Seeking taller final gear ratio

Fellow IDI devotees
I am seeking a higher final gear ratio for my rig. I installed a Gear Vendors, and what a nice difference it makes. Suddenly sitting two feet from a roaring IDI at high rpms in a van body is less brain vibrating at highway speed.
But, I'd like to get my ratio taller.
My rig;
1989 Ford E 350 / Born Free "President" converted to 4WD: 7.3 IDIT (Hypermax) - C6 - NP205 - GV - 3.54 Dana 60s - 16" rims 215/65.

Ideas:
Get a taller differential gear ratio. I have done a fair amount of searching, but am coming up dry. Is 3.54 as tall as you can get in Dana 60's? Is this true?
Put an E4OD in. A lot of work, since it is longer than the C6. I'd have to move the transfer case / GV assembly, and get two new drivelines as well as the electronic brain to run the E4OD.
Get larger tires and or rims. But the front wheels already brush the fender mudflaps when the steering wheel is fully turned. I think I'd have to move the front axle forwards, with all that entails, to make a larger tire fit in the front.

Any thoughts would be appreciated.

regards

Rolf

Google Dana 61


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ZF5 should be aprx. the same length as a C6. Of course, then there's the pedals, shifter, hydraulics,.....

I found information on Dana 61s. The source said only rear axles. Do they exist for front too?

Madpogue, you're absolutely right. I left off the option of going manual. I think this generation E series van did have an option of a manual transmission, though it might have been dropped by the year 1989.

Whats your rpms at 65 now?

L & R, I'll check for sure when I drive it Friday. Memory says I pass 2000 rpm when in C6 third gear / GV OD as I get to 55mph.

You can retrofit an e4od, or swap to a Dodge Dana 61, I think that will give you up to a 3.08 gear ratio

with zf5, stock tires and 4.1 gears i get around 2500 rpms at 65 to 70 mph. so your not far off. i always hated my c6 in the crew cab with 4.1 i was at 3000 rpms at 65 mph.
after a ton of research last year for my c6 i decided to just get a truck with zf5 and swap everything over to my crew. its cheaper if you can find a parts truck like i did.

to swap the gearing on the axles you would be around 1000 to 1200 dollars alone.
the e40d is not a bad option but is a little bit of work in the wiring and possibly troubleshooting department. i was going to go this route and get a controller for it but they are money also.

other axles would be great but your back to the fact you have to match gearing or get close in order to retain 4wd.

cheapest route might be tires and figuring out how to get them under there. your tire size 215/65/16 is 27" tall i calculated and stock 235/85/16 is 31.73" tall. this is big difference that could help your rpms. At 55mph your talking about 300 rpm difference. here is a calculator that is informative and gives you ideas about rpms, gearing and tire size.
https://www.ringpinion.com/calculators/Calc_RPM.aspx#TireHeight

L & R, tires do seem the cheapest, but for the fact that they scrape when I turn the steering wheel all the way. Every plan seems to have a big expense / PITA somewhere it it.

Kuskoal, the drop on Dodge front axles is passenger side. My Ford has a drivers side diff front axle. And the NP205 is Ford-sided. Do you know if front Dana 61s for Fords exist?

edit: I missed this from Wikipedia
- The Dana 61 was made in semi-float and full-float axles for select 4×2 and 4x4 Ford 3⁄4-ton and 1 Ton Pickups and Vans from 1974 to 1987.

DuRolf said:

I found information on Dana 61s. The source said only rear axles. Do they exist for front too?

Madpogue, you're absolutely right. I left off the option of going manual. I think this generation E series van did have an option of a manual transmission, though it might have been dropped by the year 1989.

Click to expand...

Like others said, dodge ran Dana 61s up front with the automatic 1st gen cummins but dodge axles are on the wrong side for ford t-cases. I'm not sure if ford ever ran 3.07 gears in a front axle


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Some really good aftermarket sound insulation goes a long way in those vans.

If that were my van, I would definitely go for more rubber. Something in the 265/75 range would improve the look as well, imo. Is there any sheet metal behind the tire to cut out without needing to do a lot of firewall work?

A 265/75 will have ZERO impact. It's actually aprx. 0.1" SMALLER than a 235/85. The OP wants to lower the RPMs going down the road; he's not looking at the tires while driving (I hope not, anyway....).

Well, he said he's got 215/65's. A 265/75 is considerably larger than that...

Edit::
I'm also of the school of thought that if you don't turn around to look at your ride after you park it, then you didn't buy the right vehicle

TheWesPaul, I have applied CLD tiles, then closed cel foam, then mass loaded vinyl to the dog house, the cab floor, and the doors. I researched a lot of sites, and found Sound Deadener Showdown to be the most sober and reality based. I would say it has made a difference in noise. Part of what makes me say that is now I hear all kinds of squeaks and rattles that I didn't used to hear, that were probably covered up by the noise of the roaring engine! [/URL][/IMG]