Recalibrating Speedo

[blazer88]

I bought an 84 blazer with 37x12.5x15 and 4.88 gears what do I need to do to recalibrate the speedo, I found a few things online. can somebody provide some links to sites and a brief description of the fix.

 

[THUNDERUSONE]

How far off are you?

 

[blazer88]

I am off by about 10-15mph. I found an equation to figure out my speed and mileage, but stock gears were 3.73 and now I am on 37's with 4.88 gears. Just put it around 90mph on the speedo, which comes out to 68.4mph. No way in hell I was doing 90mph, still had stupid little cars passing me, glaring at me. Gotten lots of looks from people though.

 

[xCaliK5x]

I found best way to find out, is to use a GPS. I have to mess with mine at some point, but its low on the priority list

 

[Teck]

You will have to change the speedo gear out in the transfer case. Speedo shop could probably get you what you need.

 

[Desert Rat]

I used this site when I needed to re-calibrate my Blazer: http://www.transmissioncenter.net/s...______va.htm?gclid=CPfzzMrm4J8CFQtfagodNHPZGg I went and drove my Blazer at 10 mph increments with the missus driving next to me on the cel phone. She drove 35 mph, then 45 mph, then 55 mph, then 65 mph and I recorded my speeds versus her actual speeds with a stock vehicle. Then I called the guys on that website and told them my specs. If you page down you will get to the section called "GM/Dodge/Ford Ratio Adapters". You can see that you can choose your percentage of change. The guy on the phone told me which one to choose and I just ordered the adapter on line. The adapter plugs into the speedo cable between your transfer case and the end of the speedometer cable. Very easy to install and when I had it checked later with GPS, my speedometer was spot on.

 

[Teck]

Thanks for that link, that is the stuff I was thinking of, had seen them years ago just didn't know if they were still avalible any more.

 

[Desert Rat]

I started down the path of swapping out my speedo gear in the transfer case and in the process ran into that site with the ratio adapter which made life much easier. The Internet is a wonderful thing.....

 

[4X4HIGH]

Thanks for that link, that is the stuff I was thinking of, had seen them years ago just didn't know if they were still avalible any more.

I have a "rebuildable" ratio adapter (there are two types, one is rebuildable and the other is not) if you need one, PM for details.

 

[blazer88]

Thanks for the help, you guys always have the answers and are always helpful, now i just need to scrounge up the money and join up.