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4:88s, AW-4, 33s on a DD?

My Xj's got the same basic shape it had when stock and then I got 21-25 at 75-80. Sure I;ve put a lift on and bigger tires but that's it. No rack, ect. The areo profile of mine hasn't changed at all, only the gearing and rpm's I run at. who knows... :dunno:
 
i don't know your exact setup, but let's just say you're running 5" and 33x12.50s. That's 5 additional inches of axles and suspension that are being hit by air head-on, and a whole lot more tire being hit head on, plus a lot more turbulence underneath. Also the rolling resistance of your tires is MUCH greater than stock.

I have an MJ, so no roof rack or anything else to do with the body that would negatively affect mileage. I had it at 5" with some 33s, went up to 8" with the same 33s (35s for trail) and with that 3" lift being the ONLY change, I saw a noticeable decrease in mileage, about 2 mpg.
 
Makes ya kinda glad that someone like me doesn't have a full size truck with big power... at least you didn't spill the soda's.:cry:
ChuckD said:
Ryan's jeep is insane or is it his driving. Just be careful when he offers you to go to Wendy's for lunch. :eek:


:D
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Thanks Brett for the input. Ill tell you guys this; when i cross the taller bridges in NY like the Throgs Neck in my stock Jeep it holds tight to the lanes in high winds. When i try to go fast in my 88 with 10" and 35's it's all over the lanes if i go 50+ on a realy windy day. When it was 2.5 and 31's there was no problem. When it was 5.5 and 33's there was not much difference. When it was 7.5 and 33's there was a difference. Now it outright frightens my passengers when i hit the peak of that bridge at 55 and all of a sudden the mystyrious high winds kick in and start shifting me around the lanes. To the point i have to drop to like 30 mph. What Im getting at is that there is DEFINATELY a diffence in aerodynamics with every inch of lift and at 10" there is so much more wind kicking under the truck that i have to open the windows to let it cross through the cab. There is DEFINATELY a major difference with every inch.
 
Since this thread is already on topic or 33's 4.88's and aw-4 i have a quick question. Would i need to worry about gear breakage in the Dana 30 with 4.88's??? I hear they get a little weak in D30's. I will have a 44 in the rear but dont want to have to worry to much about the ring gear in the front. Who makes gears i could trust in 4.88's?
 
90whitexj said:
Since this thread is already on topic or 33's 4.88's and aw-4 i have a quick question. Would i need to worry about gear breakage in the Dana 30 with 4.88's??? I hear they get a little weak in D30's. I will have a 44 in the rear but dont want to have to worry to much about the ring gear in the front. Who makes gears i could trust in 4.88's?
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Yukon or Dana, PM Rawbrown.

As far as weak, I feel it depends on the driver and the install.
 
Ok then would the 4.56s be better in a front d30? damn im so lost!! Im doin the same thing and im just tryin to get the best of both worlds while runnin 5 inches and 33s. I have a feeling ill end up gettin a set of 35s to try, but probably wont be running them on the street. Do yall think we could see some figures. Mpg VS 4.56s and mpg vs 4.88 on 33s? Hang with me im a lil slow on this.lol
 
Jeepin_rebel said:
Ok then would the 4.56s be better in a front d30? damn im so lost!! Im doin the same thing and im just tryin to get the best of both worlds while runnin 5 inches and 33s. I have a feeling ill end up gettin a set of 35s to try, but probably wont be running them on the street. Do yall think we could see some figures. Mpg VS 4.56s and mpg vs 4.88 on 33s? Hang with me im a lil slow on this.lol
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Once you get into the 33" tire range throw mileage out the door. It can be improved wil the propper gearing, but the rolling resistance and wind resitance are totally against you. Bottom line, lower the better for tires over 33".

If you plan on going with 35's, then 4.88's or lower is where you need to go. If you are worried about R&P strength then plan on building a different axle.

