What does these numbers before the differentials mean? (e.g. 3.55..., 4.1...)

[» p i x x e l «]

There are always these numbers, what do they say?
I have, for example, a "3.55 Limited Slip Rear Differential"
and a "4.10 Limited Slip Differential".
Whats the difference?

(Also that's my first post here so maybe I posted that in the wrong place, sorry :D)

[Apolepth]

"Axel ratio is the number of revolutions the driveshaft make compared to the rear axle. In your examples the drive shaft would turn 3.55 or 3.73 times for each rev of the rear tires. Finally the lower the number the less engine revolutions needed for a given speed, better gas mileage. Higher the number better pulling power. That is why the HD come with 4.10.

Limited slip describes the differential. When you go around a turn the tires travel at different speeds because the outside tire has further to travel. The differential allows the tires to travel at the different speeds. In a open diff if you lose traction to the rear wheels only one wheel will spin. In a limited slip if you lose traction both wheels will spin."

"Very, very simply - a higher number will give you more low end pulling power (better acceleration), and lower top speed, and, theoretically, less fuel mileage. Limited slip prevents one wheel from turning faster than the other (e.g. - spinning in mud or snow), causing the vehicle to lose traction and turn to one side."

It was faster to google you silly pixxel :P

[» p i x x e l «]

Oh okay. Yeah I knew everything except the number :D And I didn't know what I even had to google... But thanks! So I also had over torque risk problems with my 750hp Nos Roamer, should I rather take the 4.10 diff for that?

[Apolepth]

Probably

[Los.Injurus.Bob.Blunderton]

Originally posted by » p i x x e l «:

Oh okay. Yeah I knew everything except the number :D And I didn't know what I even had to google... But thanks! So I also had over torque risk problems with my 750hp Nos Roamer, should I rather take the 4.10 diff for that?

You can sometimes over-rev with the throttle down going over hill crests or bumps that separate your vehicle's tires from the pavement/ground. Let off the throttle when going airborne. Ease up a little when it's about to shift if it's an automatic shift or in arcade, so it doesn't rev so high. If you're in the final gear the rev limiter should kick in to not let you over-rev when going high speed, but don't rev into the red zone for longer than a split second, or you'll mangle the pushrods common to 70s-80s-90s engines especially ones mimicking the Domestic vehicle manufacturers. Pushrod engines are reliable but they don't like high-revs.

The person posting about the diff's posted solid info, yes it's correct.

[» p i x x e l «]

But I had over-torque problems not over-rev problems...