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I have a 67 F250 with a Dana 60 4.10 posi NP 435 tranny and my son has 68 F100 with a 351/C6 3.74 9" (the 351?C6 is out of an mid eighties van). We both are looking for better milage and are wondering about adding divorced overdrive units. I look at my options for the 250 as either a divorced overdrive or change differentials. He would like to keep his C6 as we know it is good. Any comments/suggestions. I have a couple of AODs from behind 302s believed to be good but not proven.
Only real thing available is GearVendors, which is like $2500. Not too cheap, but a very sturdy unit. It bolts right onto tranny(remove tailhousing) on the automatic, not sure, I think the NP version does too?
They don't make anything else "stock" that will bolt to a big block with OD. The newer OD 5 spds don't fit FE stuff, unless you buy a blowproof bellhousing and use a T5 or the like.
It is a 351 Windsor that came out of the van. It is a C6 that also came out of the van. I know that some campers came with a divorced overdrive but not which ones. I also know a guy that has a divorced overdrive on his late eighties F350 with a 460. I am trying to find info on used ones and how good they work.
If Your not going to work it really really hard an AOD will bolt right in place of a C6. I did it to My 73 Torino Wagon with a 351c it went for 13mpg to 16-18mpg at 75mph. I know an AOD can be built to do anything I'm not sure I'd use it to tow big trailers.
60,
In the f100 with the 351W/C6 and 3.74 9", rebuild the AOD with extra clutches, a shift kit and a larger overdrive thingy and put that in. Just make sure the truck stays in drive around town and only use overdrive going +50 mph. Otherwise the dang thing goes in and out of D-O-D-O and this kills an AOD real quick. And if any hauling is done, keep it in drive. It'll last fine.
In the f250, had the same combo, went to 3.54 Dana 60. Going 70 mph I'll get 13 mpg. Not bad for a stock fe. And the rearend cost $350, plus new U-bolts and bushings for the springs and brakes. A lot less than a gearvenders unit. Probably not as fun. And I'm still winding my 360 more than is probably wise. But, I'm not quite ready to rebuild my engine and mate it to tremec 5 speed just yet. I'll need to save more money for that project.
Only real thing available is GearVendors, which is like $2500. Not too cheap, but a very sturdy unit. It bolts right onto tranny(remove tailhousing) on the automatic, not sure, I think the NP version does too?
My vote goes to the Gear Vendors unit. The earlier ones mated right to the back of the tranny but later ones are a divorced unit. They can be found used, saw a few going on craigslist for around 1500 bucks but sometimes you can find one cheaper than that...I did! For the earlier, married units look at mid-80s F250/F350 IDI diesels in the wrecking yards, you might find one there. Might have to get the whole tranny and have the output shaft removed and installed on the back of an FE C6.
I think there was a Doug Nash O/D unit as well which was similar.
I've read about those...kinda cool, O/D's the whole tranny. Another possibility is a Brownie over/under box behind the tranny. As big and heavy as an NP435 but it would be unique...