3 speed to auto swap ???

[Evans]

I'm thinking about doing this swap and wondering what has to change to do it ...... crossmember ?? tranny tunnel ?? I thought I read something about different tranny tunnels (high hump vs low hump)....

[shifty]

If I would have went with an auto after having my 3spd on tree, I would have needed to add an automatic tranny crossmember, hack out the manual tranny crossmember, and I could have kept my normal tranny hump (low hump). You'll also need an automatic steering column, unless you plan on mounting the shifter to the floor, at which point you'll need to cut out a section of the tranny hump to mount the shifter.

TIP: A jigsaw with a fine-tooth metal cutting blade makes easy, nimble cutting of the floor panel. I tried using a Sawzall, BIG mistake. Followed up later with the Jigsaw and kicked myself for not using it in the first place.

[shifty]

PS - I have a refurbished AT crossmember if you need it. New hardware for it. You should already have the proper holes in your framerails to mount it.

[Evans]

My truck was already converted to floor shift 3 speed before I got it..... so basically I would need a crossmember for an auto.... correct ???

[ThatOneBlue67]

And a transmission cooler and lines. (Those are kinda important).

And I remember needing a new flywheel also. AND a new starter. I think... it needs a new starter if it is an inline 6 anyway. Don't quote me on the V8.

[shifty]

And a radiator that supports the tranny cooler lines (i.e. a 3-core or 4-core).

As you can see, I bypassed some of this crap because I went with a manual 6spd tranny and a new engine entirely, so .... :\

[ThatOneBlue67]

Actually, if you don't feel like swapping out the entire radiator, there are SEPERATE transmission coolers that hang right in front of the pre-existing radiator. They actually cool even better I'm told. Never had problems with mine, and I'm running a 700R4 tranny (can get pretty hot!).

[Tx Firefighter]

Yes, like Blue67 said, need auto trans flywheel (flexplate), 6 bolts for it, a starter or starter nose cone at least, two starter bolts, three torque converter bolts, auto trans crossmember, trans mount, cooler and lines, shifter and linkage, dipstick and tube, kickdown cable and bracket for it.

[Don Brace]

I went the other way and put a 3 speed OD in place of a 350. I used the auto cross member under the OD. Have not driven it as of yet. What is the difference between the auto and the manual cross members?
Don

[shifty]

Originally Posted by Don Brace

I went the other way and put a 3 speed OD in place of a 350. I used the auto cross member under the OD. Have not driven it as of yet. What is the difference between the auto and the manual cross members?
Don

Position and mounts for the manual transmission from my truck:

http://satellitehead.com/gallery/dis...=38&fullsize=1

And another picture after cleanup - note that it's only ~2.5" wide:

http://satellitehead.com/gallery/dis...=41&fullsize=1

The auto tranny xmember is mounted about 6 inches back, and notice that it's about 3.5" wide, notice the two holes near the center - only one mount on the AT xmember, two mounts on the MT xmember:

http://satellitehead.com/gallery/dis...207&fullsize=1

This is the best I can explain it to you.

That's the AT crossmember I just rebuilt that I was offering above. I will not be using it in my buildup, and really have no use for it. I bought it from board member TRUCKGUY, tore it down, ground it down, prepped and rattlecanned it. It's ready to install, be powdercoated, whatever. Total waste to keep it in my garage.

[OLDIRON69]

Originally Posted by Tx Firefighter

Yes, like Blue67 said, need auto trans flywheel (flexplate), 6 bolts for it, a starter or starter nose cone at least, two starter bolts, three torque converter bolts, auto trans crossmember, trans mount, cooler and lines, shifter and linkage, dipstick and tube, kickdown cable and bracket for it.

I just did the same swap a couple months ago. I still have not found a kickdown cable bracket for it, I have a B/M ratchet shifter that just bolts to the floor, so I welded up the hole where the 3 spd floor shifter came thru, it shifts via cable. If I need to pass, I just ratchet down and give it hell.

I used a flexplate for a '69,starter for a '77 w/auto. The '69 starter for an automatic was a no go. On my saginaw the starter bolts to the bell housing, so you will definately need a starter and bolts for the starter, I used a aftermarket cooler and there is cooler line specific for tranny fluid, it normally is about a buck p/ft. if the tranny dosen't already have cooler lines you can buy the fittings at the autoparts store (Autozone) is where I bought mine, I flared the fittings a little and used hose clamps. I made my crosmember out of tubing and a new tranny mount, was easy to build. You'll need bolts for that too...I just went to Tractor Supply and bought a couple pounds of grade 8 bolts,nuts and washers in various lengths and sizes. Having some extras around is always nice. Your drive shaft will have to be shortened, mine did anyway with the short tail TH350 I went with. New carrier bearing while I had it out along with U-joints.

[Don Brace]

Rather tan use the motor mounts on the bell housing I used the auto cross member and the mount under the three speed transmission.
Don

[Don Brace]

Evans
If you are not going to use the 3 speed mount I would be interested in buying it.
Thanks
Don

[OLDIRON69]

I also did not use the 3 spd mount right behind the motor, is this the one you are referring to? I also have the 3 spd FOR FREE if any Texas guys want it, good tranny, just wanted an auto.