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Jan. 29, 2010 11:16 p.m. iadr New Reader

Anyone want to recommend a medium duty rear axle? Overall width of the car is 71"...so track is 64-ish?. ~25-2700lbs, 315 lb-ft. Vintage looking, updated drivetrain.

Wants: Light weight factory discs or easily maintained discs with integral drum park brakes 5 on 4.5 bolt pattern slight preference to "drop out" center type, allowing easier switch of ratio availability of clutch or torsen/truetrac LSD.

Thoughts so far:

Ford 8" with Wilwood or budget aftermarket brake kit. Looks classic, probably the front runner right now. No minuses I see. How much lighter than a 8.8 is it, though?

Jeep Dana 30 or Chrysler 8.25/8.35. Weight? Discs? Volvo have Dana 30 and discs but odd metric bolt pattern.

Toyota 7.8"/8"? truck/celica RWD? how many kinds are there?

I believe the 8.8 Ford is widely regarded as suitable, but looks heavy. I believe the musclecar 8.75 Chrysler and Ford 9" are out of the picture- as are most of the other well supported muscle car/4x4 scene units- eg, Dana 44, GM stuff- due to weight.

Suzuki Sidekick Sport- very nice piece, but odd large wheel bolt pattern, limited taller gear ratios, limited LSD availability.

Throw as many brands/models at this as you like, just looking for experiences
Jan. 29, 2010 11:23 p.m. aussiesmg SuperDork

Mazda 1st gen RX7, GSL or GSL-SE are LSD and disc brake, later 83 and all 84 and 85 are stronger with bigger bearings and axles. They are surprisingly strong.

Ford 8.8 Explorer V8, LSD, 4.11 or 3.73, disc brake
Jan. 29, 2010 11:48 p.m. psteav Reader

Chrysler 8.25 could be had with rear discs in '94+ (IIRC) Grand Cherokee, and lockers/limited slips are available in the aftermarket. Durability might be a little bit of an issue with the 315 lb/ft of torque you're putting through it.
Jan. 30, 2010 12:18 a.m. RealMiniDriver Dork

aussiesmg wrote: Ford 8.8 Explorer V8, LSD, 4.11 or 3.73, disc brake

Wheel mounting surface to wheel mounting surface on disc brake axle is 59.5". Somewhat heavy, 210lbs, with discs. P-brake drum in disc. All Explorer rears have discs from '95-on (before they went to IRS). 5 on 4.5 bolt pattern. LSD is "Trac-Lok" clutch type.

Keep in mind, the differential is offset about 3" to the right.
Jan. 30, 2010 12:55 a.m. oldtin Reader

Ford 8", post 1966 (more webbing - stronger housing and straight axle tubes). GRM disc upgrade (speedway weld-on brackets - use gm metric calipers - s-10 fronts for no e-brake - cadillac seville rear calipers for integrated e-brake), lincoln lsc rear rotors (discs for $100ish). Can find 8" out of pre-mustang II stangs, granadas, mavericks earlier rancheros, falcons. Swappable 3rd member - decent amount of upgrades available - gears & LSDs. Weighs in around 150# - good for around 300 ft/lbs of torque - more for a lighter car or easy loud pedal. If you go this route - save the inner drum housing - you may need to cut out the bolt section as a spacer - also good thing is brake housing bolted to axle tube flange - no "C" clips for axles (if you break an axle, it stays put. Currie has an alum. center section that can handle significantly more torque - if you go that route, double check measurements - they don't spend a ton of time on set-up. Stock axles till they break - moser or currie for aftermarket axles (moser is cheaper IIRC). I put an 8" in my mgb (with ford 5.0 and t-5 trans) 3.55 gears and ltd slip. About 325 ft/lbs of torque - tires let go long before the rear end gets stressed. A lot of them have 3.00 open diffs - info is on the tag.
Jan. 30, 2010 6:27 a.m. DILYSI Dave SuperDork

The only ones with a drop out center that I can think of would be some Toyota truck axles. Outside of that requirement, I really like the Explorer 8.8 for meeting your needs.

If you're willing to spend, there are fabricated Ford 9" housings. Stronger than OE, and I believe lighter as well. That gets you your dropout third member as well. You'll spend some real money putting it together though.

