Overdrive possibilty question

[Jakespeeds]

This is more of an opinion question.  I am looking at a 70 Winnebago D18.  It has a 440 Dodge engine and the 727 transmission.  I have never had one of these and my understanding is that typically they are driven about 55mph on the freeway.  If I was to add a GearVendors over/under onto the transmission would a stock well maintained 440 have enough power to allow this vehicle to cruise at 65-70 and still stay in the green on a vacuum gauge?

Jake

[DaveVA78Chieftain]

Dodge did not offer the 440-3 until 73 so unless someone swapped a 440-3 into your rig it is a 413.
You would get a small improvement but a 10-15mph improvement while staying in the green is questionable.  Weight and boxy front end drive MPG on these rigs.

[Jakespeeds]

It did get a 440 swapped into it.  So chances are some kind of a power adder would be required.  Although if you feel it questionable it sounds like it would be close enough to be only about 40-50 horsepower addition.  Or more importantly about 60-70 ft/lbs. of torque.

Jake

[ClydesdaleKevin]

Part of the fun of driving these antiques is to just sit back and drive slowly, enjoying the countryside and the looks from all the people passing us...lol!

While a gear vendor unit will indeed allow you to cruise at higher speeds with the same rpms, they are extremely costly unless you can find a used unit.  For the slight gain you would get in fuel economy it would take a lifetime and a LOT of miles to pay off the expense. 

Its one of those things that you have to decide.  It won't pay itself off, but if you really want higher cruising speeds at the same rpms and vacuum, it might be worth it to you personally.

Incidently, a big bore gasoline engine in an RV gets its best gas mileage right around 40 mph.  That is according to the book we have available in the store called RX for RV Performance.  From experience and experimenting, I know this to be a fact.

If you do the modification, take lots of pictures and let us see how you do it.  We love pictures!

Kev

[Jakespeeds]

Kev,

  Thanks for the reply.  I hear ya with the taking your time aspect.  I am all for that 90% of the time.  There is one trip the wife and I take once every two years and sometimes every year.  We drive from Ventura California to Lewisville Texas.  I can take off the time I need from my business.  The wife has a job she enjoys but is held to a very specific amount of time off.  Because of that we like to make the drive each way in two days to spend more time with family.  This one trip is the reason I am asking.  We need to average about 65mph in order to make it work comfortably.  My last motorhome would do it easily.  I have used Gear Vendor units in several vehicles and am aware of the costs.  Trying to get better mpg is not really my main goal.

Jake

[Oz]

On a long trip like that, with covering long stretches of level or near level highway, and needing to do so at 65mph, if you can nod your head in agreement to the cost and work involved to get the overdrive unit, yeah, it would be something that would be of benefit at least for those trips and a cool project to boot.  Not to mention, if you needed or wanted to sell, it would be a huge selling point and could add a little extra value to the sale price.

[Jakespeeds]

Thank you for the responses.  I have a lot better of a bead on what I am going to do.

Jake

[cosmic]

I am questioning why you cant do 65 mph now?
I can do 65, mph all day long. but the rig likes 60 better. pushing 65 should not be a problem at all. I have done it for 6 hours straight in mine. Its pretty much as old as yours, I have a 440. 727 tranny.

[Wantawinnie]

Not positive what came in the 1970 models, if the gear ratio is 4.56 or 4.88 you might consider switching to 4.10 gears before spending the money on the gear vendor. A little D18 should not phase a 440 one bit. The 440 in my '73 D28 did an adequate job and that weighs around 12,000 lbs.

[ClydesdaleKevin]

No matter what you do, just take the corners slow...lol!  These old things weren't meant for the racetrack.  Solid front axles and leaf springs don't handle well around corners at speed, especially on bumps.  That's why I rarely drive my old Jeep YJ above 55.

Kev

[cosmic]

Then again. we do have very nice smooth highways up north here. makes for easy speeding. got the old girl going 85 mph this summer on a 4 lane hwy with very little traffic, and it was still pulling. Ii and I just couldn't take the wind speed for shoot, and couldn't imagine hitting a big bump.
Not my smartest stunt, but if you ever wondered. now you know.

[Jakespeeds]

Cosmic,

  I suppose it could do 65mph.  I am still dealing back and forth with the owner on a purchase price.  So I have not really had a chance to take it up to 65 and hold it for an extended period of time.  For me its not a question of if it will or not.  For an example I have a 73 Nova SS.  It would do 70 on the freeway no problem.  But having the motor wound up like that for several hours was no relaxing and kind of wore me out.  I added a 200R4 overdrive transmission and now that same 2 hour drive was much more relaxing.

  Changing the rear gears is something I figured I would have to do even after the addition of a Gear Vendors unit.  The Winnebago I drove seemed to really start hitting the beginning of its torque band about 2800 rpm.  But at what the speedo showed as 65ish the engine was at 3300 rpm.  It pulled from a dead stop very well and its shift points worked well.  But if I can take that 3300 and drop it to about 2500 at 65 without harming the low speed drive ability I would be very happy.

  But at 2500rpm it needs to be just below stoich.  If its over then I would be causing other issues and I would have to add a bit of power.  That is kind of where I was headed.

Jake