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bluej
bluej UberDork
2/14/20 6:07 p.m.

Preferably something that might actually show up in a junkyard.

You know.. just curious..

Stampie
Stampie UltimaDork
2/14/20 6:13 p.m.

IRS the Nissan 350z/Infinity Q45 (1st and 2nd Gen).

Live axle Ford Explorer 8.8 (Google Explorer door tag)

DeadSkunk  (Warren)
DeadSkunk (Warren) PowerDork
2/14/20 6:14 p.m.

Ford 7.5" from a Ranger or Mustang? Didn't come in anything with 400 ft.lb. of torque that I'm aware of, but it might take it.

jimbbski
jimbbski SuperDork
2/14/20 6:27 p.m.

How you intend to use the vehicle that this goes into is also a factor.  Like the poster about said the Ford 7.5 can take V8 power from a 5.0L but not if you do burn outs or clutch drops with it.  One that is no longer common but can be built to take it is the old Ford 8 inch.  You can still find them as I did a search last year and found a number of cars that came with it not that far from me.

MrChaos
MrChaos SuperDork
2/14/20 6:29 p.m.

8.8 from literally most fords, mustang gt's will 95% be lsd's

buzzboy
buzzboy HalfDork
2/14/20 6:57 p.m.

Toyota 8" could be had with factory LSD. Not sure how to find an LSD for one, but it was a thing.

Cactus
Cactus Reader
2/14/20 7:33 p.m.

Ford 8.8 can be built to take that easily. Not particularly heavy. Find the latest model axle you can, I forget when they switched to a higher spline count. Panthers and rangers are good sources. Could do a fabricated aluminum Ford 9", those are light, not gonna find that in a junkyard though.

ebonyandivory
ebonyandivory PowerDork
2/14/20 7:46 p.m.

A 9" is what, 195lbs? 8.8 is like 170. How light do you need it to be?

oldopelguy
oldopelguy UberDork
2/14/20 8:21 p.m.

Any axle will work with 5" wide tires.

Cooter
Cooter UberDork
2/14/20 8:35 p.m.

Exploder 8.8 isn't incredibly light, but it is incredibly easy to find cheap with a Limited Slip and a variety of gear ratios.

Cactus
Cactus Reader
2/14/20 8:42 p.m.

I've never seen an E30/E28 pumpkin die at any power level, plenty of wheel hop and broken diff mounts though. I'm not sure IRS is what you're looking for

Wicked93gs
Wicked93gs New Reader
2/14/20 8:45 p.m.

Explorer 8.8"...explorer version is easily shortened because the pumpkin is offset, cut down one side and use 2 short-side axles, if you are looking for an IRS...the 8.8 can be had from 80s or 90s t-birds and cougars in LSD(some of them) or late model S550(2015+) mustangs and can be adapted easily to most existing IRS cradles

bluej
bluej UberDork
2/14/20 9:33 p.m.
DeadSkunk (Warren) said:

Ford 7.5" from a Ranger or Mustang? Didn't come in anything with 400 ft.lb. of torque that I'm aware of, but it might take it.

I like this answer since I have a ford 7.5" already. I figured before I try and find a cheap lsd to stick in it, might as well see what other options might be reasonably obtainable. 

KyAllroad (Jeremy)
KyAllroad (Jeremy) UltimaDork
2/14/20 10:16 p.m.

The fastest SSM Miata in the country is pushing more than that through a factory torsen diff.   

 

Diffs are stronger than most of the stuff around them.

bluej
bluej UberDork
2/14/20 10:49 p.m.

There are lots of irs diff options, but I'm interested in live axles.

I don't have a target weight, just trying to get a sense of what may be out there.

What was in the back of 1st gen rx7? 

tr8todd
tr8todd SuperDork
2/15/20 5:03 a.m.

I have a 7.5"LSD  sitting in a box next to my toolbox.  Probably never going to do anything with it.  Think it came out of an Early foxbody.  Might have been a Ranger.  Can't remember.

Knurled.
Knurled. MegaDork
2/15/20 6:16 a.m.
ebonyandivory said:

A 9" is what, 195lbs? 8.8 is like 170. How light do you need it to be?

More like 220+
.

 

My 9" is around 190 but it's the lightest combo of parts I could build short of gundrilled axles. which are not an option for semifloating axles.  Stock housing.

 

8.8 is lighter for the same expense, but diffs/gears are more expensive so it is only cheaper once.  And to do an 8.8 "right" you will be cutting off the axle ends and installing Ford 9" ends so you can eliminate the C-clips, which is stronger and more reliable and easier to service.  But replacing bearings and setting up the gears means you're working on your back under the car getting dripped on, instead of pulling the centersection out and working on it in your kitchen or something.

