Speedo gear question

[pblaze725]

I hear I can get my speedometer close to accurate if I swap out the little plastic gear.

I've never done this before but after my $300 speeding ticket i figure I probably should.

I am running 35's on 1/2 tons, 700R4, NP208. I haven't swapped the diff gears out yet so they are 3.08:1 but I plan on 4.56:1.

The questions are:

What color gear should I get?

Where do I put it?



Link to parts in question:http://www.classicparts.com/Transmission/products/393/5/0

 

[K85 Octane]

do the axle gears first, you may end up close just doing those. Plus you really should anyway, not only for power, but to save the 700r4

 

[pblaze725]

I will do the diff gears soon. The question still remains.

What speedometer gear should I get for my set up?
Where does the speedometer gear go?

Edit: I found a website that answered my questions.

Link:http://www.transmissioncenter.org/GM_Speedometer_Gears.htm

 

[Fordum]

Like they say, don't bother with the speedo until you change the axle gears and see how far off it is.
You will just be throwing money away. Even if it does not come out close, you still only have to change them once.

In the meantime, find yourself an older cheap GPS and mount it on the dash. The speedometer in it is going to be more accurate than whatever you wind up with after doing the gears.

 

[K85 Octane]

I used my GPS off my ATV to get a starting point for my MPH gauge, which is way off.
90= 75 Which is a good cruising speed around here.
70-75= good for towing


Only real useful info I have:

http://www.grimmjeeper.com/gears.html

http://www.bgsoflex.com/speedo1.html

 

[blazinzuk]

What's your address I will take my speedo correcter out and send it to you, since I have 4.56s now and had 3.08s with 35s

That will get you correct for now

 

[magik235]

Edit: I found a website that answered my questions.

Link:http://www.transmissioncenter.org/GM_Speedometer_Gears.htm

I got my speedometer gear from this site. I was satisfied.

 

[pblaze725]

Like they say, don't bother with the speedo until you change the axle gears and see how far off it is.
You will just be throwing money away. Even if it does not come out close, you still only have to change them once.

In the meantime, find yourself an older cheap GPS and mount it on the dash. The speedometer in it is going to be more accurate than whatever you wind up with after doing the gears.

I have an old GPS unit that I use. I just can't see it very well in the daytime. I drive the rig to work for a week or so before I go out on a trail run. I just happened to get caught in a speed trap when I didn't have the GPS with me!
I don't see the big deal about spending 6 bucks on a gear unless it is a royal PITA to swap it out. From my understanding you just pull out the speedo cable and swap the gear out real quick. ...Or is it harder than that?

What's your address I will take my speedo correcter out and send it to you, since I have 4.56s now and had 3.08s with 35s

That will get you correct for now

Thanks Blazinzuk PM sent.

 

[munepit]

I have my speedo gear in hand. Its easy to pull out. I cant figure out which one to get. Maybe Im dumb, But I cant figure out the calculator.

 

[496truck]

The big problem is that you need to know what drive gear you have, inside the t-case. The link in post #3 is a good source of info for what speedo gears work with what axle gears and tire size.

You may need to change both speedo gears to get it right. Changing the one inside is only as difficult as removing the tailshaft housing off the back of the t-case.

 

[pblaze725]

The gears are color coded. You have to look in there & see what color the gear is, then look on the chart to identify correct match.
Anyone know what the typical stock drive gear usually is?

Guessing by the tire sizes on the chart I'm betting the stock drive gear is 15t (GRAY).
And looking at the chart for the 15t gear. / 4.56's/ 35" tire= 39t

Looking back at the chevy parts I see the closet match is 38t (big BLUE)

Is that correct?

 

[munepit]

On mine the gear I pulled out is black and has 40 teeth. The gear on the output shaft is light green. I sent photos to the guy in the above post #3. He said light green is from a ford. Weird. They are working on it though. I will know tomorrow.