The Fordson Tractor Pages Forum

my 6 cylinder conversion is bolted to a np backend, the trouble with this is road speed is really slow and i always seem to be trashing engine.
i would like to keep np backend for hydraulics and diff lock, so i was wondering is there a cog inside that i can get from a diesel major, so i can change the ratio back to faster road speed.
I am not to worried about affecting pto speed as i never really use it.
Tnaks Brett

Hi Brett,

The 4 cilinder enigine runs about 1.800 rpm maximum, I think.
I believe it's possible to give a 6 cilinder engine (savely) a higher rpm than 1.800.
Maybe that increases your roadspeed?

I have a 1961 SuperMajor (with a Major backend).
The roadspeed is about 5 km/h higher than the same tractor with np-backend.

The New Perfomance Supers had two ratio of back axle. One was a 3 to 1 ratio and the other a 4.5 to 1 ratio aprox. This was because the earlier Supers did not have enough "field Gears" around PTO speed.

If you look at the front left corner of the lift as you sit on the seat, you will see a triangular machined area. This will either have a stamped 3.3 or 4.4 depending on which axle you have. From both your descriptions I would think you have 4.4.

Ratios can be changed but you need crownwheel and pinion to do it. I used to change one local farmers ratio every year. He wanted low speed for ploughing and cultivation work and a high speed for the rest of the year.

I put a 6 cylinder Trader engine in a NP Super with the high speed ratio. She would pull a three furrow plough in 5th in light land and do nearly 30 mph on the road. You can open them up to 2300 rpm withno problem.

what are crownwheel and pinion, is it something to do with the 2 large gears in the backend, and will diesel major ones fit in my np.
Justgot back from working weekend, it was 3 hours by road on tractor,so i know my engine is good! But it would be nice to keep up with my mates power major.
thanks Brett

Pinion is the shaft that comes out of the gearbox and engages in the crown wheel that is bolted to the dif, this then drives the two large gears on the halfshafts via bull pinion shafts. It is the crown wheel and pinion that set your rear axle ratios and therefore your forward speed.

Brian i have an old diesel major rear end, will the parts be interchangable or do i have to have super major ones.
thanks brett.

Brett,
You can fit the pinion and the crownwheel to your dif. But make sure the donor tractor is pre-1960 or that it has the 3.3 ratio fitted.

The early crownwheel will be riveted on but you can change this for the special bolts.

i have got a pre 1960 backend so will try and change them over.
thanks for the advice.

hi just got round to stripping the donor backend ( after breaking my thumb).
managed to get out the pinion easily but how do i remove the crown wheel and is it the same procedure on the new performance .
the donor pinion is 10 teeth and crownwheel 35, have not checked np to see if they are the same or not.
thanks brett

You remove the bull pinions and housings. The bull pinion housing has the tapered dif bearing cup in it. You will also need to remove the crown wheel rubbing pad on the side of the axle housing.

Each Bull pinion housing also has shims behind it to set the backlash in the crown wheel and pinion. Check this carefully as you re assemble with a dial gauge otherwise all your hard work will be in vain.

Watch out because that unit is heavy and you do not want to drop it on your hand inside the housing.

Check the number of rivets around the crown wheel before taking it off the carrier. You will have to change just the ring gear as the NP Super has dif lock and the Major does not.

i may sound stupid but how do i remove bull pinion and its housing as has the large gears going into it.
can they be un bolted somewhere or do you have to pull out halfshaft and remove the big gears.

Yes you have got to get the Bull gears out of the way so that means drawing the halfshafts a little.

We have just got a new performance and it says 4 4 in the triangle would this be the fast or slow ratio

Thanks Matt

4.4 is the slow one.

Hi Matt, i still have not got around to changing my ratios ( to cold and wet), just wondering where the triangle is exactly on your np as i cant seem to find one on mine.
thanks Brett

Below is a picture showing where the triangle is (left hand front of hydraulic top cover


Thanks Matt

cheers for the picture, just been out so look at mine again scrapped off paint and still no stamp, so i am guessing that mine never got stamped.

