Limited Slip Differentials?

[mgdavis]

I have occasionally entertained the idea of putting a LSD it the back of my 2WD 1991 F150. I'd like to have more traction available to me when it's rainy, muddy, icy, etc. I'd also like it to be more or less unnoticed when I don't need it, I don't mind some noise but I don't want to have to do maintanence every week or anything like that; basically a there when I need it, forgotten when I don't kinda deal.
In my minimal research it looks like a Trac-lok unit would run me 2-300 dollars. Is this a good idea? I plan on keeping the truck another 3 years, so I don't want to sink huge amounts of money into it.
Discuss?

[Zed]

Why not just trade your 2wd for a 4x4?
Usualy cheaper int he long run.

[mgdavis]

I'm currently saving cash to buy a newish Toyota Tacoma 4x4, hence the plan to keep this one another three years. I'm not going to go into debt for a car.

[Zed]

I didnt say to go into debt, said to do a trade.
at most you would have to put out a little cash, but it'd be less than having a LTD Slip Diff Put in.

[Balog]

How difficult would it be to do yourself?

[Zed]

Usualy an All day job if you have all of the tools and know what youre doing.

[mgdavis]

A different truck is flat not happening.
I could probably get the LSD in myself, I actually moonlight as a jet engine mechanic (2A651A), so I bet I could muddle through a differential as long as I had tech data.
Does anybody know if the Trac-Lok is a decent diff, or if there is something else out there that would serve me better? Any specialized tools needed, that kind of thing.

[Brad Johnson]

Figure out what you want from the setup and go from there.  

If you drive mostly on the street and just want a litle extra help when it gets slick then you'll probably want a clutch-type unit.  These units use a stack of plates under pressure.  As you turn the plates will slip against each other, allowing the tires to track seperately.  Properly set up these units are a considerably smoother than the locker-type units, but not quite as robust.  By robust, I mean that if you get one tire hooked really well then start standing on the throttle ad infinitum, you will burn out the clutch pack (which, luckily, is rebuildable).  This is probably the unit you will want to consider.

If you do a lot of driving off road and want maximum slip protection then get a locker.  There are several styles available but all do the same thing - physically lock the differential so that both rear wheels are turning.  Be aware that lockers are great for max offroad traction, but their street manners leave much to be desired.  When you turn they start snapping in and out of lock.  If you've never been in a vehicle equipped with a true locker I suggest you find one and take a ride.  Just turning around in the parking lot will have you thinking twice about it.  The noise is akin to someone pounding on the frame with a three or four pound sledge, and the sensation is like having a really slick spot on the tire that gives a little "twitch" each time it comes around.  Not much fun at all to put up with on a constant basis, but the ultimate in traction and durability.

There are several more styles of anti-slip differentials - torsion, cone, electronic, pneumatic, solid - but the two above are the most common and most cost effective.

I don't remember which rear the '91s use, but there are a jillion of them around so somebody will make a modestly priced anti-slip diff for it.  If you've never installed a diff before I would get a shop to do it.  Getting all the settings right is critical for the longevity of your gearset and seals.  Thumb through your yellow pages and look for a driveline shop, or call one of the local off-road shops and see who they recommend.  IF you are a reasonably competent mechanic and know how to use a dial indicator then setting up the diff isn't hard at all.  It's just very precise and somewhat time-consuming.

And there is always the e-bay route...

http://cgi.ebay.com/ebaymotors/Factory-Ford-8-8-Limited-Slip-Differential-Assembly_W0QQcmdZViewItemQQcategoryZ33731QQihZ003QQitemZ130066770031QQrdZ1QQsspagenameZWDVW

Brad

[p12]

Two words.

Aussie-Locker at http://www.offroadlockers.com/

No maintenence. A little clacky during turns.

[mgdavis]

Thanks Brad. That's what I was looking for. I don't off-road, I just hate not being able to get up the small hill by my house when it's iced up. How long do the clutch type units last if you don't hammer them? If there are pre-sets to be made, it might be over my head. I think I've probably got the 8.8 inch rear-end (W.A.G.). It's a 1991 F150 4.9 I-6 5-speed, if anybody knows offhand. Unfortunatly if this is going to run much over $500 parts & labor it's probably not going to happen, I'm trying to put as much as possible in the bank towards the next truck.

[mgdavis]

http://www.offroadlockers.com/item.php/TMe81e9c/116a/06/106010/.html

This looks like what I was thinking. Cons? The site says the inside tire will spin MORE easily during turns?

