Register or Log In To remove these advertisements. |
|
|
|
Thread Tools | Display Modes |
|
01-02-2004, 12:09 AM | #1 |
Registered User
Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
|
WTF a 1.50 rear end ratio???
Ok i got to wondering why my speedo reads 83 miles an hour and my gps handheld says 65... I just put stock height tires on my truck thinking the tire height was throwing it off...well that didnt solve the problem.
so I jacked up the truck and did the spin the tire thing and count the revolutions of the driveshaft.... and it only turns 1 and a half times with 1 revolution of the tire. whats up with that?? I have never heard of a gear under 2.73 I'm not saying they don't exist just I havent seen them. Is it possible I have such a low gear? The rear end acts fine doesn't pop or anything with no slack...I get outstanding mileage and the truck could get outrun by a bicycle off the line...but once it's up to speed it rolls fine any thoughts? |
01-02-2004, 12:11 AM | #2 |
Registered User
Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
|
btw I checked 3 other cars with known ratios today and my tire vs driveshaft was dead on with all the others...the glove box says 3.07 on the rear axle?
|
01-02-2004, 12:13 AM | #3 |
Careful, they attack...
Join Date: Aug 2001
Location: Waterford, MI, USA
Posts: 1,107
|
Sounds like you are getting the diff ratio in there. If you have an open diff, then you have to spin both tires at the same time. If not, the differential kicks in and you get the spider gear ratio. Turn the driveshaft by hand, not the tires and try that...
|
01-02-2004, 12:17 AM | #4 |
Careful, they attack...
Join Date: Aug 2001
Location: Waterford, MI, USA
Posts: 1,107
|
If the glovebox says 3.07 then you it's right. You got 1.5 from the differential gears, not the ring and pinion. with an open rear and a 3.07 ratio, you would only see about 1.5 revolutions. If you turn both tires at the same time, in the same direction, it will come out right.
|
01-02-2004, 12:22 AM | #5 |
Registered User
Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
|
ok then what gives on the speedo?
|
01-02-2004, 12:26 AM | #6 |
Registered User
Join Date: Sep 2003
Location: DFW
Posts: 765
|
drive or driven gear in the trans is incorrect someone has changed one or the other some time back
__________________
The problem with America is stupidity. I'm not saying there should be a capital punishment for stupidity, but why don't we just take the safety labels off of everything and let the problem solve itself? |
01-02-2004, 12:28 AM | #7 |
Registered User
Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
|
well it had no speedo gear in the tranny when I got it. I put a brown gear out of my 72 LWB TH350 in it.
|
01-02-2004, 12:28 AM | #8 |
Senior Member
Join Date: Apr 2000
Location: Delta,Pa
Posts: 14,948
|
i bet the truck has 3.07's and at some point the transmission was rebuilt and they put new speedo gear in it and didnt use the right ones so now your speedo is off by 18 mph. you just gotta change the plastic gears inside the transmission
__________________
Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member. |
01-02-2004, 12:28 AM | #9 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
|
maybe your speedo is setup for bigger/smaller tires already!
__________________
70 longbed 496/th400/Ford 9" |
01-02-2004, 12:28 AM | #10 |
My son, my joy.
Join Date: Sep 2003
Location: Spokane WA
Posts: 463
|
I had a 77 Monte Carlo that had 2.56 gears. That thing got 22 MPG with the same 327 thats now in my truck. Only get 11-12 with it in my truck.
|
01-02-2004, 12:31 AM | #11 |
Registered User
Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
|
well it had no speedo gear in the tranny when I got it. I put a brown gear out of my 72 LWB TH350 in it.
what color gear is right? |
01-02-2004, 12:31 AM | #12 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
|
wow cat fuzz thats a big difference
__________________
70 longbed 496/th400/Ford 9" |
01-02-2004, 02:08 AM | #13 |
Careful, they attack...
Join Date: Aug 2001
Location: Waterford, MI, USA
Posts: 1,107
|
I just went to the dealer and bought a bunch of the gears, they're cheap. I think I had 3 different ones. I ended up using the white one I think. If I remember the gears were like $5 each or something like that.
|
01-02-2004, 02:46 AM | #14 |
My other Love
Join Date: Aug 2001
Location: Castlegar B.C. Canada
Posts: 4,085
|
It's hard to say whcih gear is right, best to play with them, or find a shop that can calibrate speedo's
__________________
Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life |
01-02-2004, 06:43 AM | #15 |
Registered User
Join Date: May 2003
Location: Shreveport LA
Posts: 3,170
|
http://www.tciauto.com/components/speedometer_gears.htm
www.novaresource.org/speedo.htm www.novaresource.org/speedo2.htm When checking gear ratio on an open rear end, jack up ONE wheel & do the rev counting thing, then multiply the result by two. Better yet turn the wheel TWO full turns & count the driveshaft turns for an exact answer. With both wheels up, the one opposite you can turn backwards & throw your count off. My '79 Suburban with 3.07 gear, Turbo 350, & 255/70-15's (same diameter as 235/75's) had a green (9-tooth) drive gear on the transmission output shaft and a blue (20-tooth) driven gear on the speedo cable. The speedo read the same as the radar trailer at 50mph. To slow down a speedo, use either a drive gear with less teeth, or a driven gear with more teeth, or whatever combination of the two gets you the best reading. Last edited by jimfulco; 01-02-2004 at 07:00 AM. |
01-02-2004, 11:28 AM | #16 |
Registered User
Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
|
thanks guys
I 'll put the drive gear out of the tranny I got the driven gear out of... hopefully that'll clear it all up.
I'm bookmarking those links... Thanks |
Bookmarks |
Thread Tools | |
Display Modes | |
|
|