Please Help , Explorer Lift And Gears

[Arnie897]

The don't make em....but I have one too. Check the list of useful threads on how to put a body lift on a 97 explorer.

 

[ccanuk]

to maintain current RPMs or as close to as possible at 70mph...(assuming you have 3.73 diffs) go to 4.1 for 31" tires, 4.56 for 33" tires and about 100 rpm increase, or 35" tires for a 50 rpm decrease

 

[sk1er17]

i dont want to argue here.. but im curious how you came up with those #'s? From my experience and going by what everyone has on this site, 4.56 would be way overkill for 33's. I even remember someone putting them in his truck and couldnt do over 55 on the highway... any charts to back this up?

 

[sk1er17]

actually not for nothin.. where is Moscow PA in reference to Trenton, NJ? If its close enough- ill take ya for a spin in my truck with the 35's and 4.10's so you get a "feel" for it. Its always hard to spend $1000 based on peoples opinions- or even charts for that matter.

 

[ccanuk]

km/h / wheel circumference in meters / Diff Ratio / OD Ratio = rpm
110 2.23 3.73 0.816 2507.282583
110 2.47 3.73 0.816 2263.659984
110 2.64 3.73 0.816 2117.894
110 2.79 3.73 0.816 2004.028731
110 2.23 4.1 0.816 2755.99426
110 2.47 4.1 0.816 2488.205344
110 2.64 4.1 0.816 2327.98
110 2.79 4.1 0.816 2202.819785
110 2.23 4.56 0.816 3065.203372
110 2.47 4.56 0.816 2767.369846
110 2.64 4.56 0.816 2589.168
110 2.79 4.56 0.816 2449.965419

Using the formula (km/h * 16.7)/((circumferance/diff ratio)/od ratio)

110 km/h = 69mph


I could be way off if the guy you were talking about couldn't get above 55... what size tire did he use

also I didn't look up the od ratio, I extrapolated it from the guy who said that he was at 3000 rpm ... if you can give me the right ratio, I can re do the math

 

[ccanuk]

I'm going to pop in here on this one... I'm running 4.56's with 33's on my X. At 80 I'm running at three grand on the expressway. It's not bad I guess. The major reason that I went with those gears was for the extra towing capacity for when I pull my Jeep around. The OHV that I have lacks the power that you SOHC owners have. 4.10's should be fine like Sk1er said!

so a 33" tire has a 2.64 meter rolling distance
and 80mph = 128km/h = 2133 meters/minute
2.64m/4.56 = .58 meters per drive shaft rotation
.58 * 3000 rpm = 1740 Meters per Minute
1740/2133 = .816 od ratio (ie .816 of a rotation on the crank = 1 rotation on the drive shaft)

is this right?

 

[sk1er17]

2.64m/4.56 = .58 meters per drive shaft rotation
.58 * 3000 rpm = 1740 Meters per Minute
1740/2133 = .816 od ratio (ie .816 of a rotation on the crank = 1 rotation on the drive shaft)

is this right?

Im pretty sure it doesnt work out like that. Like 4.56 is a ratio, but dividing the circumference of the tire by it doesnt give meters per drive shaft rotation.

And Arnie: are you saying that your speedo says you're doing 80mph at 3000rpms or do you have a GPS giving the speed.. cause the size of the tires screws up the odometer..


Ill stick to the last thing i said... he's gotta go for a ride in my truck before going with a gear higher than 4.10 if its gonna be a DD... id say do 4.56 for a trail rig

 

[ccanuk]

Im pretty sure it doesnt work out like that. Like 4.56 is a ratio, but dividing the circumference of the tire by it doesnt give meters per drive shaft rotation.

um, by definition it's impossible for that not to work...

the 4.56 means the drive shaft spins 4.56 times to spin the tires once
the distance the tires roll in one revolution is the circumferance

so 4.56 driveshaft revs turns the wheel once, and assuming no sliping, you travel the distance equal to the circumference of the wheel

so therefore if you divide the circumference by the revs to rotate the wheels once, you get the distance the wheels travel for one driveshaft rotation.

now if you multiply that by engine revs you get how far you would travel if the drive shaft were connected to the crank shaft.

now when you divide the calculated distance by the distance you actually travel you get the od ratio.

