th400 and np205

[MitchReed]

I have a short shaft th400 out of a 2wd Chevy and a np205 with adapter that was with a th350. I havn't had a chance to tinker with them because I am working 4 hours away from home and dont get back much. I want to put them togather. I have heard that they will bolt right up and I heard that I had to buy a special adapter. Does anyone know?

[u2slow]

A TH400 has a 32-spline output. A TH350 has a 27-spline output. If your NP205 is from a TH350 (therefore 27-spline) it will NOT FIT a TH400 without a special adapter or a collection of factory parts.

Here's a few pics of what you're dealing with trannywise ...


This is good article on the different types of GM NP205's...
NP205 Tech

[Black Dog]

As can be seen it the pictures above, the bolt pattern on the back of the tranny for the adapter is also different. TH350 and 700R4 use a 4 bolt pattern, TH400 and 4L80E use a 6 bolt pattern.

[MitchReed]

Thanks for the replies. Are the 700r4s as tough as the th400? I like the idea of having an overdrive and if it will bolt up to the np205 even better.

[u2slow]

A TH700 is on par strength-wise with a TH350. It will bolt up to a TH350-type NP205 with a special "short" output shaft or small (1") spacer. I've also heard you can cut the shaft down, but I don't know if there's enough spline length for that.

[mudslut]

you already have the right tranny but this is what you will need. first you need the turbo400-205 adapter. they are hard as hell to find. then take all the guts out of your 205 and machine the case out to accept the bigger bearing for the 400 shaft. Install the bearing put the guts back in and your done.

[u2slow]

Originally posted by mudslut:
<STRONG>take all the guts out of your 205 and machine the case out to accept the bigger bearing for the 400 shaft. Install the bearing put the guts back in and your done.</STRONG>

Not quite! <IMG SRC="smilies/thefinger.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0">

The reason you need to machine out the case is to make room for the 32-spline input gear (and bearing) that you need to swap in. Odds are you won't find that input gear without an entire NP205 attached to it. <IMG SRC="smilies/frown.gif" border="0">

[Stephen]

The inputs are still available new, we sell a lot of them for use with our Doubler kits. The factory adapter is also available new, but at about $300, so it starts looking less attractive. If you have an urge to try the 700, do some research on it, it's easy to adapt to your 205, just like outlined above.

[MitchReed]

Stephen,
When you say "we sell" do you mean you have a 4x4 shop. Tell me about your doubler. I would like to get better than 1.9/1 low range. I heard you can take the 4x4 part off of a np203 and there is an adapter available to bolt a np205 to it. This would allow 2/1 low in 2x and 3.9/1 low in 4x and the adapters for the th400 to np203 are easier to find. Has anyone heard of this?

[SMP K5]

http://www.offroaddesign.com/

[bigblaze]

like stephen said the adapter are still available and the input gear and bearing($150 + $50) that and just skip the adapter and buy the genII doubler from stephen,i ended up with extra cause i purchased the doubler

[u2slow]

ABout a year ago, one of the techs at my work went to order a TH400/NP205 adapter for a project. The GM dealer said the adapter was discontinued. It had to come in from Edmonton - they said it was the last one in captivity.


32-spline NP203 inputs sound like they're even tougher to find <IMG SRC="smilies/rolleyes.gif" border="0">

[MitchReed]

BigBlaze,
What do you have in your truck? What does np203-205 mean? I am confused do you have what I was asking about with a th400/np203 gear part only/adapter/np205. Or do you have a doubler and if so how strong are they and do they make them that will bolt between a th400 and a 27 spline np205? What can I expect cost wise?

[RocnWilly]

Coast Machine and Supply in Ventura can get the 32 spline inout gear for $110.
Instead of the 250/203 doubler you might consider a Klune-V crawler box. They have a box that will bolt to a TH400, TH350, or TH700 to the 205 with little or no adapters.
This would give you a ratio of 1.9:1, 2.72:1, or 5.1:1 low range options. <IMG SRC="smilies/smile.gif" border="0">
Just my two cents worth. <IMG SRC="smilies/biggrin.gif" border="0">
I'm currently working on this setup for my Willys wagon. <IMG SRC="smilies/tongue.gif" border="0"> Slowly, but surely. <IMG SRC="smilies/frown.gif" border="0">

[jeepruler]

Stephen I didn't know you were on this board. I got another case and a highangle driveline 1 ton cv with 12" travel for the front so lets hope I don't break another one <IMG SRC="smilies/pissed.gif" border="0"> .
Can't wait to run the doubler on the Con!
Jacent

[ 08-15-2001: Message edited by: jeepruler ]

[Jimmy]

they are full of sh!t I have a brand new nevwe used factory adapterTH400 to 205 sitting on my tool box..I bought it from a dealer. I had bought it for my doubler set up but ended up going with the Generation II and did not need it.

[u2slow]

Originally posted by Jimmy:
<STRONG>I have a brand new nevwe used factory adapterTH400 to 205 sitting on my tool box.</STRONG>

What year is yours for? This one was ordered for a 90 crewcab TH400/NP205 combo. I've heard there's two lengths of 32-spline input for the NP205. Maybe you have another version? A pic of you adapter would be much appreciated.

[DynamicCrawler]

Originally posted by Jimmy
they are full of sh!t I have a brand new nevwe used factory adapterTH400 to 205 sitting on my tool box..I bought it from a dealer. I had bought it for my doubler set up but ended up going with the Generation II and did not need it.

How much would you let it go for? Im in the need of one or I can get one from my dealer, how much did cost from the dealer where your at. Our dealership has a tendacy to rape people on parts cost.

[cheech]

I have a little different problem.I now have an SM465 /205.If I was to swap out the SM465 for a TH400 what would I need?

[DynamicCrawler]

Originally posted by cheech
I have a little different problem.I now have an SM465 /205.If I was to swap out the SM465 for a TH400 what would I need?

The same thing Im needing a 32 spline short female input shaft,

Offroad design sells them for $200, A little rediculous if you ask me considering you have to have you housing machined also to fit the bigger bearing.