NewB Questions about gears

[Johnny Wayne]

I just bought a 90 Bronco. It is supposed to have 4.10 gears front and back with Eaton lockers both front and back also. How can I tell what gears are in them and the lockers also.

 

[Justshootme84]

Jack up both tires on an axle. Spin one tire two times around and count how many turns the driveshaft makes. If the ds turns a little more than 8 times, you have 4.10 gears. The reason to do two turns instead of one is to allow for the spider gears to turn each side, that's if the axle still has spider gears in use.

IF both tires turn the same direction, you have L/S or a locker. MAy have to activate the E-locker to check it's function since it's selectable and not always on. With it off, the tires will spin in opposite directions if it acts like an open or unlocked differential.

 

[Broncobill78]

I just bought a 90 Bronco. It is supposed to have 4.10 gears front and back with Eaton lockers both front and back also. How can I tell what gears are in them and the lockers also.

Well, at this point the easiest way will be to jack up the rear of the truck so that both tires are off the ground. Place it on jackstands just to be safe. Put a small piece of masking tape on the end of the driveshaft close to the rear yoke, put the tape on there running the same direction as the driveshaft (what I mean is don't wrap the tape *around* the shaft, just put a 1" or 2" piece on there running front to back so you have a mark on the shaft) or use a heavy-duty black magic marker to do the same thing. What you're doing is just marking a referance point on the shaft so you have something you can see & follow. With the driveshaft marked do the same with one of the tires, place a piece of tape running from the tread towards the center of the rim. With both the shaft & tire marked start slowly spinning the tire & watching both markers. For ever one revolution of the tire you should see the driveshaft make 4 complete revolitions and just a part of a 5th before the mark on the tire comes back to it's original position. If you get 4 complete revolutiona and just a little bit of a 5th then you've got your 4.11's. If the driveshaft only makes 3 and a half revolutions then you have stock 3.50 gears. For 3.73's it'll make 3 complete revolutions & about 75% of a 4th. 4.56's will be 4 and a half complete revolutions, you get the idea.

Also watch the other tire while you do this. If it rotates in the same direction you have your locker, if it rotates in the opposite direction then you have a standard open differential.

 

[Johnny Wayne]

Great, thanks for the help!