Rear End Gears

[pinebear]

I have a 28ft pinnacle with a 454 engine and th400 NON overdrive transmission and 4.56 rear end gear ratio.
I am trying to find out if changing the rear end gears to a 3.73 gear ratio would be too much drag for this engine. I am trying to improve the mileage by doing this. Gross vehicle weight is 15000. We sometimes pull a 3000 lb toad. 95% highway driving.
Looking for any advice or a website that may advice on this.
Thanks,
Doug

[DAN L]

Quote:

Originally Posted by pinebear I have a 28ft pinnacle with a 454 engine and th400 NON overdrive transmission and 4.56 rear end gear ratio. I am trying to find out if changing the rear end gears to a 3.73 gear ratio would be too much drag for this engine. I am trying to improve the mileage by doing this. Gross vehicle weight is 15000. We sometimes pull a 3000 lb toad. 95% highway driving. Looking for any advice or a website that may advice on this. Thanks, Doug

how about a gear vendors 22% overdrive?
it looks like you would have an effective ratio of 3.56 in high gear/od.

Gear Vendors under/overdrive, Facts.

[Billieg]

The overdrive would be your best bet. 3.73 gears would not pull well and you might wind up getting less mpg. The best I ever got with my MH with the 454 was 6.4 mpg.

[DriVer]

Gear Vendor's Overdrive. The best solution. √

[pkmesser]

I had that powertrain in an 31 ft Pace Arrow. In the west, with the grades I normally encounter, make that gear change would not have worked, w/o a major increase in torque and horsepower. That was without a toad. As pointed out by others, you will end up running in 2nd enough that the net MPG gain may very well be negative.
Going from 4.56 to 3.73's is a big change, if you are mainly in flat country, 4.10's might work, and help on milage. Probably never pay for the gear set though.
BTW, I averaged overall about 7.0 mpg with that MH. Had a high of 8.0 on one leg of a long trip, with a tailwind, and no uphill grades. Curent motorhome is 6 ft longer, weighs about 5000 lbs more, and gets better milage, 7.39 to 7.94 average for trips of about 2000 miles. People knock the Workhorse and 8.1, but it has come a long way from that 454 3 speed.

[Mekanic]

I vote for the gear vendors OD unit OR a 4L80E trans and the required computer to run it.

[Mr_D]

We had a Ford '88 Type B MH (460 engine) with TT towing package and 4.56 gears. We put a Gear Vendors in. I gave a nice cruising rpm but we realized NO increase in mileage. It weighed 8,800#'s and we never towed another vehicle.
I doubt adding one to a MH weighing twice as much will give more mileage.