I found one (NIB) that can be put in my diff. Torsen automatically removes power from the slipping wheel and gives it to the tractive wheel, kind of like an intelligent Posi. What I'm concerned about is loss of fuel mileage. The thing looks like one of those 3-speed hubs that used to come on English bicycles, which were power-robbers (can still remember how strong I felt when I rode my first derailleured bike).

I know they're not the same, but both have lots of internal gears and clutches and so forth, and it makes me wonder what the price of better traction would be. Posi is supposed to cost more in worn tires and more fuel, but I never noticed a huge difference in mileage. I'd never seen a Torsen before, and have never seen anything on this board about them.

Any knowledge or stories of experience appreciated.

I put a Trac Tech Lok Rite or something like that in my 83 242T (now sold). There are two companies that make these auto locking rears that replace the spider gears. I forget the name of the other company. They cost $300 to $400. They are very similar to what Volvo put OEM in all RWD rears from 92 on, as I understand. The Volvo rear disengaged above 25 mph due to centrifugal force (these things are spring controlled). They drive normally, but provide power to the wheel with the most traction rather than the wheel with the least traction (like in an open rear). They disengage on turns. You want one for a Dana 30 rear. But look for the ads in the 4 x 4 and domestic V8 magazines and then call the companies to ask about a Volvo specific application. Rumor is that the Volvo version of the Dana 30 may be metric and most of these auto locking rears are SAE, if that makes a diference.

Not sure about fuel economy. I noticed no difference. I don't think much from that perspective. Spend the $400 plus installation costs on gas if you want to save money. Maybe you could salvage a rear from a later Volvo with the Volvo auto locking rear in it. Get the whole axle from the newest car possible, but make sure the speedo sensor (if applicable) matches yours and that the axle ratio is the same. Or go lower numerically if you want to save money (and lose performance), but adjust the speedo if necessary to the new ratio. You might gain some mpg or offset any loss, at some cost in acceleration.

Interesting. I was thinking that the mileage might really suffer, wasn't worried about saving a dime here and there. But I have thought about going with some kind of locking diff and a a higher ratio (lower number) on the rear. When I drive to Baltimore/DC lots of folks are doing 95 on 95, and this thing is screamin' above 80. The rear would be nice for the muddy roads and occasional snows/ice storms we have, plus it would make trips to the frozen North more enjoyable.

How hard is it to adjust the rear sensor to make the speedo read right? Or is it a matter of changing speedo's?

Depends on the speedo. The electronic ones are driven from the axle. There are two types of sensors. If you swap axles, get the right sensor. If mechanical, it is driven from the trans. The calibration is in the speedo. Swap in the right speedo. Since Volvo used a variety of ratios, you should be able to find what you want OEM. If you are doing something more radical, you will have to research more.

There are some devices for domestic cars that adjust electronic and or mechanical sender output to compensate for ratio changes. Check the ads in Muscle Mustangs and Fast Fords and call the advertisers for more info. Maybe one of these would work on a Volvo. Maybe.

Philip Bradley

Hi,

I've used a Quaiffe Torsen-type diff in a race car. I can't comment on fuel mileage difference other than to suggest that the difference should be minimal if any. The Torsen diff effectively runs "open" unless one wheel starts to slip and then it does its thing. Fuel economy should be the same as running on open diff.

I can comment on its effectiveness - I didn't think much of the diff. It didn't limit wheel spin coming out of corners all that much and my lap times increased. I went back to using a spool. It may be OK for street driving but if you're planning on using your car for track days, you may find it frustrating.

Regards,

Peter

I was thinking of having it there for regular street driving in nasty conditions (snow, ice). In your case it may have been that it reacted too slowly. I was thinking of it as an alternative to a posi, but perhaps a posi would be better after all. At least I could depend on it to get loose on every slippery corner, instead of wondering if it would....&^)

Thanks for the info,

Carl

I have a very tight PowrLok in my street car (a V8 945) and life is pretty exciting - aka fun - in the wet. I suspect for your uses, the Torsen would be better.

Peter

Check with offroad web sites. I believe they are used in four wheel drive applications. I thought there was not that much needed to make them work. I thought they used a worm gear which will not allow back torque?

Bill D.