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Old 03-13-2012, 09:24 AM   #1
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what is your gears # and tire size ????

my cargo has 3.73 with a 33" tall tire

looking to purchase E350 with a 6400 pound axle with 3.55 and when i lift it it will also have 33 or bigger how much will that change the towing power?????

so im looking to compare what others are running and if you tow with it too how does it feel???

thanks
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Old 03-13-2012, 10:44 AM   #2
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Re: what is your gears # and tire size ????

This question has one more element - which engine? I think you mentioned that the rig you're looking at had the 5.8L gas engine. If you are going with no larger than 33's you could probably get by with just locking out the overdrive while towing but you will have a sluggish start. If you are even remotely thinking of going to 35's then you'll want 4.10's at a minimum with the fairly deep OD ratio on the E4OD. Maybe keep the gears you've got and go with a just under 33" 285/75/16 and see how it feels before you spend the money on a gear swap.

FWIW, was running 35's but now have 33's with 4.10's with the old 6.9 diesel. The low torque curve of this engine wouldn't mind pulling 3.73's or probably even 3.55's with the 33's, but we're comparing apples and oranges. I'm happy with 4.10's but don't drive much over 65 either.
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Old 03-13-2012, 10:56 AM   #3
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what is your gears # and tire size ????

3.55 with 33's and 7.3
1800 rpm is 75 mph. Only tow a small trailer but do weigh 10000 lbs.
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Old 03-13-2012, 11:25 AM   #4
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Re: what is your gears # and tire size ????

my 4wheel dodge 1500 with 20" wheels and 33's has 3.91 and tows great

my 92 cargo has the 285/75/16 tires with 3.73s but i havent towed with it yet....

the 15 pass vans has the 3.55s both van have the 5.8 motor....

my buddys chevy truck with the 5.3 motor he runs 33"s and has 3.73 and pulls our boat no problem but when he pull my big trailer we had the power but gas milage went to 7 mpg....



thanks for the info
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Old 03-13-2012, 11:28 AM   #5
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Re: what is your gears # and tire size ????

Quote:
Originally Posted by rockbender
If you are going with no larger than 33's you could probably get by with just locking out the overdrive while towing but you will have a sluggish start. .

what gear you talking about when you said this 3.73 or 3.55 ?????
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Old 03-13-2012, 11:31 AM   #6
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Re: what is your gears # and tire size ????

Edited and recalculated to show the correct .71 final drive ratio for the E4OD Trans

My 92 E350 Clubwagon with the 5.8 and E4OD came stock with 245/75/16 tires and the 3.54 gears. I changed the tires to 265/75/16. I tow a fairly light trailer. Total weight of the trailer and load is usually less than 1500lbs. I also have one of the biggest aerodynamically challenged toppers on the road slowing me down. The difference in tire height between the stock 245 and the taller 265's is 1.3 inches. The 265 tire is 31.65" tall.

With the 3.54's I wasn't real happy with the way the trans hunted in overdrive pulling the trailer. At 60mph with the cruise on it couldn't really make up it's mind which gear to be in. The slightest incline and the thing would start to hunt.

The van is in the shop right now getting the gears changed to 4.10's. I'm also having Detroit Truetracs installed in both the front and rear diffs.

I was curious about what kind of rpm increase the gear changes would give me at 60mph and 70mph. I found a website that does a rpm calculation if you give it final drive ratio of transmission (.71 for the E4OD in overdrive), tire size, diff gear ratio and vehicle speed.

http://vexer.com/automotive-tools/speed-rpm-calculator

This is the information I got from the website.
Final drive ratio of E4OD in overdrive .71
Tire size 265/75/16

60mph.....
3.55 gears......1625rpm
4.10 gears......1892rpm
An increase of 267rpm for the lower gears

70mph......
3.55 gears......1892rpm
4.10 gears......2185rpm
An increase of 293rpm for the lower gears.

I have no idea what increasing my rpm between 267 and 293 at cruising speed will do the fuel economy. I'm hoping the increase in rpm will convince the trans to stop hunting and find it's happy place in overdrive.

After I get the gears changed I will need to get the speedometer re-calibrated so the brains that control the transmission shift pattern has the correct information coming in.
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Old 03-13-2012, 12:10 PM   #7
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Re: what is your gears # and tire size ????

I'd wait for feedback from John (Gnarvan)! He is doing exactly what you are thinking of, and I'm interested myself to see how the re-gear works out.

I'm cheap, so I'd leave the 3.55's in and go with reasonable tires (maybe even the size on Gnarvan). If you lock out OD, you'll be sitting around 2100 RPM's at 55-60 which should get you into your powerband with the 5.8 without revving super high while still leaving you the option of cruising at 2000 rpms at 70 with the OD on while not towing.
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Old 03-13-2012, 12:18 PM   #8
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Re: what is your gears # and tire size ????

if i do a gear change it would be for a long time.... yea i have always got better gas milage running at 2000 rpm at highway speeds.....

and towing the big trailer ill be pulling 4500 to 7000 pounds maybe 4 or 5 times a year.... ill try to leave the towing to my truck but if its a long weekend i want the option to tow with the van then i can have something to sleep in

thanks for all the info
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Old 03-13-2012, 12:34 PM   #9
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Re: what is your gears # and tire size ????

If Mr Wicked does go with 33's and a heavier trailer his transmission hunting problem will be worse than mine.

There is a conversion available to change the overdrive mode in the transmission. They are set for overdrive on at ingition on. This means you have to manually select overdrive off. You can change that to overdrive off at ignition on as long as you remember to turn the overdrive on whenever the situation allows it for better fuel economy. In the E4OD the overdrive off button does NOT change the shift points in the first 3 gears. All it does is lock out the overdrive.

Sometimes I'm surprised I can remember my name. There would be no hope of me remembering to turn the overdrive on all the time. I decided to do the (hopefully) proper fix by changing the gears.

Gnarvan should be out of the shop sometime tomorrow or Thursday. I'll give it a road test Friday or Saturday and report back to the forum. Since it snowed last night here on the valley floor there should be plenty of slick snowey/muddy roads within 10-15 miles of me up the Columbia River Gorge to test the Truetracs and new gearing on.
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Old 03-13-2012, 12:41 PM   #10
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Re: what is your gears # and tire size ????

some good freinds of mine own a trans shop so i know all the does and donts....

my 2003 dodge hemi i cant tow with the over drive on specaily with my 30ft trailer

so yes if i towed the big trailer witht he van ill lock out the od ....
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