Differential upgrade

[Bernie Hurren]

Hi All

It will still run without the spacer one car in our club here in Australia has been running with a 3.9 diff for years without the spacer.

Bernie

[deckell]

Thanks bernie i measured the 4.7 diff and the 3.9 and there is 20mm difference, dont worry i was tempted to go with out the spacer but erred on the side of caution. regards Derrick Smith.

[jefflee]

Hi all,
Has anyone fitted a 3.54 diff. to a p2/3 6 cylinder ?

[Steve6]

Good Morning All,
Thank you to everybody who has chipped in on this thread, the information has been very useful as I would like to make my P3 75 a little more 'long legged' for more relaxed cruising. I wondered though if anybody has real experience of which is the sensible ratio to go for? At the moment it is 4.7 : 1, so 3.9 would seem a good option, I'm wondering if 3.5 is a step too far? I don't really want to be dropping to 3rd on gentle gradients, but it would be nice to put 3rd where 4th is now for country roads, and have 4th as a sort of overdrive for main roads. I 'd be very grateful for any advice, thoughts or comments.
Many thanks
Steve

[bifda]

Are any of the diffs being removed 4.88:1 ratio as used on the earlier cars?
If so does anyone want to sell their original diffs?
Please message me.

[jefflee]

Hi,
I have a 4.88 diff. for sale on eBay, but please be aware this is for all 34/36 models with 6 splines and totally different to
the 4.88 diff. fitted to 4cyl. cars after 1939 when these were 10 splines and fit most models into 60s (including early landys).
PS. I'm looking for a 3.9 diff. if anyone can help.
cheers Jeff.

[luli]

I have a spare 39-47 10 splines 4.88 diff, and looking for a 4.3 replacement.

[jp928]

Let me throw another idea in here, actually based on experience. I bought a 50 P4 (cyclops) from gent many years ago that had been updated some - P3 gearbox with a Laycock overdrive, and the std diff. Also had a 90 engine in it. It was a real dream, the overdrive worked extremely well, the change up or down being better many modern automatics.
The overdrive bolted right up as I recall, and one of the stock joiners (internally splined sleeve from gearbox output to overdrive input) fitted. Needs a switch somewhere handy - wiring from a P4 would do the job.
Overdrives came in 0.83 (20%)and 0.78 (28%) ratios - possibly too steep for a P3 75 to pull. P4 and P5 fitted with them were electrically inhibited from being engaged in any gear other than 4th.

jp previously P2,P3,P4,P6,P6b, RR, Disco

[luli]

Since my last post I was able to get 1:4.3 diff and fit it in my LHD 1947 Rover 10. The process and results are described here: http://wp.me/pXLKy-2yh, here http://wp.me/pXLKy-2CK and here: http://wp.me/pXLKy-2DJ