Converting to Automatic? What do I need?

[Huskerboy2]

I'm thinking about converting my 4x4 '72 Blazer from a factory 4 speed to an automatic. What all do I need? Crossmember, steering column, linkage, remove clutch from pedal assembly, clutch rod block off plate for the hole in the firewall, etc. It's got a bolt in high hump, since it's a 4x4, would it have been a high hump whether it was an auto or 4 speed? How hard is this. I would probably go with a stock type tranny. TH350 or 400? Any thoughts on a good tranny? Thanks guys.

[NWD02]

My truck appeared to be a factory 3 on the tree truck. Of course by the time I found it in a field it had been molested. If you look at my build forum you'll even see a huge "custom" floor shift hole someone was nice enough to add. While at the metal shop the hole was fixed. I'm putting in an auto column and already found the automatic shift linkage for it. I installed a turbo 400 tranny behind the 5.7l 350. When buying the stock converter and flywheel there was a little confusion but I got it all figured out. The motor is a 91 truck block. It sounds like you're list of parts you'll need is dead on.

If you're going to do floor shift I think you could use the same column you have now just buy the floor shift linkage. If column shift the linkage and column is a must.

Since I'm no expert maybe someone else can add to or correct me.

[WorkinLonghorn]

Cooler lines,cooler (unless your radiator already has one),modulator vacuum line,kick-down bracket and linkage,crossmember (I have one extra),shift linkage,dip-stick,different speedo cable (?),driveshaft(s) lenghthened/shortened,torque converter,different starter(?).

[thesteppenwolf]

..oks, since there is talk of auto/columns....I have a '71 4x4, with a worn column....what is the possibility converting it to a floor shifter?..where can I get one if it is possible?

thanks

[NWD02]

Thanks Longhorn.... now I need to make sure I have it all for my build too....

[mrein3]

Originally Posted by Huskerboy2

I'm thinking about converting my 4x4 '72 Blazer from a factory 4 speed to an automatic. What all do I need? Crossmember, steering column, linkage, remove clutch from pedal assembly, clutch rod block off plate for the hole in the firewall, etc. It's got a bolt in high hump, since it's a 4x4, would it have been a high hump whether it was an auto or 4 speed? How hard is this. I would probably go with a stock type tranny. TH350 or 400? Any thoughts on a good tranny? Thanks guys.

Been there, done that.
I went from a 3-speed manual to a th350. In a 72 Blazer a th400 wasn't a factory option but it was later so you can use one. The th350 was offered and in fact the tranny, adapter, and transfer case in my K10 are out of a 72 Blazer. Your driveshafts and crossmember, if sticking with stock 67 - 72 pieces from a NP205 transfer case setup are the same.
You need:
auto tranny
tranny to transfer case adapter
transfer case
radiator that accepts tranny cooler lines
transmission cooler lines
transmission shift linkage (I got Blazer stuff on my pickup that I bolted on with no modifications so truck or Blazer should work)
steering column with auto shifter

Your factory driveshafts and crossmember are the same. GM was smart on this. All transmissions available in a 4x4 with an NP205 transfer case have an adapter to get them to spin the transfer case. GM made the overall length of the transmission and adapter the same length on all 1972 models. And they bolted the adapter to the same spot on the crossmember. That is why you want to get a transmission, adapter, and t-case out of a donor. The one silly thing they did is make all the transfer cases behind manuals with 10-spline input shafts while the th350 has a 27-spline input shaft on the t-case. If you decide on a th400, that is still different but I've never dealt with one of those out of a later model truck.

To do the swap the procedure is simple but because of the weight of all this stuff it is a logistical issue. You remove driveshafts. SAVE THEM. I'll say it again you put the exact same ones in with no modifications. Remove the crossmember. Then remove the 4-speed, adapter, and t-case. Install th350, adapter, and t-case. Install crossmember. Replace driveshafts.

Install cooling lines, linkage, and steering column.

I strongly suggest you install an aftermarket, external tranny cooler. After my swap I did a test. I used to fish bass fishing tournaments and had a tourney 100 miles from my house. My first practice weekend for this tournament I towed my boat without the external cooler. The one town I had to go through with stoplights had my tranny temp gauge pegging in the 200-220 degree range at the red lights. The next weekend I made the same run in similar temperature conditions and stopped at the same lights with the tranny cooler installed. This time the tranny temp never got to 200 at the stop lights.

My clutch pedal is still hanging there after only about 5 years so you don't HAVE to remove it. It is kind of funny at the boat ramp when somebody jumps in to help me and 'pushes in the clutch'.

Sorry this turned in to such a long post. I hope it helps.

[mrein3]

Oh, one more thing. Your speedo cable is the same. Same length, same everything. If your truck or the donor has something other than 3.73 gears in the differentials, you'll have a little speedo corrector unit between the transfer case and the speedo cable. Simply put your truck back together the way it is now. That is you you have a corrector in there put it back. If your donor comes with one and you currently don't use one, leave it out.