Quaife limited slip

Lets say you have a rear end thats not really built to handle the power you plan on running thru it. In this case size matters. Could be anything, such as a Ford 7.5 in a Mustang that really needs an 8.8. Will installing a Quaife limited slip into the rear end make things better or worse for the longevity of the rear end gears? I'll argue that one wheel spinning every time you over power the rear end relieves the stress on the gears, as opposed to the limited slip biasing all that power and keeping the force on the gears. Does this make sense, or am I the idiot that just called a guy out for spending a couple of Gs on billet axles and a Quaife in the name of rear axle longevity, when what he really needed was a different rear axle???

Is this for a drag racing application, road racing, autocross, or general hooning?

For drag racing I think it won't really affect it one way or the other. When too much torque goes through that rear end, snap it will go, especially now that he's upgraded his axles.

A quaife can reduce things like wheelhop that make sudden and catastrophic diff failure more likely.

I do think he's wrong in thinking that it will allow him to get away with an inadequate diff for the application though.

Street use and occasional track days with sticky tires. I'd say he would be OK if it was just going to be driven on the street, but tracking a car on a road course with sticky tires, is a whole other level of brutality.

Is the common point of failure in your axle example, the axles, the carrier, the bearings, or the gear set?

If it's an axle problem, the new axles may solve it and the new differential won't matter.

If it's a carrier problem, the new differential may solve it.

If it's a gearset or bearing problem, he's put more load on those parts with the Quaife. That might bite him in the rear.

In reply to Toyman01:

or its the issue like the Dana 35 where it was barely adequate at stock power levels and you are just as likely to break it on stock power with stock sized tires.

But imo as long as tires lose traction before the axle breaks i think it should be fine. Easiest way to break an axle at least in the 4x4 world is to add a pair of TSL Boggers to a stock axle. You have too much traction which breaks parts, well actually its the sudden gain of traction in a low traction situation that breaks stuff.

Never seen a broken axle or even a damaged one in this application. Seen broken wheel studs, bearing failures and gear sets that wipe themselves out. Pulled many apart to see chipped gears and lots with massive wear grooves machined into the gear teeth. I'm guessing most of the damage I have seen is done once the pinion bearings wear a little and the gear mesh isn't optimal.

Quaife ain't cheap

Breaking traction (or wheel hop) will break things much, much faster than keeping traction with a bunch of power. The shock load that occurs when you re-gain traction is what typically breaks things (especially when off-road).

If it's not seeing clutch dumps off the line, the LSD will probably help a bit (certainly won't hurt). Especially considering that 1 wheel peels can chew up spider gears in some diffs.

You're probably correct but if you have to ask if you should have called someone an idiot, I'd say you probably shouldn't have. :)

tr8todd wrote: Never seen a broken axle or even a damaged one in this application. Seen broken wheel studs, bearing failures and gear sets that wipe themselves out. Pulled many apart to see chipped gears and lots with massive wear grooves machined into the gear teeth. I'm guessing most of the damage I have seen is done once the pinion bearings wear a little and the gear mesh isn't optimal.

Then the axles were probably a waste of money and the added traction of the Quaife is going to exacerbate the common problems. Gear and bearing failures aren't easily solved. That's a design issue. Usually not enough bearing, or too short pinion shaft and snout. It could also be flexing the center of the axle. The second is difficult to solve. The first can be helped by frequent bearing changes. He would probably be money ahead to have spent the $$$ on a better axle.

Is he known for breaking stuff? If so, expensive lessons are the most memorable. If he has any mechanical empathy, it may hold up just fine.

Would be better to know the exact rear end we're talking about here. We might know common failures and fixes that might be better/cheaper than a Quaife.

I was asking if I was the idiot, so lets get that clear. Its a stock TR7/TR8 5 speed axle. Didn't mention it before because not many of you on here have any experience with them. Don't want to brag, but I'm the go to guy when it comes to breaking things related to TR8s. There's a reason why most of the hipo TR8 builds are running either Ford 8.8s or Dana 44s. Same can be said for the MGBV8 builds.

What part are you breaking? The more details you give out the better (possibly) the answers. Why not just swap in a 9" Ford rear and be done with it?

Chas_H wrote: Why not just swap in a 9" Ford rear and be done with it?

Because they're heavy, so there's lots of downsides if you don't need that much strength.

You do bring up a good point. I once did consider a Quaife for the exact reasons you bring up. The Saab 900 Transaxle is not exactly a strong unit when dealing with a normally aspirated 2.0, the turbos tend to tear them up much faster. In my case, they wipe out the gear sets from the power transfer causing warpage in the case. I was thinking that a Quaife would keep that power from rapidly transferring from one side to the other and back again.

Not that I am going to race my 900, but it would be nice not to have to worry about destroying my nice newly rebuilt Transaxle

In reply to rslifkin:

Not that heavy if an aluminum center section is used. Leaf springs and solid axle is heavy no matter what rear. But something else might be wrong, depending on what keeps breaking.