REGEARING TO 4.11 FROM 3.07

The math for those tires would be 3.07*33/27.7 =3D 3.66. So to keep it like stock you would use 3.73. Numerically higher if you want get your RPMs higher on the highway or for better off road performance.

I run 33's with 4.10 gearing and for me its a perfect fit for an all around vehicle. I had 31's with 3.07 gearing and hated it after a awhile Not sure if your year/type wrangler came as a 4 cyl but you could swap in some 4 cyl axles with 4.10 gears. I did on my YJ.Best upgrade I ever did. Thats what I did before I got my 8.8 in the rear :-)

Sorry, but it's widely held that 4.10 is correct for 31/32, 4.56 is for 33's and 4.88 for 35's.

Carl

And 5.38s in Real Jeeps. God Bless America, Bill O|||||||O mailto: snipped-for-privacy@aol.com

I'm not disputing that those gear ratios would work the best, but you stated that they would be closest to stock, and that is simply not true. It is a simple mathematical equation to calculate the proper gear ratio, and nothing more.

Chris

Carl S wrote:

She had 215's....

You are wrong.

Mike

c wrote:

OK, so her tires are 27.6" instead of 29". The same formula still applies.

Mike Roma> She had 215's....

As long as everyone and their dog is jumping in here 3 times, I may as well add my 2 cents. I have a CJ7 running 33s and 4.10 gears, used to have

I should have been more specific. 4.56 gears turning 33" tires will restore stock performance. The lil bit of extra gear makes up for extra wind resistance, tire wieght, ect.

Carl

Fair enough. I wasn't trying to start crap or anything, I just want to make sure that Tracie gets accurate information. A gear swap is not something you want to mess up on and have to do twice. For as much as she drives on the highway, I would personally lean toward the 4.11s. It might be a good idea for her to run at 2200RPM or so on the highway to see how it affects her fuel mileage. I don't think it will change drastically though.

Here are the comparisons for 4.11 vs. 4.56 at 60mph:

Chris

Carl S wrote:

Only problem with your math is that your assumptions are off a little. The tire circumference is accounted for but the mass distribution is off significantly for power calculations - those 33's will take significantly more power to accelerate (or to stop, for that matter - first hard stop with stock brakes is a real eye-opener!) and they have way more exposed surface area for drag. Both are significant when addressing highway performance. A simple multiple will NOT restore the feel.

To restore stock 'feel':

Carl

I understand that. The RPM calculations are there simply so she will know what to expect her engine to turn while she is on the highway. If you read the rest of the posts, I did recommend 4.11 gears, which is more then just compensating for the tires. Also, you will see that she did ask if 3.73 or 4.11s were better. With gas prices what they are these days, and her driving 70 miles per day, fuel economy is also a concern. In her case, I don't think she is going to lose much mileage though. What she loses will be from the increased tire weight and wind drag more than the gear change. Like I said in another post, if her engine is lugging while she's on the highway, the gears could even help her mileage a bit compared to what she has now. If it were my vehicle, I would use the 4.56 gears, but I don't drive much on the highway. She probably needs to decide between the 4.11s and 4.56s. I didn't recall anyone recommending the 3.73s.

Chris

First of all, for your type of driving, I would recommend the 4:11s if you're SURE you won't want 35s when you upgrade. 33s and 4:11s are a nice all around combo which I think you'll be very happy with. Secondly, what I would do, is find some lightly used complete Rubi D44 axles and just simply swap them out when you do your suspension lift.

tw

Tracie wrote:

Just so that I understand, the D44 axles would just be replacing the axle shafts and the differential housings ONLY, correct? It would not be replacing the gearing again?

While we're on the topic.... Since I have upgraded from 28s to 31s, can that cause the engine to lug or ping? I generally keep the RPM's around 2200-2400 in 5th gear (I have a 6 speed). In the higher gears after the engine is warm and mainly while going uphill (little or big), I get this noise on the passenger side that sounds VERY similar to the soft top side window 'pinging' against the metal support bow when the wind blows. I can't quite distinguish if that's it, or if the engine is pinging because I am not 100% sure whether it's coming from the front or the back. It's a high-pitched noise. It is NOT rhythmic or steady, but rather comes and goes intermittently. This noise does NOT happen at city/town speeds of 50 mph or lower. I ran a tank of 89 through her, and it seemed to be drastically reduced after 1/4 of the tank was used and for the rest of the 3/4 of the tank. I have now refilled again with the 89 and the noise is back. I have not used 1/4 of the tank yet, so I don't know if it will be reduced again once I get to that point. I do have a tendecy to 'stuff' as much gas in the tank as I can get (even after the automatic shuf-off on the spout kicks on). Would this be causing the problem too?

No.

A Dana 44 is a complete housing that includes the case, the gears, the axles, the brake mounting plate, the emergency brake, everything must be changed including the brake shoes or pads.

D35 gears don't fit a D44, they are a different size.

Not sure about the driveshaft.

If you have ABS, then things get even more complex.

Mike

I do not have ABS.

TW -- How complicated would it be to just switch out the axles like you're suggesting? Would this be easier than just upgrading the gearing? Or does everything that Mike mentioned have to be changed too even if you just upgrade the gearing from stock to 4.11? Would I need D44 for the front AND rear? Or do I just change the rear 35s to