71' 3 ott to 4 speed or auto

[hotrod 80]

Looking at a 71' Blazer with lots of parts for $300 ( i can't pass it up ). The young man pulled the motor out to replace a freeze plug and it is in the back . Anyway . it is no power steering and no power brakes and 3 speed on the column . I am wondering how hard it is to swap to a 4 speed granny or 350 automatic . How hard are the parts to find or will any 4x4 trans go to any case ? I had a 3- speed in the 67' and it always had linkage problems . Also how had is it to put power steering & brakes on ? I am new to the older Chevy 4wd world .

[Yukon Jack]

I swapped a SM465 4 speed into my 69 K20 to replace it's three on the tree. I was told there was a chance the bellhousing hole was slightly different for two different transfer cases but since than I've heard that they are the same. I used a different bellhousing so I never had to figure out if there was a difference.

If you swap transmissions and are staying manual, you will want to get the adapter and coupler sleeve that goes between the transfer case and the new transmission. Your transfer case will probably be an NP205 from the factory and it shouldn't be too difficult to find an SM465 and proper adapter. If you can get a picture of your transfer case we can confirm. There is a slight chance you might have a Dana 20 transfer case.

Expect to pay $100 to 200 for the tranny and adapter. You can often get a complete SM465, adapter, coupler sleeve and NP205 for about $300.

If you have an NP205, the length difference between the three speed tranny and the 4 speed is made up by the adapter so you shouldn't have to move your transfer case crossmember or mess with your driveshafts.

If you have a Dana 20 and you swap to an NP205 you will need to drop your existing transfer case crossmember down 1".

Nothing wrong with the Dana 20 but if you have one, now would be a good time to swap in a complete NP205 and SM465.

Power steering is pretty simple to add. You'll need a 4wd power steering box and power steering pump. If you get them off of the same donor vehicle you won't have to worry about whether the ends are correct. I put one in my 69 K20 from like a 78 K20 and it was an easy bolt in swap.

I'll let someone else speak about the power brake booster swap.

[swyfor5]

Right on Yukon! I have the Dana 20 in my 70. Right behind a 465 4 speed. Debated about swapping out the 20 for a 205, but gonna stay with the 20 for now. I would never want to wheel with a 3 on the tree setup, not that you couldn't. Because I have, in a 72 K5 with a 250 6 banger, and it wheeled real good!

[hotrod 80]

Thanks for the replies guys . I tried the search feature , but this is the info i was looking for . The transfer case has 2 sticks . Probably pick it up friday . Picks to follow .