[mtnbkr]

A friend of mine has an Aussie Locker in his Jeep.  It's primarily an offroad vehicle, but he drives it around town some.  He likes the Aussie.  I've driven it offroad and didn't notice any issues.

Chris

[mgdavis]

http://www.pirate4x4.com/forum/showthread.php?t=167389

Practical experience with the Aussie-Locker. Sounds promising.

[Brad Johnson]

How long do the clutch type units last if you don't hammer them?

Probably longer than the rest of the car.  About the only time I've ever seen a LS diff need a rebuilt is if it was completely and totally abused.

If there are pre-sets to be made, it might be over my head.

The presets and loading is actually pretty simple - a dial indicator and some marking paste are all it takes - but it does take time and some knowledge of what you're doing.  A good shop can have the diff swapped so fast it will make your head spin, but that's because they know exactly what they're doing.  If you do it, plan on at least a full day rolling around in the driveway.  The physical swap is nothing major.  The time part is in getting all the clearances and loading set.

Brad

[mtnbkr]

If they ever make an Aussie for a 3rd Gen 4Runner, I'll probably get one.  Then again, they've been promising one for 2-3 years now. 

Chris

[Ezekiel]

I use a Detroit Locker in the back of a '69 Mustang with 4.10 gears.

Yes, it "clacks" a little during turns.

Lockers are, however, damned near indestructable and leave you a twin set of tire marks, every time.

Clutch-type units (or gears or viscous couplings) NEVER actually "lock" the axle and will always retain a measurable amount of slippage.  As such, they are much, MUCH better than an open differential, but purely a compromise in comparison to an actual LOCKING unit.

It all depends upon your desire.

[Brad Johnson]

Clutch-type units (or gears or viscous couplings) NEVER actually "lock" the axle and will always retain a measurable amount of slippage.

Depends on the clutch pack preload.  You can load the clutches to the point it would take an act of congress to get them to slip, but only if the diff body is strong enough to take it.

Brad

[Ezekiel]

And at the expense of extreme clutch wear: but you make a very valid point.

Clutch-type units (or gears or viscous couplings) NEVER actually "lock" the axle and will always retain a measurable amount of slippage.

Depends on the clutch pack preload.  You can load the clutches to the point it would take an act of congress to get them to slip, but only if the diff body is strong enough to take it.

Brad

[Tallpine]

I've had this same idea for my old 76 GMC 2wd ...

Probably the easiest thing is to just get a complete LS rear-end from a salvage yard, and put the whole thing in yourself.  Unless I'm mistaken, the only things to mess with are the spring u-bolts, driveshaft, and brake lines.  You would have to re-bleed the brake system.

[Brad Johnson]

And at the expense of extreme clutch wear: but you make a very valid point.

That's from too little preload (more slip).  A lot of preload should result in less clutch wear but will impact around-town driveability accordingly - popping around corners, strange handling characteristics, etc.  Get them too tight and they won't slip at all ... might as well have a spool at that point, which is such a joy to try and get around a tight corner.

Brad

[Ezekiel]

Ugh!  I cannot even imagine as, occasionally, my Locker "chirps" the tires in tight turns... 

might as well have a spool at that point, which is such a joy to try and get around a tight corner.

[erik the bold]

    One thing not mentioned with a 'locked' differential, is that when your tires begin to lose traction, BOTH will have lost traction.  Meaning, that on ice, you're heading for the ditch towards which ever way the road is crowned. Sideways.

 In slippery conditions, judicious use of the go pedal is definitely recommended.

Best bet would be swapping out the complete rear axle assembly, or taking it to a competent axle shop for the conversion.  Call one up, they may even have parts in stock...

[Gewehr98]

Ugh!  I cannot even imagine as, occasionally, my Locker "chirps" the tires in tight turns...

Yee-haa!

Try some huge Mickey Thompsons attached to a narrowed Ford 9" rear end, with spools in the pumpkin.  "Chirp, chirp, chirp, chirp" on every corner.   

[Ezekiel]

In a straght line?  "Fabulous!"

I put a HUGE amount of miles on my '69 Mustang every year, however, and that just wouldn't work. 

Of course, every 5 years she disappears over the winter for a re-fresh...

I think our original poster has many options here, he just needs to determine how much $$$ he has and how hardcore he desires to be.

[Brad Johnson]

Try some huge Mickey Thompsons attached to a narrowed Ford 9" rear end, with spools in the pumpkin.  "Chirp, chirp, chirp, chirp" on every corner.

[/size]

A little speed and a light enough ride will turn that "chirp, chirp, chirp" will turn into "hop, hop, hop...".  Guaranteed to get your attention if you aren't expecting it. 

Brad