Need Overdrive Trans - Any such Beast???

[bmc69]

[ I see about the same as U that there is a sweet spot on mph, it's just a shame that our EB's it is about 62/63????? And the speed limits are 65-75 here. I will check at diff speeds, its easy for me since I drive my pony to work 52 miles round trip (WHEN its not too cold!! - Soft top);D

We're good. And that's a fair chunk of daily mileage for an EB as a DD.

Did you know that the aerodynamic drag becomes the dominant resistance to rolling at speeds above about 40 mph...and that the aero drag is 56% greater at 75 mph than it is at 60? Even just going from 60 to 65 brings a 17% drag increase.

Invent a ground effects kit for the EB..dropped Targa-style front end, air dams, rear skirt with spoiler..;D

 

[DirtDonk]

Unfortunately for my Bronco (not so bad in the mid-seventies with the 55mph speed though) the sweet-spot is between 55 and 60. With 55 being consistently better.
My '89 Caddy (not too aero either, but not bad) with 4.5 V8 and freeway gears would get a full 29-30 mpg, but only at between 60 and 63 max. 28 if the ground wasn't perfectly level.
Toyota Corolla, best at 60. '95 Mustang, best at 60. F150 with 302 and automatic w/2bbl and computer controlled ignition w/3.5 gears, got 12 under any condition. No power under any conditions either. Toyota pickup, crappy mileage no matter what!
The old Buick, now it could get into the 23 mpg range with it's old 430ci V8 with Quadrajet and total freeway-flyer gears (something in the high 2's!) at between 70 and 75.
My old 4-carb Corvair (VERY aero) was humming along at a 3750 rpm with it's low 3.55 gears and tiny tires, but got it's best mileage (30 to 32 mpg) at 70 mph, but only when going uphill, like to Tahoe or semi-uphill like to SF. Otherwise it's max was 26 to 28 mpg.
The only time my F350 with 400 2bbl got a whopping 13.3 mpg was at 55 with a full load of crap, where the truck weighed in at 8850 lbs. on level ground at a super steady speed between gas stations on the way to Oregon. On the way back, empty, at the same speed I reverted to the normal 10 to 11 mpg. Even when I filled up after the long downhill sections near the border. Downhill!

Every vehicle seems to be different, but they also seems to mostly follow the rules about less aero vehicles prefer less speed, and some carbureted vehicles actually get better mileage with the throttle pushed farther open for a given speed (uphill and/or loaded). EFI depends on the tuner and what they knew of course, but has some similarities to the carbs sometimes.
All my carbureted cars got better mileage at higher rpms and speeds than at lower. All my carbureted trucks got their best mileage at lower speeds and higher throttle openings.
My '03 Buick 3.8 V6 gets a consistent 28-29 at any speed between 55 and 70. But will get 31 when loaded with 5 people and all their gear for a week. Go figure. There's that higher throttle opening again maybe? Lower ride height perhaps? Dunno, but I like it.

All this is over years of checking almost every tank of gas, religiously, due to either business needs or just for fun.

Paul

 

[1970mule]

Just wondering if you have a wide band sensor. That is one of the best ways to find out just how your engine is behaving. That being said i don't have one yet but wheni get the chips thats a must. I have a pretty stock rebuilt 302 with a 351 cam in there, 33's 4.11 gears and the stock 3 speed that will be switched to a nv3550. i drive like grandma with her special glacoma medicine. I like 55 so does my bronco. if i stay 55-60 i get about 15 mpg. but a lil past ill get like 12mpg in the city its like 10 mpg sucks.
but what makes me very mad is that my buddy has a 427 stroker 35s and 4.11 gears also EFI like mine and he gets 15mpg or more he has the C4 trans in his tho. if you keep trying and are patient i am sure 16 is very doable.

The way i see it we sink mony into these no matter what, so what does it matter if you spend 3k or so to try and get 1-2 mpgs. DO it do it.

 

[1970mule]

yeah i hate that ppl drive so fast now too. I drive 55-60 on the freeways all the time. I need to get a special pass blinker in the shape of a middle finger and little lights that says "F U pass me already "

 

[73azbronco]

Ahh, my dads F150 with a 460, 10.5mpg in the city, hiway, loaded/ empty, pulling a four ton trailer. 10.5mpg, made figuring gas easy.

 

[broncokak]

Ahh, my dads F150 with a 460, 10.5mpg in the city, hiway, loaded/ empty, pulling a four ton trailer. 10.5mpg, made figuring gas easy.

Yup, good old 460s. Same mileage no mater what. And all the power you would ever need. Great engine!

 

[kc15842]

15+ 68 EB sport

I have a 91 HO, 4.11, 33's, D20 with a 91 AOD. I get 15+ on the freeway. 72 MPH is about and a 2100 RPM.