Knurled.
Knurled. MegaDork
2/15/20 6:20 a.m.
bluej said:

There are lots of irs diff options, but I'm interested in live axles.

I don't have a target weight, just trying to get a sense of what may be out there.

What was in the back of 1st gen rx7? 

Mazda 7", weighs about 160lb with GSL-SE brakes, lighter with GSL brakes and lighter still with drums.   Gears actually interchange with NA8/NB Miatas.  It probably would not handle a 400ft-lb engine, and gearing options are limited.   In drag racing you'd blow the gears out, in any kind of grippy cornery competition you'd twist the housing (feels like it is stamped out of 16-gauge sheetmetal) and start breaking axles.

 

And thus, why I went to the lightest 9" that I could build...  The extra 30lb sucks but I'm not going to pretzel it.

Streetwiseguy
Streetwiseguy MegaDork
2/15/20 6:46 a.m.

8.8 is probably the easy choice.  9 inch is probably getting hard to find for no money in a junkyard.  8.5 GM 10 bolt would also work, if you happen across one from a car, and they used them until recently in trucks, but they are likely too wide, wrong bolt pattern and so on.

dherr
dherr HalfDork
2/15/20 7:02 a.m.

I see you are in DC, I have a Ford 8.8 LSD out of a Thunderbird Turbo coupe, that I'll sell for cheap if you don't want to go digging in the junkyard. 

bluej
bluej UberDork
2/15/20 9:39 a.m.
tr8todd said:

I have a 7.5"LSD  sitting in a box next to my toolbox.  Probably never going to do anything with it.  Think it came out of an Early foxbody.  Might have been a Ranger.  Can't remember.

Re-heh-heally. I shall message you shortly.

Curtis73
Curtis73 MegaDork
2/15/20 9:42 a.m.

The amount of torque the axle can handle has a lot to do with too many factors.

Vehicle weight is huge.  Assuming you always have traction, 400 tq could be put through a Miata rear in a Locost, but it could blow the differential out through the cover of an 8.5" GM in a truck towing 10,000 lbs.

The Ford 8.8" is a good one.  It is completely a corporate ripoff of a GM 12-bolt.  Seriously, look inside one of each and tell me that Ford didn't just make a reverse-engineered copy of GM's axle.  Either one will work, but I suspect the GM is a bit heavier... if for no other reason that they were only used in bigger GM vehicles and are therefore wider than an 8.8 from a Ranger or Explorer.

The 9" doesn't have to be heavy, but it will be expensive.  There are aluminum carriers that lighten thigns a little.  The nice thing about a 9" is that the entire axle housing is stamped steel and the differential carrier bolts onto it as opposed to other axles with a large, cast iron "pumpkin" with steel tubes pressed in.  This means that the whole housing can be built with less weight as it is now responsible for less of the load.  It's like the FWD of the axle world.  Locating all the torque in the front subframe of a car makes the rest of the car basically a trailer, whereas sending torque to the rear means the whole vehicle is carrying the torque stress.

GM's 8.5" is ubiquitous and inexpensive and has been known to take 500tq or more in 4000-lb vehicles.

bluej
bluej UberDork
2/15/20 9:45 a.m.
dherr said:

I see you are in DC, I have a Ford 8.8 LSD out of a Thunderbird Turbo coupe, that I'll sell for cheap if you don't want to go digging in the junkyard. 

I do have an exploder 8.8 w/lsd and calipers I pulled from a yard already. I'm not sold hard between the 7.5 and 8.8. It will really depend on which combo I can put together w/ an lsd for cheapest. I'll check what I have into the exploder sticks, but I it was full jy price if that makes sense.

I've got the 7.5" in the truck already so it makes a lot of sense to stick with that being the lighter option and already in budget. There's even money this truck will end up seeing more torque from a larger motor in the long run, so I need to consider that as well.

I think I need to see what the weight diff really is between the 7.5 and 8.8.

Knurled.
Knurled. MegaDork
2/15/20 9:49 a.m.

The Explorer 8.8 is rather heavy for its width compared to other 8.8s because it has super thick axle tubes, and disk brakes are heavier than drums.

Curtis73
Curtis73 MegaDork
2/15/20 9:49 a.m.

I have a 9" housing and a dozen used loaded diffs, but you won't like how much I would ask for it.  It's a brand new, never used axle modified with a drain and a higher fill plug for circle track/stock car.  My problem is, I don't think it will work for the application I want so I might sell it.  When I originally measured it, I had it upside down.  It looks to be shortened on one side more than the other, meaning it was set up for an off-center engine.  It would need to be used in a narrower car where you could shorten the other tube enough to get things back to center.

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