M1078 final drive ratio ?

[1951M1078]

I'm having a hard time with a engine RPM calculator .If I use a 46" tall tire and axle ratio of 3.9 at 1 to 1 and a speed of 50 MPH I get 1424 RPM. I do not think this is correct ? What am I doing wrong ?

Been playing with the Axle ratio . I and have found at 55 mph with a 5.4 it would be 2169 rpm.

Any ideas ?

I don't have my tach in yet.

The reasion is I have been thinking about going to the 16.00 R20 tires.

Randy

 

[f8617]

There's an additional 2-to-1 added by the spider/bevel gears on the axle ends...7.8-to-1 total ratio.

I'll bet you cry every time you drive uphill on 53inch 16R20 tires.

 

[res0wc18]

If you put 16 R20 tires on there you would definitely need to adjust the fuel and boost settings to their maximum. With this it would be tolerable but still about 50% low on power needed.


I'm not even sure if those tires will fit on a stock height rig. Does anyone have any pictures of a M1078 with the 16 R20 53" on it?

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[mkcoen]

I'll bet you cry every time you drive uphill on 53inch 16R20 tires.

I come close on the 46" MV/Ts. I've tried peddling faster but it didn't seem to help.

 

[1951M1078]

Yep, their to big !

Thanks

 

[frank8003]

Do Not read this
Old guy flaming, something to do with stuff He had to do a few times, ignore following.....

I wanna take a full military rig meant for feeding tanks and troops and make it go really fast with 50MPH brakes. I wanna go thru anything anywhere with just me driving. I really don't want to do the 4 hours of maintenance for every one hour I drive. I wanna put tires and wheels on like I don't even understand limitations of bearings. I want what I want or I don't want it- Popeye.....................

I want a new Ford Raptor but did not hit the lottery.
It is OK about the lottery no win
If I could just talk the wife out of the hot rods,
new Cadillacs and Camaros then I could go back to my hobbies

 

[res0wc18]

Ha.

Frank8003: classic!
And yes sir.
When I restored my M715 people kept telling me I put too small of tires on it, being 35" and I designed it to be used let alone abused without breaking so I said 35" is plenty on a GM Dana 60 and 14 bolt at full GVWR thank you very much lol

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[1951M1078]

Frank, what was that ? LOL

No ,I was just looking for the 60 mph at 1900 rpm.

Anybody know what the tran's has for gear ratio's ? Must have a over drive in 7th and maybe 6th ?
Randy

 

[res0wc18]

I believe .65 in 7th

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[res0wc18]

Also since it will be asked here is a pic of my baby

.

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[1951M1078]

Anybody with a tach get 1852 rpm at 50 MPH ? Checking the calculator .

Wonder if the tran's computer could be taught to start in 3 gear ?

 

[scottmandu]

If you put 16 R20 tires on there you would definitely need to adjust the fuel and boost settings to their maximum. With this it would be tolerable but still about 50% low on power needed.
I'm not even sure if those tires will fit on a stock height rig. Does anyone have any pictures of a M1078 with the 16 R20 53" on it?

They will fit on the rear but won't clear the hydraulic tank on the winch trucks or the box steps on the front when turning.
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