Need speedometer gear advice
Thread Starter
Racer
Joined: Nov 2013
Posts: 338
Likes: 8
From: South NewJersey
Need speedometer gear advice
I just changed my rearend to 4.11 gears from 3.07 can I just change the driven gear that goes into the trans or do I have to change the drive gear also. I just got the thing back together and I dont want to drop tyhe trans AND pull the tailshaft . Is there another way? Like just changing the driven gear .
Team Owner
Joined: Sep 2003
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I just changed my rearend to 4.11 gears from 3.07 can I just change the driven gear that goes into the trans or do I have to change the drive gear also. I just got the thing back together and I dont want to drop tyhe trans AND pull the tailshaft . Is there another way? Like just changing the driven gear .
**I did intend to mention that for a 700R4 there's NOT a combination drive/driven that works with "MOST" of the popular C4 tire combinations. What size tires do you have?
Last edited by WVZR-1; Mar 13, 2016 at 09:20 AM.
Thread Starter
Racer
Joined: Nov 2013
Posts: 338
Likes: 8
From: South NewJersey
Right now I have 275/40/18 I measured and got 26" BUT I plan to get Nitto 295/35/18 and I think they measure 27".Do you know much this will effect my speedo error issue? Right now I am at a 6 mile an hour difference at 18-20miles an hour and as I go faster Holy cow!!!
Team Owner
Joined: Sep 2003
Posts: 25,384
Likes: 2,736
Right now I have 275/40/18 I measured and got 26" BUT I plan to get Nitto 295/35/18 and I think they measure 27".Do you know much this will effect my speedo error issue? Right now I am at a 6 mile an hour difference at 18-20miles an hour and as I go faster Holy cow!!!
Using that information you can determine the % of error and correctly determine regardless of tires used the values and the error created by the changes.
If the METRIC function of the speedometer functions correctly it might be possible to correct that to MPH so do the drive using the KPH function of the speedometer but noting the differences on the GPS still in MPH, 30, 40, 50 and maybe 60 KPH on the speedo.
We used to change the early analog "dual display" MPH/KPH so that it displayed speeds in excess of 120MPH but of course odometer was never correct.
Thread Starter
Racer
Joined: Nov 2013
Posts: 338
Likes: 8
From: South NewJersey
I found a really cool app for my phone called Ulysse. It showes MPH, 0-60,0-100,and 1/4 mile plus ALOT of other stuff and it was free. That is how I found when my speedometer reads 24 mph my phone gps reads 18. My cor is a 1984 so I dont think I have VSS or any of that "new" stuff. LOL
Team Owner
Joined: Sep 2003
Posts: 25,384
Likes: 2,736
I found a really cool app for my phone called Ulysse. It showes MPH, 0-60,0-100,and 1/4 mile plus ALOT of other stuff and it was free. That is how I found when my speedometer reads 24 mph my phone gps reads 18. My cor is a 1984 so I dont think I have VSS or any of that "new" stuff. LOL
Thread Starter
Racer
Joined: Nov 2013
Posts: 338
Likes: 8
From: South NewJersey
Oops. I thought I should have checked into that before I typed it. lol
I have seen others make reference to it at times on here but always thought it was something in the tuned port or later cars. Thanks for the info. I guess I better find out what it is and see how it may be able to help my situation.
I have seen others make reference to it at times on here but always thought it was something in the tuned port or later cars. Thanks for the info. I guess I better find out what it is and see how it may be able to help my situation.
Team Owner
Joined: Sep 2003
Posts: 25,384
Likes: 2,736
Oops. I thought I should have checked into that before I typed it. lol
I have seen others make reference to it at times on here but always thought it was something in the tuned port or later cars. Thanks for the info. I guess I better find out what it is and see how it may be able to help my situation.
I have seen others make reference to it at times on here but always thought it was something in the tuned port or later cars. Thanks for the info. I guess I better find out what it is and see how it may be able to help my situation.
I know how to convert the MPH to KPH but I'd like to use your numbers for comparisons, and see the error on the KPH scale.
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Thread Starter
Racer
Joined: Nov 2013
Posts: 338
Likes: 8
From: South NewJersey
OK... switched to KPH ...when the dash speedo reads 96 kph the gps read 47mph...when in MPH mode the speedo read 57 and ths gps read 46...these numbers are plus and minus 1 or 2 miles per hour as the digital read outs on both dash and gps are constantly moving.