I wasn't far off I was off by .026 or 2.6%... here are the new calculations

km/h - wheel circumference in meters - Diff Ratio - OD Ratio - rpm
110 -- 2.23 -------------------------- 3.73 ------ 0.79 ----- 2427
110 -- 2.47 -------------------------- 3.73 ------ 0.79 ----- 2191
110 -- 2.64 -------------------------- 3.73 ------ 0.79 ----- 2050
110 -- 2.79 -------------------------- 3.73 ------ 0.79 ----- 1940
110 -- 2.23 -------------------------- 4.1 ------- 0.79 ----- 2668
110 -- 2.47 -------------------------- 4.1 ------- 0.79 ----- 2408
110 -- 2.64 -------------------------- 4.1 ------- 0.79 ----- 2253
110 -- 2.79 -------------------------- 4.1 ------- 0.79 ----- 2132
110 -- 2.23 -------------------------- 4.56 ------ 0.79 ----- 2967
110 -- 2.47 -------------------------- 4.56 ------ 0.79 ----- 2679
110 -- 2.64 -------------------------- 4.56 ------ 0.79 ----- 2506
110 -- 2.79 -------------------------- 4.56 ------ 0.79 ----- 2371
110 km/h = 69 mph

2.23m = 28" tire * 3.14
2.47m = 31" tire * 3.14
2.64m = 33" tire * 3.14
2.79m = 35" tire * 3.14

since the 110 km is comming from actual distance traveled, if you pick a tire size and ratio that results in rpms that are close to the results of stock ratios and tire sizes, you might not even have to re calibrate your speedo

Can people who have different gears and tires compare their RPMs and speed to this chart?

If the torque converter doesn't lock up, then there could be some variation depending on load

 

[ccanuk]

KM/H - Wheel Circumference in Meters - Diff Ratio - OD Ratio - RPM
110 -- 2.23 --------------------------- 3.55 ----- 0.79 ----- 2310
110 -- 2.31 --------------------------- 3.55 ----- 0.79 ----- 2230
110 -- 2.39 --------------------------- 3.55 ----- 0.79 ----- 2156
110 -- 2.47 --------------------------- 3.55 ----- 0.79 ----- 2086
110 -- 2.55 --------------------------- 3.55 ----- 0.79 ----- 2020
110 -- 2.64 --------------------------- 3.55 ----- 0.79 ----- 1951
110 -- 2.71 --------------------------- 3.55 ----- 0.79 ----- 1901
110 -- 2.79 --------------------------- 3.55 ----- 0.79 ----- 1847

110 -- 2.23 --------------------------- 3.73 ----- 0.79 ----- 2427
110 -- 2.31 --------------------------- 3.73 ----- 0.79 ----- 2343
110 -- 2.39 --------------------------- 3.73 ----- 0.79 ----- 2265
110 -- 2.47 --------------------------- 3.73 ----- 0.79 ----- 2192
110 -- 2.55 --------------------------- 3.73 ----- 0.79 ----- 2123
110 -- 2.64 --------------------------- 3.73 ----- 0.79 ----- 2050
110 -- 2.71 --------------------------- 3.73 ----- 0.79 ----- 1997
110 -- 2.79 --------------------------- 3.73 ----- 0.79 ----- 1940

110 -- 2.23 --------------------------- 4.10 ----- 0.79 ----- 2668
110 -- 2.31 --------------------------- 4.10 ----- 0.79 ----- 2576
110 -- 2.39 --------------------------- 4.10 ----- 0.79 ----- 2490
110 -- 2.47 --------------------------- 4.10 ----- 0.79 ----- 2409
110 -- 2.55 --------------------------- 4.10 ----- 0.79 ----- 2333
110 -- 2.64 --------------------------- 4.10 ----- 0.79 ----- 2254
110 -- 2.71 --------------------------- 4.10 ----- 0.79 ----- 2196
110 -- 2.79 --------------------------- 4.10 ----- 0.79 ----- 2133

110 -- 2.23 --------------------------- 4.56 ----- 0.79 ----- 2968
110 -- 2.31 --------------------------- 4.56 ----- 0.79 ----- 2865
110 -- 2.39 --------------------------- 4.56 ----- 0.79 ----- 2769
110 -- 2.47 --------------------------- 4.56 ----- 0.79 ----- 2679
110 -- 2.55 --------------------------- 4.56 ----- 0.79 ----- 2595
110 -- 2.64 --------------------------- 4.56 ----- 0.79 ----- 2507
110 -- 2.71 --------------------------- 4.56 ----- 0.79 ----- 2442
110 -- 2.79 --------------------------- 4.56 ----- 0.79 ----- 2372

110 km/h = 69mph

2.23m = 28" tire * 3.14
2.31m = 29" tire * 3.14
2.39m = 30" tire * 3.14
2.47m = 31" tire * 3.14
2.55m = 32" tire * 3.14
2.64m = 33" tire * 3.14
2.71m = 34" tire * 3.14
2.79m = 35" tire * 3.14

 

[Arnie897]

And Arnie: are you saying that your speedo says you're doing 80mph at 3000rpms or do you have a GPS giving the speed.. cause the size of the tires screws up the odometer..

