I havn't been able to find a sure answer on this. Does a j30 vlsd affect speedometer? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

240sxDann · 08-05-2008, 09:36 AM

I just picked up a 93 coupe, and it has a j30 vlsd. Does this affect the speedometer? It does also have 18" wheels on it with 245/45 tires on it, so I know that affects it some. Main reason I'm asking is because either my speedo is acting funny (as in reading way faster then I'm actually going, which wouldn't make sense with bigger wheels, they would make it read slower) or this things a lot faster then I expected it to be. At about 6k rpm 4th gear I'm at around 100mph. (on a closed course obviously

) So my question is would the j30 affect my speed and make it read way off, or does that not make any difference?

*fliprayzin240sx* · 08-05-2008, 09:55 AM

Shouldnt make any difference...

TTrx7Pete · 08-05-2008, 10:37 AM

Quote:

Originally Posted by 240sxDann

I just picked up a 93 coupe, and it has a j30 vlsd. Does this affect the speedometer? It does also have 18" wheels on it with 245/45 tires on it, so I know that affects it some. Main reason I'm asking is because either my speedo is acting funny (as in reading way faster then I'm actually going, which wouldn't make sense with bigger wheels, they would make it read slower) or this things a lot faster then I expected it to be. At about 6k rpm 4th gear I'm at around 100mph. (on a closed course obviously

) So my question is would the j30 affect my speed and make it read way off, or does that not make any difference?

Speed is read at the transmission. I'm not familiar with the final drive ratios of the factory 93 coupe and a J30. This can affect your speed, but not the reading of it. The speedometer gets it reading by the teeth turning on the transmission, from there an algorithm is performed which translate the speed of the transmission into MPH or KMH.

As for rim/tire size, there are some calculators online that you can input tire size from the factory and get a resulting tire size for different sized rims. These calculators pretty much allow you to upsize the wheel while maintaining an exact or close to exact overall wheel/tire diameter.

240sxDann · 08-05-2008, 12:43 PM

Quote:

Originally Posted by TTrx7Pete

Speed is read at the transmission. I'm not familiar with the final drive ratios of the factory 93 coupe and a J30. This can affect your speed, but not the reading of it.

But the speed it would be reading would be incorrect then right? The sensor says "the transmission spins this many times in x amount of time, so I must be going this speed" however, thats set up for stock gearing. With different gearing, the sensor reads the same amount of revolutions, and it assumes you have stock gears, so its gonna read the same, when in reality, the differential gearing is either making you go faster or slower at that given speed of the shaft the sensor reads off of, as compared to the stock gearing. Yes?

projectRDM · 08-05-2008, 12:49 PM

Ratio is the exact same, 4.08:1, unless you got a later model J30t diff, which is 3.92:1. Even that would only be off 1-2MPH.

Search would have told you that. The Q45 is the only R200 diff with a lower ratio.

240sxDann · 08-05-2008, 03:14 PM

Quote:

Originally Posted by projectRDM

Ratio is the exact same, 4.08:1, unless you got a later model J30t diff, which is 3.92:1. Even that would only be off 1-2MPH.

Search would have told you that. The Q45 is the only R200 diff with a lower ratio.

I apologize, I wasn't sure what to search for. Thank you for the responses.

08-05-2008, 09:36 AM	#1
240sxDann Leaky Injector Join Date: Dec 2005 Location: PA Age: 33 Posts: 83 Trader Rating: (1) Feedback Score: 1 reviews	I havn't been able to find a sure answer on this. Does a j30 vlsd affect speedometer? I just picked up a 93 coupe, and it has a j30 vlsd. Does this affect the speedometer? It does also have 18" wheels on it with 245/45 tires on it, so I know that affects it some. Main reason I'm asking is because either my speedo is acting funny (as in reading way faster then I'm actually going, which wouldn't make sense with bigger wheels, they would make it read slower) or this things a lot faster then I expected it to be. At about 6k rpm 4th gear I'm at around 100mph. (on a closed course obviously) So my question is would the j30 affect my speed and make it read way off, or does that not make any difference? __________________ 93 Chuki Coupe<95 Zenki-Sold<89 Zenki Coupe-Parted<89 Zenki Hatch-Sold

08-05-2008, 09:55 AM	#2
fliprayzin240sx Man w/ CTSV & a Car Seat Join Date: Aug 2002 Location: Tampa Posts: 17,998 Trader Rating: (19) Rides Gallery: fliprayzin240sx Feedback Score: 19 reviews	Shouldnt make any difference... __________________ If you think Zilvia has too many assholes... CLICK HERE!!!

08-05-2008, 12:49 PM	#5
projectRDM Post Whore! Join Date: Dec 2002 Location: Atlanta Age: 47 Posts: 13,812 Trader Rating: (12) Feedback Score: 12 reviews	Ratio is the exact same, 4.08:1, unless you got a later model J30t diff, which is 3.92:1. Even that would only be off 1-2MPH. Search would have told you that. The Q45 is the only R200 diff with a lower ratio. __________________ FORMERLY R240NA Learn what's really going on and protect your assets now before they're gone forever: www.paypalsucks.com

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