I can't remember if I posted in this thread, but if not, I'll at a 'me too' to the growing list of people who think a welded diff is a really bad idea on public roads. Hell I'd probably be against them, even for just the changes they make to corner entry and mid corner handling when everything is 'optimal' environmentally. But in the wet, it goes from 'far from ideal' to 'outright dangerous to you and everyone around you'

Spring tension isn't the whole picture with a SLL. Much of it is linked to how tight the tolerances are inside the unit. I got mine down to about .002 And although it'd done a turn or three it beats an open diff anyday.

jmac, i read all the previous pages of this thread, i don't remember seeing your posting :)

kinda hope for your enlightenment :)

i run a locker in my golfcart and it just makes it a whole lot funner hahahh

As others have said, a spool or locked center is harder on axels, uni`s and gearboxes. On slow tight corners the inside wheel(less loaded) is trying to travel the same distance as the outside wheel. This causes the tire to kind of skip on the road causing masive backlash through the driveline.

Because the inside wheel is trying to travel the same distance as the outside during cornering, the car will generally understeer a fair bit until the steering input is opening up on corner exit.

On a race car, geting the power down early is very important and the understeer can be tuned out of the car to a point. Even cicuit cars with locked centers will never be as free into corners as a car with a limited slip.

On a road car, the first thing i would recomend is GOOD tires. Then if you still need more drive , go for a limited slip center..
Or work on the suspension.

locked diff is common in malaysia, as the drift scene is now on the rise. many of my friends locked their diff (mostly KE70 owners, not datsun). yes, the bushing on their ride tends to wear out faster. and dont mention about tyre wear, a new pair of tyres every two months!

I can confirm that Locked diffs do indeed break axles. I broke one today. Plus the spring loaded locker works better than I gave it credit for. With only one wheel drive, it lights up like nobodys business.

I've been running one for the last week or so, went for a pretty long burn today. The squealing/chirping is the most annoying part about it, second to that is the axle tramp that comes with it when the power is put down (hoping that's the right term).

Apart from that I do not think the turning ability of the car has been affected as much as I was led to believe.

The noise is annoying though, when the bitumen is hot (42 degrees celsius today here in Adelaide) the wheels make a right racket and attract alot of unwanted attention, you can see other drivers going round the round about looking your way.

But apart from that all I can honestly say is if you have a turbo engine or something with alot or torque on hand you would have to be very familiar with the car and engine because I can definitely feel how it would 'step out' with any sudden snap of the throttle.

Having said that the only consistent thing in this thread is the advice to be cautious. Once you do that you're pretty much okay.

Locked diff? Not too bad at all.

This trick won't work as well on datsuns, which are a very light car and can sometimes spin both rear wheels on takeoff, but it's worth a try anyway.

Over the years the right rear wheel is 'lifted' by engine/driveline torque and the left rear is pushed down. We only really know about the right rear lifting as it tends to spin the right rear on a hard launch in a straight line. With years and years of this happening, the right rear springs will sag a bit more than the left rear (over an inch in some cases on other cars). So then it is 'double' as bad, not only is the wheel lifted on acceleration, but it's already starting from a place where it has less downforce.

SO what you can do is (absolute cheapest option) swap the left and right spring packs over. this isn't possible on all cars, and I haven't done it on a datsun 1200 personally, but I think it would work fine. Then the left rear is that inch or so 'higher' then you launch hard, and th right rear lifts, and they even out, so you can get a much harder launch, even with an open diff. Of course you still would get better results from a locker.

This wheel lift under power, well it might be an inch or so under launch in first gear, but obviously it will be far less as the engine has less 'leverage' in the higher gears. So for a circuit racer, once you leave the start line, you'll have slightly uneven cornering (it will corner a little differently left and right hand corners) from uneven corner weights. In this situation, what I'd personally do is to swap the springs side to side, but then use a thin lowering block (as long as possible to help prevent axle tramp) on just the right hand side (maybe half the difference between left and right rear ride height) and try it with a few mm change in thickness until you come up with the most consistent corner exits - so that left and right hand corner exits feel the same, or as close as possible to it.