After I did the lift and the gears I changed out the speedometer gear on the T-case to fix the speedo. I also have the GPS in there that is usually right on par with what the speedometer is reading. Every once and awhile it will show that my speedometer is reading fast though...only by 1 mph or so.

As for those charts....who knows? Looks confusing to me. All I say say is that with my 33's, 4.56's and the OHV engine I'm reading around 3k at around 80mph.

 

[ccanuk]

Hi Arnie... If I get time I'll build a calculator for this that will include imperial measurements... I learned metric so they are easier for me...

when I calculate what you should get for 80 MPH with 33" tires and 4.56 ratio diff, in OD you should get 2917 RPM which is really close, and probably wouldn't be a registerable difference on the gauge.

Hows your MPG with that setup?

 

[Robb]

Stock:
-235/75/15 (29"); (assuming this)
-3.55 r&p (as stated)
-.75 tranny gear (OD on the 5R55E)
-60 mph
=1850rpm

Stock with 35s:
-35" tires
-3.55 r&p
-.75 tranny gear
-60 mph
=1535 rpm

35s with 4.10s:
-35" tires
-4.10 r&p
-.75 tranny gear
-60 mph
=1771 rpm

35s with 4.56s:
-35" tires
-4.56 r&p
-.75 tranny gear
-60 mph
=1970

These are just rpm calcs............too tired to get into "power band" math right now.

 

[Arnie897]

Hows your MPG with that setup?

Pretty bad. I usually get around 14 mpg on the expressway :frustrate

 

[ccanuk]

using my excel spreadsheet...

60mph 29"tire 3.55 0.75OD 1848 RPM
60mph 35"tire 3.55 0.75OD 1530 RPM

60mph 35" tire 4.10 0.75OD 1767 RPM
60mph 35" tire 4.56 0.75OD 1965 RPM

I got pretty much the same numbers... when I use .75 instead of .79 and even then I was only off by 90 RPM

But if you go to 35" tires and 4.56 gears you should be able to stay in your power band, and might not even have to change your speedometer

14 on the Highway eh? doing... 55mph on twisty backroads up and down hills I get 19, which I was estatic about, in the city I get 12-13

 

[Rhett]

Continuing with what Robb was talking about..the "power band" is important when you lift and add bigger tires...you have to be sure that your new setup will keep the engine in a good power band. Otherwise your rig will be slow off the line and get bad gas mileage. Your gear ratio and tire size should result in an RPM that will, on average, give you the most power on the pavement (or not pavement).

 

[off-road97Xplor]

ok thanx for all the help guys. but heres the question. 4.10 or 4.56. ??? Skiers been the man with helping me and i trust him with 4.10s and maybe he'll come over to PA and give me a spin in the future,

 

[off-road97Xplor]

but from what Arnie says 4.56 gears dont seem so bad, excpet for MPG....

 

[sk1er17]

To be honest my gasl mileage ranges from 12-14.. maybe 14.5 when i go skiing..

however, that was with my last engine... that exploded a few weeks ago. And i only have 50 miles on my new engine right now- lol so totally ignore those numbers and we'll be in touch.

And you know, 4.56 may not be a bad choice. My deal is that since i have the 4.10's its not worth the money to go to 4.56, especially considering its not slow and seems to be good RPM's for my commute. "However", since you have to spend the money anyways, 4.56 might be something to consider- know what i mean?

And yea, before you spend the $$ id be happy to take you for a spin.

And one last thing, you going with 35's or 33's? arnie has 33's and i have 35's.. but i also have some 33's that i need to get rid of

 

[off-road97Xplor]

sry bro, but 35's ALL THE WAY!
wow poor engine
Anyway i might go with the 4.65s since im gonna need to go through deep snow here in PA, and i dont wanna ruin the tranny

 

[sk1er17]

Yea, i just checked it out- you're not that far away from Camelback... we used to have a condo there until this past summer.

If you were going with 33's, id say 4.10's. But seeing where you live, and going with 35's- 4.56's are probably the way to go dude... its flat around here... some of those hills might be a problem especially in deep snow.

yea, and the engine had 145K miles and 2 bad hydrolockings in its history... suprised it went as long as it did. And thats why i put the same one back in there