speedometer error/replacement gear options
#1
speedometer error/replacement gear options
I'm new to these trucks...and I've just noticed that my speedometer on my daily is quite innacurate. When it says I'm going 60mph my gps shows 55...any ideas?
1986 22rte 4x4
Plate on the door says 225/75 R15
Actual tire size is 235/75 R15
This should make the speedo a tiny bit out the OPPOSITE way!
That's about a 10 percent difference!
1986 22rte 4x4
Plate on the door says 225/75 R15
Actual tire size is 235/75 R15
This should make the speedo a tiny bit out the OPPOSITE way!
That's about a 10 percent difference!
#2
Registered User
a bigger tire would actually cause the speedo to read low not high.
If you notice here http://www.miata.net/garage/tirecalc.html with a 235/75 R15 tire on a 225/75 r15 stock sized truck: When your speedo says 60 MPH your real speed should be 61.3 MPH a 2.1% difference.
Sorry to make your problem seem worse, but......
If you notice here http://www.miata.net/garage/tirecalc.html with a 235/75 R15 tire on a 225/75 r15 stock sized truck: When your speedo says 60 MPH your real speed should be 61.3 MPH a 2.1% difference.
Sorry to make your problem seem worse, but......
#4
Contributing Member
iTrader: (3)
Might be that someone has swapped gearing in your axles at some point, perhaps for larger tires. Now with ~stock size tires, your speedo is off. You could check the axle axle gearing (should be 4.10 for a 5-speed):
- http://www.4crawler.com/4x4/4R_TechI...oDetermination
- http://www.4crawler.com/4x4/4R_TechI...oDetermination
#6
Registered User
#7
a bigger tire would actually cause the speedo to read low not high.
If you notice here http://www.miata.net/garage/tirecalc.html with a 235/75 R15 tire on a 225/75 r15 stock sized truck: When your speedo says 60 MPH your real speed should be 61.3 MPH a 2.1% difference.
Sorry to make your problem seem worse, but......
If you notice here http://www.miata.net/garage/tirecalc.html with a 235/75 R15 tire on a 225/75 r15 stock sized truck: When your speedo says 60 MPH your real speed should be 61.3 MPH a 2.1% difference.
Sorry to make your problem seem worse, but......
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#8
Might be that someone has swapped gearing in your axles at some point, perhaps for larger tires. Now with ~stock size tires, your speedo is off. You could check the axle axle gearing (should be 4.10 for a 5-speed):
- http://www.4crawler.com/4x4/4R_TechI...oDetermination
- http://www.4crawler.com/4x4/4R_TechI...oDetermination
Not very likely that there could be something wrong with the speedo cable or something?
#9
Registered User
turn the tires by hand and count how many times the driveshaft turns. or vice versa, turn the driveshaft by hand and count how many turns the tire makes.
#10
Registered User
#13
So untill I get the time to jack er up and spin the wheels...
when Im going 50mph(actual) in 4th gear im revving @ 2500rpm
I did 4th as 4th is typically a 1:1 ration in most 5spd transmissions and most of you dont have the tall 5th that i have in my r151f
anyone care to post what theyre revving @
Thanks
when Im going 50mph(actual) in 4th gear im revving @ 2500rpm
I did 4th as 4th is typically a 1:1 ration in most 5spd transmissions and most of you dont have the tall 5th that i have in my r151f
anyone care to post what theyre revving @
Thanks
#15
My speedo is off by exactly 10% and my odometer is off by around 7%. I've calibrated my self that if the runner reads 80, I'm doing over 70 but it looks like 80, which feels like I'm making good progress. And, I have the mpg's of 80mph too!!
#16
HELP! speedometer gear info needed
I have a 86 turbo reg cap 4x4 pickup with the manual r151f.
When I got the truck the speedometer was way off. The truck had 4.10 gears and the stock sized small tires. I switched to 31x10.5 r15 and the speedometer was accurate (checked via gps)
Now I have changed my gears out to 4.56 and the speedo now reads 5-6 miles fast. IE it reads 65 when I'm actually going 60 (checked via gps)
Can you tell which gear the trucks that came with 4.56 gears and 31" tires had?
I think my trucks been messed with before. It had 4.10 gears and the factory sized small tires(as indicated on the door plate) however the speedometer was very inaccurate. When I put the larger 31" tires on the speedometer became accurate(checked via gps) even tho it still had 4.10 gears. Now I have changed the gears to be a factory setup(4.56 with 31x10.5" tires) and the speedo is out again (it reads around 65 when I'm going 60)
What new speedo gear do I need?
All you math wizards I could use some help.
When I got the truck the speedometer was way off. The truck had 4.10 gears and the stock sized small tires. I switched to 31x10.5 r15 and the speedometer was accurate (checked via gps)
Now I have changed my gears out to 4.56 and the speedo now reads 5-6 miles fast. IE it reads 65 when I'm actually going 60 (checked via gps)
Can you tell which gear the trucks that came with 4.56 gears and 31" tires had?
I think my trucks been messed with before. It had 4.10 gears and the factory sized small tires(as indicated on the door plate) however the speedometer was very inaccurate. When I put the larger 31" tires on the speedometer became accurate(checked via gps) even tho it still had 4.10 gears. Now I have changed the gears to be a factory setup(4.56 with 31x10.5" tires) and the speedo is out again (it reads around 65 when I'm going 60)
What new speedo gear do I need?
All you math wizards I could use some help.
Last edited by jeetS; 09-09-2011 at 08:36 PM.
#18
Registered User
#19
no.
The speedo should read correct. I have a stock setup. i.e. 31" tires and 4.56 gears
the speedo only read correct when I had 31" tires and 4.1 gears...which is not a factory option.
I would like to put it correct, but I don't know which speedo gear to buy.....
Its strange that my truck is like this...unless someone has been in there before and at some point in its life the truck had 31" tires and the owner had the speedo gear corrected.....
The speedo should read correct. I have a stock setup. i.e. 31" tires and 4.56 gears
the speedo only read correct when I had 31" tires and 4.1 gears...which is not a factory option.
I would like to put it correct, but I don't know which speedo gear to buy.....
Its strange that my truck is like this...unless someone has been in there before and at some point in its life the truck had 31" tires and the owner had the speedo gear corrected.....