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Gear Ratios

E

Ewenm

NAXJA Forum User
Location
Gold Coast Australia
Can anyone help me with a gear ratio enquiry.....

i want to lower the diff ratios in my basiclly stock '94 xj i believe it has Dana 30 diffs front and back and 3.55 gears i wanted to go to 4.11 gears but my mechanic tells me that the existing carrier cannot be used and will need to be replaced he also recomends that if doing this i may as well do lockers front and back

what i want is to get a better gear set to suit my towing needs is it possible that he is wrong or that if right could i look at 3.8? gears and retain my carriers and rear trak lock i dont want to be cheap but at the same time don't want to just through money around needlessly

Any comments

Regards Ewen
 
do you know what rear end you have? ive never heard of a dana 30 rear on an xj, maybe 35 but i have a 94, manual with an 8.25 rear. the 8.25 will hold up to 4.56 with no carrier change, not sure when the danas top out, your mechanic may be right about that one. as far as lockers, i think here he is trying to get some money from you. if all your looking to do is tow, the new gears should be fine, if you want to tow in heavy conditions, or through rough trails, then get the lockers, but if this is a street rig, ditch the lockers, go positrac at most up front.
wheels are meant to spin at different speeds when turning because of the differences in the radius they are traveling on. lockers do basically what they say, lock. many times road manners are hurt by this, not to mention your wallet too.

go with 4.1 if you want, 4.56 will probably cost about the same too and you can fit em. dont get the lockers if you dont want to spend money, youll be spending damn near 1000-1500 for all of it, not including instilation.
 
ouch didnt see australia. yea imports are a b**ch huh? dont go lockers man unless you need em for traction in heavy conditions. the d30 carrier needs to be changed around 4.1s so anything above that would contend pricewise. im goin 4.56 with that my 8.25 needs no new carrier. for you, im not sure how their built in austrailia, so i dont no what rear you have... sorry, if you want a lot more towing power, be prepared to spennnnnddd ...

Just Empty Every Pocket
 
Ewenm. first step is determining which rear axle you have. If it is the Chrysler 8.25" it will have a well-devined flat bottom on the housing casting... if it is the Dana/Spicer 35 it will have a flat oval overall shape.

The 8.25" can accept up to, and no lower than a 4.56:1 ratio and you can retain the carrier for it.

The D35 rear (if 3.55) can accept up to 4.88:1 on the carrier that holds your 3.55:1 ** the D35 is not our most loved axle around here, but across the pond you might have to dance with who ya brought to the party?

The 94 D30 front axle should be a reverse rotation (high pinion) and will accept up to 4.88:1, but will need another gear carrier to accept any gear lower than 3.55:1.
 
Ewenm, I may have a carrier for 4.11s for the D30 for sale soon (brand new) if ya interested. (Do you use the ausjeepoffroad.com ozzy jeep forum too?) They are about $A160. Im in Melbourne.
 
I tow with my XJ also and went with the 4.10/4.11 route.

Works great and even on my 30" tires I'm actually getting better mileage. Did both rear ends myself, upgraded the rear(8.25) to 29 spline and Detroit Tru-Trac. The D-30 front will require a new carrier.
I got everything from Randy's Ring and Pinion, $1200 U.S.

This ratio in a XJ makes it feel like you have a monster under the hood! It really wakes up a sleeping giant!
 
when you say you did it your self did you have to change the carriers, and what did you do about setting up the diffs ---pinnion to ring gear lash etc.

or did you just pull them out and send them to a diff shop

what i am trying to find out is weather i can lower (numerically) the diff ratios from 3.55 to what ever (3.8,4.1.) without changing carriers

Regards Ewen
 
Ewenm said:
when you say you did it your self did you have to change the carriers, and what did you do about setting up the diffs ---pinnion to ring gear lash etc.

or did you just pull them out and send them to a diff shop

what i am trying to find out is weather i can lower (numerically) the diff ratios from 3.55 to what ever (3.8,4.1.) without changing carriers

Regards Ewen
Click to expand...

4.11 is numerically higher than 3.55, just to clear things up (here in the states anyhow)
 
yea but in gearing 4.1's are a lower ratio than 3.55

im sure the guy knows that 4.11 is bigger than 3.55 its how (not only us in the states)
describe the ratios between ring and pinions. 4.88s are a lower gear ration than 4.1 and vice versa

he just wanted to, im guessing, clear any confusion about thinking he wanted to lower his gearset in his diff case which would seem looney...
 
Ewenm said:
No i was not aware of that web site i'll check it out what do you want for your carrier ( it's for the front diff i guess as the rear is a 35--is that right?0
Click to expand...

$160 (its what I paid) + freight

yeah its for the D30 (front diff)

how long till you need it? Im still not 100% sure yet, depending on whether I get the cash to put a tru-trac in, which doesnt require a carrier.
 
correct, however at the risk of debating over words, when one goes from a 3.55 to a 4.11 diff ratio it is generally refered to as being a lower diff ratio although the number is as you stated numerically higher. the effect is that the wheels require a higher engine revs to maintain the same road speed all other things being equal I.E:gearbox ratios being the same
 
think of it as kind of a lower, well, speed. the ratio describes the difference in rotation of the pinion to 1 rotation of the large ring. in 3.55 say, the pinion must spin 3.55 times to make the ring spin once, in 4.10s however the pinion must spin 4.1 times to make the ring spin once, effectively giving you a slower rotation, lower gear ratio, and a much higher rev at high speeds...
 
going back to my original post i have a '94 xj limited and i tow a 4000+lb boat about 5-6 times a year i have an add a leaf in the rear and i was running 31x10.5 pirelli scorpion tyres. the jeep struggles with this and i droped my tyre size back to 28" (standard size) now it just looks ordinary. so what i want to do is raise it a little all round change the diffs to 4.11 and then go back to 31" tyres. lowering the diff and increasing the tyres will still leave me slightly lower geared than stock, so this would make everything hunky dory

except that my mechanic is telling me i have to change carriers to go from 3.55 to 4.11 and the bill is $5500 (inc lockers back and front) so my thought was could i comprimise and go to a 3.8 or something around that and retain my carriers and then only be up for gears and labour.

Ewen
 
i say why lockers?? they are a huge part of that bill, especially since the mechanic wants you to have top of the line parts so theres more cash flow.
if you ask me, id say the lockers would only hurt your road manners, unless that boat is being towed on a mountain, you shouldnt need them, the gearing should clear any power mess up if your worried about losing traction while towing, maybe let off the skinny pedal a little bit!! lol im just messing, but seriously id ditch the lockers unless you really want them.
 
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