Crown wheel/Pinion ratio

[AdrianNPMajor]

Could anyone let me know how to tell if my NP Super Major has a standard 4.375:1 crown wheel/pinion ratio or the faster 3.5:1 ratio?

Kind regards

Adrian

[Brian]

Number is on a machined, flat, triangular area here on the axle housing. Will be either 4.4 or 3.5.

[AdrianNPMajor]

Hi Brian

Many thanks for your reply. I had heard this was the place to look but the machined triangle on my NP Super is blank. I have just rung a friend and his NP Super has has 3.3 engraved in the triangle (apparently, the second digit is definitely a 3 and not a 5).

3.5 would be logical, given that this is the gear ratio. How can we explain the mysteries of a blank triangle and one that is inscribed with 3.3?!

Kind regards

Adrian

[Brian]

It should be 3.3, I type too fast sometimes.

The numbers there will not always be correct, we changed a lot of difs for customers both to high speed and low depending on their requirements. We had one customer who used a Super on Rotopads, for heavy ploughing, who had his tractor changed every Autumn to the 4.4 ratio and every Spring back to the 3.3 ratio.

Yours must have missed being stamped. Run the two tractors side by side at the same revs in the same gear, there is quite a difference between the two ratios and it will easily be seen.

[AdrianNPMajor]

Many thanks Brian.

Adrian

[AdrianNPMajor]

Hi Brian

Just following up on this post, when you changed the crown wheel to get a different ratio (3.3 or 4.4) did you have to change the bevelled pinion as well? And how did the two crown wheels differ? A friend of mine has one of each back ends and both have the same number of teeth on the crown wheel.

Do you happen to know what these markings mean on the crown wheel in the photo? One appears to be the date of manufacture.

In the second photo you can just see (sorry it's out of focus!) the 4 4 marking. This is an unusual position for it, isn't it?

Best wishes

Adrian

http://www.flickr.com/photos/73163549@N ... otostream/

http://www.flickr.com/photos/73163549@N ... otostream/

[Brian]

They change as a pair, you cannot use one without the other, not even ones of the same ratio.

Your friend may have two marked the same but one may have been replaced. I cannot remember the different number of teeth off the top of my head, sorry.

Fords marked things all over the place, your numbers are not in the usual place.

[AdrianNPMajor]

Thanks Brian. Any idea how many of each ratio were produced? Was it roughly equal for example or was one option much rarer than the other?

[Dandy Dave]

Look Here...

http://www.fordsontractorpages.nl/phpbb ... ear#p11415

A topic we covered a while back. Dandy Dave!