518-618 Torqueflite Valve Body Swap

[bajajoaquin]

In my ongoing scheme to eventually swap my 727 for a 518, 70NPORT's post about the kickdown and the reply about interchangability of valve bodies got me thinking.

I've read that all valve bodies can be swapped onto all torqueflites (at least, they will fit). If a 618 is a stouter transmission with the same gears as a 518, but a different valve body to tune it for the Cummins, can a 618 be used for a 440 with a gas-engine 518 (and a new bell, of course)?

 

[F Preston]

Bellhousing problem big time - I'd research if the 618 guts will fit in a '71 or later 727-B case. If so - it would be rather cool.

 

[bajajoaquin]

The case isn't the issue. You can swap in a new bell. The 518 has been done, several times. The "Guts" don't get you there, since the 518/618 have the same gear ratios as a 727, but they have an overdrive in the tailshaft, which makes for a different case.

 

[F Preston]

Gotcha - I reckon the tailshaft won't bolt to a 727, correct?

I know all about the old stuff - and avoid the new stuff like the plague. The youngest vehicle I own is a '78 Magnum XE.

 

[70bigblockdodge]

I think the 618, is just the designation for the trans to go onto a Cummins as apposed to magnum later 618 with the RE48 have 5-6 pinion front planetarys all of which can be swapped into each other.

 

[bajajoaquin]

Yes, that matches my understanding. 518 was the LA Torqueflite, and the 618 was the Cummins Torqueflite. They have the same gear ratios, but I understood the 618 to be a bit beefier. But the valve body is tuned to the power characteristics of the diesel, so wouldn't be a good choice as a straight swap.

I have also read that the valve bodies on Torqueflites are all interchangeable (as supported on the kickdown thread). So it got me thinking that I could get a 618, a 518 valve body, and the rest of the parts for the conversion and skip rebuilding a 518 with beefier parts. If/when I do this, it's going to be a major project, and anything I can do to reduce my time on it would be to the good.

 

[70bigblockdodge]

I guess since you are going to cut bell housing off and add a JW or such might as well cut it off a 618, what about tailshaft is it the same? Seems easier to me just add any parts to a 518, the forward clutch pack would be the weakest point if it only has 3 plates in it, which I don't know if they even came like that, the 3 pinion is nothing to worry about unless you are planning to abuse it or build the motor.

 

[bajajoaquin]

Abuse, build? No. The plan is for a mild rebuild with 440 Source Stealth heads, a mild cam, aluminum intake and HP manifolds. If budget permits, I'd take advantage of the .69 OD to swap in 3.55 gears as well (that's still about 15% taller than the 2.94s on the freeway). Actually, the only way I'd do the swap is if budget permitted rear gears, since I don't really have a need for a car turning over 1600RPM at 65.

But that's a good reality check. A rebuilt 518 should be plenty stout for my needs. Thanks.