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Overdrive options ...we need them

Unread postby Acesneights on Wed Sep 18, 2013 6:01 am

As we all know this rigs were built in the 60's and 70's when the speed limit was 55 and gas was cheap.
Those days are gone not to mention the pain of listening to my motor screaming at 60. So in my hunt for a better way I posted up at Moparts.com(no affiliation to this forum).
Learned quite a few things. Rather than regurgitate the info and plagurize I'll
Just post the link. I recommended watching all of the links and vids.
Seeing John Schnieder was cool.
Ultrabell certainly provides a nice option.
http://board.moparts.org/ubbthreads/sho ... ost7841622
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Re: Overdrive options ...we need them

Unread postby Operation68Travco on Sun Sep 29, 2013 9:20 am

IMHO, going with an Overdrive is probably going to be an expense that will never pay off. Let's not forget that the discussion noted is about 3000-5000 pound cars. Not 7500-12000 pound RVs.

So, once you've gone to the extremes of actually installing an overdrive trans, doing the gears properly, etc, you'll probably only experience real benefits with a tailwind or going downhill.

It's important to note, I think, that with a lower RPM situation due to overdrive, your engine may be laboring big time. The result? Poor gas mileage.

Which is probably why you were looking at OD in the first place! :D
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Re: Overdrive options ...we need them

Unread postby Acesneights on Sun Oct 06, 2013 2:03 pm

I disagree. My M1008 was 1:1 with the TH400 and got about 13 hwy and could not comfortably go over 60 mph. The truck weighs about 6800 lbs empty. After I swapped in an NV4500 with .70 OD My mpg went up to 18 and I can cruise comfortably at 70. In the case of Travco I am not sure if you have driven one of these yet but mine at 55 sounds like it's screaming. I am not all that concerned about mpg increase although I am certain there will be some but more so just being able to cruise at 65 without the engine sounding like it's gonna hand grenade. I firmly believe that is why alot of the 70's cars , the engines only lasted 90-100k and then started burning oil. It's not good having it run 3-4000 rpms for a 6 hr trip.
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Re: Overdrive options ...we need them

Unread postby Operation68Travco on Mon Oct 07, 2013 10:24 am

I have driven a Travco, of course, but I guess I just didn't notice. I also drive a 63 Valiant with a 3 speed automatic, and I guess I'm just used to loud cars :)

I guess I just worried that people would read this thread, do a massive change to their rigs and then wonder why the MPG didn't increase measurably. I still see Overdrive as an expense that probably wouldn't ever pay for itself.

On the other hand, if there were a study or two saying that OD offered a real difference in MPG, sign me up.

I think cheaper ideas like an HEI conversion are going to get you better benefits, and with much less heavy work and expense.
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Re: Overdrive options ...we need them

Unread postby Roadrash on Wed Oct 09, 2013 12:53 am

Acesneights wrote:I disagree. My M1008 was 1:1 with the TH400 and got about 13 hwy and could not comfortably go over 60 mph. The truck weighs about 6800 lbs empty. After I swapped in an NV4500 with .70 OD My mpg went up to 18 and I can cruise comfortably at 70. In the case of Travco I am not sure if you have driven one of these yet but mine at 55 sounds like it's screaming. I am not all that concerned about mpg increase although I am certain there will be some but more so just being able to cruise at 65 without the engine sounding like it's gonna hand grenade. I firmly believe that is why alot of the 70's cars , the engines only lasted 90-100k and then started burning oil. It's not good having it run 3-4000 rpms for a 6 hr trip.


I suspect the MPG gains you experienced had a lot more to do with going from an automatic to standard transmission. The TH400 has a non locking torque converter which generates a lot of heat. That heat comes at the expense of MPG.
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Re: Overdrive options ...we need them

Unread postby Operation68Travco on Wed Oct 09, 2013 9:14 am

Roadrash wrote:I suspect the MPG gains you experienced had a lot more to do with going from an automatic to standard transmission. The TH400 has a non locking torque converter which generates a lot of heat. That heat comes at the expense of MPG.


