Im wanting to put a 518 automatic into my 70 cuda to cut back on highway rpm. Its going behind a mild 340. Just wondering what kind to look for. Some say lockup and some say not. And whats the best years? I know this has been talked about on here a lot but I read a lot of different opinions in the archives.

94 and up was the electronic lockup if memory serves. The older ones didn't have lockup and the overdrive on the 94+ is electronically actuated but on the older ones was it electronic as well or was it hydraulically engaged/disengaged?

my 94 ram has a 46rh..

so they probably went to electronic shift in either 95 or 96...which is a 46re

The rh doesn't have the lockup does it? Only the re?

yes..the 46rh is a lock up.

Would I better off with lockup or without it?

I think its the 96 + that have the hard to use shift system, the first ones had 2 pin connectors, those are the ones that are not lock up, and the three pin ones are a lock-up, the one i got outta a 94 3500 van is lock-up i think, i haven't really looked too close becuase its been too cold until today. i think all the 95 and down are electronic OD and lock-up when they have it. I am not 100% on all this but thats what i have read.

When I've done it I used lock up trannys...Why not? take advantage of having a loose convertor that with the flip of a switch it locks 100% & in the case of the two conversions I've done it dropped about 200 rpm..It feels like another gear...I'll be the first to tell you don't load it heavy in O/D or with the convertor locked...But than it's not like you'll be towing a 5,000 lb trailer with your E body.... I actually set them up to shift automatically but also installed a toggle thar locks out O/D & L/U..

Alright ill try for a lockup tranny then. I almost got one from a 91 dodge van that wasnt lockup yesterday.. good thing I didnt get it heh. How else can I tell if its lockup other than if its 3 wire?

PATC trans has the instructions. The 2 pressure switchs are from a 350 turbo trans and are the 3rd gear clucth switch. The run about $6 ea from a trans supply and you can get different ppressures. I went with 50 and 40 psi. The lock up vacuum switch is from an 86 chevy caprice and is the convertor swith. It runs $40 from any parts store. BWD # TCL 11

You want to try to find a non lockup around 90-91. If you go with a non lockup you can put any 727 convertor in it. But not with the lockup trans. You'll also need to swap out the bellhousing with an untrabell for the 727. It's alot of work but well worth it.

Why do I need to swap the bellhousing?

You don't.That's only for a BB. Here's one thing you will run into. https://board.moparts.org/ubbthreads/show...e=1#Post5008097

Still kindly confused though on if I need lock up or not.

Unless you are running a high horse big cam motor use the lock up.With the stock convertor. It works great.

Its going to be a 340 with possibly magnum heads and a mild street cam... so I wouldnt call it high horsepower heh

Mines behind a street driven 408 stroker in the truck in my sig pic..

i want to use my stock lock-up converter behind the magnum after its warmed up, just gonna have a nice street cam with more gear now that i have the OD

That's the great thing about the swap. I can go to a 3.73 gear for racing and end up with a 2.56 in od. Just shut the od off and go racing. With a 3.91 you end up with 2.75 od.