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· Man of endless projects
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i myself perfer 4.88 for 35s, espeiaclly for towing, climbing, offroading in general. but 4.56 is considered the norm. only reason id do 4.10 is if you are saving money by using a D50/D44HD third member in the front that came factory 4.10 but id still consider that too low

the advantage of overdrive transmissions like E4OD is that you can go with a stupid high ratio and still turn less rpm than a non-overdrive trans like a C6. so id take advantage of that and run the higher ratio and gain alot of torque

for example a truck that has a C6 trans and 3.55 ratio and 35" will in a perfect world see about 2216rpm at 65mph. but this is not a perfect world and C6 will have converter slippage of a couple hundred rpm so more like ~2400rpm @ 65mph.
now lets take a E4OD with a lockup converter and OD ratio of 0.71 ratio. with that OD ratio, 65mph 4.88 gear and 35s is about 2162rpm and no slippage due to converter lockup.
just as a point, with an E4OD trans, 5.38 gears, 35s and 65mph would be about 2384rpm, around what the C6 would be at highway speed but be a stump puller at low speed. but that would be overkill of axle ratio for most scenarios

dont fear the gear. these engines were originally designed to run around 3k rpm for long distances on highway. for example a stock truck with 29" tires, C6 trans, and 3.55 ratio would be running around 2675rpm at 65mph before converter slippage. more like 2800-2900 in real world

heres a generic chart. ignore the colors. you would multiply these numbers by 0.71 to find out what rpm you would be at with E4OD
 

· Man of endless projects
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11,233 Posts
at 65mph you will be around 2440rpm. it will feel high and you might not like it, but its still less than an average C6 truck. i myself would find that very driveable. i am running 4.56 with 32s in my F250 for years and kinda regretted not going 4.88 for towing
 
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