What Rear gear ratio 93 E350 IDI / fuel economy? - Diesel Forum

505live · 04-15-2008, 02:17 PM

Thanks for the help on my many random questions so far, now I've got a new one. Does anyone know what the stock rear gear ratio was on my 93 E350 IDI? 3.73? Or VIN decoder? I searched archives but could not find anything specific to E-series. It's a ghetto DIY camper conversion that use for road trips (minimal around town), and I have no intention of towing heavy with it (probably not more than ~5000 lbs if I got a bug and got a travel trailer). I generally cruise it around 70mph on the freeway, and estimate I'm getting around 14mpg or so. Changing the rear gears to perhaps a 3.08 seems like a good way to get some better fuel economy. I just had the E40D rebuilt in December, and I'm not about to drop $4K into a gear vendors OD. (That's more than I paid for the van!). I have no tach, so I'm not even sure what RPM I'm cruising at, and if the drop in RPM at 70-75mph would put me in a more favorable point in the power band. And, I make my own B100 so I'm not able to measure fuel economy very accurately.
Suggestions? Hints? Smoking the crack?
Cheers,
Nate

blageurt · 04-15-2008, 02:21 PM

One way is to read the sticker on the door to get the axle code . . . another is to look on the rear pumpkin for the metal tag. A third is to use a Gps and calculate the final drive using math.

505live · 04-16-2008, 01:42 PM

Thanks for the info, so what are peoples thoughts on changing rear gears for fuel economy? Is it worth while? Or is it as controversial as a 205 deg T-stat?

blageurt · 04-16-2008, 02:14 PM

Since you have an IDI , you can basically run anything in it without damaging the injectors, unlike a powerstroke. I would convert it to SVO and never look back. . . You probably have the 3:55 anyway, which is the highest available for the vans.

u2slow · 04-16-2008, 02:32 PM

3.55 and 4.10 are the stock ratios.... I find the models with OD trans tended to have the deeper (4.10) gears.

For the D60, the 'tall' end of the spectrum is 3.33, 3.54, and 3.73. You may have a hard time getting the 3.33 gear unless you get it directly from Ford, Dana, or a wrecking yard.

IMO, the ratio change is worth it if you log a lot of highway miles.

505live · 04-16-2008, 04:22 PM

Thanks for all feedback!
I'm currently making/burning my own B100, but also doing an SVO conversion has much appeal (esp. w/ skyrocketing methanol prices). My primary motivation is to increase range on road trips, my goal is 2000 miles... I figure the on-board tank + ~100 gallons should be close, and if I can up the gears and get a little better highway mileage it should be do-able. This vehicle isn't my daily driver, but 95% interstate road-trip cruiser so a gear change probably makes sense if I have the 4.10, but going from 3.55 to 3.33 isn't probably worth it. Gotta look when I get home from work and see what is in there.

van_350sd · 04-16-2008, 04:42 PM

I have the E-350 SuperDuty 2000 Extended van PSD 7.3L and I have the 3.55 rear and the 4r100 tranny with the Sonnax The Sonnax valve and Tricumulator springs.

It helped the tranny shift smooth and I'M sure it helps the MPG Mileage.

I use the RPM on the AIC/ACPM to adjust the best settings while on the Highway in Cruise Mode. 68-72 seems to be the magic numbers for speeding. And 60 when in a 55.

I can't believe Diesel is 4.20 a gallon in some places here, hess has it at 4.08 yesterday.

Kaliburz · 04-17-2008, 01:35 AM

Look at your VIN sticker on the driver side door striker area. It will have a code for a rear axle there.

I just recently acquired a 1990 E350 Club Wagon w/ the 7.3L IDI. Mine has an E4OD and 3.54 axle. The code on mine is a C3. I crawled under it and checked also and it is a 3.54 Dana. Might be a limited slip, but I didn't look at the tag that long. Oh, there "should" be a tag on the rear axle cover. IF it's a Dana axle, the tag will be bolted down on both ends- easy to miss if you are looking for it in low light (missed mine the first time) AND if you're assuming it's just just bolted on one end.

Automotive What is my Ford rear end ratio, do I have positraction

The link above lists that the C3 code is a limited slip 3.54 (used in 1992-1998). It should help you decode your sticker so you don't have to go under the van.

If your axle code on the sticker starts w/ a letter, it suppose to be limited slip (so says the info I've read/been told).

I'm guessing your van is much heavier then mine. With mine, the limited driving I did, I got 14.7 MPG, but I packed the tank (so say 14.7-15mpg). This was mainly country/high way with a few in town stuff.

I was thinking of putting a GV on mine also, so I can tow IN OD, but not the factory OD, but I'm waiting for a 'deal' to pop up. I picked up a GV and mounted it on my F150 (an 1983 none the less!!!) behind the C6 to get overdrive. Why? Because I'll never get rid of the truck

. I thought it was a good price for a 'new' unit. (If you look in the 7.3L IDI section, look for the 1990 van and my 'handle' and look in here, the van section. I linked the van info on a post of mine. I got it off of Ebay...... 1800. With tax, transfer, etc, just just under 2100....)

I'm going to be going some hiway driving and I'll see what kind of fuel economy I can get.

505live · 04-17-2008, 11:59 AM

Thanks for the link! Per the door tag axle code = C5, I've got a limited slip 4.10. 3.55 might be worth it, definitely the 3.33 if I could find it. Maybe get extra 1-2 mpg?

SuperbeastVan · 04-17-2008, 12:44 PM

If you have the wheel well room you can also install a taller tire and cut that ratio down a bit. The taller the tire the better mileage you can get. Just make sure you recalibrate the speedo when you swap anything.

Kaliburz · 04-20-2008, 04:13 PM

Well, got some MPG info. This was on free way driving and city, but mainly freeway. But the freeway had hills and I was throttling it so it kicked out of OD to drive. I was between 60-70 MPG, sometimes at 75 when straight. I 'packed' the fuel tank, so the MPG might be a tad bit off. I was getting 14.7MPG (again) on the way back. The trip there, mainly highway, was about 13.8MPG, but I was running late so I was trying to hold 75 all the time (with the hills and wind, wasn't easy- had a head wind too.) Total miles traveled was over 400 round trip.

I just went to fuel up and on the way back, the brakes were getting 'weak'.

Might have to put another post about that. I'm guessing it's the vacuum pump is starting to go..... the 'BRAKE' light came on a bit, but went off (but peddle felt like an old 1950's pickup w/out power brakes!!!!)

505live · 04-21-2008, 10:39 AM

Thanks for the info, sounds like I really need to measure it accurately with the 4.10s. The rough estimates I did shortly after I got it put it right at about 13-14mpg on the freeway ~ 70mph. It would take a while to recoup the $400-$600 investment to change the gears if it adds 0.5-1.0mpg. Thanks again for taking the time to get the data!

Nate