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Discussion Starter #1
I know MPG topics here are as frequent as gas after eatin Taco Bell, but I am running a little experiment so please bear with me. I have a 94 wit 302 and a E4OD fully rebuilt with about 7000 miles on it. I make frequent long distance trips thru hilly country.

To the point I have started driving it with the OD switched off and have not noticed any real drop in MPG, my tranny shifts less, and the power for gettin by granny is right there when I give the skinny pedal the push. Anyone else have any exprience or numbers about runnin with the OD off?

Thx,
B-Train
 

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I had to run across the state (about 150 miles) into a 25 MPH headwind in my old `86 with an AOD once. I couldn't get it to stay in OD, so I just shifted out of it. Instead of 15 MPG for that trip (my usual), I got about 8, and ran out of gas. Obviously, some of that is the headwind, but some of it is the higher revs, too, I'm sure.
 

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this is exactly why i am overgearing my truck. with my AOD, it drops out of the power range at 65 mph, and i actually push a little further down on the gas pedal to maintain the same speed (especially on an incline or in a headwind). i'm going to try running 5.13s with 35s to hopefully make my OD much more useable, which according to my calc. gets the truck into its power range at 65, and also will give me a little leeway for 36s, and will help with the extra mass of the tires.
 

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Zombie Hunter
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wakeav8b said:
i'm going to try running 5.13s with 35s to hopefully make my OD much more useable, which according to my calc.
Wow. I'd definitely do some thread searches about that, and look into it a little. 5.13 is an AWFUL steep gear for 35's. Some guys with 40's and do nothing but wheel their Bronco don't even run 5.13's. Probably within the year i will have 35's and i am only planning on re-gearing to 4.11's, simply because the 4.56's are to steep for what i use the truck for. I am just making a suggestion, it's just my opinion.

B-train.

Are you running stock tires? The current 31's cause my E4OD to kick in and out of OD even on the slightest incline. But since Ohio is mostly flat, i don't run into it very often. When i get into the hills of PA, i will just shut the OD off.

The reason your not seeing significant differences in gas mileage is probably because your not running in OD very much. If you've increased the tire size, you've changed your power range, which means the tranny is going to kick down more to make up for lost power. You would definitely see a difference if you were running on flatter ground.
 

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green ones make me horny
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Bronco Rob said:
Wow. I'd definitely do some thread searches about that, and look into it a little. 5.13 is an AWFUL steep gear for 35's. Some guys with 40's and do nothing but wheel their Bronco don't even run 5.13's. Probably within the year i will have 35's and i am only planning on re-gearing to 4.11's, simply because the 4.56's are to steep for what i use the truck for. I am just making a suggestion, it's just my opinion.

B-train.

Are you running stock tires? The current 31's cause my E4OD to kick in and out of OD even on the slightest incline. But since Ohio is mostly flat, i don't run into it very often. When i get into the hills of PA, i will just shut the OD off.

The reason your not seeing significant differences in gas mileage is probably because your not running in OD very much. If you've increased the tire size, you've changed your power range, which means the tranny is going to kick down more to make up for lost power. You would definitely see a difference if you were running on flatter ground.
:stupid

i think 5;.13 s are really low for that size tire. i would use those if i was running like 44s on a D60 or something like that.
 

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Discussion Starter #6
Yeah I put a set of 31's on it about a year ago... my mileage isn't bad with a 302 and 107,000 on it. I get about 12 in town and 14 on the highway. Got the parts on order for 6's tune up. It's been in the family since 94, so its a keeper hubs packed every 2 years, new RA bushingins in 2000, new fuel pump and sender 2001, Alpine head, heck besieds the 302 almost eveything has been gone over. I just started getting gutter cracks which make me a little crabby
 

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Bronco Rob said:
Wow. I'd definitely do some thread searches about that, and look into it a little. 5.13 is an AWFUL steep gear for 35's. Some guys with 40's and do nothing but wheel their Bronco don't even run 5.13's. Probably within the year i will have 35's and i am only planning on re-gearing to 4.11's, simply because the 4.56's are to steep for what i use the truck for. I am just making a suggestion, it's just my opinion.

B-train.

