Rear End

[digithead]

So my 1973 I just got has 351C and 4 Speed, marti report says code 2 for 2.75 rear end? The PO did not do restore. So it may or not be. If its a 2,75 what do I have a dog out the hole but 120MPH top end? I guess from searching FORUM you may be able to tell me RPM vs. MPH and I would be able to guessimate what I have? I've never pulled a rear end so I wouldnt know. Its still winter in NY so I have not put it on road for test yet. TIA.

 

[Jeff73Mach1]

Put car on jackstands, Place a chalk mark on the bottom of the driveshaft. Put car in neutral. Have someone turn a tire one full rotation while you count rotations of the driveshaft. 3 full rotations of the driveshaft to one rotation of the tire is a 3.0 gear.

 

[digithead]

Put car on jackstands, Place a chalk mark on the bottom of the driveshaft. Put car in neutral. Have someone turn a tire one full rotation while you count rotations of the driveshaft. 3 full rotations of the driveshaft to one rotation of the tire is a 3.0 gear.

Thanks, I love simple!!!

 

[turtle5353]

Yep, exactly what Jeff said. That's the easiest way to get a rough idea what you have.

 

[73pony]

Mine currently has a 2.75 open. It is pretty doggy off the line. My 94 Dakota has more get up and go. But what is nice is the RPM when out on the highway. Smooth sailing. I am doing a T-5 swap currently to ditch the FMX that is leaking and starting to slip so I will see how that does before I make a final decision on what to put in the rear. You do have the 4 speed and I think 1st gear on those was pretty low so it might not be too bad in your case.

 

[will e]

Put car on jackstands, Place a chalk mark on the bottom of the driveshaft. Put car in neutral. Have someone turn a tire one full rotation while you count rotations of the driveshaft. 3 full rotations of the driveshaft to one rotation of the tire is a 3.0 gear.

If it is an open diff don't ya want someone holding the other tire stationary? I always forget how this works.

 

[midlife]

Put car on jackstands, Place a chalk mark on the bottom of the driveshaft. Put car in neutral. Have someone turn a tire one full rotation while you count rotations of the driveshaft. 3 full rotations of the driveshaft to one rotation of the tire is a 3.0 gear.

If it is an open diff don't ya want someone holding the other tire stationary? I always forget how this works.

No. If you move the driveshaft to move the tire, then either axle may move. But moving one tire moves the driveshaft directly.