4AB & 4AD Diff's

[Stephen]

Hi Everyone .. The diff in the 4AD I am restoring is pretty ordinary after sitting out in the weather for 20 plus years, but I have acquired a 4AB diff in very good condition .. The question is will it fit in the 4AD Housing OK, are they the same ration, and how do I interpret the marks on them.. the marks are hard to read and look like handwriting and numbers engraved on the crown wheel ? .. Regards Stephen

[kabu]

Hi Stephen,

I have an understanding that the roadsters with the smaller 1100cc engine (like 4AB) had a different rear axle ratio than the 1500cc 4AD. I found information that 4AB has a ratio of 5.43:1 and 4AD has 4.875:1. The twin carb version 4ADT has even longer ratio of 4.44:1.

If you have the differential open you can quite easily check what the gearing ratio is by counting the teeth on ring gear and pinion and dividing them. For instance the 4ADT rear axle has 40 teeth on the ring gear and 9 on the pinion -> 40/9=4.444

Regards,
Pekka

[Stephen]

Thanks for that Pekka .. did as you suggested and get a ratio of 5.428 which makes the spare I have a 4AB diff ,.. so I will recondition the 4AD diff that I have in the car to keep it standard .. Regards Stephen

[Peter McKercher]

Just a reminder to all - this and much more information is on the NASOC site. Check http://www.singercars.com/profiles/index.html?pnl=1_2 for technical specifications of post war Singers including the gear ratios.

[Stephen]

Thanks for the info Peter ..I have studied these sheet and have found them a great help... but when your presented with diff wrapped in a old bed-sheet in a dilapidated cardboard box, that had "Singer" written on the side, it helps to know how to calculate the ratio of said diff, so Iu could then go to the info or data sheets to confirm they type of Singer it possibly came from, and without Pekkas help I would not have know how to do that..
I thank both of you for helping with the problem
Regards Stephen

[Peter McKercher]

Stephen

Hands on experience from members around the world is the benefit of this bulletin board. My comment was intended to remind people also of the huge volume of information buried within the bowels of the site in general. It's not always easy to find, however.

[Stephen]

Hi Peter .. no problems, I appreciate any and all advice on Singers .. I trawl thru the various Singer sites and Internet in general, and your right, sometimes it is hard to find exactly what you need to fix a problem, and only those that have been there can help ..
I appreciate all advice that comes my way..
Regards Stephen