Speedometer not calibrated after installing new axles

[Ed 05 TJ]

Hello everyone...

So I just installed new axles on my tj. Went from stock dana 30/35 with 307's to dana 44 with 4.88's on 35's.

Speedometer has not been calibrated yet. I hv 6 speed manual.

So I'm driving at about 30 mph but my speedometer shows about 50....when on fwy goin 55 it shows around 90. Does that mean that the ring and pinion/gears are actually turning as fast as speedometer?

If so, that would obviously damage the new gears right? I have not put in 500 miles yet.

Thank you in advance for your replies.

 

[Jamesval035]

I went from 373 to 488 and was 10mph off. Got this and fixed it.
https://www.quadratec.com/c/reference/jeep-speedometer-gear-tooth-chart
I don’t see you messing anything up with an axle swap

 

[CharlesHS]

According to the chart; you need to purchase the 39 tooth gear and the stock one is a 30 or 31.

 

[tworley]

Your gears are fine. Just get a new speedo gear as shown above that goes into the transfercase and you'll be set

 

[Jamesval035]

I did this a couple weeks ago. Took all but 5 min.

 

[Ed 05 TJ]

I was driving it and it did a cracking noise in rear axle and it smelled like something was burning...it lost power to the gears. Was wondering if I messed up the gears by burning the gears because even tho I was driving 40, speedometer said I was doing 65

 

[Brian83]

Pop the cover and take a look. If you messed them up there will be big chunks of metal laying in the bottom

 

[tworley]

I was driving it and it did a cracking noise in rear axle and it smelled like something was burning...it lost power to the gears. Was wondering if I messed up the gears by burning the gears because even tho I was driving 40, speedometer said I was doing 65

Your speedometer and gears are separate. The issue you have in your rear axle is not related to the speedo. The only thing wrong with your speedo is that it is not registering the correct the mileage (or speed as you can tell). To figure out what is making the cracking sound its best to pop the diff cover off and see what is going on as @Brian83 suggested. Or, take a look at the ujoints. The fact that no power is getting to the axle suggests your pinion is trashed, which could mean the burning smell is gear oil. Just a thought...

 

[89grand]

Everyone has to change the speedometer gear to a different one when changing gear ratios. I did too when I went from 3.07 to 4.10. The speedometer being off has zero effect on the ring and pinion. It only effects your ability to know what speed you're going.