 

[AZ69EB]

Idaho Slim, I just posted this on the chat forum for the same issue. Take a look at this option for you:

Another option for the 435 is a range box in front with the choice of an overdrive or under-drive gears. Most people pick the overdrive option unless you need to crawl.

The overdrive gears will let you split the gears more efficiently and provide a true overdrive while still having one of the lowest 1st gears available. The range box is all gears and is rock solid with another shifter leaver.

Now you have the standard 4 forward gears and reverse or an option for 8 forward and 2 reverse gears. You can split each gear.

The 3rd gear, then 3rd gear with overdrive, 4th gear and 4th gear overdrive is great for passing and cruising. Most people complain about the large jump between 3rd and 4th gear in the 435. This solves this problem efficiently.

It also keeps the drivelines shorter than some of the other options like the ZF5 or 4R70W. You still have room if you want to add the 203-range box behind the 435 to under-drive all gears again for crawling.

The gear choices would be crazy at that point, but impressive for both on road and off road activities!!!

We have two members in the AZ Classic Bronco Club with the range box in front of the 435. One has a D20 and the other have an Atlas behind the range box / 435 combinations. Both love it.

Just another option to think about.

 

[AZ69EB]

Idaho Slim

FYI - I have the zf 5 speed, 4.88 gears, and 33" tires. I can cruise at 65 mph at 2500 - 2600 rpm. I can pass anyone if needed without the engine screaming too much.

As for gas mileage, it is in the mid to low teens. I really don't know and don't care, as it is a recreational vehicle.

I just drove it 650 plus miles road trip without the wheeling mileage. It drives down the highway great.

I only have about a 68:1 crawl ratio. I wish it were closer to 100:1. Need to have more control in 1st / low range.

My next option is changing gears in my D20 or going to a Stack t-case. With the ZF5 drive shaft length is a major concern. Currently, my front and rear drive shafts are 28.5” long.

If I had it to do all over; I would of picked the overdrive range box in front of the 435 with the 203 then the D20 t-case or the NP205 t-case.

With your gearing you would have about 110:1 crawl ration with and over-drive option.
6.69 x 2 x 2 x 4.11= 110 Plus, the ability to have overdrive for high way cruising.

Not bad for a street / trail rig.

Just another option.

 

[Idaho Slim]

Some update info;

My MSD coil has been affecting my performance (mileage) it was toast, got stranded in the back country chasing wolves/coyotes) grrrr. So the new one really woke the motor up, and I had some mph & rpm numbers off also due to tire diameter calcs:

32.5 inch diamter BFG's;

60 mph = 2600 rpm = 14.2 mpg

65 mph = 2800 rpm = 13.4 mpg

70 mph = 3000 rpm = 12. 1 mpg

35 BFG's going on tomorrow ! Will update in a few weeks.

Merry Christmas, SLIM.

 

[Justafordguy]

Some update info;

My MSD coil has been affecting my performance (mileage) it was toast, got stranded in the back country chasing wolves/coyotes) grrrr. So the new one really woke the motor up, and I had some mph & rpm numbers off also due to tire diameter calcs:

32.5 inch diamter BFG's;

60 mph = 2600 rpm = 14.2 mpg

65 mph = 2800 rpm = 13.4 mpg

70 mph = 3000 rpm = 12. 1 mpg

35 BFG's going on tomorrow ! Will update in a few weeks.

Merry Christmas, SLIM.

Good to know, can't wait to see what the 35s do for ya.

Merry Christmas to you too.

 

[Wyflyer]

Good to know, can't wait to see what the 35s do for ya.

Merry Christmas to you too.

My guess is it won't be 10.5 miles per gallon

 

[76Broncofromhell]

Some update info;

My MSD coil has been affecting my performance (mileage) it was toast, got stranded in the back country chasing wolves/coyotes) grrrr. So the new one really woke the motor up, and I had some mph & rpm numbers off also due to tire diameter calcs:

32.5 inch diamter BFG's;

60 mph = 2600 rpm = 14.2 mpg

65 mph = 2800 rpm = 13.4 mpg

70 mph = 3000 rpm = 12. 1 mpg

35 BFG's going on tomorrow ! Will update in a few weeks.

Merry Christmas, SLIM.

My stock 2V 302 got 10-11 highway.

I built a 408 and stopped keeping track. All of you claiming 16-20 mpg are lying. I don't care about being nice or making friends, but I can tell you something with the aerodynamics of a toolshed cruising at freeway speeds, with a carburetor and no overdrive is not going to equal a Ford Ranger in economy.

Short answer: an OD transmission will never pay for itself in an Early Bronco. Ever. Yes, I have one, but nothing on the Bronco is done with cost in mind.