There was also a Dana 44 (I think) with an aluminum center section IIRC. I think it came on Jeep Grand Cherokees at some point. Jeepers hate them, but it might work for you. EDIT - Here's a short write up - http://www.jeepforum.com/forum/f19/zj-aluminum-dana-44-a-493742/
Jan. 30, 2010 7:15 a.m. tr8todd New Reader

Pick up two Ford explorer axles. They have one side that is 3 inches longer than the other. Narrow the long side to match the shorter and use the two short axles. Now you are in the ball park and have everything you are looking for. After you remove all of the unwanted Ford pieces from the rear end, it comes out to around 170 pounds. That's what I put under my TR8 that is getting the turbo. Took about 10 hours to do including installing the new brackets I had to make. A good source of axle info for swaps is a site called the ranger station. If you want a slightly lighter weight, go with either a car based 8.8 or a 8.0 from a ranger or other 5 bolt Ford.
Jan. 30, 2010 7:26 a.m. Jensenman SuperDork

From a Grassroots perspective (inexpensive with easily available upgrades) the Exploder axle with discs will be the best choice. 5- 4.5" bolt pattern.

The S10/Jimmy/Blazer axle would be another good one from a parts availability standpoint. F body rear discs easily adapted. 5- 4.75" bolt pattern. It seems there were some variants with 5- 5" pattern, so measure carefully.

The Jeep Dana unit could be used, but I saw a lot of those things eat bearings and R&P during my stint there. 5- 4.5" bolt pattern.

When I was rooting around on t3h int3rweb for axle parts a while back, I ran across this site: http://www.ringpinion.com/ Prices are pretty darn good for the more common R&P's. For instance, 4.88 gears for the 8.8 axle are $177.00, Jeg's is cheaper on some stuff but they don't even show that ratio being available. They are not guaranteed to be quiet, but for a Challenge car who cares?
Jan. 30, 2010 7:28 a.m. aussiesmg SuperDork

RealMiniDriver wrote:

aussiesmg wrote: Ford 8.8 Explorer V8, LSD, 4.11 or 3.73, disc brake

Wheel mounting surface to wheel mounting surface on disc brake axle is 59.5". Somewhat heavy, 210lbs, with discs. P-brake drum in disc. All Explorer rears have discs from '95-on (before they went to IRS). 5 on 4.5 bolt pattern. LSD is "Trac-Lok" clutch type.

Keep in mind, the differential is offset about 3" to the right.

Really so the 8.8 in my challenger has imaginary disc brakes. The V8 Explorer does have discs.

All beam axle rear ends are heavy, the 8.8 is a lot less than a 9" and if you want strong you need metal.

I removed the handbrake components, drum style park brake.
Jan. 30, 2010 8:33 a.m. P71 SuperDork

94-04 Mustang GT's came with a Ford 8.8 with 5 on 4.5 rear discs, Track Lok LSD, and were relatively small and light (compared to the Exploder and P71 versions anyways). Center section is near centered as well.

Don't discount the Ford 7.5 either. Grab one from an 83-86 TBird Turbo (4 lug rear drum) and swap out the axles/brakes for Ranger versions (you'll need two of the short side ones) to get the rear discs/5-lug. It gives you a centered pumpkin, 3.47 LSD, and easily worked on discs in a compact and light package that is pretty strong as well. Bonus points for being dirt cheap.
Jan. 30, 2010 9:12 a.m. patgizz Dork

if you are near northeast ohio i know where a nice clean 8.8 disc brake 5 on 4.5 fox body rear axle is
Jan. 30, 2010 9:45 a.m. RealMiniDriver Dork

aussiesmg wrote:

RealMiniDriver wrote:

aussiesmg wrote: Ford 8.8 Explorer V8, LSD, 4.11 or 3.73, disc brake

Wheel mounting surface to wheel mounting surface on disc brake axle is 59.5". Somewhat heavy, 210lbs, with discs. P-brake drum in disc. All Explorer rears have discs from '95-on (before they went to IRS). 5 on 4.5 bolt pattern. LSD is "Trac-Lok" clutch type.

Keep in mind, the differential is offset about 3" to the right.

Really so the 8.8 in my challenger has imaginary disc brakes. The V8 Explorer does have discs.

All beam axle rear ends are heavy, the 8.8 is a lot less than a 9" and if you want strong you need metal.

I removed the handbrake components, drum style park brake.

I wasn't disputing the V8 Explorer having discs. I was pointing out that from '95 on, they all have discs.

