RE: How hard to convert 4x4 manual to auto

[ScottH]

Hey guys, new to the 4x4 world, actually dumb would be a better description. Anyway will soon be getting a 71 K20 with a 4 speed in it and was considering eventually converting to an automatic. Can anyone give me an idea of what is involved in terms of work, parts, difficulty, etc?

Any info is much appreciated.

Thanks.

[CUSTOM/10]

Scott;

I've done this but it was a few yrs back, so I may have forgotten some details.

If it has a NP205 transfer case you will need a transfer case from an auto truck or get an adapter from ( Advanced adapters ) This is do to the splines being differant from auto-standard transfer cases. ( If you get an auto transfer case make sure you get the auto adapter that went with it. These are getting hard to find ) You will also need the following parts :

Auto sterring coloumn
Auto shift linkage
High floor hump for an auto ( or patch yours )
Auto brake peddle set-up ( might be able to remove your clutch peddle )
Radiator with tranny cooler & tranny fluid lines
Auto fly wheel
auto starter

If it had a NP205 and you stay with a NP205 you can still use the crossmember in the same location and your drive shafts will also be fine.

Gary

[ScottH]

Gary, thanks for the info. Next dumb question, how do I identify the transfer case?

[CUSTOM/10]

There should be a tag bolted to one of the covers on the case that would have the numbers 205 and a date on it. If nothing been changed a 71 should have a NP205 in it, here's a pic of one.

[Devil'S Ride]

I have a trans cooler, and column shift linkage if you are interested.
As far as the swap goes, I just went from auto to manual...so its pritty much a reverse. Yes, you can just drop the clutch pedal from the 'swingset' an leave the hanger there. but then you have to remove the linkage etc, patch the floor, swap steering columns, unless you get a B&M ratchet type shifter....I used a quicksilver on my auto for about a year and a half and I love it. If you did this it wouldnt be necessary to swap out columns. You would need a new trans tunnel cover, unless you patched yours, and if you use a floor mount shifter like the quicksilver, it will require five holes drilled through. (its pritty easy) Most likely, unless your four speed has a slip yoke, you will need new drive shafts, ( if it is a slip yoke 465 with a 205, a TH350 auto and NP203 xfer case will bolt right up for the rear shaft) You would need a radiator built for an auto trans then plumb the lines.

For now thats all I can think of off the top of my head, let me know if I can help any more.

[ScottH]

Thanks for the info guys. I haven't picked up the truck yet so this is just a bit of research so when I do get it I can decide options.

As always I appreciate everyone's help.

[Devil'S Ride]

just IMO....I love stick shift over auto. The mileage is better (not like that matters on a big truck) its more fun to drive, the low gear of the 465 combined with 4 wheel low will take you up a wall, you get better power transfer to the ground, and your engijne doesnt spin up "empty" rpms because of a torque converter.

I just much prefer the manual to the auto....you might drive it for a while and see what you think....I know a couple of guys that did the conversion you are talking about, and they hated it. The said it went from a truck to a minivan, the power was lost and so was the fun....

Just tryin to give you some outside opinions......so, whatever ya do, enjoy!

[mrein3]

No offense to mr. devil but I went from a manual to a th350 and still say this was the best upgrade I ever made on my truck.

The driveshafts are all the same on 1971 4x4s. The adapter is different lengths depending on the transmission which was designed to make the overall length of the tranny/transfer the same.

You need a complete th350/adapter/np205. Put a new drive sleeve in the adapter while you have it on the ground (approx $90 at the dealer). Check the adapter for cracks. Get new seals for the adapter. This is what keeps the ATF in the th350 and the gear oil in the xfer.

You'll also need an auto steering column and the transmission linkage.

The speedo cable screws off of your manual np205 and on to your auto np205. No modifications necessary.

One more note. The np205 behind my 1971 manual transmission setup did NOT have the tag on it that CUSTOM/10 mentioned above. Neither did my "new" one out of a 1972 Blazer. However I have seen pictures of 205s with this tag. So don't be afraid if your transfer case does not have the tag. Just compare it to the picture above.

[Mudder]

You can go with a floor shifter to keep from having to change the column. I also just tucked the clutch petal under the carpet in case I wanted to go back to the 4speed, that has been done. Not really noticeable. I used a 203/350 and did have some drive shaft issues. I do remember replacing the front for sure.