer and bolt it on, not sure of the price or availability (can't find anything on it...)

2. get a new tailshaft for the 700r4. $172 from A.A.

Below is a link to what i think is the right tailshaft for the job...
So is this the correct tailshaft i need to do this swap???
https://eshop.advanceadapters.com/c...-gm-np205-adapter-kit-28r-50-6900-50-6900.htm

Anyone ever done this or had any problems with it, someone was saying the 203 is too heavy for the 700r4 case and will break it, I don't understand how it could break it, unless support imporperly...:eeek:

Any suggestions? I have thought of getting the th400, but i am not sure of it's O.D. whether or not it would allow streetability like the 700r4. I have also thought of having my 700r4 build a little more hardcore or buying one built also, those are a couple other options, I just hate to have to sheel out more money for it after i just dumped money into it for repairs...

4xrick · Apr 7, 2008

well the adapter would be simpler and cheaper but i would not advise doing that at all. I don't know anyone who has ever run a doubler behind a 700r4 but then I would never do that or even run a 700 in a wheeler.
if you do this you need to build extra supports and basicly run a second crossmember, the weight of the doubler will cause the end of the tranny crack and eventually break I did and have seen a couple other people do it with even a th400 which is way beefier than a th350 or 700r4.
are you trying to install the tailshaft yourself?

JThompson · Apr 7, 2008

I, personally, would just retrofit an iron-case manual up in there and not worry about all this shizzle :awesomework:

:stirpot:

Boonie Buster · Apr 7, 2008

I hae a transmission guy to do the trans. work, I am still not understanding how the weight of the t-case is going to break the transmission ( I am going to have the t-case and tranny properly supported for torque and weight) so how is it going to break other than utter self destruction....

And yes, I too have seen this setup ran behind a th400, I would almost rather run it behind a th400 if I knew that it would have the same O.D. as the 700r4 but i don't (haven't researched it fully yet) so....ya... i dunno what i am gonna do....

WHITE TRASH1 · Apr 7, 2008

I was told by a chevy parts guy there is a factory spacer available to retrofit the 700r4 where a th350 used to live. Supposed to be cheap too, google is your friend.

Boonie Buster · Apr 7, 2008

I have yet to find it, prob. looking for the wrong thing...:eeek:

HillbillyPlumber · Apr 7, 2008

No overdrive on a TH400

JThompson · Apr 7, 2008

With you staying with 4.56 and going to a 42" tire, do you really need overdrive....? :flipoff:

Can you divorce them? You have the length, and can probably source a d-shaft from a shorter rig to run behind it all.

Boonie Buster · Apr 7, 2008

no... no divorced cases...

Boonie Buster · Apr 7, 2008

HillbillyPlumber said:
No overdrive on a TH400

ya, read that last night, so i am sticking with the 700r4, i jsut can't seem to find the spacer and for some reason my computer is not allowing cookies on the advanced adapters website to let me look at the tailshaft again

WHITE TRASH1 · Apr 7, 2008

A & Reds Transmission Parts
2501 E Truman Road
Kansas City, MO 64127
(816) 483-7337

The part # 7Q35A and it sells for around $50.00. Trim about 1/8" off the end of the 700r4's output shaft and from there its all bolt-up.

Like I said, google is your friend

Boonie Buster · Apr 7, 2008

****in' yahoo!!!

:haha: :haha: :haha:

Thanks man.:kiss:

Boonie Buster · Apr 7, 2008

WHITE TRASH said:
A & Reds Transmission Parts
2501 E Truman Road
Kansas City, MO 64127
(816) 483-7337

The part # 7Q35A and it sells for around $50.00. Trim about 1/8" off the end of the 700r4's output shaft and from there its all bolt-up.

Like I said, google is your friend

So this is just a spacer that goes on the back of the tranny and keeps the same bolt pattern to the front of the stock tranny to t-case adapter, correct? not sure if i said that right, but it is the same 4 bolt pattern on either side of the spacer...as on the back of the tranny...correct...?

WHITE TRASH1 · Apr 7, 2008

th350 and th700r4's have the same 27 spline output and 4 bolt pattern. The 700's is just longer. So yes, same shiat different length.

Boonie Buster · Apr 7, 2008

http://67-72chevytrucks.com/vboard/showthread.php?t=128495&page=2

i needed visual confirmation and this is what i found:awesomework: that is exactly what i was talking about.