NP435 Questions

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Jan 3, 2012 | 11:10 PM

JB78f150

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From: Virginia Beach, VA

NP435 Questions

Well I was reading the NP435 conversion? thread and it sparked up a thought. What rear end gears will make the granny first just a regular first gear? Or would this make fourth gear unusable? I have 285 75 r16 tires. A 460 swapped engine. Not sure what other info you will need but ask and I will answer them.

Jan 3, 2012 | 11:13 PM

85e150

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The gear remains the same. If you gear tall enough to HAVE to use that gear, you are looking at gear ratios taller than are available for your axles.

What are you converting from?

Jan 3, 2012 | 11:16 PM

JB78f150

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Not sure whatever it came with from the factory. Could I put like a 3.00 or 2.75 in the rear end it wouldn't do anything?

Jan 3, 2012 | 11:39 PM

HIO Silver

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From: NorCal

Quote:

Originally Posted by 85e150six4mtod

The gear remains the same. If you gear tall enough to HAVE to use that gear, you are looking at gear ratios taller than are available for your axles.

Sorta.. the gear remains the same but the effective drive ratio is changed.

Quote:

Originally Posted by JB78f150

Not sure whatever it came with from the factory. Could I put like a 3.00 or 2.75 in the rear end it wouldn't do anything?

IIRC, 2.75 is the lowest ratio available off the shelf. There are companies that make lower (numerically) rear end gears but they are special order and expensive. I've read that some Bonneville guys use something like 2.29 or 2.47.... but they've got alot of distance to ramp up and enough HP to propel the vehicle and maintain the given velocity. Alot of 'em also use a push truck to get it moving.

6.69 x 2.75 is over 18. Use larger diameter tires and it will reduce that multiplier. You'll have to calculate the difference in percentage of your existing combination versus the planned combination to figure out how much it underdrives the effective gear ratio. My bump has an NP435 and 3.25 rear gears on stock tires and I hate it. I can stick it in first gear, nurse it at idle, and I can walk faster than that thing. TKO-500 time!!!

Jan 3, 2012 | 11:44 PM

85e150

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You have 8 lug wheels, not a 5 lug half ton jobs. The half ton axles will have the 2.75 etc ratios, but axles like the Dana 60 have a 3.54 minimum.

Find out what kind of axles you have.

You'd be better off converting to a ZF or NV 5 speed and leaving your axles alone imo.

Tall axle ratios and low transmission ratios are not a good combination.