The Dodge Challenger Message Board

When I got my car I was told it had a 3.55 sure grip rearend. The pig is a 741 casting. I put the car up on jack stand today to do the tire/driveshaft trick to figure out the gear ratio. First off only one of the tires moved, I thought both did if it was a sure grip, second the driveshaft only turned 2 times for one turn of the tire. What does this mean?

If the other wheel had rotated easily in the opposite direction then you would not have a sure-grip.

Because it did not move at all you need to investigate further.

If the brake is holding on a bit on that wheel it will cause this no matter which type of rear end you have. So make sure the other wheel can move easily.

If it does move by hand it means the sure grip is a worn so it is only kind or half working?

Unless the other wheel moves freely in the same direction as the one you are turning, counting the number of turns will not work.

Try doing it the other way.

Put the car in neutral and turn the driveshaft (use a screwdriver in the UJ or something) and see if the wheels will both move the same now. Then count how many times you have to spin the shaft to get one exact revolution of the wheels.

Thanks dave, I tried it the other way and both wheels turned when I turned the driver shaft, took 4 turns this this for 1 wheel turn. Both wheels feel tight when you turn them so im thinking the e-brake might be too tight. I was hoping to have this figured our by carlisle so I can get a different spedo gear while there. My spedo reads 10mph too fast and i have right gear assuming the rearend is 3.55.

If both wheels turned the same way and you were accurate with your counting then it looks like you have a 4.10:1 rear gear.