That will get you about the best you can hope for with an open diff. Interestingly, as far as rear spring/ride heights go, I'd actually make a suggestion to do this even if you plan to fit an lsd or locked diff. Test it with the open diff, and play with rear ride height/preload until you get it as good as possible, and then fit the lsd or locked diff.

You'll also tend to find that if you have adjustable rear shocks, you can get a bit better corner exit (it will probably not 'feel' quicker, so you'd have to really check lap times or something) by softening the rebound damping rate on the rears. This would help prevent it lifting the inside rear during a hard corner (not that it is a huge issue with datsun 1200s, though it probably makes a difference on a ute) Of course you can only go so far with that adjustment before it affects mid corner and corner entry too much. Like everything in car modification, there isn't some 'magical' setting, it will always be a compromise of one area or many areas to come up with the setting that gets the best overall lap times (or performance or whatever).

Speaking of suspension settings, and open diffs. You may have heard of HQ racing. It's done here in Aus and I think in NZ too? It started well over 20 years ago or so, and it uses an early 70s 'family' sedan (the hq holden) with 202ci 6 cylinder (with very few modifications allowed, and a controlled spec camshaft and no head porting) and 3 speed manual. They must run an open diff too.

Well about 15 years ago (maybe more) one of the car magazines did an article where they took a bunch of older musclecars, and some modern (for the 90s) day ones that were owner modified, and also a hq race car. They tested them on the 1/4mile drag racing, and also on a race track. Not surprisingly, the HQ racer, due to large car, small underpowered engine, open diff, only 3 gears etc, came dead last in the drag racing times. But when they went to the track, it was the fastest one there.

Now people could definitely argue that the driver was experienced as a hq race driver, and his car was well setup, and perhaps that some of the owners of the 'classic' musclecars didn't want to risk damaging their rare and priceless car that they spent a fortune on. You could say that about some of them, but not all surely.

But the point is that a well setup car, even with an open diff can get around a circuit reasonably quickly. The driver (I can't remember their name) was clearly 'good' but maybe not Michael Schumacher or Sir Jack Brabham good. But what they did have was the advantage of 'knowing' their car well, and knowing how to make the most of it.

On a related note, I used to speak with a mini racer who did hillclimbs mostly at the stage I knew him. Between him and his wife, they were about the fastest mini hillclimb competitors of the time, sometimes even being the quickest under 1600cc outright (which isn't a bad achievement with a mini a-series powerplant). Anyway, whilst clearly their car(s) were well setup as far as suspension goes, after it was setup properly, they didn't tinker with it, aside from checking it/maintenance and replacing anything in the suspension that was worn. And the bloke said straight out that he used to see some blokes adjusting this and that then trying to get it better, but it ended up they were spending all their time hoping that some magic new adjustment would transform the car, and they weren't spending enough time properly getting used to the current setup/capabilities. And he was certain that that was one of the big advantages he had. he'd gotten it 'dialled in' and then spent the timing mastering the driving side of it.

Point being, given the potential risks of running a locked diff in the street, well if I couldn't get an lsd for an affordable choice, I'd stick with an open diff, and focus on two things - setting up the car as good as possible (and that too can be done cheaply relatively speaking) without 'going nuts' on different settings day in day out and then practising/testing the car and learning its limits (obviously do this somewhere safe and legal)

A bloke at work here in NZ used to race an HQ. the class swallowed up lots of holden parts. They wound it up a few years back becuase they were getting too old, and it became unviable to have a field of them anymore.

On your analogy though JMac, the muscle cars woulda had v8's up front, making them turds in terms of handling. which is why a good hemi 6 will own a V8 falcon round a tight circuit. (Just ask Alan Moffat about how well the phase III did here in NZ)