92 4x4 Axle / Gear Ratios

[sumncguy]

During the front end rebuild I did not do the axles because I wasnt sure of the Gear Ratio.
So that I could find out about the Gear Ratio, I took the truck to a 4x4 mechanic and had him do the rear end service.
I asked if he could check the ratio and let me know what it is.
He told me I had 4.09 gears back there. Does that actually mean 4.10s ?

Also; please correct me if Im wrong, I understand that I must have the same gears up front as I have in the back.

I am looking into the 4x4 right now. The transfer case and the drivers side wheel is engaging but not the passenger side. I do have a new hub in hand which I will test tomorrow.
Jack up the front of the truck, put the new Hub on, turn the wheel to make sure the axle spins.


All of this brings me to the real questions which are ..

1. Which model front axles are interchangeable. I'm guessing for my truck 89-92. Are there later models that are compatible ?
2. I contacted Dana directly who advised that they no longer make front axles for my truck. Does this mean it is strickly a junk yard part or is there an aftermarket available?
3. The big question is .. what does the gear ratio have to do with the Axle ?

Pardon my ignorance with this stuff .. never dug into it before.

Thanks for the help !

 

[ericbphoto]

4.09 would be 4.10 for our axles. This number is the ratio between the number of teeth on the ring gear and the number of teeth on the pinion gear inside the differential. That is the big chunky part near the center of the axle. A normal "open" differential allows the wheels to turn at different speeds when you go around corners because the wheel on the outside of the turn has more distance to travel than the wheel on the inside of the turn. The drive shaft coming from the transmission, or in this case the transfer case, connects to a flange at the differential. That flange is mounted to the pinion gear shaft. The pinion gear turns the ring gear (larger gear with more teeth) which, in turn transmits motion and power to the axle shafts going to the wheels. That is what the gear ratio had to do with your axles.

Your axles should be identified in two places. One is on the axles themselves. The rear on your truck should have a metal tag attached to one of the cover bolts. I believe your front axle may have a sticker somewhere or it may have worn away. The other place for this info is on the sticker on the driver door jamb. There will be an axle code number. We have some great articles about axles in the tech section of this site. I'll link to one in a minute. Your front axle will be either a Dana 35, Dana 28 or a hybrid mix of the two. Your rear will be either a Ford 7.5" or Ford 8.8" axle. That number comes from the diameter of the ring gear.

Your problem with the front not engaging could be as simple as the hub needing to be disassembled, cleaned, lubricated and reassembled.

Axles and gears tech page

Axle tags and door codes

 

[sumncguy]

Thanks I'm going to find out this morning if the tape wheel spin and drive shaft turn count works up front and look for label info.

Then put the new hubs on and test 4x4.

 

[4x4junkie]

The Dana35 (not the hybrid) was the only front axle put under '92 4x4s (the D28/35 hybrid came forth for 1993, the D28 of old went away midway thru the 1990 models).


Something to be aware of...
4.10:1 axles were not a factory option on 1992 4.0L 4x4 trucks, so certainly you may want to dig a little deeper on that to verify if maybe a previous owner might've swapped them (1992 4.0L 4x4s had 3.73:1, 3.55:1, and 3:27:1 as available ratios).

Good way to check without taking anything apart is to mark the rear driveshaft, jack up one rear wheel, and then rotate the wheel exactly TWO complete revolutions while counting the number of turns the driveshaft rotates.*
3¾ turns of the driveshaft = 3.73:1, slightly more than 4 rotations = 4.10:1, and so on.

*Note that this procedure only works with open or limited slip differentials (all factory stock differentials). If you have an aftermarket mechanical locker (Detroit, Lock-Right, etc.), then both rear wheels need to be jacked up and you rotate both wheels together exactly ONE rotation while counting the driveshaft rotations.