4.56 on 31's

[Levathain]

Now I'm just waiting for my engine to go out so I can do a 4.2 L stroker to make up for the power . Also I got USA standard gears from complete offroad, they had front and rear with master install kit, was like 520 bucks n I got front carrier since you have to for 90 bucks. So was 619
Shipped if anyone is interested. N the USA standard gears aren't loud like some people say.

 

[cal]

why wait for it to go out?

start doing the stroker now, and sell your running 4.0 off to make up some of the cost.

 

[Levathain]

Well after spending so much money recently I need a breather to save up

 

[markw]

Well that sucks. Thanks for following up. It makes you wonder why 'half' the people are 'ok' with it though.

At least I'm only getting the rear done today. If the 4.10's don't cut it, I supposed I'll sell off an organ and regear the rear again before I do the front to match.

Because most people are flatlanders or don't tow, or don't load their junk down with lots of armor, spare tire, tools, camping gear. It's not like us west coast guys have no clue, we've been there, driven up the mountain pass at 50mph in 3rd, or had our transmission hunting for gears because we had the wrong set in the axles.

 

[XJEEPER]

Well that sucks. Thanks for following up. It makes you wonder why 'half' the people are 'ok' with it though.

Adding to what Mark said......many are unwilling to admit that they took the wrong advice and now have buyers remorse. Many of us aren't afraid to share our personal experiences, including our mistakes, in hopes that others can learn from them. I can't believe this thread is still going........but I hope it helps some folks from flushing their hard-earned money down the toilet.

 

[Tony_SS]

Yeah, if I lived out west and wheeled like you all did, will a loaded down rig, no doubt I would've went 4.56.

From what the OP described, it sounded like 4.10's would have been ok with his 31's. Apparently not!

Now I'm eager to see how they work for my application.. not getting my hopes up

 

[cal]

its not too late to go 4.56 tony..

 

[markw]

I'm part of the 4.10's and 31 crowd. Why regear twice?

 

[grainofsalt]

Let's go deeper on the subject, I have a '98 with 4.6l and AX-15, Would 4.88s be too deep for 31s (current) or 33s(wishlist)?

 

[markw]

stick with 4.56's, you loose 1 tooth of contact with 4.88's on the front D30. 2 teeth vs 3.

 

[cal]

stick with 4.56's, you loose 1 tooth of contact with 4.88's on the front D30. 2 teeth vs 3.

ignore what he said.

while technically true, if you look at the gear sets people have broken, as many 4.56 gears break as 4.88 gears... there doesn't seem to be a practical difference in strength.



AX15. 4.56. 31's.
55 = 2147 rpm
65 = 2538 rpm
75 = 2928 rpm

ax15. 4.88. 31's.
55 = 2298 rpm
65 = 2716 rpm
75 = 3134 rpm


it would work ok. you'd spin a little fast on the highway, but your motor shouldnt care about 3000 rpm's. no one elses does..

ax15. 4.56's. 33's.
55 = 2017 rpm
65 = 2384 rpm
75 = 2751 rpm

ax15. 4.88's. 33's.
55 = 2159
65 = 2551
75 = 2944




go drive around. use 3rd and 4th, check out those RPM ranges and make the decision for yourself.

 

[cal]

For the people who are following this and want to do the math for their own setup:

http://www.grimmjeeper.com/gears.html


You can put in 2 combo's and compare them side by side, and then change the variables one at a time and recalculate until you find what you're looking for. The 4.0 series of motor seems to like running ~2700 RPM's on the highway but is still very happy up to the low 3000's sustained and finds the mid 3000's fairly comfortable indefinitely.

 

[sidriptide]

Now I'm just waiting for my engine to go out so I can do a 4.2 L stroker to make up for the power . .

it's a good upgrade, but not actually the answer to your problem.

it reminds me of an arguement i had with a freind when we were young hotrodders. he put a Holley 750 double-pumper on his cammed 350, and spent $$ a new name-brand HEI ignition installation because "the hotter ignition will burn the addition gas" he was dumping into the engine.

a month later i bought that Camaro from him for $250 because it was a P O S...

just as any other modification, for any vehicle for that matter.
the over-all system that is your XJ, is essentially "matched" to eachother.
if you change one thing, it generally effects something else. the larger the change you make, the more pronounced the effect.

dont focus on the mathematics of the gear change, because "ideal" and "i can live with it" are all open for interpretation.
make sure the new 4.10s really are a bad choice before throwing any $$ at a new engine or even new gears.
can YOU "live with it"?? learn from the experience and think your next step thru completely, looking at the big picture while you do it....
i'd likely consider your 4.10 set-up something i can live with. i've had both AW4 and AX-15 XJs on 33s and 4.56s but never 31s, but i figured it would be a reasonable set-up if it were the final stage of the axle build.

above all, remember it's the interweb..... someone always knows better than you from their own keyboard, and someone else will always tell you what is "optimal" using some mathematical chart...
filter it all and move ahead.....

 

[Tony_SS]

Sorry to beat the horse here, but I just wanted add my experience for those who might search this later.

I had 4.10's put in the rear this week and I am running 31's. To me it feels like it did when my Jeep was stock. It behaves really well and has nice road/highway manners. I expect to pick some mpg's too. I'm satisfied with my choice on the 4.10's.

Now with that said, my Jeep is NOT weighted down with gear/heavy bumpers etc. If yours is and you primariy do heavy trail riding, towing, etc, then you'll want to go with 4.56's even on the 31's. my .02.

 

[markw]

It makes it quite a bit better than stock gears with 31's doesn't it.

 

[Johnnie Walker]

I have 4.10's with 31's. It's nice, Got great deals on my geared axles, definitely better than stock gears.
I would have considered 4.56's given the opportunity to regear vs plug n pray geared axles.

 

[markaboo929]

Today I installed a JY 4:10 and I am on a 235/75-15" like a 29"...Man do I absolutely love it!!...so does the 4.6 stroker

 

[Miller88]

Today I installed a JY 4:10 and I am on a 235/75-15" like a 29"...Man do I absolutely love it!!...so does the 4.6 stroker

Tire roaster!

Any figures on MPG from the stroker, 4.10 gears and stock size tires?

 

[markaboo929]

Not yet..I will post when I check after a few tank fulls.But it was getting around 18-20 with 3:55's

 

[ftwelder]

I got an 8.8 for my AX15 XJ with a 3.73 and was considering re-gearing the front to match. I have now changed my mind and am going 4.56 stock R&P in the front and something with a full carrier and the lower gear for the rear. Thanks for pushing me over the top! :cheers: