NP205 Adaptor Differences:3spd vs 4pd?

[special-K]

I have a`71 K/10 with a 3spd/NP205 and I want to swap-in a 4spd.What do I need?From what part to what part?

[Ace in the hole]

3 on the tree to 4 speed muncie with granny?

[Yukon Jack]

You need the adapter between the 4 speed and the t/c along with the coupler, then you're good to go.

[Ace in the hole]

Ya, if you are talking the manual tranys I noted, just the adapter and coupler. I am in the process of doing that to mine right now. Near as I can figure there is about 1/8" to 1/4" difference in the total length between the three speed and it's adapter and the 4 speed and it's adapter so it should bolt right up with minimal fudging.

My 4 speed came out of a 2 wheel drive so I also had to change the main shaft to the 4 wheel drive 10 spline but other than that looks like it is a straight swap.

[special-K]

So what`s different in the coupler/adaptors?These are 3spd-only parts?What about the automatic coupler/adaptor?Is that it`s own animal,too.I`ve been wanting to find a complete 4spd/NP205 set-up to swap in.I`d rather keep the 3spd set-up complete for someone else. I have a complete TH350/NP205 set-up in a donor/parts truck,but I want the 4spd.This is for my`71 K/10 (K/30)project.I really like running the 4spd set-up in my Highlander and that`s the "feel" I want in the shortbed.I have "4L80E" in my signature.I`m not sure,I`m thinking that would be nice in the`72 Sierra which is already automatic.That trans is still in the`91`Burb and I may just rejuvenate that,yet.

[Ace in the hole]

From what I have been able to gather, the adapters for the different tranys are made for the specific trany in regards to the bolt up pattern and length needed. The couplers may be specific to the adapter too. I know that the coupler I took out of my 3 speed adapter is longer than the one in the 4 speed adapter. It also depends on the spline count, normal 3 & 4 speed 4wd tranys of this era trucks were 10 spline output, not sure about the automatics output. Later models had either 27 or 32 splines and different length outputs, can't remember which, but the main shafts were really about the only differences and can be changed to suit your needs.

[special-K]

Thanks.I`ve just always kept things together up to this point and needed to know what fit`s what.This helps alot.

[1969 GMC]

The TH350 has a 27 spline male output, a sleeve, and it's 205 has a 27 spline male input.

Like Ace said, sm465/205 are 10 spline with the sleeve until 1980, which was the last year for the 465/205 in half and 3/4 ton trucks. The K30 only carried the 10 spline for a few more years, then in 84ish or 85ish, got a 32 spline 465/205 with no sleeve, and a long 32 spline female input on the 205. Those setups are kinda hard to find (ok nearly impossible), but would be the "best" way to go IMO...they also have the oem hydraulic clutch.

the 465 only ever had 10 and 32 spline mainshafts. In the 80's, the half and 3/4 tons got NP208's or NP241's (depending on year) behind them. These both had the 32 spline setup. However, the smaller trucks with automatics (TH350/4L60/E) were always 27 spline. Anything with a TH400/4L80E will be 32 spline, at least as far as '91, I don't know a whole lot about the newer trucks.

EDIT: that is good to know about the 3 speed adapter and sleeve. I've never had my hands on one before. I know the Rockwell's is different, I'm wanting to say shorter but I haven't seen it in a while, its lying somewhere in a barn at my parent's place. I think the SM420/rockwell adapter uses the same sleeve, but again I've only ever seen pics of one.

[special-K]

Thanks for the breakdown.

[Yukon Jack]

A little info to add to this. When I bought my 69 K20 it had the three on the tree with the Rockwell. I got a 4 speed plus adapter for the Rockwell t/c from a boardmember but the coupler didn't come with it. I was able to take the coupler from my 3 speed/Rockwell combo and have it cut down and then it worked just fine for the SM465/Rockwell configuration. The 3 speed's adapter and couple was longer and I believe that was done so the overall length of the 3 speed/Rockwell and 4 speed/Rockwell stayed the same.

[special-K]

Thanks,I`ll have to look into that when I get it all apart.I was just considering finding a complete 4spd/205 set-up to do the swap.But,if I can use what I have that would be great.

[duallyjams]

would you be interested in a rockwell set up

[duallyjams]

are you still looking for a rear

[special-K]

I have all NP205s and want to stay with them.I have a complete TH350/NP205 in a`70 Blazer and the truck this 4spd is for has a 3spd/NP205(`71 K/10).I`m selling my 4spd truck and realized how much I like the way it drives.Plus,I have K/30 axles and 37" Swampers for it and want it "tough`n`trucky".I have a spare 4spd,too.Just want the complete package.

About the rear...The truck I`m selling has the HO52 in it with a Locker,it`s 4.10.I`d like to switch the jackpot out with another 4.10 with good ring&pinion.It can be an open diff.I`m using an HO52 in the above truck instead of the 14-bolt.I already have another HO52/Locker/4.10 for it,but would like to have the spare parts.
So...what ratio is yours?

[duallyjams]

mine has 4:56 gears

[Conroe trucker]

Will you email me a pic of your TC shifter?
I am concerned mine may not be correct.
CUSTOMAL@FLASH.net
Thanks,
Mike

[Old Chevy Mech]

Originally Posted by duallyjams

would you be interested in a rockwell set up
Attachment 311865

Which 4 speed is that?
Thanks!

Frank

[duallyjams]

sm465

[Old Chevy Mech]

Thanks!