 

[Oatmeal]

Have you maybe considered an Advance Adapters' Ranger gear spliter?
Fits between the bell housing and trans and adds about seven inches to the length of the drivetrain....moves the trans/t-case and of course, the crossmember back.
No clutch linkage mods and it will get the shifter out from under the heater box!
It'll give you a whole range of gear selections....16 forward and 4 reverse (if you factor in low range)
Been thinking of going this route...if I can somehow find the money

Hans

 

[HoosierDaddy]

and you decided that you are the kingshitdaddyknowitall of eb's

BMC , I hope you don't mind , but I'm stealing that title ... unless you really want it. ;D

EDIT:
Done ,
<<< , not sure which version I like better over there , the title or the info below the avatar.

You should C&P that into your signature.

 

[nvrstuk]

yeah...

...I read all 4 pages of posts on this thread...here I go...

My first EB, a '68 (like DirtDonk back in the '70's) I consistently got 17-18mpg with a corrected odometer, on 27" tall tires, stock 3.5 gears, small 4 bbl at 60mph. At 55mph (national speed limit back then) I had many trips at 19mpg. The key was the 289 which got much better mileage than any 302 EB I ever had or drove. Any smog engine got terrible mileage ('72 and later). I actually found my original log book recently from those days of filling up at and writing down the # of gallons used and miles for years and years with my different Broncos.

On a manly man 9 day drive with 8 other EB's to the Rubicon and back from the PNW, I averaged, yes averaged 14.5 mpg with 35"s, 4.10 gears, ZF/NP203/D20, QJET, there, back including wheeling and for appr 100 miles I was averaging 80mph (we lost everyone-trying to catch up). My rig got better mileage than ALL of the other rigs including the 5- 5.0 fuel injected rigs. Did I mention that I ran a 351W with over 100K miles on it that I built in '86? All mileage and gallons used were verified by other guys on that trip. Yes it can be done.

MY Dad's rock stock 69 Bronco got his best mileage at 15mpg. After headers, a small 4 bbl with alum dual plane intake he got 16 mpg but a ton more power. It could finally breathe.


As soon as I began adding bigger tires (aerodynamic drag), steeper gear ratios, faster cruising speed (speed limit went from 55mph nationally back up to 70mph) I started losing mpg. Add body lift, suspension lift, 37" tall tires and you are driving a big cardboard box... oh, weigh in your tire/wheel combo at over 110lbs now compared to 40lbs/tire back then and it's all about apples and apples...

Good luck. If you want "great" mileage, dump the engine you've got and stick in a 289 and go back to drive train specs that are close to what a stocker was back in the day!

 

[AZ69EB]

nvrstuck,


I don't want to hijack this tread so I sent you a pm.

 

[Ranchtruck]

I consistently got 17-18mpg with a corrected odometer

Having an accurate odometer or applying a conversion ratio when calculating fuel mileage is crucial when throwing around mpg numbers. A lot of the "big tires cause bad mpg" is due to people using the now too-low odometer reading to calculate the per-tank economy.

Right now I'm running smaller tires on my toyota, so when I'm going 65 the speedo is reading 72. I'd calculate excellent MPG out of it if I took the odometer reading at face value. Using the conversion factor I'm only getting 19mpg.

 

[Idaho Slim]

Having an accurate odometer or applying a conversion ratio when calculating fuel mileage is crucial when throwing around mpg numbers.

I highly agree, hence why I reposted my numbers I re-calculated my tire od difference and I also found that you can put about 2-3 gallons into the rear tank before it has standing fuel, that adjusted my numbers.

One point, I am not oblivious to the fact an OD won't pay for itself real quick via better fuel mileage (always known that), my quick calcs say it would take about 40 months to break even if I spent $3000 for an OD, (which is prolly low est.?) and went from 13 mpg to 16 mpg. That is assuming I run about 1600 miles a month, which is WAY more than I would since it is not a daily driver year round. But modifying my EB is one of my enjoyments, as long as the Pony is not down all the time which greatly interferes with my driving it.

In that light, I most likely will call it good with the 35's and slow down to 65 and hope for 13-15 hwy.

The AA gear splitter is interesting tho, cost?????
I

 

[nvrstuk]

...

X2 Idahoslim... Most of my numbers are from 50 or 100 mile checks on mileage markers on the freeway. So many people use the gauge to check mileage, the speedo gears are off, and they are never diligent in making sure all the variables are accurate each time. Estimating doesn't count when figuring mileage... my dash was covered with pencil with mileage marker numbers, gallons used, and mpg when we did the 2000+ mile round trip Rubicon run. Hard to be off when you fill up every 200-300 miles figuring mileage at each stop. Double checking mileage on speedo's with several other rigs (that are dialed in also).

Oh well, this has turned into another mpg thread...