Shackle lift MPG Drop???

Hey guys, I installed a set of AllPro 3 inch leaf springs a few months ago, decided i wanted to fix my "taco lean" and installed a set of Toy Tech adjustable shackles. i have the drivers side set at the top hole setting and the passenger is one hole lower. my gas mileage was fine with just the leafs. no big change from my 2 inch aal. BUT, when i installed the shackles my mileage dropped from 18-21 to 15ish. i did a carrier bearing drop so i dont think its the u joints and i also did the brake valve proportioning lift so i dont think it has to do with the brakes. all i can figure is the ride height change is affecting the amount of weight over the rear wheels? maybe? i dont know, what do you all think?

 

bump

 

I can't imagine why adding those shackles would cause a change in MPG, unless the change in driveline angle is causing some binding. Try lubing all the u-joints.

BTW, I'm pretty sure that you shouldn't be using the different relative shackle holes on opposite sides. Is this what Toytech suggested?

 

they didnt say anything about it when i called about my setup. all the u joints have been lubed.

 

well I was getting 18 to 19mpg and when i installed my allpro 3" lift and went from 245's to 265's my mileage drop to 15mpg

 

I doubt anything related to your shackles is lowering your gas mileage that significantly. Its got to be something else.

 

Any other changes recently, like tires?
Check the tire pressures.
Dragging brakes?

I would swap back the original shackles to confirm thats the problem.

 

i did front break pads in February, maybe thats it. how would i fix it if they were touching the rotors?

 

How many tanks did you calculate on with each setup (just springs vs spring and shackle)? I agree that the only things that have changed are increased drag over stock, but little to no variation between with shackles and without, and possibly a driveline bind, but I don't think that is likely. Sounds more like a math error to me.
Edit: your brake pad might not be seated all the way in the caliper. Lots of pain meds right now so hard to explain, but jack the front, pull wheel and shine a flashlight in to see if pad is on the rotor. Can have a buddy press brake pedal and check clearances. Pad may not be seated correctly, which would cause +drag on your unsprung mass.

 

not a math error, i have the scantron II hooked up.

 

feels like there is more resistance now when rolling. it a 5 spd and it seems like i cant coast as far now.

 

so check out your front brakes.

 

After driving a while, if any brakes are 'dragging', that wheel hub would feel hotter than normal. That would be the first check.
Parking brake could be partially engaged.

Also, if your A/C clutch is on, that would be additional load on the motor, but that would only make about a 2 mpg difference.

 

okay. how much of a gap should i see between the pads and rotors?

 

The hub temp would probably require an IR thermometer to be of any use, and then again if both are dragging what is the baseline temp... Too many mpg's for the AC clutch.

 

Enough so that they dont contact the rotor. Right now just checking to verify that they are not making contact. I'd have a buddy mash the brake pedal a few times and verify they release cleanly as well.

 

my ac clutch shoul be just fine i replaced it way back in october and didnt see any change in anything from then until the shackles and brake change happened.

 

copy that. ill check it after work and report back.

 

Good luck, hope you are able to identify the problem. Let us know how it goes!

 

last time i changed plugs/wires was late 2013 do you guys think this might be something a tune up could fix.