Question about speedo gear/tire size

[HallNBallz]

I finally got my speedometer working, and i dont think it is reading correctly.. I have 32" tires on there, and it seems like at lower speeds it is correct, but i get to about 55 on the highway it starts readin like 70 or 75 sometimes about 80... IS this due to my tires? should i change to a lower teeth gear?

 

[AdamDude04]

I finally got my speedometer working, and i dont think it is reading correctly.. I have 32" tires on there, and it seems like at lower speeds it is correct, but i get to about 55 on the highway it starts readin like 70 or 75 sometimes about 80... IS this due to my tires? should i change to a lower teeth gear?

I recomend buying a navigation unit..most tell you the estimated MPH speed. This will give you a ball park idea of what speed you're going. Mine is fairly on dot with 31" tires (factory OEM size)..most the time there is a 1mph difference, probably due to accuracy issues between the satilite and navigation.

If you think it's got accurate speed readings at lower speeds but way off at higher speeds, something is wrong sensor/cluster wise - not mechanical (i.e. tires, gears). And I don't think you're on the freeway driving on ice...

I don't know the exact cause, but I do know it's not tire/gear related.

 

[Seabronc]

I agree, changing the gears will not fix this. All you would get by changing the gears is inaccuracy at a different speed. It sounds more like a speedometer problem or perhaps the speedo cable.

Good luck,

>-

 

[HallNBallz]

Ill hook up my tom tom tommaro, thanks fellas

 

[Seabronc]

Another possible thing to look at would be the drive gear inside the tail piece.

Good luck,

>-

 

[HallNBallz]

Another possible thing to look at would be the drive gear inside the tail piece.

Good luck,

>-

yea i just been through a 1 week mess tryin to find a new drive gear, finally found a brand new one...everything is new accept the speedo cable, bc all the ones i buy will not fit into that fitting that goes into the transfer case.. I wish there was a website or somethin that told me the factory speedo gear and transfer case requirements.. i just used yellow speedo gear/yellow drive gear bc thats what was already on it, thanks for ur input

 

[Krafty]

did you count and compare the number of teeth on the speedo gears you replaced to see if they had the same number of teeth as the ones you had removed? also how did the gps test fair out?

 

[HallNBallz]

did you count and compare the number of teeth on the speedo gears you replaced to see if they had the same number of teeth as the ones you had removed? also how did the gps test fair out?

yea i counted and compared, whenever im bord at its not 5 degrees out, i may go out out and check er one more time lol /emoticons/[email protected] 2x" width="20" height="20" /> , yea i hooked up my tom tom, and yea she's running every bit about 10-12 mph over at all times, so i keep er about 65-70mph to go 55mph actual... its very smooth, not jumpy at all, the shop keeps tellin me its the tires, but i dont see 32" tires messing up the speedo that much.. i really dont have a clue what do to, just happy ive got a speedo that somewhat works, lol

 

[Krafty]

if the tires were going to through out the speedometer your truck would be going 60 when the speedometer says 50. bigger tires makes your speedometer say slower than the speed of the truck. you just need to put on 44's and your speedometer will be accurate again.hahah

 

[HallNBallz]

if the tires were going to through out the speedometer your truck would be going 60 when the speedometer says 50. bigger tires makes your speedometer say slower than the speed of the truck. you just need to put on 44's and your speedometer will be accurate again.hahah

yea that would be the cheapest way to go huh, ha :lol: , i guess i may try changing the cable, but i cant find one that fits, they are all to big at the end that goes into the transfer case

 

[Seabronc]

yea i counted and compared, whenever im bord at its not 5 degrees out, i may go out out and check er one more time lol , yea i hooked up my tom tom, and yea she's running every bit about 10-12 mph over at all times, so i keep er about 65-70mph to go 55mph actual... its very smooth, not jumpy at all, the shop keeps tellin me its the tires, but i dont see 32" tires messing up the speedo that much.. i really dont have a clue what do to, just happy ive got a speedo that somewhat works, lol

OK, You gave some information that I must have missed before. If it is always off by 10 - 12 MPH, then you can correct it by changing the gear on the end of the speedo cable.

 

[HallNBallz]

my formula looked like this 31x18

-------= 17.43, would going to a 17 teeth gear (from 18) really help a 10-12 mph difference?

32

Or should i just try it and see? thanks fellas