Speedometer gear

[vinb]

Run a 31 tooth with the 3.23 gear & 275/60/15 tire
Run a 33 tooth with the 3.55 gear & 275/60/15 tire
I drove down the highway after 3 miles, the speedo was off about a 1/2 to 1 tenth..
RPM was about right....

[Changin Gears]

Ok, I have installed my new 32 (black) gear and went out with my GPS.  At 60 on the GPS I was running 45 on the speedometer!  15 MPH off, now what do you guys suggest.  Again I am running a 3:23 SG with P275 60 BFG's (28")

thanks,
Mike

Your 33% off, so you would need 10 or 11 fewer teeth on the speedo gear (smaller gear will spin faster, making the speedo read higher).  I don't belive there is a 21 or 22 tooth gear.  Sounds like you have speedometer problems.  Is the odometer off also?

[vinb]

Easy,  just have someone with a late model car (digital dash) ride along side you at a specified speed and see what you have.
But if you have a 31 tooth in there it has to be correct unless you have a speedo problem.

With the 4spd you have no slippage and the rpm's should be 2327 rpm @ 60 mph & 2714 rpm @70 mph...

Hope that helps......

[Bullitt-]

I have an Excel spreadsheet that calculates the speedo pinion tooth # based on variables you can change such as rear ratio & tire size...Anyone that want it PM your email address with request.     

[vinb]

bullitt99, is this the one?
http://www.moparts.org/Tech/tech/img/4SPEEDchart.xls

Also, I saw another one that you could put in your data and it would have a working tach & speedo from a B-Body, can't remember where I seen that one before...

[Bullitt-]

bullitt99, is this the one?
http://www.moparts.org/Tech/tech/img/4SPEEDchart.xls

Also, I saw another one that you could put in your data and it would have a working tach & speedo from a B-Body, can't remember where I seen that one before...

Yes that's the one, last time I looked they had removed it. & this one for automatics
http://www.moparts.org/Tech/tech/img/AUTOMATICchart.xls

[Husker Cuda]

I plugged in my numbers and it shows a 31 (30.25) gear, I'm running a 32 but it surely wouldn't be off that far so I must have speedometer issues?  It seems like I have to be going 10 or 15 mph before it even comes up off of the pin, could the needle just need pulled off and reattached on the zero location?  It does seem pretty smooth once it gets above 15 or 20 mph.

Mike

[Chryco Psycho]

I have never tried that but it could work 

[Bullitt-]

I'd think clean & lube the mechanism would be the next move. 

[Alaskan_TA]

I agree, make sure the speedo cable is clean, the jacket & the inner drive.

I have a used 31 tooth here you are welcome to it if you want to try it? If so, email me with your mailing address.

[Husker Cuda]

Thanks for the offer Alaskan, Let me do some work on the speedometer first and then I'll see how far I'm off.   

[MEK-Dangerfield]

Thanks for the offer Alaskan, Let me do some work on the speedometer first and then I'll see how far I'm off.   

You are the first to try to calibrate your speedo with a GPS. I just wonder how accururate a satellite millions of miles away is?  I was reading 80MPH at 60, but I have NEVER seen someone reading SO slow the other way. The lowest speedo gear here is 26 teeth, so I question how you are doing this. Just get someone to drive a steady 60 MPH ahead of you, and see what you read.


  Mike