Need advice/opinions (Auto to Manual & Parts Mix-n-Match)

[AaronJen]

Since this is only my second post, I apologize in advance for my total lack of computer skills/proper etiquette. Also, I hope I'm asking this question in the right place.

Sorry if this is long-winded, but I want to make sure I give everyone enough background info to help me out. I promise they won't all be like this.

Here's my situation:

After reading as much as I possibly could on this site over the course of about 6 months, I bought a '90 K5 which had a Goodwrench 350 installed, but otherwise appeared to be bone stock with a 700R4 transmission.

I wasted no time adding ORD's frame repair kit (frame wasn't cracked, but figured I'd head that off while I was ahead), and steering brace. That went pretty smooth, so I decided I'd start searching for a Dana 60. Found an NOS 60 and swapped that in. I'm still working on the brakes, but that shouldn't be too much hassle to fix. (A 14BFF is coming after I sort out my little issue below)

Continuing on with my front-to-back buildup, I bought a rebuilt TH400 mated to a big-bearing round-faced NP205 from a guy my wife works with. It had a slip-yoke, but I didn't think it would be a big deal just to replace it with an SYE, so I got it. My plan was to swap this combo in, but after a little more reading, I decided I'd like to go with the SM465. I want absolute durability, but I also wanted to be able to run a little bigger than a 35" tire without having to swap in anything lower than the 4.56 gears.

This is where I have run into my question about what to do. It turns out that the NP205 I've got is one of the apparently rare synchro units, which I'm not a fan of, plus it has the long 32 spline input. My intention was to replace the front and rear outputs with 32 spline units to match, but to do that, from what I read it will require changing out everything on the front output--shift rails to bearings and shafts, apparently none of it is interchangeable.

I want to use the 32 spline SM465/NP205 combo for its improved strength/durability over the 10 spline model. I have seen a few for sale here and there, but since I have already got an NP205, I'm wondering if it could be made to mate to a 32 spline SM465 from a salvage yard, or if I would be money ahead just to sell it and buy the factory setup I want, assuming I could still locate one reasonbly priced.

Can anybody point me in the right direction? What should I do?

Thanks in advance for your help.

Aaron

 

[bp71k5]

Continuing on with my front-to-back buildup, I bought a rebuilt TH400 mated to a big-bearing round-faced NP205 from a guy my wife works with. It had a slip-yoke, but I didn't think it would be a big deal just to replace it with an SYE, so I got it. My plan was to swap this combo in, but after a little more reading, I decided I'd like to go with the SM465. I want absolute durability, but I also wanted to be able to run a little bigger than a 35" tire without having to swap in anything lower than the 4.56 gears.

I don't know the real differences, but a th400 or SM465 are both very durable, especially with the th400 (big bearing) 205. I doubt you would gain much (if any) strength by using a 465. That's just my take.

It turns out that the NP205 I've got is one of the apparently rare synchro units, which I'm not a fan of, plus it has the long 32 spline input. My intention was to replace the front and rear outputs with 32 spline units to match, but to do that, from what I read it will require changing out everything on the front output--shift rails to bearings and shafts, apparently none of it is interchangeable.

I don't know much about the newer 205's, but the 205 attached to the th400 will already have the large 32-spline input, rear 32-spline output, and a 10-spline front output. You can swap in a new 32-spline front output without changing the shift rails (unless the synco'd units don't work like that)

I want to use the 32 spline SM465/NP205 combo for its improved strength/durability over the 10 spline model.

If you've got a 400/205 combo already setup and your truck is setup for an auto trans, th400/205 seems like the strongest/easiest combo. If you just prefer the manual shifting, then that's a different story and I don't know how rare the 465's with 32-spline output are.

 

[broncoman6524]

Strength wise, they are both about equal.

It just depend on what you want to drive, stick or auto.

You should be able to swap a 32 spline 465 onto that 205 easily. The hardest part will be finding the correct adapter. The trans should be fairly easy, any 465 mated to a np208 will be 32 spline.

Where in florida are you?

 

[AaronJen]

Thanks for the input guys. To clarify things a little bit...
I am looking at the SM465 simply because there are no overheating issues to worry about and no pumps to fail, etc. They are just simple gears and a clutch. Also, from what I've read, anything much bigger than 35's with a 700R4 and 4.56's is just a burnt transmission waiting to happen.

Apparently, with a TH400, you can run bigger tires with those gears simply because the transmission is tougher than the 700R4, but it's a dog around town due to the higher first gear. That's why the SM465 looks good to me. You get the lower first gear, which would enable you to run a little bigger tire, plus you don't have to worry as much about overheating issues like you would with the automatic.

I may be missing the whole boat on this, and if so, someone please set me straight.

As for mating my 205 to the SM465, what adapter would I need, since the one I have uses the long input?

Thanks again for the help so far.

Oh, Broncoman, I'm just North of Gainesville.