Fools like me are just trying to squeeze every bit out of our OEM Junk. The D30 housing is really where the problem lies, not the R&P. Trussing can help, but you would be probably be better off with a different axle.
 
i also imagine the 4 kc lights on the roof and the 2 on the nose arent gona help much ether. I would like to change out the axles but im just a e 4 in the army and dont make the big bucks. I do how ever have my eyes on a early 70s 3/4 ton dodge with some massive axles under it. That will be a ways down the road though.
 
I think which gearing depends on driving style. If you need to drive 80 on the freeway get 4.56s. If you need to use OD climbling grades get 4.88s. If you need the best gas mileage slow down. I love teh 4.88s of the line, but I've had to slow to 70 on the freeway. However, it seems I've started getting some vibes at 75+ (probably not related to gear change) which have required me to slow a little. For me, my real world calcs indicate that I'm ging about 80 at 3000 rpm, 70 at 2700 or so. I've got about 30K on my MT/R so they measure in at a little less than 32" I think. Gotta remember the ACTUAL tire diameter when calculating RPMs. Milage at 80 has been about 12-13, at 70 14-16. 4.88s were too low for me at first because my 120 mile commute traffic averages 80 mph. I didn;t like the high rpms, and people didn't like me going 70. Now that I'm used to going 70 I like the gears. Awesome offroad.


Here's a chart I modified from 4wheel parts or something a while back for different speeds and .7 overdrive:

http://pages.sbcglobal.net/basalt51/gears/OD-gear chart.htm

Colors are based on teh "optimum" rpms ranges for certain driving types.
 
OK now my next question.....how dificult to change out the gears is it. I am good with a wrench just havent attempted gears yet. Do i need just standard tools or do i need a case spreader?
 
im not exactly sure what tools are needed but i know it isnt the easiest to do. I would reccomend having a shop or friend that know what thier doing install the gears. If you mess it up you will need a new R&P and thats about the price of having it installed
 
i did my gear change well over 2 years ago with a friend and it still runs awesome with no howls or anything like that. I spent like 170 on a dial indicator which i think was too much but without it i dont think there is any proper way to set backlash. We did not use a case spreader and instead used a dead blow mallet to TAP it in slowly but surely. A pinion depth guage is recommended but at the price I could not afford it and instead my friend said trust me, and well, he was right. Also if u can elongate old bearings than do it b/c i spent extra bucks in twice having the thing all ready to go but the shims were not correct and you could see where there was a hair of space on one side of the carrier bearing more than the other, resulting in having a machine shop cut the old ones off and then having to again purchase new ones to be pressed on. Shop press too is neccessary. Have a good install kit and thread lock and make sure to torque everything down to the specifications provided. Run the marking compound to see that your teeth are making proper contact, not more to the top or bottom of the tooth, but the marking compound should be in the middle. And if it's in the middle it does not neccessarily mean that it's right b/c the second time we took it apart was because there was a hair more of space on the passenger side shims that were against the carrier but yet it still marked right on the teeth. It was a job but its not that hard.
 
Oo i think ill jus have the shop do it. Will i be able to use my stock carriers. or will i need new ones.....4.88's
 
@!#$ Ok..hmmm any idea on where i can get the new carrier? ei Junk yard? Are the thick gears for the stock 30 35,or if i run 4.56 do i still need to change out my carriers.....im runnin the 30 35 setup
 
Jeepin_rebel said:
@!#$ Ok..hmmm any idea on where i can get the new carrier? ei Junk yard? Are the thick gears for the stock 30 35,or if i run 4.56 do i still need to change out my carriers.....im runnin the 30 35 setup
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Yes you need to change your carrier, there are no thick gears for the other axles. D30's break is at 3.55, the D35 is at 3.73. Chysler 8.25's are the only axles that you do not have to change the carrier for.

Before putting that money into your D35, Please consider buying a better axle. D44's can be found, Chysler 8.25 (29 spline, but limited to 4.56), Ford 8.8 and the Toyota rear axles are good swaps also. They all have there +/-'s but they are all better than the D35.
 
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