71 Blazer 4 speed to Auto swap

[rano]

I have a stock 71 K5 Bazer (that is pretty much all apart) with a 350, 4 barrel, 4 speed and AC. The truck is from out west. My kid is going to drive it mainly in the city and want an automatic. What would I need to do this? Is the transfer case different? Different mounts? It looks like the 350 came with a TH350 in 71. Are the drive shafts different lengths? I am ok with using an aftermarket floor shifter.

[Critter]

There are A LOT of things to answer and all the solutions will can be found around this website. I will try to answer a couple of them.

a) yes, a 71 4x4 auto would have been a th350

b) I'm 99.9% positive that the transfer case would be mounted in basically the same place regardless of auto or manual, so yes, the drive shafts lengths will be the same.

c) the transfer cases are almost identical, the only difference is the input shafts, your manual will be a 10 spline whereas an auto would be 27 spline in 1971. However, the input shafts can be changed relatively easily

d) your adapter between the manual sm465 and np 205 transfer case is different than the one for a th350/np205. The good news is the automatic setup is real easy to find and probably the cheapest option there is. Referring back to point "c" above, in my opinion it will be easiest to find a complete th350/np205 setup rather than trying to piece it together and swapping your current 205 input to match.

There is more to it of course, but I covered some of major stuff. Hope this helps.

[Jtrux]

I agree with everything posted above but I just wanted to point something out. I have a 4 speed in my blazer and at times i've considered going auto with it BUT if you do it, it will take approximately the same amount of time, effort and most important $$$ to go with an overdrive such as a 700R4. If you get one on Craigslist or from a junk yard it won't cost you anymore to get the 700R4 and rebuilding it will be marginally more.

I just don't think it would be worth the effort to go with a non overdrive tranny in a swap like this. And you might even get better gas mileage as well.

I vote against the floor shift mostly cuz I just think they don't look that good and you can get the right steering column at any junkyard for 20-40 bucks.

Good luck and let us know which route you go...with pics of course

[Thealien]

Originally Posted by Jtrux

I agree with everything posted above but I just wanted to point something out. I have a 4 speed in my blazer and at times i've considered going auto with it BUT if you do it, it will take approximately the same amount of time, effort and most important $$$ to go with an overdrive such as a 700R4. If you get one on Craigslist or from a junk yard it won't cost you anymore to get the 700R4 and rebuilding it will be marginally more.

I just don't think it would be worth the effort to go with a non overdrive tranny in a swap like this. And you might even get better gas mileage as well.

I vote against the floor shift mostly cuz I just think they don't look that good and you can get the right steering column at any junkyard for 20-40 bucks.

Good luck and let us know which route you go...with pics of course

I agree with going with an AOD transmission!

[rano]

If I go with the 700R4 what needs to changed?

[Critter]

Once again, LOTS of info on this site on this subject. Run a search for 700r4 swap.

Here's a few links to start with.

http://67-72chevytrucks.com/vboard/s...highlight=700r

http://67-72chevytrucks.com/vboard/s...ght=700r4+swap

Basically you need this installed in the 700r4 and then move the engine forward 2 inches to the "2wd engine location". There are other methods to achieving this swap, but the adapter shaft I linked to is probably the most popular and well documented here on the internet.