Can I swap my 3.07 gears into a 3.73 posi rear axle?
- Thread starter TJTony
- Start date
I definitely would. the 4.0 likes to rev. It's really happy cruising at 2500rpm or higher.
I should have qualified in that post, that where I live, there is no flat. Everything is up or down. By Colorado standards, the stretch I drove the most was "flat" but it averages a 1% grade over 30 miles.
But yeah, I would absolutely consider 3.73 in your position and I would be surprised if your mpg didn't improve.
You wont see a big change in mileage changing gears, certainly not enough to offset the cost of regearing. A good reason to do it is performance on the trail. Trying to improve fuel economy on a TJ is time wasted. Obviously you should fix problems but you aren't going to see any real gains with gears. @Jerry Bransford runs huge tires and spends allot of time on the trails, sure gears make sense for him. You... no.
You are absolutely correct. So, to confirm, my current setup is the oem 6 speed, the oem 3.07 non posi gears and 31" tires. Most of my driving is highway and I am not experiencing any problems. Given the general consensus, that the 3:73 posi is of marginal value, I should continue with my current setup. Agreed? You all have been tremendously helpful.
I don't think anybody's suggesting going to the expense of a regear here. OP said he had a line on an LSD axle which he'd like for the snow, and it had 3.73 in it already. You can buy front axles with ratio to match for $200 all day and swap both out over a weekend. Seems to me like an easy and inexpensive upgrade that's likely to make it more enjoyable to drive and won't hurt the fuel economy even if it doesn't help it.
The issue was, that only the 3:73 posi was usable, the axle was junk. So, I was contemplating installing the 3:73 posi into my TJ, which has an oem 3:07 non-posi rear. The first negative that one of the fellows raised, was that my Dana 35 axle w/n accept the 3:73 posi w/o expensive work. The 2nd. negative raised, was that the Jeep posi w/n all that great to start with. The consensus, as I read it, was to forget this project.
Btw, as a point of info to Forum members, this 3:73 axle was on CraigsList in either Vermont or Mass. The seller was looking for $100 or BO.
The track I was on is because you only run 31's, you can get by with a factory axle ratio, and 3.73's are super common, so if you can get a good deal on a pair of axles configured the way you want, rebuild the LSD (the big problem is the clutches might last 50-70k miles, so a used one usually has little to no limited slip function left) you could potentially get out of it under $500. Just trying to point out there's a way to get there affordably....I didn't realize the axle was junk. The gear setup is what ruins the whole value proposition. There's pretty much no way around spending about $600 per axle to do that.
Freedom in 4low; your are correct. I am going to change the axle(s). I check CL every day and have posted a note at my local NAPA store, looking for good posi axle(s).
I've already started lubricating the various nuts and bolts that will have to be removed. Fortunately, when I purchased my TJ, I wire brushed, primed, painted and undercoated the undercarriage. So now, everything should come off relatively easy. With the arrival of warm weather, this will be a weekend project.
I've already started lubricating the various nuts and bolts that will have to be removed. Fortunately, when I purchased my TJ, I wire brushed, primed, painted and undercoated the undercarriage. So now, everything should come off relatively easy. With the arrival of warm weather, this will be a weekend project.