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Gunna
13-04-2010, 06:59 AM
Hi All,

I've been hiding away in Jetski land but that will be over soon.

Just wondering if anyone in the Nova world has put in a Torque Bias Diff into a 1966 swing axle box?

And how does it handle?

I'm setting up for some 1/8th and quarter mile racing and wanted some input of what to look out for when it comes to handling. Don't want to learn the lesson after the incident.

letterman7
13-04-2010, 11:02 AM
Is that the same basic unit as a Quaife? There are several guys here in the States that run Quaife units on their race Bugs and dune buggies, but I don't think they take them on the street. IIRC, the differential is too "stiff" for street use and going around corners makes for an interesting experience. I'll see if I can find some of the threads concerning them when I get a moment.

Spacenut
13-04-2010, 12:41 PM
I've heard similar stories about Quaife diffs in the UK. They all use clutch packs, which remain engaged up to a certain torque, and then slip suddenly and lock up again. This leads to a lot of banging as you go round a corner, and obviously increases the effect of understeer. I've driven LSD-equipped Mopars with both clutch packs and cone clutch diffs and the latter are much more suitable for street use. Unfortunately I do not believe there are any cone clutch (or softer-engagement) LSDs available. Bottom line is the clutch pack is for racing use (or I guess spirited off-road driving in the case of buggies and sand rails), not for the street.

My worry with a swing-axle 'box is that with the camber angles changing with suspension movement, grip will be lost. Then you add the LSD with its snatching clutch pack and you could in for some real fun on a wet roundabout. Clearly for 1/4 mile work you want both rear tyres to hook up cleanly and with swing axles that means reducing suspension movement to a minimum. This is of course the complete opposite to the normal dragsters which advocate softening the rear suspension. That doesn't mean running with rock-hard tyre pressures though :D

Once you have both tyres hooking up, then the LSD comes into its own, distributing the torque optimally to whichever tyre has the most grip. The ultimate extreme is of course a locked diff (Detroit Locker, etc.), which has no slip at all - you just accept monsterous axle hop when negotiating corners. I've seen some street used cars with locked diffs, and ladder bar suspension (allows no body roll), but these are optimised for one thing and are very uncomfortable to drive.

If it was my money I would invest in an IRS back end first, with properly rated coil helper springs to limit suspension travel and add progressive roll stiffness. That will improve the handling on the street as well as improving performance on the strip. Then you will be able to see if an LSD is worth the extra expense.

Have fun!

Lauren

Gunna
13-04-2010, 02:29 PM
Is that the same basic unit as a Quaife? There are several guys here in the States that run Quaife units on their race Bugs and dune buggies, but I don't think they take them on the street. IIRC, the differential is too "stiff" for street use and going around corners makes for an interesting experience. I'll see if I can find some of the threads concerning them when I get a moment.

Thanks Letterman,
Yes, this is similar to the Quaife TBD (not a clutch type LSD) but due to waiting for the last 50 days for Quaife to have one in stock and someone mentioning the GT is another small level higher in quality, I went with them. It was here in 5 days from order.
I've heard and seen how locked diffs act on the street in an Izusu Bellett (small 4 cylinder car) and it wasn't nice in corners. But wicked around dirt track hill climbs.
Any threads links would be nice if you can spare the time.
Dean

Gunna
13-04-2010, 02:50 PM
As usual Spacenut your very helpful.
It just took a few hours to get my head up to speed. LOL.
Firstly this is the Torque Bias Differential (which maybe called a cone diff, not sure on terminologies) as oppossed to the clutch type diffs which seem more popular.
I went this way specifically for the 1/4 mile racing, but with the ability to drive street to get to the track and back.
I understand your prefferance to IRS setup but the last thing on the to do list is to change the suspension from swingarm to IRS. I just don't want to go down that track due to skill and time limitations. So I'm kinda married to the swingarm (for better or for worse). The other thing about dragging the IRS is that the CV joints on the bigger cars tend to chew out on a regular basis. I know the CV's are relatively inexpensive but again "time" is a limitation.
The rear end will have to be "setup" and no doubt this'll be a little time consuming but once set I will hopefully be able to forget. I'm looking for a balance of street and drag but with a bias to the race side of things. Wanta have my cake and eat it too.
The other thing I have planned to go in is the support bars for the frame horns (see pics). I don't want to have to do this part again. Bending the frame horns to the chassis would be painful. This will obviously give greater stiffness to the back end as well.
But the minor details of how this diff "locks up" when driven in street and drag is what I'm trying to find out. I'm too likely to treat it the wrong way and end up in the sidewall on the track or in a drain down the road.
I do a lot of reading but not much understanding. Occasionaly the light does come on in a "arrh-har" moment.
Thanks again for your input,
Dean
PS These pics from the supplier, not of the Eureka.

