Speedo/Odometer Off pretty bad

[cfiiman]

I have a 94 RT10 and my speedo and odometer is off. I noticed it on the highway bringing it home and checked it with the mile markers on the road. The odometer clicks over 1 mile for every 8 tenths actually so it is putting 20% more mileage on my car then it is suppose to and the speedo at higher speeds can be up to about 13 mph off or so according to my gps. With 9000 miles on the car it may actually have more like 7500 original miles depending on how long this has been going on. Can someone point me in the right direction to fix this? I fixed a similar issue on my wife's accord a while back and it was a speed sensor but I was thinking maybe this car is a little to old to use one of those but wasn't sure? My gauges are analog (not sure what the newer ones are). To my knowledge the rear gears are stock so I don't think that is the issue b/c the rpm's seem to be inline with what others are that I have read about. Thanks for any help

 

[ILLSMOQ]

stock wheels and tires?

 

[Bill Pemberton Woodhouse]

Sounds like a case of someone putting gears in the car and not getting a speedometer recalibration kit installed --necessary for 2002 on back.

 

[cfiiman]

Yes, wheels and tires stock, and I did think about the gears, but I run very low rpm at speed, it doesn't feel like gearing although I don't have much to compare it to.

 

[CitySnake]

Are you the original owner?

 

[cfiiman]

Are you the original owner?

No, second owner, but I bought from a dealership specializing in high end vehicles so I never got to talk to the original owner, but it may be worth a call to see if I can get his number!

 

[CitySnake]

No, second owner, but I bought from a dealership specializing in high end vehicles so I never got to talk to the original owner, but it may be worth a call to see if I can get his number!

That % is just WAY too far off for a factory calibration. Something was swapped out of which you were never made aware. It may be a good mod if it was the rear end, but as others have mentioned, part 2 is the recalibration. When you say "low RPM" at highway speeds, can you recall the speed/rpm more precisely? Even shorter rear end ratios run pretty low rpm at 70 mph in 6th gear.

 

[AZTVR]

Sounds like a case of someone putting gears in the car and not getting a speedometer recalibration kit installed --necessary for 2002 on back.

I fixed a similar issue on my wife's accord a while back and it was a speed sensor but I was thinking maybe this car is a little to old to use one of those but wasn't sure? My gauges are analog (not sure what the newer ones are). To my knowledge the rear gears are stock so I don't think that is the issue b/c the rpm's seem to be inline with what others are that I have read about. Thanks for any help

If you verify that the gears are stock, then you can pursue the speed sensor idea. It is on the driver's side of the transmission just below the shifter.

 

[Ricketts]

Sounds like a case of someone putting gears in the car and not getting a speedometer recalibration kit installed --necessary for 2002 on back.

This was my guess.

 

[cfiiman]

Ok thanks, I have talked to the dealership who has called the original owner and they are suppose to get back with me, I'll let you all know thanks again. So the speedo does work off a speed sensor then, not just a plastic gear on the end of the cable?

 

[RT/ED]

Easy way to check rear gear ratio. First chock both front tires on each side of the tires. Jack up rear of car (both sides)and place on jack stands. Put transmission in neutral.

Rotate one of the rear tires one full revolution and count the number of times the drive shaft fully rotates . If it is a stock rear end, the drive shaft should have rotated just slightly over 3 times (3.07). Higher number turns means a higher gear ratio, i.e, 3 1/2 time means you have a 3:45 or 3:55 ratio, etc.

 

[vancouver-gts]

Ok thanks, I have talked to the dealership who has called the original owner and they are suppose to get back with me, I'll let you all know thanks again. So the speedo does work off a speed sensor then, not just a plastic gear on the end of the cable?

Correct!

I almost guarantee you the rear gears were swapped out.
I'm the third owner of my 99 and the previous owner didn't know what gears he had .He leased the car in 2001 from a dealer in Edmonton and didn't have info from the original owner on swap.When I bought my car I checked the rotation on my wheel compared to the drive shaft and sure enough it was a 4.10 in there. I've ordered the Unitrax calibration box from JonB and it's all good now , except my odo shows a lot more since 2001 than the real milage.

 

[cfiiman]

Easy way to check rear gear ratio. First chock both front tires on each side of the tires. Jack up rear of car (both sides)and place on jack stands. Put transmission in neutral.

Rotate one of the rear tires one full revolution and count the number of times the drive shaft fully rotates . If it is a stock rear end, the drive shaft should have rotated just slightly over 3 times (3.07). Higher number turns means a higher gear ratio, i.e, 3 1/2 time means you have a 3:45 or 3:55 ratio, etc.

Thanks for the tip man

 

[RT/ED]

Keep us posted!

 

[cfiiman]

That % is just WAY too far off for a factory calibration. Something was swapped out of which you were never made aware. It may be a good mod if it was the rear end, but as others have mentioned, part 2 is the recalibration. When you say "low RPM" at highway speeds, can you recall the speed/rpm more precisely? Even shorter rear end ratios run pretty low rpm at 70 mph in 6th gear.

ok tested it today, I was turning approx. 1400rpms in 6th at 75mpg indicated which is probably somewhere around 63 or 64 actual mph, do I have gears?

 

[vancouver-gts]

You should turn 1250 rpm in 6th gear at 60 mph with stock 3.07 gear . I turn about 1750 with 4.10 gear at 60mph in 6th .

 

[RedEnuf93]

Jack up the wheels and count the drive shaft rotation vs. wheel rotation. (as mentioned in previous post)
No need to do quessing, it takes 10 minutes (no highway runs needed) and youll know what they are. Easy as hell...

 

[cfiiman]

yeah as soon as I get to my father's house where the lift is I'll do that, just thought I'd post my findings since someone asked.

 

[JonB]

The most simple check is with a handheld GPS....you MUST know someone who has one?
if you are off 16% its a 3:55. If you are off 22% you have a 3:73.

Or Your wife could pace you at 50 mph indicated..........see what you read vs her?

Or, count the drive-shaft rotations vs the wheel as noted. It is easier if you MARK the shaft. Use the valve-stem to mark the wheel rotation

I suspect that you have a 3:73.....

 

[cfiiman]

Jon,

Thanks for the info, what do I need to do to fix it when I found out the if it is the gearing?

 

[eucharistos]

 

[plumcrazy]

Jon,

Thanks for the info, what do I need to do to fix it when I found out the if it is the gearing?

if youre happy with the gears, buy a calibration kit for it. i think jonB at partsrack.com sells them

 

[anaconda666]

Sounds like you are off exactly the same as my car with 3:73's. Mine is not recalibrated either. Ron.

 

[cfiiman]

Good to know ok so is it difficult to install a recalibration kit?

 

[eucharistos]

I have a 94 RT10 and my speedo and odometer is off. ..... so it is putting 20% more mileage

....If you are off 22% you have a 3:73.....I suspect that you have a 3:73.....

Sounds like you are off exactly the same as my car with 3:73's. Mine is not recalibrated either. Ron.

mystery solved

 

[eucharistos]

if youre happy with the gears, buy a calibration kit for it. i think jonB at partsrack.com sells them

same jonB that posted above in case you don't know

 

[JonB]

mystery solved

Glad I could help....... find me by clicking on my screename / profile at left <

Thanks

~~~~:<~ JonB

 

[vancouver-gts]

I've ordered the Unitrax calibration box from JonB and it's all good now ,

Jon , I guess it's hard to help people who refused to read info here . My info is a few days old already

Ps; in case CFIIMAN reads this , Jon also carries all the parts he may need for the big brake kit !