NP 240 swap for modern alternative? 57 D300

[BGBOSSMAN]

WOuld love to get rid of the granny 1st (I know sacrilege) in favor of 4 usable gears or even 5- is there an easy answer?

I know that there are companies that make bell housing adapters and I am not afraid to have to move the shift lever back a bit if need be. It would make all the difference in driving this thing to have a more user friendly trans though.

Maybe a way to replace the rings in my current trans?

[Aaron S]

What motor have you got in this thing? There are a lot of options for transmission swaps that require varying amounts of modification to employ.

There is a close ratio version of the NP435 that would bolt right in, but it's still an unsynchronized spur gear first so you have to stop to get it in first gear, and second is too high for second gear starts.

You might consider the gas engine version of the NV4500, these came behind 318's and 360's in mid 90's trucks and are fairly easy to find. This will get you fully synchronized with a low first and an overdrive.

If you're sure you really don't need a first gear you can use an A833 four speed and have a relatively slick shifting tranny with car like gears that should be a fairly straightforward swap. These were available in cars and some trucks into the 80's, and some of the later models have an overdrive fourth gear.

As far as the difficulty of the swap, I don't know what to tell you except that its likely to be easier if you have the poly V8 engine than the flathead six... if you're still running the original motor.

[BGBOSSMAN]

Truck has stock 315V8 and I dont mind the stop to get in first. Just the lack of top end and overall mismatch between todays driving speeds and the gears. The 240 just leaves me wanting to be up or down one at all times if you know what I mean.

The truck is 2wd so swap should be simpler than 4wd. Which would you suggest? ever done any ofthese?

[Aaron S]

I haven't done any of these swaps, yet... I have looked pretty seriously at the NV4500 and the A833 for a 68 W300 I'm putting together, either one would be a fairly "easy" swap. I want to get away from the NP435 to get a better gear split and smoother shifting... a lower first gear would be nice, preferably one that is synchronized. However, the small block I have built has become so ridiculous I will probably need to go with a five speed from a medium duty truck to handle the power (the diesel version of the NV4500 would take the strain but there's an issue with the throwout bearing not playing nice with the clutch fork in the gas bellhousing, go figure). So I'm not sure where I'm going yet, an NP540 or maybe a Clark could be my best bet.

For a modern, highway friendly transmission for your application I would suggest taking a good look at the gasoline NV4500 first. That will get you synchronized, with an overdrive and a decent first gear that you don't have to use but is nice to have when you've got a load on the truck. And it shouldn't be too hard to find one or be super expensive to aquire.

The 315 is a great motor (I have several) and since it shares the same bellhousing pattern as all early hemi engines because it is the same block as the tall deck dodge hemi's, adapters are available from Hot Heads to mount just about any transmission you would like to it. The early Dodge, DeSoto, and Chrysler hemi's are each unique motors, that is to say parts do not interchange between brands, but they all use a common bellhousing bolt pattern that is also shared with later 318 poly and LA engines... the adapter plates are pretty much just to correct indexing and spacing issues that come with the different cranks (if you're using a transmission with a Chrysler bellhousing).

Plan on having your driveshaft altered a bit (no big deal). Other issues you may encounter are the need to use a different starter and flywheel or flywheel ring gear, a different clutch plate (due to various input shaft splines) and getting your clutch linkage to play nice with the new parts. That being said, the basic problems associated with a transmission swap will be the same for any transmission you choose to use, even (gasp!) an automatic. Using something that came off of a small block Dodge V8 should help to limit compatibility issues, make the swap more straightforward, and minimize the amount of fabrication necessary to make it all work correctly.

I hope you're finding some of my ramblings here helpful. If you're anything like me you will now spend hours surfing the internet filling your head with gear ratios, spline counts, part numbers, model designations, and various other automitive trivia guaranteed to get you strange looks when you bring it up at your next dinner party. But then, that's part of what makes this lifestyle so much fun!