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Discussion Starter #1
I know 1990 broncos just need a new gear to help correct the speedo.

I just got a ticket for doing a 61 in a 40. My speedo said I was doing 40!!!!

How many tooth gear do I need to correct the speedo with 3.55 gears and 40 inch tires. Atleast to get me close??

LMK ASAP!!!!

Also, where the the old tooth lcoated? How hard to install?

Thanks,

Kyle
 

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That's not enough info to figure out the gear size. Do some searching - there are several sites with gear calculators, and I've posted a link to at least one that will do speedo gears. I've also posted pics of the gears. This thread has some of that info.
 

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Is it really that difficult to judge the difference between 40 and 60mph? I realize it needs to be fixed but you make it seem like you couldnt tell and that it wasnt your fault
 

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BigBody said:
How many tooth gear do I need to correct the speedo with 3.55 gears and 40 inch tires. Atleast to get me close??

Also, where the the old tooth lcoated? How hard to install?


Kyle
You won't find a speedo gear that can correct that much with those tires. It will take a combination of regearing the differential and depending on what you do there then you may still have to change the speedo gear.

To see what tooth count you need, you need to know what the tooth count is on the one you have. Then multiply it by the old tire size and divide by the new tire size. That wil give you the tooth count you need without redoing the gears in the differential. I'm sure you won't come up with a tooth count that exists on any production speedo gears.

3.55s and 40 inch tires must give you horrible power characteristics. Temporarily you just need to keep the error in mind. Didn't you ever wonder why you seemed to be going so fast compared to every one else.

Goood luck,

:thumbup
 

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It is easy to install, and is at the end of your speedo cable. It is either on the back side of the transfer case or in the differential. Not sure on your truck. Just follow the cable.
 

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Discussion Starter #6
The truck seems slow. I always just try to go the same rate as everyone around but no one was around. The truck drives like a pig so I honestly didn't know it was 60. I didn't even think the darn thing would hit 60. I had parked it for a few weeks and beend riving my new truck. It had slipped my mind that the speedo ws off in the first place.
 

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BigBody said:
The truck seems slow. I always just try to go the same rate as everyone around but no one was around. The truck drives like a pig so I honestly didn't know it was 60. I didn't even think the darn thing would hit 60. I had parked it for a few weeks and beend riving my new truck. It had slipped my mind that the speedo ws off in the first place.
That rear end gearing is why it drives like a pig. You are way outside the acceptable powerband. If this is mainly a road machine and you highway cruise around 65, your differential gearing should be aroune 4.56 to 4.88. Once you gear that you way will be able to find a spedo gear that will make your speedometer accurate.

Good luck,

:thumbup
 
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