Mopar Action On-line – Tech Questions


Tech Question

Joe Befumo, Pleasant Mount, PA, 1989 Dodge B250 360

I recently bought an extremely clean Dodge B250 Ram Wagonwith the 360, TBI, 727 TorqueFlite, and posi rear. It has 120,000 miles onit, and everything runs fine, so I’m just in no real rush to do anything.On the other hands, I’d like to keep my eyes open for appropriate parts asthey come available.

I’d like to improve the 13mpg gas mileage by replacing the 727 with anA-518, which I understand is a feasible swap. Better still, I’d like tofind a 1999 donor wreck with the 360 magnum, the 518 tranny, and whatevercomputers, wiring harnesses, and sensors I might need. My questions are:

1. Would you happen to know what the rear axle ratio was that year withthe posi?

2. Is the Magnum/518 swap pretty straight forward, or are there unpleasantsurprises awaiting me?

(Actually, what I’d REALLY like in there is a Cummins 5.9 diesel, or a 5.7Hemi, but I’ve already been told that either of those would be prohibitivelydifficult.)


The Sure Grip rear axle could be almost any ratio, there were manycombinations based on GVW, wheelbase, tow pkg. or no, tires/wheels optioned,etc. The most likely gear would be 3.55, with 3.21 or 3.90 distinctpossibilites. Go look at the tag, underhood sticker, or just count thedriveshaft revs needed to turn the rear tires exactly one revolution. BTW,it’s almost certainly a 9.25″ axle.

A 360 / 518 swap is 100% feasible. The only practical way to do this is tofind a wrecked ’93-’03 Van so equipped, and swap everything – including ALLwiring, eng./trans./converter/mounts, computer, gas tank / pump, etc. I haveno idea why you have fixated on 1999! There are no major hangups as long aseverything comes from the same year donor. If you try to keep your originalinstrument cluster, you might have to “workaround” the speedo cable dealdepending on the year of the donor.

This swap can be sucessful with early hydraulically shifted 518s, or laterelectronic ones. Again, the key is EVERYTHING FROM ONE DONOR. If you starttrying to do the old Chinese take-out restaurnat deal: One from column A,one from B, etc., this will quickly degenerate into a bottomless Pandora’sbox!

The Cummins would be tough, but the 5.7L could certainly be done, althoughit’d be a bit tougher than the 360 Magnum.



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