gear question

[e_parise]

The P.O. of my car said he re-geared my cruiser but was unsure of the ratio. Is there an easy way of finding the ratio without pulling it all apart?

 

[Corbet]

Compare the rotation of your drive shaft to the rotation of the wheel/tire.

 

[Grench]

Are you on Stock 31" tires? Just noticed his sig line... 35s.

If you had stock 31" tires...
Drive down the road. Check speed with a GPS until you are going 60MPH per GPS. Check the speedometer. Is it right at 60MPH? If yes, you
are not regeared. (Or you have a speedometer correction system that you don't know about.)

With 35s, do the test and then post your RPM at 60MPH here.

If you do not have access to a GPS, set the cruise on the highway and have the passenger time how long it takes to go 1 mile on flat terrain. At 60MPH it should be 60 seconds.

Note the RPM and transmission gear (OD or D) and tire size. Post it here.

There are also threads with gearing/speed/RPM tables in them if you look hard enough.

 

[LARRYG36]

A Chace Car with a Cell Phone works too.

 

[Atoyot1031]

You can also do it with a helicopter.

But seriously, the driveshaft/wheel rotation is the easiest IMHO...

 

[96r50]

You can also do it with a helicopter.

But seriously, the driveshaft/wheel rotation is the easiest IMHO...

Agreed, just disconnect your DS from the 3rd member, use some chalk/paint/sharpie/blood to mark a spot to use for reference, then count the rotations of the tire/hub.

 

[e_parise]

60 mph at 2100 rpm

 

[Ting]

Did you buy a new truck?

 

[medtro]

Agreed, just disconnect your DS from the 3rd member, use some chalk/paint/sharpie/blood to mark a spot to use for reference, then count the rotations of the tire/hub.

What is the purpose of disconnecting the DS?

 

[Grench]

To count the revolutions of the tires to compare to the count of the revolutions on the drive line.

 

[Corbet]

60 mph at 2100 rpm

Is that 60 MPH on your speedo or off a GPS unit.

If its off your speedo it will not tell us anything. Your speedo reads at the T-case so changing the gearing in the axles will have no effect on the relationship of actual speed and your engine RPM. Honestly I don't think this is the best method anyway. My tach reads off by as much as 300 RPM verse an OBD display anyway.

Your best bet if no access to GPS is to put it on jack stands and pull the rear driveshaft to manually rotate the rear wheels to compare the rotations of the axle verse drive line.

 

[GXO]

removing the DS makes turning the axle easier at the pinion...you can also do it with N/N in tranny and t-case.

 

[Corbet]

removing the DS makes turning the axle easier at the pinion...you can also do it with N/N in tranny and t-case.

But please make sure your vehicle will not roll away when your under it.

 

[Letsgomoreplaces]

to be sure

To be sure, just raise ONE rear wheel, put t-case in neutral. Rotate the wheel TWO FULL revolutions, and count the number of driveshaft revolutions.

 

[CJF]

To be sure, just raise ONE rear wheel, put t-case in neutral. Rotate the wheel TWO FULL revolutions, and count the number of driveshaft revolutions.

There ya go. That's by far the simplest method, no?

 

[Grench]

If you're concerned that the PO may have put the wrong gears in one end or the other, do it front & rear to compare.


Oh, and BE SURE TO CHOCK THE WHEELS!

With the transfer in Neutral and the rear lifted the truck will roll. Never put your life on the parking brake or the park pawl holding either.

YMMV.

 

[medtro]

removing the DS makes turning the axle easier at the pinion...you can also do it with N/N in tranny and t-case.

Why not turn the wheel? It is easier to turn the wheel.