Brian, you wrote:

Brett,
You can fit the pinion and the crownwheel to your dif. But make sure the donor tractor is pre-1960 or that it has the 4.4 ratio fitted.



I thought the problem was a slow tractor and to increase the speed he needed to install a 3.3 ratio?

Kjetil

Finger trouble Kjetil. You are right and I have changed the original comment.

If he counted the teeth right. 10 x 35 he should have a ratio of 3.5 to 1. Or three and half turns on the Pinion, to 1 on the Crown Gear, or as we call it over here,a Ring Gear. Dandy Dave!

This was a most interesting topic... I have a september 1961(yearmodel 62) super major, which rear end ratio would I most likely have? Will have a check at it tomorrow but guesses would be fine aswell

Quick edit aswell, the quick and dirty way instead of counting teeth would be to measure the circumference of both gears and divide the larger one with the smaller, correct?

EDIT:
Of course I just had to have the ratio I didn't want... it said 4.4 in the triangle

Does it means all pre-60 models have a 3.3 ratio?

Foxen wrote:This was a most interesting topic... I have a september 1961(yearmodel 62) super major, which rear end ratio would I most likely have? Will have a check at it tomorrow but guesses would be fine aswell

Quick edit aswell, the quick and dirty way instead of counting teeth would be to measure the circumference of both gears and divide the larger one with the smaller, correct?

EDIT:
Of course I just had to have the ratio I didn't want... it said 4.4 in the triangle

To be a 3.3 ratio. It would have to be 10 X 33. Or 10 on the pinion and 33 on the ring, or crown, gear. Gears are always measured by the transfer of teeth. Pulleys, on the other hand are measured by the circumference. But, may not be as accurate in the real world as there is slippage, and the way a V belt will ride in the V grove of the pulleys to contend with. A worn belt will make a difference also. Gears always have a positive tranfer of power. Unless they loose some teeth of course. To figgure rear ratios, Always divide by the smaller number of teeth into the larger number, and that will give you the ratio. Flat belt pulleys also always have a crown to keep the belt riding in the center. This would also make a slight difference in calculating the feet per second/ minute to RPM. Dandy Dave!

Kjetil wrote:Does it means all pre-60 models have a 3.3 ratio?

Looking up the parts at CNH there are 2 different ratios.

The first being 3.5 to 1, From 1952 until 11/30/60
The second being 3.5 to 1 from 1/11/ 60 to 12/31/64
The third being 4.375 from 1/11/60 to 12/31/64

For all practical purposes, 4.4 on the case would be close enough for identification. Dandy Dave!

Dandy Dave wrote:

Kjetil wrote:Does it means all pre-60 models have a 3.3 ratio?

Looking up the parts at CNH there are 2 different ratios.

The first being 3.5 to 1, From 1952 until 11/30/60
The second being 3.5 to 1 from 1/11/ 60 to 12/31/64
The third being 4.375 from 1/11/60 to 12/31/64

For all practical purposes, 4.4 on the case would be close enough for identification. Dandy Dave!

That leads to a question aimed at our guru, Brian:
Does the ratio from pre 1960 fit in a 1961/62 rear end? I suppose that it makes no difference if you take both the pinion and the crown gear from the same rear end and don't mix a pre 1960 pinion with a post 1960 crown gear?

Edit:
What exactly must I do to change these btw? Take off the brake housings, pull the axles, loosen the bull gears and pull them off, and then? How is the pinion fixed on the axle and how do I go about measuring in a correct gear lash?

Edit2:
I don't care much for the differential lock on my super major so I am simply wondering if it's possible to replace my 4.4 differential assembly with a 3.5 assembly from a major or power major? I mean, do the bull pinion shaft splines match up or did they change somewhere in between models?