Gear Ratios

[djf36]

I have a F-450 CC on order. I am going to install a F-350 bed on it.
The rear end is a 488LS. Is this very low or does the diameter of the 19.5 tires compenste?

Thanks for any imput.

[crewzer]

The V10 & 4.88 combo is good for 24,000 lbs GCWR; with a PSD it's good for 26,000 lbs. From your other post, you won't have a problem towing a 9K trailer...

Standard tires on the 450/550 are 225/70R19.5. They'll be about 32 ins in diameter -- maybe a smidge larger than the 235/85R16 or 265/75R16's on the 250/350's, so there's really no "larger" tires/wheels compensating for the lower axle ratio.

That 4.88 is a major part of where the 24K/26K GCWR comes from. For example, the 450/550 equipped with a PSD and a 3.73 or a 4.10 is rated at a 20K GCWR - the same as the 250/350.

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crewzer -- Y2K F250 SD 4X2 CC SB XLT 5.4LV8 AT 4.10LS TTPkg Black/Silver

[Aaron Ruble]

CREWZER, If lowering the gear ratio from 3.73 to 4.10 increases the GCWR (alonge with springs etc.), and lowers the MPG, What would be involved in making the change and at what cost?

By reading the threads, you become aware that some folks are running over limit, and this may help some of them but safety before fuel costs.

Besides, Smokey pays half the cost of any up-grade that improves safety.

[crewzer]

Aaron,

I'm not sure where you're going with this...

Lowering the rear axle from 3.73 to 4.30 with the V10 increases the GCWR from 17K to 20K; going from 3.73 to 4.10 won't buy much. However, I'm not sure the emissions or trans schedule programming for the gassers would be happy with this "horizontal" change.

I'd discuss the complete requirement, the cost, and any possible warranty impact with a Ford dealer...

Re a "vertical" upgrade, all of these vehicles come with factory GVWR certifications. Changing the springs and/or axles doesn't change these certs.

I wouldn't consider any of these mods on a fairly new vehicle until after the 3 year/36,000 mile warranty expires. Even then, I doubt if I would make such changes.

If someone has a truck with a 17K GCWR and decides they need (want?) one with, say, a 26K rating, my suggestion would be to sell the old truck and buy a new one.

It might be cheaper, it would almost certainly be safer, and it would come with a new warranty .

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crewzer -- Y2K F250 SD 4X2 CC SB XLT 5.4LV8 AT 4.10LS 4W-ABS TTPkg etc. Black/Silver plus 285/75R16D tires, trans cooling fan, TT gauge & Magnefine filter.

[This message has been edited by crewzer (edited 10-29-2000).]

[Aaron Ruble]

Good job Crewzer.

There are a lot of reasons to trade a vehicle (or not trade as the case may be), but safety should certainly strengthen one's resolve to conside a new tow vehicle.