Another thing to keep in mind about the 8.8: Mustangs (and Rangers, IIRC) have 28-spline axles, Explorers have 31-spline.
Jan. 30, 2010 3:40 p.m. iadr New Reader

New problem with the Ford 8in is that it doesn't come in a 3.73. Closest are 3.55 and 3.80. I'm dealing with a front 3.73 & a viscous drive transfer case and I can't get the tire sizes close enough to not burn up the coupling. I can get to as close as 7 revolutuons per mile different, and that's doing stupid stuff with tires sizes. Anyone know how the fluid coupling deals with that? The VW Syncos used to have a viscous drive with slightly different raitos to keep the drive partly locked up.. or so I read online some time ago.

So how much do disc brake 8.8's weigh? Well over twice what the Sidekick Sport axles does, Ive heard- 135lbs to 285 lbs.

I thought I'd found gears taller than 4.3 for the Suzuki, but no dice. There is a clutch type LSD. no prob there.

Overall, it's a very nice looking piece. The 4x4 guys swap in 4.3 GM's and they seem to stand up.

I'm slightly interested in the Mazda.
Jan. 31, 2010 10:46 a.m. wheelsmithy New Reader

I'm using the toyota space van rearend-4X2 truck is the same except has ford 5 lug pattern. A local 4X4 shop set up the Detroit TRUTRAC including new bearings, but not new gears for about $600, including the new locker (almost $500 itself), but not gears. Complete rearend was $75 at pull a part. So, I guess the 8.8 (try an explorer for discs, LSD, etc) is a better choice. 8.8 probably weighs more, though.
Jan. 31, 2010 11:04 a.m. DILYSI Dave SuperDork

iadr wrote:

New problem with the Ford 8in is that it doesn't come in a 3.73. Closest are 3.55 and 3.80. I'm dealing with a front 3.73 & a viscous drive transfer case and I can't get the tire sizes close enough to not burn up the coupling. I can get to as close as 7 revolutuons per mile different, and that's doing stupid stuff with tires sizes. Anyone know how the fluid coupling deals with that?

I ran through some calculations just for a point of reference. Calculated the difference between a 23.875" tire and a 24" tire. Leads to a delta of 4.5 revolutions per mile. Thus - If you're fronts have worn the tread down 1/16" more than your backs, a stock car is dealing with 4.5 revolutions. Put the tread depth differential at 1/8", and you're now at 9 revolutions per mile. Throw in pressure differentials, turning, etc. that a stock AWD has to deal with, and my gut feeling is that a viscous drive can handle a 7 revolution / mile differential just fine.
Jan. 31, 2010 2:30 p.m. iadr New Reader

Yeah, that's doing dumb stuff with the tires- ends up taller & narrower in the back. Raw is 15-ish turns diff per mile with 4-square ;) tires.

For tolerance, I tried checking it out- the lastest electronic stuff is insane. Rockland Standard gear quote a GM diagnostic test where you mark a "chalk" mark on each of the tires at 6oclock and drive forward, on straight level ground and if any of the tires' marks move by more than an inch or so in ten turns, chances are it's the tires setting the codes. So an inch in 80-odd feet, and the electronics "knows". Help me with the math, but doesn't that mean that .85 turns in a mile is a problem? We have 80feet which is 960 inches. One inch divided by 960inches=.001041667. I multiply that by 815 tuirns per mile, which would be 0.85. or did I miss a 100 multiplier for percent? Subie have a spec that the circumference can't vary more than .25". Volvo same On the other end Porsche come with staggered's on their awd Carerra's that equate to as much as 2%. I'm at 1.856% The transfer case is going to be from an Eagle- from everything I've read they are very tolerant. I joined an Eagle site and have queried them. Same as a Grand Cherokee and some small Cherokees but w/o the low range, and came bolted to a T5. May pirate4x4 would know SUV rules of thumb? How much does tire inflation change Rev's per mile?

Back to the original post, the Toyota or the the 8" ford still lead, then Mazda Rx7 (pics, anyone??) , then the Ford 8.8.
Jan. 31, 2010 2:49 p.m. Jensenman SuperDork

Um. 3.73 gear ratio was never available for the Mazda, AFAIK. Only 3.89 and taller. Don't know about the Eagle case, but when I worked for a Subaru dealer the tolerance was +/- 1/4" (.250) between any two tires. That's not a hell of a lot.

I keep thinking an 8.8 will be the best solution from a grassroots standpoint. That ringpinion.com site shows 3.73's for an 8.8.

http://www.ringpinion.com/ProductDetails.aspx?ProdID=1917
Jan. 31, 2010 5:14 p.m. RealMiniDriver Dork

Axle tag from an 8.8. The "L" between 3 and 73 indicate locking diff. Non-locking diff would be "3 73".