Help Me With My Axle Code. I'm Lost!
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Postmaster
Joined: Aug 2005
Posts: 2,992
Likes: 2
From: Lancaster, MA
Help Me With My Axle Code. I'm Lost!
OK, so here's what's up. My door sticker says that I have a 3.73 open rear. I know for a fact that it is open, but I don't believe the 3.73 gear part. I'm pretty sure my speedometer is off by 5 MPH. When going 70 according to the speedometer (really 65) I'm running slightly over 2000 RPMs. When running 75 (really 70), I'm turning more towards 2350 RMPs. I checked my axle tag and all i came up with was this : 73 10.5 1C 29. I'm the second owner, so who knows what the previous owner did. The speedo being off and the truck being level leads me to believe that he origionally had 33s on it. So anyway, if anyone could help me out with that code, it'd be great. I've looked everywhere. Also, when new gears are installed does the shop put on a new tag usually?
Elder User
Joined: Sep 2006
Posts: 622
Likes: 0
From: Lincoln, NE
My calculator says a 4.10 and 33" gets you 2279 at 70. And if, in fact, they changed the gears, I dont think most shops have extra tags around. Those just come from Dana. More often than not they just pitch the old one and you go on with life without a tag.
Good excuse to change your diff fluid. Pop the screws loose and count the teeth while its open if you really want to know.
Good excuse to change your diff fluid. Pop the screws loose and count the teeth while its open if you really want to know.
Cargo Master
Joined: Aug 2005
Posts: 2,051
Likes: 1
From: Alberta, Canada
With the factory 265/75-16 tires and 3.73 gears it should be about 2140 at 75, 2000 at 70 and about 1860 at 65.
Changing to 4.10's would give you 2355 at 75, 2200 at 70 and 2040 at 65.
I don't have my spreadsheet programmed for the rolling diameter of standard size tires.
An easy way to check your gears is to jack up the axle and turn the wheels with the transmission in neutral. With a mark on the driveshafte count how many rotations it turns with one rotation of the axle. if it turns 3 and 3/4 rotations you have 3.73's, if it turns just over 4 then 4.10's, and so on. It can also be done with just one wheel jacked up, but the driveshaft rotations will be half of above.
Changing to 4.10's would give you 2355 at 75, 2200 at 70 and 2040 at 65.
I don't have my spreadsheet programmed for the rolling diameter of standard size tires.
An easy way to check your gears is to jack up the axle and turn the wheels with the transmission in neutral. With a mark on the driveshafte count how many rotations it turns with one rotation of the axle. if it turns 3 and 3/4 rotations you have 3.73's, if it turns just over 4 then 4.10's, and so on. It can also be done with just one wheel jacked up, but the driveshaft rotations will be half of above.
