Manual vs Auto

[swyfor5]

I know it's been done before, but I am researching transmission options. My K5 has the stock 4 speed trans that will need rebuilt for my resto. Plan is to go 1 ton axles and was looking for feedback. I can rebuild the 4 speed, or swap in an auto. Really thinking of going auto, but don't want to change the crossmember etc. Any thought's?

[Jtrux]

An auto swap is easy seeing as how they came with them from the factory but your 4 speed shouldn't need rebuilding, maybe resealing but the SM465 is a stout 4 speed. I'd stick with it personally.

[swyfor5]

Thank's. Kinda leaning towards keeping the stick. I remember "rocking" my way out of being stuck more than once!

[special-K]

X2 on reseal is all the 4spd will need.I changed a 3spd toauto and was easy,but I had a complete donor.

[Burt4x4]

Just say No to Slushbox/FireBomb

Never had an Auto, I like the security of having a manual tranny. Heck you can even bump start your rig if yer starter dies..just to mention one Pro.
I saw an Auto overheat and spit tranny fluid onto the exhaust
3 fire extingushers later the fire was out

[special-K]

^...Dat`s a big fryin`pan ya got ratdere.

[mrein3]

Originally Posted by swyfor5

I know it's been done before, but I am researching transmission options. My K5 has the stock 4 speed trans that will need rebuilt for my resto. Plan is to go 1 ton axles and was looking for feedback. I can rebuild the 4 speed, or swap in an auto. Really thinking of going auto, but don't want to change the crossmember etc. Any thought's?

I can answer the crossmember question - you already have an auto crossmember. It is the same as the stick crossmember.
Back in 1972, GM was modular before anybody thought of the term. ALL the transmissions in 4wd Blazers that were in front of a NP205 work on the same crossmember. GM made the difference in length and mounting in the transfer case adapter. They all bolt to the same crossmember in the same place. To swap transmissions you need to get a complete donor: transmission, adapter, and transfer case. The 3 and 4 speed manuals had a 10-spline input shaft so they interchange but the th350 had 28 splines. To interchange the NP205 out of a manual, you need the transmission and adapter that came together from the factory.

Make sense?

Further, you can swap items out of a truck into your Blazer or vice versa. In fact, the th350 and NP205 in my longbed came out of a 1972 Blazer. I removed them myself and installed them in my truck. I used the same crossmember and driveshafts with no modifications.

Don't forget if you do go to an auto you need a different steering column and the shifter linkage. You also need to think about tranny cooling lines.

One of the best things I ever did is put an automatic transmission in my truck. It makes life SO much easier at the boat ramp. Also this past winter I put a plow on my truck. Once again I would hate to burn up a clutch pushing snow around my driveway.

I do miss the "shift on the fly" capability I had with my standard transmission. There are times, though infrequent, that I wanted the lower gear range of 4 low without needing the front hubs locked. With the straight stick I could simply jam the clutch to the floor and shift the case. With the auto in there now I need to come to a complete stop and put the tranny in park to shift to four low.

[swyfor5]

Awesome guy's, decided I'm keeping the stick!

[swyfor5]

Now, I again don't know what to do. I think I've decided to swap out my dana 20 t-case for a np205 case. I still want to keep the 4 speed manual, cause I don't want to change the steering column or etc. When swapping in the 205 is there any changes to the floor hump, or the rubber boot, etc?

[Yukon Jack]

You'll need to drop your transfer case crossmember down 1" and of course have the NP205 adapter and I think the side mount for the transfer case is different but I'm not positive about that. I'm trying to remember but I can't be sure if the shifter location is the same or if I had to open up the hole a bit for the NP205 shifter.

[swyfor5]

Yukon, I'm guessing I need to drop the t-case crossmember 1" because of driveshaft angle? Been looking at the cv shaft setups, and maybe that's the way to go? If I remember right the 20 has the output shaft centered, and the 205 is offset, right? I get confused easily!

[mnwirehair]

I have more of a question than a response. Thinking of doing similar swap. I currently have a 350 eng-4 speed standard- with rockwell transfer. would like daily driver have complete donor th350 with np transfer. can I install a floor shifter vs colum? Minimal talk about the rockwell will all bolt up the same? thanks. Engine is currently out.

[swyfor5]

Wow, I don't have a clue! Anybody know?