I've heard similar stories about Quaife diffs in the UK. They all use clutch packs, which remain engaged up to a certain torque, and then slip suddenly and lock up again. This leads to a lot of banging as you go round a corner, and obviously increases the effect of understeer. I've driven LSD-equipped Mopars with both clutch packs and cone clutch diffs and the latter are much more suitable for street use. Unfortunately I do not believe there are any cone clutch (or softer-engagement) LSDs available. Bottom line is the clutch pack is for racing use (or I guess spirited off-road driving in the case of buggies and sand rails), not for the street.

My worry with a swing-axle 'box is that with the camber angles changing with suspension movement, grip will be lost. Then you add the LSD with its snatching clutch pack and you could in for some real fun on a wet roundabout. Clearly for 1/4 mile work you want both rear tyres to hook up cleanly and with swing axles that means reducing suspension movement to a minimum. This is of course the complete opposite to the normal dragsters which advocate softening the rear suspension. That doesn't mean running with rock-hard tyre pressures though :D

Once you have both tyres hooking up, then the LSD comes into its own, distributing the torque optimally to whichever tyre has the most grip. The ultimate extreme is of course a locked diff (Detroit Locker, etc.), which has no slip at all - you just accept monsterous axle hop when negotiating corners. I've seen some street used cars with locked diffs, and ladder bar suspension (allows no body roll), but these are optimised for one thing and are very uncomfortable to drive.

If it was my money I would invest in an IRS back end first, with properly rated coil helper springs to limit suspension travel and add progressive roll stiffness. That will improve the handling on the street as well as improving performance on the strip. Then you will be able to see if an LSD is worth the extra expense.

Have fun!

Lauren

Spacenut
13-04-2010, 08:28 PM
OK, a fully triangulated framework tying together the frame horns and shock towers is good. If you are determined to stay with swing axles then limit the jacking effect by fitting a Z-bar, or a camber compensator (I prefer the Z-bar as it works in both bump and rebound). There is no reason why you cannot stiffen the rear spring rates with coilover shocks with properly rated springs. This will help to limit the body roll in corners, and help to increase weight transfer under acceleration, which is what you need to get those tyres to hook up. It all counts for nothing if the camber change reduces the contact patch. Nova Nigel used 2.25" ID coil springs to assist his torsion bars. I calculated 90 lb/in would provide the optimum suspension frequency, so you could start from there and see what's what. I can't remember the length of the spring but if you arrange it so that the torsion bars take the bulk of the static load and the springs work in compression you should be onto a winner!

I'd still wait until you have tried all of the above before investing in an LSD, but that's up to you. Sorry, its not an LSD, although I can't find a clear explanation of how it works - its gear-driven, and when a wheel is unloaded, it acts like an open diff. So no snatching, and no additional understeer. I'm guessing its like my roller bicycle brakes, gear generated friction. I still feel that the other modifications descibed above will be more effective...

Lauren

Gunna
13-04-2010, 09:19 PM
OK, a fully triangulated framework tying together the frame horns and shock towers is good. If you are determined to stay with swing axles then limit the jacking effect by fitting a Z-bar, or a camber compensator (I prefer the Z-bar as it works in both bump and rebound). There is no reason why you cannot stiffen the rear spring rates with coilover shocks with properly rated springs. This will help to limit the body roll in corners, and help to increase weight transfer under acceleration, which is what you need to get those tyres to hook up. It all counts for nothing if the camber change reduces the contact patch. Nova Nigel used 2.25" ID coil springs to assist his torsion bars. I calculated 90 lb/in would provide the optimum suspension frequency, so you could start from there and see what's what. I can't remember the length of the spring but if you arrange it so that the torsion bars take the bulk of the static load and the springs work in compression you should be onto a winner!

I'd still wait until you have tried all of the above before investing in an LSD, but that's up to you. Sorry, its not an LSD, although I can't find a clear explanation of how it works - its gear-driven, and when a wheel is unloaded, it acts like an open diff. So no snatching, and no additional understeer. I'm guessing its like my roller bicycle brakes, gear generated friction. I still feel that the other modifications descibed above will be more effective...

Lauren

Thanks Lauren,
I have a camber campensator (see pic) which is planned to go on as well. But I'll have to look up what a Z-bar is.
The coil over shocks is a brillant idea. Thanks again. I was wondering how they tune the rear end. That was one of those aah-haa moments.
I have coils overs for the front due to the previous owner(s) having the suspension way to low. Looked good but very impractical.

I've already invested in the GT diff upon advice from the gearbox rebuilder.

I think I now "get" what you mean by how the diff will handle. But I'll end up re-reading the post 6 times before it sinks in.

I've also added a pic of the empi heavy duty axle(s) which will be going in. I read somewere that the swayaway units were snapping under load with the second batch that they made. So if anyone is looking into axles, beware.

Dean