1989 F350 neds a new tranny

[Skiprdog]

Hey Everybody,

I am new to the forum and also new to diesels, so please bear with my *newbiness* I recently purchased a 1989 Ford F350 from a neighbor of mine, because the price seemed right and also because it already had a utility bed on it (I wanted to put together a welding rig) It originally had a 7.3L in it, but the guy I bought it from said he got the truck from an engine rebuilder, and that that guy put a 6.9L in it. After a few tweaks I finally have it running good, but one thing I think I am going to have to change is the transmission. It has a 3 speed C6 automatic in it now, which from what I understand is a good trans for what it is, but my problem is that three speeds with no overdrive seems to severely limit my top end speed-wise, not to mention the scary effect it has on fuel economy.
So, I guess my question is can anyone recommend a trans swap that would make sense in my situation, whether manual or automatic with overdrive? I love the truck and I love the diesel aspect of it, but that trans in it now is just killing me. I am fairly clueless where drivetrains are concerned, so any and all suggestions would be welcomed!

 

[clutch]

welcome, the 6.9 is a good engine, it has thicker cylinder walls than the bored out 7.3, and while the C6 is stout, as you have seen, leaves something to be desired in regards to highway driving. One thing you may want to look into is a Gear Vendors, under/overdrive, bolts on behind the tranny, you have to shorten the driveshaft, but it doubles your gearing/gear ratio, or something to that effect. Last I checked they do run a couple grand... Don't know much else about auto's, but yeah a 4spd swap might be what you are looking for, I have the a 5spd, ZF5, I believe it is, but as you may know, doing a manual swap will be a bit more labor intensive, unless your truck already has the hole...
good luck hopefully someone else has better insight for ya, take care