turbo 350 trans to 4spd manual question

[westy32]

i have a 76 k20 chevy 4x4, has a 350 motor... and i was wantin to change it from the automatic turbo 350, to the 4spd, w/ the L gear, would i need to change the transfer case as well, or will i be able to use the same transfer case that was attatched to the turbo 350, if im notmistaken i believe the transfer case is a np205, its the all time 4wheel drive one.. thanks a lot

[Russell]

You've got an NP203 if it is fulltime 4x4. I'd personally suggest switching over to a 205 along with the SM465.

You will need the 465 / 205 + its mount, clutch stuff, driveshafts, manual lockouts and a 465 / 205 high hump for the cab floor.

The 465 / 205 combo can be bought for between 3 - 6 hundred for a 10 spline setup, more like 1000 for a 32 spline setup, which is far stronger, and eliminates the spline collar that wears down and strips out on the 10 spline setups. Hopefully you can get the mount with the tranny / t-case, if not, should be able to find one on here, or CK5 pretty easily.

The clutch is actually fairly easy to install as well. You will need to take your dash apart, and take the brake booster off. The whole pedal assembly then comes out, and you can bolt the new one straight in. Personally, I'd suggest going with a hydraulic clutch from an 85+ truck. Far easier on the leg, and if you do any offroading, it doesn't get bound up like the mechanical clutch. Either way, you will need to drill a hole in the cab along with bolting in the respective pedal assembly. You will also need a flywheel for the engine, and a pilot bearing pressed into the end of the crank, along with a clutch disk + pressure plate. An automatic truck will not have any of that stuff on it stock.

Driveshafts shouldn't be too tough to find. I do believe that the TH350 / 208 trucks used the same front shaft, but the rear shaft must come from a 465 / 205 setup. If that isn't an option, you can probally have a two peice 2wd rear shaft shortened down, or a single peice shaft made.

As far as the floor hump goes, you should be in good shape there as well. I imagine your truck already has a high hump seeing as it is 4x4, so you can either just cut holes for the 465 and 205 shifters, or unbolt the current solid hump, and bolt a stock 465 / 205 hump in to replace it.

Finally, you will need to add a set of manual lockout hubs onto your front diff. Right now it is always locked in for the full time 4x4, and that does nothing but cause a lot of drag when your truck is in 2wd with the 205.

I can't think of anything else you'll need to convert... I changed mine from a 2wd 3/4 ton TH400 equipped truck to a 4x4 3/4 ton SM465 / 205 equipped truck, and it wasn't too tough at all.

[westy32]

alrighty, i'll make a list of all that. my local junk yard guys are taking everything out of a truck tha ti took there a while ago, kinda messed up w/ that, it had a brand new clutch in it and everything very low miles, truck was just so rusted, and i think the frame was broke, and my buddy took some stuff off of it that he needed, and we just robbed things here and there, but the cab that i have on my truck used to be set up for a stick, but me not thinking i was ever goign to switch it over, took the pedal assy out, and the high hump out, and junked it all. i bought a conversion kit for my transfer case a while ago, to conver it from all tiem to part time 4wd, if possible i was just going to use the transfer case i have, is the np205, all time or part time, i believe the tcase that was in that truck was maybe alltime, im not 100% sure. but if my 203 will match up to the tranny, then i would like to just use that, and save a few bucks, i believe the yard is cuttin me a deal, since i did bring that truck in, he said pry like couple hundred bucks, and maybe trade a few things. let me know what u think

[Russell]

Well, I'm not sure about bolting a 203 to the SM465, but I'll look into it and see what I can come up with

A driveshaft change would be a definite in that case as well.

[Russell]

Alright, I just did some reading, and the SM465 was bolted to the 203 from the factory, but, it isn't quite that easy.

The 203 is much like the 32 spline 205s, it has a female input, and the transmission's output shaft slides directly into the input shaft.

Now, that means that you'd have to have a 10 spline 203, but your TH350 203 is a 27 spline unit. Unfortunately, the 10 spline units were only found in 74, and the occasional rare 75 K5s. So, while its the most popular, its also the toughest case to find.

Again, I'll suggest switching to a 205, just for simplicity's sake.

[westy32]

thanks for looking in to that, in that case, i'll probably just leave the transfer case thats on the truck, the more i think about it, i remember there being lockouts on the front hubs, the 205 is the part time correct?

[Russell]

Yep, 205 is a gear driven part time case. By far the toughest t-case made by GM. Its sole weakness is that shaft that goes between it and the transmission.

Again, just to be totally clear here, your existing 203 will NOT bolt to the standard transmission, even if you were to locate the correct adapter. The spline count between the SM465 and the NP203 is totally different (10 spline vs 27 spline), while a common 10 spline NP205 WILL bolt to your SM465

[akram]

Russell, you sound like the man, I've got a 77 Chev 1/2 4X that I'm wanting to switch from a 4 speed to an auto. I'm looking at finding a donor truck, 97 or newer to get the vortec 350 and swap out the tranny, tcase (or not?) engine, computers, and steering column. I'm new to this site and am looking for someone who has done a swap like this, any tips or where to look?

[Russell]

akram -- I'll send you a PM so we arn't cluttering this post up