I live within a 30 minute drive to dozens of trails and the national forest where I do most of my offroading. here is the chart I used:

http://www.therangerstation.com/tech_library/gearandtirechart.html

It said that it was based on 65 mph in 4th gear at 1:1 ratio. I have a fifth gear that should bring the rpms down to 26-2800 on hwy at 65 which is good by me. Let me know if I am missing something.

use this one its really nice <img src="/forums/images/graemlins/cheers.gif" alt="" />
http://www.grimmjeeper.com/gears.html

Ummmm....that one is way better! thanks

I like the one you used better than the polk-a-dot-eeee SOB in the other one! I can't SEE that thing with my old eyes.
If you look at the first one and see the 27/28 inch tires and 4:11's your ride came with compared to your present 33" ones. You will see the rpm is near the same at hiway speed with the 4:88's as it was from the factory.
This means you will lose a bit of power from having to TURN them big meats...but you will GAIN lots of power from where you are now.
I like graphs that show everything right out there in the open...not ones that only show what you ask for..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

The only advantage of those rear disks might be maintenance. I've still got drums and haven't had any issues though. But I also don't get out on many good trails that much any more - 2 or 3 times a year for a long weekend. Other than that it's all beaches. Not complaining. <img src="/forums/images/graemlins/smile.gif" alt="" />

You might try to find a Dana 44 out of a stock '87 XJ Cherokee or MJ Comanche with the tow package, it's almost a direct bolt in, with the spring perches and shock mounts needing to be moved. It comes with larger, 10 x 2.5" drum brakes with finned drums. The track width is exactly right, too. 8.8" axles have a narrower track and the diff is offset more to the side than the Jeep axle, which can result in a driveline vibration at highway speed. The driveshaft may need to be shortened 1", depending on your lift, since the Dana 44 diff pinion gear is longer than the one on the 35 axle.

The Mopar 8.25" axle from a late model XJ with stock 29 spline shafts is plenty strong, too. Also, almost a direct bolt in, too! KJ Liberty 8.25 axle rear disc brakes will bolt to this axle (junkyard discs) if you have to have discs.

The Explorer (and KJ) rear disc brakes have very weak parking brake functioning because the effective size of the park brake drum is only around 6" diameter and the parking brake shoes are only about 1" wide. The problem comes up especially with large tires with a manual trans (no Park !).

A '94-'95 YJ dual diaphram brake booster and master (from one with the ABS system) is a great upgrade for the '91 YJ, too. Adapt the late model prop valve for more rear braking. A ZJ prop valve will work great for 4 wheel discs.

$2K sounds kind of steep to me for an 8.8 install especially since it doesn't even include a locker and it's not that complicated of an install. You should carry in the axle and have them just do the welding and gear set up and save yourself the labor that they'll get you for and invest that money in a locker. I did my install in like 3 hours by myself and wasn't even rushing. I did mine for around $1k with 4.56 gears, locker and brackets, for my set up the brackets were actually one of the biggest expenses behind the locker.
Here's a basic breakdown of what you'll need as you have a basic leaf spring set up and don't need to worry about additional brackets :

Ford 8.8 Flange to 1310 Yoke Adapter for driveshaft = $20-$30
Ford 8.8 Spring perches - $30-$40
Ford 8.8 Shock tabs - $15-$20
97+ Ford Explorer 8.8 axle with disc brakes- $100-$300 probably less if you get a less desirable drum brake set up.
Gears: $150-$180
Gears install kit - $75-$100
Gear install - $150-$200
locating & welding spring perches & shock tabs: 1 hour basic shop rate $50-$80
Should run anywhere from $600 to at the very most $900 for just the rear if you do the labor yourself which would be maybe an hour or two if your going slowly. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Fred R.

1 hour to locate and install perches and shocks?
That is asuming that the housing is cleaned stripped sanded and D/Aed. Welding tubes to the center section is a 8.8 must. Installing new seals and bearings while you are in there?
Anyone can throw an axle conversion together, it does however take skill and know how to set pinion angles, plumb and install the new brake lines for the disc conversion, not to mention welding the perches.

When we do a an axle swap it all looks and works like brand new, not like a junk yard axle was swapped in by folks in a hurry to save a buck. 2 K is on the cheap side, but if you feel confident that they will warranty the job and make right any problems? By all means. Also if tire size is kept to 33-35" tires max and the trails are not super crazy, the d30 will live for years, making the rear 8.8 swap worth doing.

SD

Well I stated 1 hour shop labor IF he carried it in because I based this on the fact that it only took me about 20-30 mins to take measurements for a more complex install involving lower control arm brackets, upper control arm brackets, t-bar bracket and coil buckets off the old axle and translate that over to the 8.8. Pinion angle was also measured off of the old axle with a basic magnetic angle finder I got at Homedepot and since I had no vibes at my lift height with my old axle it work perfectly on the 8.8. Another 10-15 mins grinding off the old perches and shock mounts on the 8.8 (I would imagine that it would take just a few minutes for a shop with a plasma or torch cutter) so as you can see doing this swap was NOT brain surgery and even more so if it's going to be done for a basic leaf spring set up.

The list I provided were the BASICS for what is needed for a swap to be done on an 8.8. Aside from the axle that I got for about $100, EVERYTHING else was new. For my set-up, my rear disks on my D35 were new along with the brake pads and since the calibers were also in good condition I swapped it all over to the 8.8 as it was a DIRECT FIT since the 8.8 was already set-up for disks (unit from a 98 explorer. I did replace the seals and bearings, and took the axle to have the gears set up (Superior Gear brand with Timken carrier & pinion bearings) at a reputable gear shop that have done three vehicles for me so I know they do good work and it ran me $175 in labor, and that's in the SF Bay Area so I would imagine that it would probably be less expensive in other parts of the country. To sum it up, I've had this set up for almost 2 years running it hard, locked and with 35's with ZERO problems, leaks, whines, vibes or anything else so I know my swap was not done haphazardly to "save a buck" as it was so eloquently stated. I just knew what I was doing, did my research and proceed intelligently, so stating that it can be done for less than $1K is WELL within the realm of possibility. <img src="/forums/images/graemlins/cheers.gif" alt="" />

Fred R.

Fred it is not that you, (oh exalted one) can't clean an axle with mear stone knives and bear skins for tools. It is more that it can't be done well (even with plasma)in that kind of time. What I mean by "well", takes the fastest tech I've got a good 2-3 hours. The result however...the axle housing looks better than new. No rust, no dirt, no old paint and a finish that has no gouges, pits or even sand marks or poorly sanded waves. Is is possible to cut that time down and have an axle that looks ok, sure. Depending on the shop doing this job (never seen one that makes a housing look like new like we do)but if they take pains to do a top flight job, it will look like it and it will cost.
Shops that do this sort of work everyday take pride in a job well done and they have something you don't...overhead.

SD