Are you running stock tires? The current 31's cause my E4OD to kick in and out of OD even on the slightest incline. But since Ohio is mostly flat, i don't run into it very often. When i get into the hills of PA, i will just shut the OD off.

The reason your not seeing significant differences in gas mileage is probably because your not running in OD very much. If you've increased the tire size, you've changed your power range, which means the tranny is going to kick down more to make up for lost power. You would definitely see a difference if you were running on flatter ground.

Ya i did quite a bit of searching on it and started up a thread on it. I had the same concerns.

http://fullsizebronco.com/forum/showthread.php?t=64094&highlight=5.38

my 302 just seems to pull best at 2000+ rpms on the highway. Currently it drops down to 1800 rpm's at 65 resulting in a lot of shifting unless on flat land with no headwind. Before it downshifts, that gas pedal has gone down quite a bit costing gas mileage as opposed to just keeping it in third. You also have a 351 and my AOD may have a higher gear ratio (not sure-but the AOD is .67:1). According to my calcs, I'll be turning 2145 rpms in OD with 35s at 65. A couple others posted back that 5.38s actually are a great gear to run with 35s and the AOD (only with the 302), others said to low. I'm going with 5.13s because (hopefully) that puts me into the power range and will keep me in the power range even with 36s. If i remember right, i'd still only be turning 3300 at 95 mph. If you see a bunch of these :doh0715: :banghead :doh0715: when I post my results, you'll know I went to low of a gear
 

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One Cold North Dakotan
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I almost always avoid OD on my SROD (3 speed + OD manual). I'm running 31's with 3.55's and a 302 also. I dont have near enough power to keep it going in OD. With no wind and perfectly flat ground I have to have the pedal to where it starts to get hard to press... I think that's when the second butterfly valve starts to open in the carb, which is alot of gas. Even then I can only do 65-70 mph with it if i'm lucky. If there is any headwind at all it won't keep speed. However, in regular drive I have much more acceleration/speed and get much better fuel mileage. At 65 mph my truck is running about 1500 rpm's in OD or about 2300 in regular drive. Because of that it doesn't have the power it should when it's running that slow. I drove from 50 miles away to college in OD and used a quarter of a tank yesterday. In regular drive I could have made much much further and been making 16+ mpg. My poor old engine needs some serious work, but that's how I run it now. By the way the reason I ran it in overdrive a fair bit yesterday was because i drove almost 700 miles round trip to pick up my NP 435, 208, bellhousing, and brand new clutch and pressure plate. I have a serious head gasket issue, as I went through over 7 quarts of oil driving it that amount of miles. When I got home it wasn't even on the dipstick. Don't even bother criticizing me, because after being completely broke buying this all I had was a bit of canadian money and no gas stations would take it, so that's all I could afford. It has gotten worse though this trip and I won't be able to drive it until I fix it. Anyway I guess that doesn't have anything else to do with this subject, just explaining why I used awful overdrive (to keep friction down as much as possible). So yes, I guess what it comes down to is which ever gear takes less pedal. You'll probably have to judge it by headwinds and things like that as I do. If I have a nice 50 mph tailwind I'll use OD and cruise down the freeway just fine. Hope it helps somewhat.
 

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wakeav8b said:
Ya i did quite a bit of searching on it and started up a thread on it. I had the same concerns.

http://fullsizebronco.com/forum/showthread.php?t=64094&highlight=5.38

my 302 just seems to pull best at 2000+ rpms on the highway. Currently it drops down to 1800 rpm's at 65 resulting in a lot of shifting unless on flat land with no headwind. Before it downshifts, that gas pedal has gone down quite a bit costing gas mileage as opposed to just keeping it in third. You also have a 351 and my AOD may have a higher gear ratio (not sure-but the AOD is .67:1). According to my calcs, I'll be turning 2145 rpms in OD with 35s at 65. A couple others posted back that 5.38s actually are a great gear to run with 35s and the AOD (only with the 302), others said to low. I'm going with 5.13s because (hopefully) that puts me into the power range and will keep me in the power range even with 36s. If i remember right, i'd still only be turning 3300 at 95 mph. If you see a bunch of these :doh0715: :banghead :doh0715: when I post my results, you'll know I went to low of a gear
My bad, didn't look at your Bronco Info. Didn't realize you didn't have that extra 49 c.i. of motor.
 
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