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Rear end gears

I was told by a truck mechanic that he could put  different gears into the rear end of my 1987 Gran Villa and I would get better gas mileage and either higher speeds or better low end torque depending on the gears. Mine has a Ford 460 gas engine with a four barrel carb. Am wondering if this is true? He took the tag number off the rear end pumpkin and called the number in. He was told he would need to remove the back plate and look at what gears were in there before doing so. Any opinions or technical advice gratefully accepted before I delve into this. don't want to spend a lot of money for only a two or three mile per gallon increase.
EMT living in Missouri. Recently purchased 1987 Gran Villa 36 Ft. long,460 Ford engine with 40,000 miles on it, new tranny has 3000 miles on it, coach has 75000 miles on it, new 5000 watt genny new fridge, new tires. Am both excited and scared out of my wits at the size of this beast. Love it but need time to become accustomed to it's size.  I'm sure it will take time to experience all the secrets this RV has to offer. Any and all advice gratefully accepted.

Re: Rear end gears

Reply #1 –
I don't see a way for a change in gearing to make even 3 MPG difference.

I suspect the break even point on doing that would be NEVER unless you drive many thousands of miles a year.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Rear end gears

Reply #2 –
If he does not know what gears you have how can he say you will get better mileage?Best way to get better mileage is to drive slower.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Rear end gears

Reply #3 –
One would not be advised to worry about fuel mileage and changing anything is not going to make much difference. But all gear changes come with an offset: higher max speed lowers ability climb steep mountains, etc. But some changes for power if too low can be helpful.

Google search to educate yourself on all topics someone claims will be helpful. Not a good idea to blindly accept someone else's opinion even if stated as fact.

Re: Rear end gears

Reply #4 –
I would not consider this on any vehicle unless
1. I already had to change because of a failure/wear
2. Changing the purpose that the vehicle was intended for.

So if you plan on drag racing or doing tractor pulls with your Foretravel I would say go for it. LOL
Jeff & Carolyn
1999 36ft. U320 Foretravel

Re: Rear end gears

Reply #5 –
A 2 or 3 mpg increase on something getting 5 or 6 would be a great improvement,what do you get for mpg.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Rear end gears

Reply #6 –
She gets 6 miles to the gallon. :-(  Thank you for all the replies. Guess the smart play is just to be thankful I have an engine and tranny in good shape for a rig that old and not cause more problems. The mechanic said he called the factory with the number on the metal tag on the rear pumpkin. They told him he would need to inspect the gears in there to make a determination what type of gears to replace them with.  Maybe slightly smaller tires might help with the fuel mileage.
EMT living in Missouri. Recently purchased 1987 Gran Villa 36 Ft. long,460 Ford engine with 40,000 miles on it, new tranny has 3000 miles on it, coach has 75000 miles on it, new 5000 watt genny new fridge, new tires. Am both excited and scared out of my wits at the size of this beast. Love it but need time to become accustomed to it's size.  I'm sure it will take time to experience all the secrets this RV has to offer. Any and all advice gratefully accepted.

Re: Rear end gears

Reply #7 –
What is your RPM at 60 mph?
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Rear end gears

Reply #8 –
Wonder why the original engine only lasted 35k miles,not to discourage you but if you like rving consider getting what you can for it and get a diesel pusher,many good ones out there.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Rear end gears

Reply #9 –
1 MPG increase to 6MPG is 20% increase. Huge.  What is your RPM compared to desired RPM?  SLOW DOWN! Loose some weight. Keep your tire pressure at upper ratings. Still running carburetor? Look into modern fuel injection and engine management systems controlling engine and transmission operation. Unfortunately it will ultimately  never see a return on investment. Manufactures will want your ideas for 3+ MPG increase. Ultimately it takes so many BTUs to  Overcome the coefficiency of drag and weight. Personally I would look into a Gearvenders overdrive before reagearing. Going to smaller tires is actually increasing your RPM but lowering engine power demands.

Re: Rear end gears

Reply #10 –
Daydreaming about increased gas mileage is fun, but eventually you must face reality:  you are pushing a big heavy brick shaped vehicle through the air.  Your 7.5L gas engine is relatively small and underpowered.  Nothing you can do to your engine or drivetrain will make a big difference ($$$) in your gas mileage.  If you are getting 6 MPG that's really not too bad...our 40' coach (8.3L diesel) gets 8 MPG on average.

Getting 6-10 MPG from big class A motor homes is just a fact of life.  Some do a little better than others, but they all suck (literally).  Grin and bear it!

As noted in previous posts, the speed you drive is probably the biggest factor influencing gas mileage.  Another big factor is wind direction.  Driving into a stiff headwind (or pulling long uphill grades) can really kill your MPG.  Try to stay out of the secondaries on your carb as much as possible.  Do your traveling on nice calm days, and find the "sweet spot" where your engine and drivetrain seem happiest...usually around 60-65 MPH the way our early model coaches are geared.  Then relax and enjoy the ride!