Great discussion. I'm in total agreement with this. I just assumed that Aces was talking an automatic-to-automatic swap. An automatic to manual swap is very much an apples to oranges type of comparison when it comes to MPG.
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Re: Overdrive options ...we need them

Unread postby Acesneights on Wed Oct 09, 2013 8:44 pm

While I will agree that Manual will give better mpg in my case the OD helped alot too. Like I said before the swap The engine was screaming at 60. Now i can cruise at 70-75. Much easier on the engine. Less rpms, less fuel.
Don't know about you guys but my 270 sounds like it's screaming at 60. I'd like to get that final ration to .70
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Re: Overdrive options ...we need them

Unread postby 77Travco on Thu Oct 10, 2013 8:20 am

I think my engine turns around 3500rpm at 70 and 4300rpm at 85 but I need to re-install a tach to be sure. (needed it for my hot-rod)
I usually try to keep it at 60 or 65 to get better fuel mileage but that sure gets old fast out here where the speed limit on I-10 is 80mph. Just another reason to stick to the back roads and enjoy the slower more scenic routes.
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Re: Overdrive options ...we need them

Unread postby Acesneights on Thu Oct 10, 2013 6:03 pm

77Travco wrote:I think my engine turns around 3500rpm at 70 and 4300rpm at 85 but I need to re-install a tach to be sure. (needed it for my hot-rod)
I usually try to keep it at 60 or 65 to get better fuel mileage but that sure gets old fast out here where the speed limit on I-10 is 80mph. Just another reason to stick to the back roads and enjoy the slower more scenic routes.

:o :shock:
Wow...Mine scares the crap outta me at 65....I guess I am just used to diesels.
I have never taken mine over 65.
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Re: Overdrive options ...we need them

Unread postby slickandrewstravco on Mon Nov 18, 2013 12:33 pm

Hey Gang..
Definately look into the Gear Vendor's line of over/under units if you're wanting an extra gear on that T-Flite.

The Argosy that we just sold was a Chebby 454/TH475 (overbuilt 400) , and the rig unit weighed about 9,000lbs. and it had a Dana 70 butt with 4:56's in it.

If you kept it at 60mph or below you'd get an honest 10mpg, turning like 3,700..... BUT over 60, the engine screamed like a Banshee at like 4,300 rpm and ABSOLUTELY DRANK gas.
It has A LOT to do with te shift point setup, and a WHOLE LOT to do with your rearend gearing.

BUT....with the Gear Vendor installed, we could get comfortaby 70-80mph out of it on the flats, and it would return 12-15mpg. turning about 3,300 or so.

The best part of the Gear Vendor is that you can use it as a splitter between gears, say like first, first over, second, second over, and so on.. or use it as an underdrive to get a little more oomph going uphill, like in West By-God Virginia.

They allegedly use 'em up to 1,200 horsepower, and something like 1,200 lbs./ft torque in dragsters and so on.

They're on the pricey side, but we got one for 1200 dollah used... didn't look used to me, though.
I guess it cost like $200 to shorten the drivshaft, too.

Anyhoo... it sure made a huge difference to me. I liked that the engine wasn't being as taxed, and we did get a little better mileage.

Gotta remember... these ain't no Prius's we drive, and besides... we don't need to spend our geeters on motels and restaurants when we're traveling, when we're already carrying our bedrooms and kitchens with us!

ALSO....If anyone knows somebody trying to unload a non-computer Gear Vendor for the 727...LEMME KNOW RIGHT AWAY!
I wanna put one in this 320, postee hastee!!!
The PO didn't have it set up too well, but I think with a carb rebuild or retrofit, some new wires and plugs, and a Pertronix in the distributor, I oughtta be able to squeeze about 10mpg out of it. With all that AND a Gear Vendor, maybe even 12!!!!!

CHEERS!
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