Awesome site!
Ok, here is the deal. I have owned a '90 V6 4x4 PU for the last 10 years. It had stock gears and I ran 33"s. I had an outboard speed converter installed after I got a ticket for speeding, not knowing exactly what my speed was . Long story short, I recently bought another truck with same make and model. Swapped engines and trannies. Now I have the converter on my new truck. It has 5.29 gears and 35"s.
At freeway speeds on my old truck, my speedometer read about 10 miles under what I was actually going. (Hence the converter).
My new truck reads higher than actual speed. (I called a friend while I was following him and asked his speed).
My question is: With my bigger tires and gear changes, does this make the speedometer correct again? I know with only one or the other, it will be off. Should I remove my converter?
Thanks a bunch!

 

There is a site floating around on here somewhere that will help you tell how bad your speedo is off. But the best way is to just go get it recalibrated(sp?)

 

You're best bet is to use a GPS or a buddy next to you to figure out what your speed really is. Since you've swapped things around, you may not have a good baseline.

 

+1 for GPS

I would not trust that the speedo was right in the first place. I went from 31's to 33's and the speedometer reads 70 MPH when the GPS says 69 MPH - not enough to worry about! Obviously, the speedo couldn't have been too accurate to start with!

 

Thanks for the replies. A couple of hours ago I pulled off the converter to see what difference it would make. I had my brother drive in front of me in his car, and when he got to 60, that is exactly what my speedometer said. I am happy it is correct now, but I do not know why. I figured with and big tires it would be way off. It is cable-actuated to the transmission, so I do not see how the gearing in the diffs would make a diff. Maybe the owner B4 me did some other things I do not know about.

 

35s and 5.29 is close to the stock gearing tire ratio.

 

Yep, if you changed the tires to 35s and did not change the gears, your speedo will be way off. Changing to the correct gears (for 35s, 5.29s are pretty close) will return your overall gearing to stock and make your speedo (and, by the way, your engine power) back to stock again.

 

Sweet truck Phil! I am in Portland. We should go wheeling sometime.

 

When I had my stock gears and 33's my speedo read 5 mph slower than I was actually going at 70. I regeared to 488's and now my speedo reads 5 mph faster than I am actually going. Kinda weird.. but yes regearing will change your speedo.

 

Anybody need a converter for stock gears running 33"s? It will make your speedometer correct.

 

Does it return engine power as well?

Does it come with the 33s?

 

Actually it does come with the 33s, but I do not think I can roll them that far. :bounce2:

 

Why not, it's down hill all the way...

 

I think Shasta would get in the way. Wanna help?