Need P/N for 4.11 Speedo Cog

[Marty Rogan]

Hi Guys,

I went to check Brian Little's website to find info on the various speedo cogs. I recall someone saying lately that the link has changed, but could not find that post.

I have recently acquired a 4.11 diff and need to change the cog in my '83 ZX 5spd to match it.

Does anyone have the P/N? The new link to Brian's site would be great to have too.

Thanks!

Marty

[Arne]

http://classiczcars.com/forums/showt...ghlight=garage

[Marty Rogan]

Thanks Arne!

Marty

[sblake01]

32703-78104 is what you're looking for. I don't believe the number shows on the Z car garage site.

[sblake01]

The 20 to 23 tooth gear requires a different sleeve than the 16 to 19 tooth. Here's the entire list at Coutresy Nissan.

[Marty Rogan]

The 20 to 23 tooth gear requires a different sleeve than the 16 to 19 tooth. Here's the entire list at Coutresy Nissan.

You are right, the website only gives you the tooth count and color. He also states that the red cog from the 4.11 won't fit on the ZX sleeve and to use the white cog from the 3.90 instead. This Courtesy info would solve that problem.

Thanks Stephen!

Marty

[sblake01]

He also states that the red cog from the 4.11 won't fit on the ZX sleeve and to use the white cog from the 3.90 instead.

He say's that? So in Brian's opinion being a little off is better than being way off?

[bradyzq]

If you're not using stock diameter tires, now is your chance to include that difference in your calculations too.

[Marty Rogan]

If you're not using stock diameter tires, now is your chance to include that difference in your calculations too.

Good point Brady! I am using 225/50/15's on the car. I guess I will need to play around with the speedo calculator to see which gear set gives the smallest amount of error.

Marty

[bradyzq]

According to my calculations, you effectively have a 4.265:1 rear diff, taking your tire size into account. That's a 3.7% difference from 4.11:1, which means you'd be closer with a 21 tooth gear (pn 32703-86401).

Of course, all this assumes your speedo was accurate before you changed wheel/tire combo and diff!

[bradyzq]

If your speedo was already off, here's how to calculate another way. And it's probably a good idea to try this out anyways.

Head out on the highway where there are mile markers.

Drive an indicated 60MPH, which is 1 MPM (mile per minute) for exactly 2 miles.

Time the amount of time (we'll call it T) it takes to cover those 2 miles in seconds.

Your actual speed in MPM is 120/T.

So, take your existing speedo gear tooth count T/120.

Teeth(needed) = Teeth(actual) x T/120

[Marty Rogan]

According to my calculations, you effectively have a 4.265:1 rear diff, taking your tire size into account. That's a 3.7% difference from 4.11:1, which means you'd be closer with a 21 tooth gear (pn 32703-86401).

Of course, all this assumes your speedo was accurate before you changed wheel/tire combo and diff!

Datsun gauges accurate, ha, that's a good one, !!

[Marty Rogan]

If your speedo was already off, here's how to calculate another way. And it's probably a good idea to try this out anyways.

Head out on the highway where there are mile markers.

Drive an indicated 60MPH, which is 1 MPM (mile per minute) for exactly 2 miles.

Time the amount of time (we'll call it T) it takes to cover those 2 miles in seconds.

Your actual speed in MPM is 120/T.

So, take your existing speedo gear tooth count T/120.

Teeth(needed) = Teeth(actual) x T/120

Not a bad idea. It will have to wait till the car is out of hibernation though. Pretty soon, ... spring is finally coming! Man it's been a long winter.

Thanks for the ideas and info.

Marty

[bradyzq]

I'm with you on the hibernation thing. Maybe I'll see my Z in May.....

You're welcome!