720 with j18 motor and 5 speed gearbox 4.55 differential

[mikuni50]

Hi everybody,

 

Does anybody knows what type and gearbox ratios we have in this truck?

 

the informacion plate shows me fs5w71b but i am trying to find out the gear ratios set.

The next ratios has been count when it was open but this set is so strange for me:

 

1. 4.217

2. 2.537

3. 1.638

4. 1.000

5. Not open the back case.

 

In the internet there is no informacion about this "set ratios" .

I will appreciate any help about it.

 

 

[datzenmike]

Interesting. Here the lowest 1st gear is 3.592

 

I suspect your numbers are wrong. That is a huge jump from 4.217 down to 2.537 2nd gear. ???

[mikuni50]

Thanks for reply,

 

But as i wrote before, the theeth numbers between

 

 

4. 21-32 : direct

3. 28-26. : 1.076

2. 30-18. : 1.666

1. 36-13. : 2.769

 

So,

 

Factor : 32/21 : 1.523.

 

1. 1.523 x 2.769 : 4.217

2. 1.523 x 1.666 : 2.537

3. 1.523 x 1.076 : 1.638

4. Direct : 1

 

Possible?

 

 

thanks in advance.

 

 

 

 

 

 

[ggzilla]

Input Ratio: 32/21 = 1.524

 

1st 1.524 * 36/13 = 4.220

2nd 1.524 * 30/18 = 2.540

3rd 1.524 * 28/26 = 1.641

4th = 1:1 direct drive

 

It is possible. We didn't get a 720 with such a small engine,which would need more gearing to get moving. So they may have fitted a "granny gear" to it (extra steep 1st gear).

 

But unlikely since 2nd gear would be such huge drop as Mike pointed out.

 

Compare to this:

[mikuni50]

Thank you very much for the explanation, so this gearbox will be only suitable for trucks but not for sedans or coupes...

 

 

[mikuni50]

For drag cars....

[datzenmike]

It's a little high geared for a car but you could run a lower number differential like 3.354 or 3.545 or taller tires or both.

[mikuni50]

Got it!

 

Thanks again and best regards from Perú.

[mikuni50]

Hi, is possible to fit this box into any L engine? I've got the original inox trans plate but from a J engine...

[DanielC]

the J-18 transmission probably will NOT bolt up to a L-engine. The L engine is tilted right about 15 degrees.

[Willdatsun]

J engine is different to any other Datsun engine I know, it is based around Austin /BMC engine and has imperial fittings. Gearbox is unique to it. Gearbox came in floor and column change versions, but I have only seen 4 speed ones.

[ggzilla]

While Nissan was building Austins, they created the Datsun C engine, then the E engine, then later the J-series engine. All improve upon the original Austin B-series engine.

 

I believe the E and J use the same gearboxes. But the L bolt pattern is quite different.

[mikuni50]

Many Thanks!