NB8A speedo out by 10kmh!

hks_kansei · Postby **hks_kansei** » Sat May 07, 2016 8:36 am

I've done it the both wheel way and it's accurate enough to find the ratio give or take a couple of decimals.

The trick is that you rotate the tailshaft, and count the wheels.

RS2000 · Postby **RS2000** » Sat May 07, 2016 11:33 am

May be so, but a couple of decimals could show a 3.9 as a 4.1 or 3.6.
Both wheels free to rotate would be spot on for a diff that is locked.
Cheers

Theenyx5 · Postby **Theenyx5** » Sat May 07, 2016 2:34 pm

Appreciate the help everyone. Will be taking a look tonight or tomorrow.

Theenyx5 · Postby **Theenyx5** » Sat May 07, 2016 11:34 pm

Ok,

Tried the single wheel up method.

18.25 (rough) turns on the shaft for 10 turns of the wheel.

So 3.6 diff? Meaning NB8B?

noobee · Postby **noobee** » Sun May 08, 2016 8:56 am

something has gone wrong there,lol.thats 1.825/1. were you under the car turning the tailshaft or turning the wheel?correct way is turn tailshaft until you see wheel go one revolution forward.
Mick

Theenyx5 · Postby **Theenyx5** » Sun May 08, 2016 9:21 am

noobee wrote:something has gone wrong there,lol.thats 1.825/1. were you under the car turning the tailshaft or turning the wheel?correct way is turn tailshaft until you see wheel go one revolution forward.
Mick

Went off RS2000's method.

18.25 x 2 / 10 = 3.65?

hks_kansei · Postby **hks_kansei** » Sun May 08, 2016 9:44 am

Your method sounds correct

And the result shows a 3.6 (nb8b was 3.67 I think, but people just say 3.6 for convenience)

If it's a 3.6 diff that would explain the Speedo error.

Theenyx5 · Postby **Theenyx5** » Sun May 08, 2016 9:46 am

What recommendations do you suggest?

I read that the 3.6 would be lower acceleration per gear. What would have dríven the previous owner to put a 3.6 in over a 4.1?

This will be only a road car fyi.

hks_kansei · Postby **hks_kansei** » Sun May 08, 2016 2:51 pm

Often the 3.6 is put in as a torsen swap since a lot of torsens come with it fitted already.

Personally I'd swap to a 4.1 ratio, better acceleration etc.

You can either buy a different from an nb8a, or have a diff shop put the new ratio gears into three current diff.

Theenyx5 · Postby **Theenyx5** » Sun May 08, 2016 6:18 pm

Looks like the cheapest fix would be to change the sensor over the diff.

What do I need to know about the differences between the speed sensors?

Nevyn72 · Postby **Nevyn72** » Sun May 08, 2016 7:34 pm

Theenyx5 wrote:Looks like the cheapest fix would be to change the sensor over the diff.

What do I need to know about the differences between the speed sensors?

It's actually just the plastic gear wheel on the end of the sensor that's different but you may have difficulty sourcing this by itself.

As for the 3.6 being fitted?
- lower acceleration but better fuel economy, what's more important to you?
- You may have scored a LSD with your car! Worth checking out....... :mrgreen:

Theenyx5 · Postby **Theenyx5** » Sun May 08, 2016 8:29 pm

Nevyn72 wrote:
Theenyx5 wrote:Looks like the cheapest fix would be to change the sensor over the diff.

What do I need to know about the differences between the speed sensors?

It's actually just the plastic gear wheel on the end of the sensor that's different but you may have difficulty sourcing this by itself.

As for the 3.6 being fitted?
- lower acceleration but better fuel economy, what's more important to you?
- You may have scored a LSD with your car! Worth checking out.......

My understanding is its an open diff if I am able to Jack one rear wheel up and spin the wheel? Or am I mistaken? How would you know if it's lsd?

Nevyn72 · Postby **Nevyn72** » Mon May 09, 2016 8:55 am

Theenyx5 wrote:My understanding is its an open diff if I am able to Jack one rear wheel up and spin the wheel? Or am I mistaken? How would you know if it's lsd?

Not with a torsen. :wink:

To be certain you open it up but that's a bit extreme.....
Park half on the road with one wheel on a gravel verge (find a quiet spot).
Power off 'enthusiastically' and if the wheel on the gravel just spins it's an open diff, if you take off and/or both wheels spin it's an LSD.

93_Clubman · Postby **93_Clubman** » Mon May 09, 2016 1:03 pm

With Torsen 1 you can also just undo the oil filler plug to check if it's a Torsen - have to look at pics of Torsen 2 to see if this will work due to some changes between T1 & T2, ie from memory, T2 inside centre casing was more enclosed.