Speedometer out of whack with new 3.73's - Off-Road Forums & Discussion Groups
GM Standard SFA Trucks & SUV's All discussion of full sized Solid Front Axle Trucks, SUV's to include Suburban

Reply
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 10-22-2002, 04:22 PM
BigBlueZ71
Guest
 
Posts: n/a
Speedometer out of whack with new 3.73\'s

Alright, when my truck was brand new it had 3.42 gears with stock tires (265's). I then installed 285's on the truck (32.8in, now about 32.5" b/c of wear). Now as some of you may know, truck now has a 3.73 rear gear ratio. And now my speedometer seems to be showing that i'm going much faster than I acually am. Or perhaps before I was going much slower than I actually was. Here's the question, what kinda formula can I use to determine how fast i'm going, seems to get more out of whatck the faster I go, 30 feels 30...40 feels 35....50 feels 45. whats the ratio b/c I know on the highway i'm gonna be reading way over what i'm actually doing.
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 10-22-2002, 04:25 PM
 
Join Date: Apr 2000
Posts: 1,545
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Speedometer out of whack with new 3.73\'s

go to www.4lo.com they have gear reatio calculators there tha twill help you figure it out
90K5 is offline  
post #3 of (permalink) Old 10-22-2002, 04:36 PM
BigBlueZ71
Guest
 
Posts: n/a
Re: Speedometer out of whack with new 3.73\'s

I think what i'm really trying to ask is how can I get the speedo to read correctly. What I dont want is the speedo racking up miles I haven't actually put on it. I know there's some plastic transmission thing that sets the gear/speed ratio. anybody know where it is and how to swap it out....
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 10-22-2002, 06:30 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: Speedometer out of whack with new 3.73\'s

can't remember what year your truck is but im quite sure you have electronic speedo, no cable, no gears. you eather have to get your "speed sensor buffer" (is what they called it) caliborated or replaced. rancho i believe sells those, there are couple more places but i can't remember. (by the way, its the bar of soap sized flat white plastic box behind the glove box a little to the left and down, one or two plugs) want mine, i fried mine, it reads 0 all the time [img]images/graemlins/smile.gif[/img] i could cheat, if you just pull it out your tranny wont shift. my new one reads 10% or so over, which adds a crap load of miles (forgot about gearing when i got it from a bone yard) but at least i get the oil changes done on time.
post #5 of (permalink) Old 10-22-2002, 06:36 PM
 
Join Date: Apr 2000
Posts: 1,545
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Speedometer out of whack with new 3.73\'s

I got my VSS recalibrated for $100 at a shop in Dallas. before that i went to 4lo.com and wrote down the speeds in increments of 10 and kept the piece of paper in my truck
90K5 is offline  
post #6 of (permalink) Old 10-22-2002, 08:39 PM
Carpal \'Tunnel
 
wrath's Avatar
 
Join Date: Nov 2001
Location: Waukesha, WI
Posts: 3,323
Thanks: 0
Thanked 1 Time in 1 Post
 
Re: Speedometer out of whack with new 3.73\'s

You can buy adjustable vehicle speed sensors. I forget who makes them but they do exist.

With bigger tires than stock you'll actually be going faster than your speedo reads. Since you've probably still got a taller final gear ratio than stock you're probably going faster than your speedo shows.

I know with my 2.73s and 33s (versus 235x75r15s) my truck is going 35 when my speedo shows 31.
wrath is offline  
post #7 of (permalink) Old 10-22-2002, 09:02 PM
BigBlueZ71
Guest
 
Posts: n/a
Re: Speedometer out of whack with new 3.73\'s

you're halfway right, yes, my speed was actually faster than what my speedo read, with my 33's, BEFORE the gear change. that was with 3.42's. now I have 3.73's with the 33's, and I believe I am actually going slower than what the speedometer is telling me
post #8 of (permalink) Old 10-22-2002, 10:12 PM
 
Join Date: Apr 2000
Posts: 1,545
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: Speedometer out of whack with new 3.73\'s

Actually it is probably pretty close. my 4.11's and 33's, up from 3.42's and my speedo was way off the other way. I wouldn't be surprised if it was pretty close
90K5 is offline  
post #9 of (permalink) Old 10-24-2002, 04:36 PM
BigBlueZ71
Guest
 
Posts: n/a
Re: Speedometer out of whack with new 3.73\'s

Found a SuperLift VSSM module part #32013. Made for GM trucks/suv's with 3.73's and 32.5" - 33.5" tires. Direct replacement for the stock VSSB module.
Here's the kicker, $50 shipped. How's that for one hell of a deal.
post #10 of (permalink) Old 10-30-2002, 05:52 PM
**DONOTDELETE**
Guest
 
Posts: n/a
Re: Speedometer out of whack with new 3.73\'s

i put 33's on my blazer with 3.73's got a ticket for 68.7 and the speedo said 50
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome