37's + E4OD + 4.88's = ?

[Dejomo]

So for those that have seen/read my first thread on Oilburners I'm trying to resurrect my 98 5.4L E350 EB in the form of a 92 7.3L IDI E350 EB Ambulance...

without adding too much confusion I'm curious to know if anyone can tell me what, if any, problems I may run into with the tire diameter/transmission/axle gear ratio I'll be using?

Knowing that the E4OD's OD is a 0.712, my tires are 37's(probably closer to 36.5's), and my rear ends gear ratio is 4.88:1 my engine RPM should be around 2050-2075ish at 65mph

at 75mph the engine would be turning at 2360 to 2400 RPM

Does anyone see an issue with cruising down the freeway like that?

Thanks

 

[FordGuy100]

I don't see any problem. I would probably want 4.56's though but thats just me.

 

[DaytonaBill]

If your math is right (I'm too tired to check it right now) your rpm would be the same as with a 265/75/16 tire with 4:11 ratio...

That's what I have and it's the same range rpms as your application...

 

[freebird01]

Its a bit on the high side for rpm. Will it work...sure but your fuel milage may suffer a bit. Mine was 285's w/ zf5 speed and 3.55's and 70 was around 2250 and it was pretty happy there....75mph and it would start to kill the mileage

 

[rjjp]

Should be fine, slightly higher RPM than stock with 4.10, but that should help getting those tires turning. On a side note, is this E350 4x4?

 

[bike-maker]

I'm looking buying some 37's for my truck (hummer tires)
With 4.10's and 37's, it should be geared really close to a truck with stock size tires and 3.55 gears. If I go this route, I'll throw a 3.55 speedo gear in there and check the accuracy.

 

[Dejomo]

Should be fine, slightly higher RPM than stock with 4.10, but that should help getting those tires turning. On a side note, is this E350 4x4?

nope my 98 E350 is 2wd. She has an ARB airlocker that gets me about anywhere I need to go.

Up until the engine let go I had plans to build it out as a 6x4... tandem rear drive axles with the tough-as-nails I-beam suspension in the front.

I even went so far as to fabricate a gear box out of the guts of an NP205 and marry it to a D60 axle. If you want to read the thread where I hashed out the idea it's on pirate4x4.

 

[Dejomo]

I'm looking buying some 37's for my truck (hummer tires)
With 4.10's and 37's, it should be geared really close to a truck with stock size tires and 3.55 gears. If I go this route, I'll throw a 3.55 speedo gear in there and check the accuracy.

That sounds like a good little experiment.