Re-gearing axles

[Matt]

Yeah I knew I had 3.73s... wasn't sure if you guys had a different package that came with 3.42s or something.

Ill have to look up our trans gears to be sure... but from my experience, going from 3.73 to 4.10 is very rarely worth the cost. Especially in these vehicles. ... 3.73s should work well offroading with up to a 32" tire when backed by the 4.7 or 5.7 (depending on the trans gears). If you're going to a good sized 33 then 4.10s would indeed be better.. but at that point you might as well go with 4.56.

From a mathematical standpoint, 4.10s with 33s gets you back to stock gearing, but not stock power. The increased weight and rolling resistance and moment of inertia still eat away at performance. Going with 4.56 in this case will utilize some mechanical advantage AND bump up the power output for a given speed (you know what HP and torque curves look like) which will help compensate for those power robbers.

4.30 would actually be ideal for 33s.... but its not a common gear.

....again, I haven't looked at the trans gears yet but I doubt its going to be far from what I'm expecting.

[Sal-XK]

Ya 4:56 would be nice when I get my 35's installed.

[07JeepXK]

I dont think I totally agree with your statement. I do agree that going from 3.73's to 4.10's isnt that big of a jump. However if they ever do come out with gears for our Jeeps and 4.10's are all thats available then it would definately be worth it to me since I would only have to pay for parts and can get them installed for free. Now dont get me wrong 4.56's would be a better option since I do plan on going with bigger tires but ill take what I can get.

My XK does fine with 3.73's and 32's while off roading but I ALWAYS stay in 4 Low. If I had 4.10's though, my XK would be better off on the Mountainous roads on my 5 1/2 hour drive to play Army once a month and result in slightly better gas mileage too.

BTW: did the math....it looks like 4.10's with 32's would be equivalant to stock gearing....not 33's.

[Matt]

Yeah I said its usually not worth the cost.... if you get them installed for free and that's all that's available, then that's a different story altogether. Devil is in the details.... I do my own installs so it'd be free for me too, but I wouldn't go through the trouble unless I was putting 4.30 or 4.56 in.

Are stock tires 245/65 or 245/60? If they're 245/65 then equivalent tire size is 32.4" which is what most 33s measure... so we could split the difference and say 32 to 33.

[Matt]

Just read that over and wanted to clarify a bit... since i think we're both actually on the same page.

My main point was if you're running 32s or smaller on these vehicles and have to pay full price to re-gear ($1500 in my area), the jump from 3.73s to 4.10s really isn't worth the cost. I've done a lot of work in this area and just wanted to point out that the difference between those gears will barely be felt in the butt dyno... so if someone read this thread and then dropped $1500 on a 4.10 gear set, i'd feel bad when they're gravely disappointed in the mediocre results.

But like you said... if 4.10s are all that's available and you can get them installed for a good price, then every little bit helps. From my personal experience, i wouldn't put more than $500 into that change for 32" tire on these vehicles.

.... if 4.30s or 4.56s were available, we wouldn't even be having this discussion

[Sal-XK]

I have a question since I think you two can answer with experience and knowledge not just a guess. Since it seems the 8.25 27 spline has more options to it instead of our 29 spline. How hard or even possible would it be to put the change the spline out and drop down to the 27?

[07JeepXK]

Just read that over and wanted to clarify a bit... since i think we're both actually on the same page.

My main point was if you're running 32s or smaller on these vehicles and have to pay full price to re-gear ($1500 in my area), the jump from 3.73s to 4.10s really isn't worth the cost. I've done a lot of work in this area and just wanted to point out that the difference between those gears will barely be felt in the butt dyno... so if someone read this thread and then dropped $1500 on a 4.10 gear set, i'd feel bad when they're gravely disappointed in the mediocre results.

But like you said... if 4.10s are all that's available and you can get them installed for a good price, then every little bit helps. From my personal experience, i wouldn't put more than $500 into that change for 32" tire on these vehicles.

.... if 4.30s or 4.56s were available, we wouldn't even be having this discussion

I hear you. The only way I would consider putting 4.10's in is if there is no chance they would ever make any other gears. Cause If I had the choice, id definately go with 4.56's due to future plans.

I have a question since I think you two can answer with experience and knowledge not just a guess. Since it seems the 8.25 27 spline has more options to it instead of our 29 spline. How hard or even possible would it be to put the change the spline out and drop down to the 27?

Im not sure why you would want to do that? What are you trying to buy for your rear axle that you cant find in a 29 spline? A 29 spline 8.25 is going to be a hair stonger then a 27 spline for obvious reasons. They make differential covers and an ARB for the rear. What more do you need?

[Matt]

I have a question since I think you two can answer with experience and knowledge not just a guess. Since it seems the 8.25 27 spline has more options to it instead of our 29 spline. How hard or even possible would it be to put the change the spline out and drop down to the 27?

Honestly im not sure... i haven't done much work with these particular axles.

I can't believe how little aftermarket there is for these things

I recently came in contact with an employee at a [somewhat] local dealer that specializes in aftermarket equipment for jeeps, including gear changes.... i'll have to get a hold of her to see if she knows anything about more gear options for these axles.

[Sal-XK]

Just thinking outside the box since all those gears listed on the site in the OP were for the 27 spline. Just brain storming

[bigmaninds]

I called this place called Randys Ring & Pinion and they say they have gears for the Commander front and rear. They send me an email with gears (4.56) and the master install kit. They say it will run 900 for all of the parts. Any thoughts? I plan to order them next week. They guarantee this will fit.
This quote was prepared for you by:
Allen Booher
+1(425)347-1199
ext. 5570
Please call me directly at the above extension to finalize this order.

Quoted Parts List:
Qty Part # Description Price Ext
------------------------------------------------------------------------
1 YG C8.25-456 8.25 CHY 4.56 R&P (_ $349.38 $349.38
1 ZG C8.0-456 8.0IFS CHY 4.56 R&P $190.88 $190.88
1 YK C8.25-B '76 & UP CHY 8.25" M $116.32 $116.32
1 YK C8.0-IFS-C '03 & UP 8.0IFS CHY $285.73 $285.73
------------------------------------------------------------------------
Subtotal: $942.31
Shipping TBD

Thoughts?