3 speed to th350 swap

[Kyle70SWB]

Hey guys, I think I have all the parts ordered (minus the flexplate) for my 3 speed to th350 swap, and after what feels like weeks of research (probably only a few hours total), I have a few things that I am stumped on.

I will be doing the swap at work, on a lift on a Saturday off, and the truck will have to drive back out the same day, one way or another.

I found this article, and decided it was something I HAD to do.. I love the idea and look of it.. http://www.trucktrend.com/how-to/int...er-conversion/

What I am stumped on now, is which flexplate to use.. The truck isn't sitting right here where I can get to it at any time, so I am not sure what starter is on it. I can tell you that it is a 305 from the early 80s.. casting 14010201 which is a 2 piece rear seal, and internally balanced. Thankfully that gets my choices down to 2 flexplates.

I am also trying to figure out where/how/which way to get a vacuum source for the transmission.. Do I just run a vacuum line up to the 2 barrel?

Finally, neutral safety switch.. as I said above, I am using my original 3 on the tree column, not swapping out columns. What am I supposed to do for the NSS? ground it out? constant hot?

I think these are the only things I still have to figure out before the time comes to pull the trigger.



*Side note* If there is anyone in Houston who is swapping from auto, and wants 3 on the tree, I am willing to do some trading of columns, etc.

[kehstr]

the vacuum is simple, run the line up to a plug in the intake. see images below. You really don't even need a neutral safety switch, it's just a safety think that really isn't needed, so you can just bypass it
Attachment 1477107

[kehstr]

[Kyle70SWB]

any idea of a technical name for that, or where I can find one?

[hugger6933]

It is known by several names vacuum port, tee or elbow. Jim

[Kyle70SWB]

Thanks for the help Jim..

Oh, any idea about wiring up the reverse lights?

[kehstr]

how are the 3 on the tree's reverse lights wired originally?

[Baddflash]

From my experience with later model vehicles the nss and reverse lights should be on the shift module on the trans, should just be a matter of running one side (typically ground) of the reverse lights through that switch. The nss can be connected by running the original wire that fires the starter through that module than to the starter motor.

[Baddflash]

Original reverse light switch is located on the column near the floor.

[Baddflash]

Ps if your truck is original manual trans there is no nss switch.

[kehstr]

On a stock automatic column, the neutral safety switch, and the reverse lights are together at the base of the column right near the firewall. So that is why i want to know how the reverse lights work on a 3 on the tree, so i can tell you how to switch things to work.

[9teen69]

You can just plug in your reverse light connector to the new Auto column neutral/backup switch. I just did the swap myself last month.

[9teen69]

Oh, sorry I see you are re using the column. A new NS/backup switch should mount up, I believe.

This should help.
http://67-72chevytrucks.com/vboard/s...d.php?t=478107

http://67-72chevytrucks.com/vboard/s...d.php?t=404553

My backup light switch on the lower column had the little nub worn down. I put a new switch and it worked. If you are not worried about the NSS function then just keep the manual backup switch on your column

Someone can correct me put I believe a NS/backup switch from an auto should mount to the 3OTT column.

[Kyle70SWB]

thanks for the input... the idea of using the manual column saves a stack of cash that can go towards all the other stuff it needs.

I am not as worried about the NSS, as long as there are no starting issues.. I know I will put it in park lol. (remote start is way down the line, and would like to avoid any issues

The reverse lights are more of a "must have" since the state inspection requires them, and I do NOT want to rig up a switch to turn them on and off.

[Kyle70SWB]

now I feel like a real idiot.. I hate transmissions, and everything related to working on them..

It is my understanding the th350 is vacuum controlled right? Yes.. ok good

Do I still need a kickdown cable? or does the vacuum pressure shift the trans up and down?

[kehstr]

the kick down is still needed, the vacuum hose will just tell the trans when it needs to shift. I know that it is possible to turn a three on the tree column into a auto column, I've seen it done, i'm just not all that sure if the neutral safety switch bolts up. Do the 3 on the tree columns have a neutral safety switch?

[john]

Source for vacuum fittings if your local parts houses don't have any.
https://www.paragoncorvette.com/c-22...-fittings.aspx

[Kyle70SWB]

I found a LOKAR switch that can be either NSS, or backup lights.. guess I am going to order it to handle the light issue.. as far as the NSS, guess I will just have to remember to put it in park lol