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Rear end gears

Reply #11 –
We've had the same discussion before. Most likely gear in the ored is 4.1. 
Your engine should be happiest with that gear for tire size and mass  .
The modern efi will return some fuel savings over the gear change . Imho.
Also look at tire size. I just installed the 9 r tires to reduce the rolling mass and unneeded load .
Also I swapped to electric cooling fans in conjunction with enough solar to drive them  . Big gain in fuel use.  An easy plus 1 and  2. 
Short story is that it's gunna burn a lot of gas vs the diesel . 30% more .

Re: Rear end gears

Reply #12 –
If you are getting 6 mpg then you are doing better than most with the 460. That coach was made for flat land and 50-55 mph. They were way under powered. I used to work for Foretravel during the time those were built and replaced many engines in the rear engine gas GrandVillas.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Rear end gears

Reply #13 –
Folks - this is a tech topic regarding rear end gears in a specific Foretravel.  I split out the "other vehicle MPG talk" to keep this on topic.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Rear end gears

Reply #15 –
Grey Wolf-- if I were set on doing something to the rear end I would put a high/low splitter in front of the differential-- If memory serves me right (may not) you can get a 15 to 20% lower end and a 15 to 20% higher end.  You could use the low side for climbing hills and the high side for flat land.
The splitter is bolted to the front of the differential and the drive shaft is then cut to appropriate length
Just my 2 c worth
Chris
1999 U 320 DGFE
Build Number 5523
Chris & Elka Lang
In the field, Lonoke AR

Re: Rear end gears

Reply #16 –
The bottom line on all these mods is that your spending $10 to save $5.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Rear end gears

Reply #17 –
Grey Wolf wrote: "I was told by a truck mechanic that he could put different gears into the rear end of my 1987 Gran Villa and I would get better gas mileage and either higher speeds or better low end torque depending on the gears."
Yes, but:

Three things, two of them closely related.
Better fuel economy.  I'll talk at length about that at the end.
Higher speeds.  Unless you run out of horsepower first.
Better low end torque.  Yes.  This is a given when you install numerically higher gear ratios.

"We" own and operate a U225 UniHome powered by a 5.9L 12-Valve Cummins in-line six. And we measure and calculate 11 miles per gallon.  Mixed driving.

We used to own and operate a 1986 Rockwood powered by a Chevrolet 454 truck engine through a Hydamatic truck 3-speed transmission.  A good tune up took us from 4 MPG to 5 MPG a 25% increase in fuel economy.  Extensive tuning of the Quadrajet carburetor brought us up to 7 MPG on the highway IF I kept the vacuum gauge at a higher number than 5 inches of mercury.  I chose a spring that kept the Adjustable Part Throttle enrichment valve in carburetor closed until 5" Hg.  Once that opened: 5 MPG.

I agree with John44 in that you're looking to spend $10 to save $5.  Or to put it another way, and keep in mind there is no Return On Investment, everything you spend is an expense for which you will never see your money again, How long will it take for you to earn back your expense, how long will it be before you can enjoy your savings?  That Ford 460 was used in many pieces of heavy equipment and I think you're doing best to just keep filling the fuel tank.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Rear end gears

Reply #18 –
Comes down to "felling better" look at the cheaper price for gasoline vs diesel and that will bring your cost per mile to drive the coach closer to the diesel rigs .Felling better is what we are all in pursuit of.
Dub McBride 1996 270

Re: Rear end gears

Reply #19 –
Dub--I feel better already!!!
Chris
1999 U 320 DGFE
Build Number 5523
Chris & Elka Lang
In the field, Lonoke AR

Re: Rear end gears

Reply #20 –
Thank you to all the people who have offered advice and opinions. It really means a lot to have options and an information source to go to owning these types of rigs. I drove different types of ambulances for thirty seven years, and learned a lot, but a class A RV is a totally different animal. I thought the newer type ambulances were big until I climbed behind the wheel of this thing. Mine is what I would refer to as vintage. I enjoy working on her to keep her on the road. Kinda like owning a 57 Chevy. Thankfully the Eighties type technology is simpler to work on compared to todays. I'm always learning something new about  working on this RV. This site gives us all the ability to work on our rigs while we are on the road, helping us save money.
EMT living in Missouri. Recently purchased 1987 Gran Villa 36 Ft. long,460 Ford engine with 40,000 miles on it, new tranny has 3000 miles on it, coach has 75000 miles on it, new 5000 watt genny new fridge, new tires. Am both excited and scared out of my wits at the size of this beast. Love it but need time to become accustomed to it's size.  I'm sure it will take time to experience all the secrets this RV has to offer. Any and all advice gratefully accepted.