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Putting in a 4.10 rear E-350

 
  #1  
Old 05-15-2019, 07:19 PM
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Boondockdad
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Putting in a 4.10 rear E-350

2003 E-350 7.3PSD has 3.55 open rear (BOM 606845-1)

Been towing my 9600# trailer for about three years now and she does OK, but struggles. Especially in the mountains. On the flats there's no problem at all. Helps that my trailer is very aerodynamic.
Really loaded up the rig this last trip out and noticed my tranny temps were much higher.. pushing 215 when the ambient was over 75 degrees. I'm sure the front mount 4 bike rack didn't help with airflow.

Before I move on any other mods, I want to swap in a 4.10 trac lok (Got stuck for the first time where I keep her stored. Open diff sucks).
Anyway, want to do it myself. Never done one. Been researching (books, forums) swapping out the diff parts and basically what I've found is it's very tricky. As much art as it is science.
I don't want to drop $1k on new parts, tools and then just eat up the gears with bad lash or whatever.

So make long story longer, I'm thinking swapping the whole rear end axles and all. Looks like they're $500-$900 on ebay. I'll check the yards around here.

Questions:
1. does the PCM need reflash with a different rear?
2. does it affect speedo?
3. do I need the exact BOM for my year (606845-6)?
4. is my reasoning sound?
5. is there anything else I should be aware of?
 
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Old 05-16-2019, 09:37 AM
DesertSmoker
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I would recommend swapping the whole rear end with another one that has 4.10 or 4.30 gears.

Questions:
1. does the PCM need reflash with a different rear? Nope
2. does it affect speedo? Nope
3. do I need the exact BOM for my year (606845-6)? Yes it will help with getting a rear axle from a junk yard
4. is my reasoning sound? That is a personal call between effort, time and cost.
5. is there anything else I should be aware of? Yes figure out the Axle codes that will work for your E-350. I would really recommend getting a Eaton True Track and not use the factory LS.
 
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Old 05-16-2019, 10:25 AM
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Thanks Desert. I was thinking 4.10 was too much even... maybe just 3.73. I've got one sitting in my garage from my buddy who swapped a 4.53 into his E350 V10.
Way too revvy for me. Pulls like champ tho.

If I go with an Eaton I'm guessing I'll have to just do the gear swap myself.

Maybe I could do the heavy lifting, then find a master mechanic on craigslist and have him come out and "certify" the install?
 
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Old 05-17-2019, 06:14 AM
Jakerichards1
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Bang for buck

Junk yard !!!!

if you are not familiar with the good old yards in your area a complete rear with factory ls is cheapest. If you are in the northeast it can be hard to find one with less rust. If you have 1000$ you want to put in your rear the go for the premo tru trac

And rev range change from 3.55 to 4.1 is less than 300 rpm. However you will feel it easier to tow.

I assume your rpm at 65 in od is about 1700? Can you listen to 2000 all day and see lower temps?
 
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Old 05-17-2019, 09:51 AM
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when you put it that way 300 rpm doesn't sound like much.. but, the GCWR jumps from 16,000 to 20,000 according to the Ford specs.

also gotta say, the Kilmatz soundproofing I put in is great. Seriously. By far the best mod I've done so far... bang=buck
one $50 box did the front cabin, doors, a-pillars.
Highway driving I had to almost yell when I was talking to my wife in the passenger seat. Now, we can talk at normal level.
Probably do the headliner if I put in a light bar up there.
 
 


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