I apologize. I'm sure this question is very elementary to many of you? But, at the risk of sounding very stupid...what exactly is an open differential? What are the pros/cons of it? 
Open diff?
- Thread starter CarFreakGT
- Start date
mfp4073
Founding Member
open means that the rear wheels are not "locked" together. Meaning if one spins the other goes nowhere. Great for daily driver street cars....because when you go around a corner the outside wheel has to go further than the inside wheel. An open rear lets this happen nice and smooth. Posi (a chevy term), traction loc, detroit lockers, and such are made to make both rear wheels go forward no matter what. For drag racing this is good. The traction loc uses a clutch pac to make this happen and some slippage is possible (meaning corners are not as bad...but wet roads are hell) . The detroit locker is a a mechanical setup and much rougher to deal with.
Thanks, mfp! Good explanation. So, it sounds like for a daily driver and maybe future road course car, an open diff is desirable.
fvike
Member
There is a 3rd option, the True-Trac. It is a torque sensing differensial (torsen type) that transfer power to the wheel with the most resistance. If you are driving straight ahead, you have equal resistance on both weels, and it is locked. When comming to a turn, the outer wheel has more resistance, and get most of the power, and the inner wheel is opened up. The True-Trac is without clutches and springs (gear driven), so it wont wear out, and should be quiet.
dennis112
15 Year Member
mfp4073
Founding Member
CarFreakGT said:
as far as road course setups and what is good or not you need to talk to some of the other classic guys who have been doing it for awhile.
BullittStangV8
Founding Member
Open diffs arn't always the best choice for road race cars. That would mean that if you are in a turn, and one wheel starts to spin, you now have NO power going to the ground. (your classic one-wheel peel action.) In this case, an example would be how you could be going around a turn, and the inside wheel lets say starts to slip. You couldnt get any acceleration out of the car until taht wheel regains grip, since the other wheel is just going along for the ride and providing no power. IMO a better option is a dif. that allows you do direct powe the wheel that has grip. That way you can still drive yourself out of the turn.
Another option is the spool. This permanantly locks the rear axles together. Great for drag racing, no good for road racing or a street driven car (meaning daily driver). In this case, the rear tires cannot have differing speeds. (I would think this would lead to spins in race car set ups.)
Another option is the spool. This permanantly locks the rear axles together. Great for drag racing, no good for road racing or a street driven car (meaning daily driver). In this case, the rear tires cannot have differing speeds. (I would think this would lead to spins in race car set ups.)
red65
Member
+1to BullitStang's response -- an open diff is no good for a road course unless you're driving a Miata 
- or something else where wheel spin won't be an issue. You'll find that this won't be the case for your car unless you pull three or four spark plug wires. A Traction Loc differential is a fine place to start - there are lots of fancier alternatives once you start getting your car sorted out
- or something else where wheel spin won't be an issue. You'll find that this won't be the case for your car unless you pull three or four spark plug wires. A Traction Loc differential is a fine place to start - there are lots of fancier alternatives once you start getting your car sorted outA posi and a detroit locker do far from the same thing. A posi doesnt give you full lock, hence the term "limited slip" even tho pretty much anything can fall into that category. A detroit locker, when locked acts exactly like a spool, only difference is when the power is off, it acts like an open diff. Posi's usually use clutch plates and they dont give full lock up like a detroit or spool.
And spools are awesome for road racing. The predictability of a spool is the best. With a detroit or posi, you never know when its going to "lock" and that can send you for a ride. They are the hardest on drivetrain because somethings got to slip, especially with big sticky tires. You dont even notice it at speed tho, just those tight u turns.
valley82
Member
Every pickup truck I've ever owned has had limited-slip (ford's term) rear ends. I don't know how it compares to the rest of the rearends but I can tell you that it does make the truck do a two wheel burnout, and as for daily driving - no problem. I can tell you on an icy road if you stomp on it the truck gets pretty sideways because of both tires spinning.
BullittStangV8
Founding Member
Spools's are dificualt in some race cars tho, as they drastically affect that balance of the car (understeer vs. oversteer). I agree that they could possibly help you reach the limits of tire break out in a more linear manor, however throwing a spool in a car that had a limited slip/open diff, and not adjusting the suspension accordingly to balance the car out again...could make for a poor handling car.
Personally, I like the stock dif. set up in my 01 mustang. The only issue is that the clutch packs wear out. Now, when I go around tight turns on the auto x and get on the gas, I get one wheel peels because the clutch packs arnt able to keep enough pressure.
Ill be going with a spool in the 65, as the car is a drag set up car. For a street car, that wont see drags, go another route. For a race car, I still lean away from a spool.
Personally, I like the stock dif. set up in my 01 mustang. The only issue is that the clutch packs wear out. Now, when I go around tight turns on the auto x and get on the gas, I get one wheel peels because the clutch packs arnt able to keep enough pressure.
Ill be going with a spool in the 65, as the car is a drag set up car. For a street car, that wont see drags, go another route. For a race car, I still lean away from a spool.
krash kendall
Active Member
I have a minispool in my car as it was the only affordable option I had at the time (28 bucks vs. hundreds) and I could get one in my hands that day. The reason I had to do this was a broken cross shaft resulting in blown spider gears. The minispool fits inside the diff and connects the axles together.
Going in a straight line is great, but in the corners it goes from understeering (due to fighting the rear because all it really wants to do is go straight) to suddenly oversteering and rolling the body. Coming out of the corner is easy, again because it wants to go straight. Parking lot navigation is a real pain as well.
Spools are really hard on tires no ifs, ands, or buts about it. I just bought a new pair of rear tires and am currently looking for a decent open differential to help them last.
Having driven with it for a year or so now, I would have to say it is totally inapropriate for a street car.
Going in a straight line is great, but in the corners it goes from understeering (due to fighting the rear because all it really wants to do is go straight) to suddenly oversteering and rolling the body. Coming out of the corner is easy, again because it wants to go straight. Parking lot navigation is a real pain as well.
Spools are really hard on tires no ifs, ands, or buts about it. I just bought a new pair of rear tires and am currently looking for a decent open differential to help them last.
Having driven with it for a year or so now, I would have to say it is totally inapropriate for a street car.
development1 said:
Do you know if this system is fairly quiet? One knock that I heard about Richmond Gear stuff in the past is that it's loud. Anyone have any idea?
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