mpg is terrible...Why?
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mpg is terrible...Why?
i have a 1986 ford bronco II 2.9V6 it has a 9 inch lift and 31 inch tires right now it idels at about 1k and when im driving at like 50 its at about 2200rpms i was wondering why its so high is this normal? and my mpg is about 7... for a 2.9 v6 thats a little low i think anyways a ihave a 97 dodge ram 5.9 with a 6inch lift and it gets like 10.6 so why would this be getting such bad gas milleage rpm's to high leaks something? any idea comments or tips would be greatly appriciated.
Thanks.
Thanks.
Senior User
Joined: May 2005
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From: Green Valley, AZ
you have a NINE inch lift and 31's?!? That's crazy. You can just about fit 31's without a lift.
I don't know why your truck is idling high - maybe a vaccum hose is off. 2200 rpm at 50 isn't so bad. But the reason your mileage sucks is that you have a nine inch lift and dinky tires. Your aerodynamics are going to be terrible, and stabilty must be nonexistant. How do you not roll the truck?
I don't know why your truck is idling high - maybe a vaccum hose is off. 2200 rpm at 50 isn't so bad. But the reason your mileage sucks is that you have a nine inch lift and dinky tires. Your aerodynamics are going to be terrible, and stabilty must be nonexistant. How do you not roll the truck?
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yeah it used to have 37inch
swampers
but the tread wear on those are horrible and i just put some 31 inch a/t its a bronco II i mean they stock sit like low riders...i mean the tires are to small but not as bad *** you would think ill post some pics on here could it be the map sensor
Senior User
Joined: May 2005
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From: Green Valley, AZ
I get the impression that you bought the truck lifted. If so, the previous owner probably geared it down... When you switched to the smaller tires, it effectivley changed the overall gear ratio. Your engine will turn more rpms with smaller tires, less rpms with bigger tires.
I bet it feels like it has a LOT of acceleration power right now.
I bet it feels like it has a LOT of acceleration power right now.
Senior User
Joined: Oct 2006
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From: Blue Springs, MO
If the tires that are curently on the truck ar bigger then the truck orriginaly came with and the spedo was never calibrated to the new tires then your going to be traveling a farther didtance then what the odometer shows this will give you a slightly lower MPG reading also having your truck nine inches higher in the air will cause greater wind resistance thus giving you les MPGs. Your truck is 20+ years old and probably like mine has never been rebuilt. Every thing from the engine to the wheel bearings are probably well worn this causes more friction on the moving parts wich relates to less MPG. If you want good MPGs then do a total rebuild of every thing or buy somthing else.
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From: new braunfels ,tx
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Post Fiend
Joined: Jun 2002
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From: Atlanta GA
With 31s, assuming the speedo gear was never changed (it will read slow and low) and the axle gears were never changed, with an automatic you should get about 15 mpg using the current setup and with a standard about 18 mpg. Note: This is from your readings, in reaal life it is probably getting 15+ with the auto and 18+ with the manual.
The best thing to do is pull off the rear axle cover and count teeth Pinion and ring gear teeth, then pull off the transfer case cable and count teeth and note color.
This will give you an idea of what is what, knowing it had 37s (which I find incredible) and not knowing the above is just chasing your tail.
A picture of your front and rear axle covers would help. I don't see how the stock Dana 28 held up to even on road use with 37s.
The best thing to do is pull off the rear axle cover and count teeth Pinion and ring gear teeth, then pull off the transfer case cable and count teeth and note color.
This will give you an idea of what is what, knowing it had 37s (which I find incredible) and not knowing the above is just chasing your tail.
A picture of your front and rear axle covers would help. I don't see how the stock Dana 28 held up to even on road use with 37s.
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pictures are finally here (but from a cell phone)
This is a Work in Progress I'm gonna chop the top re paint it swap axles bigger tires thinking about going to 11 inch lift new tranny, 302 in it etc. but here it is now. 1986 Ford Bii 2.9 ,9 inch lift ...31's....yep well enough b/s here they are.
there's like a foot or more between the tires and the well but yeah here she is nine inch 6 suspension 3 body
there's like a foot or more between the tires and the well but yeah here she is nine inch 6 suspension 3 body
Carpenter Local 745
Joined: Apr 2006
Posts: 5,794
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From: on da beach
Why are you worried about you existing mpg when you are going to replace everything any way.
I would just start getting the parts and go from there. You should get better mileage when you get the work done. It all sounds like it can be done, maybe you can get axles from a 66-77 Bronco or running gear from a newer Jeep.
Looks like your BII has good traction, being that it can climb 90 degree/vertical walls.
Find your driveline parts ASAP before it all disappears.
I would just start getting the parts and go from there. You should get better mileage when you get the work done. It all sounds like it can be done, maybe you can get axles from a 66-77 Bronco or running gear from a newer Jeep.
Looks like your BII has good traction, being that it can climb 90 degree/vertical walls.
Find your driveline parts ASAP before it all disappears.
Post Fiend
Joined: Jun 2002
Posts: 13,873
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From: Atlanta GA
Hi,
I think if you measure against another Bronco II you will find the body lift is more then three inches and it is not lifted as much in the back as it is in the front.
I would say the body lift in the middle/front is probably 6+ inches. I just went out and measured mine and from your pictures it looks like a lot more then 3".
I think it has more suspension lift in the front then the back too.
Anyways, a work in progress and I can see why it might get bad mileage.
If it was me, I would drop the body down to 2".
Then I would hunt down the bigger front and rear axles first so you can properly gear the stuff.
I guess the most important question is what size tire you are planning to run in the long term since that would determine what else you are going to do.
Are you planning off road much (since you are cutting the top) or strictly on road use?
BTW: Thank you for the pictures!
I took the liberty of rotating them and sizing them so it would be easier for others to view on-line. Just right click with the mouse and use "save picture as" and upload them to your gallery.
I think if you measure against another Bronco II you will find the body lift is more then three inches and it is not lifted as much in the back as it is in the front.
I would say the body lift in the middle/front is probably 6+ inches. I just went out and measured mine and from your pictures it looks like a lot more then 3".
I think it has more suspension lift in the front then the back too.
Anyways, a work in progress and I can see why it might get bad mileage.
If it was me, I would drop the body down to 2".
Then I would hunt down the bigger front and rear axles first so you can properly gear the stuff.
I guess the most important question is what size tire you are planning to run in the long term since that would determine what else you are going to do.
Are you planning off road much (since you are cutting the top) or strictly on road use?
BTW: Thank you for the pictures!
I took the liberty of rotating them and sizing them so it would be easier for others to view on-line. Just right click with the mouse and use "save picture as" and upload them to your gallery.
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it was supposed to be three but the pics were taken in my buddies house out front the truck is on unlevel ground the front end and rear sit level I'm real obsessive about that so i measured, they are the same. there is a 4 inch bushing between the body and frame i measured the drop bracket for the supports arms on the lift and it is 6 so i guess it has a total of a 10 inch lift i want to put 35's on it and i don't really want to mud in it more or less a trail truck(for show when I'm done) little mud little hill like just off road driving not lets see how fast i can tear it up just for fun and no not a daily driver its being used by my GF now until she gets her new car then it is in straight project mode but yeah that's it i think it looks pretty good but when I'm done it will look a lot better but for now it is alright.
,thanks
,thanks