differencial ratios

Jorgenson

Member
good evening everyone.
are the differencial of 2000, 3500 o. 3500S identical or have they different ratios?

best regards
jorgen
 
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They are all different, but all interchangeable*. 2000 has a different casing to the 2200 & V8, 2200 casing is the same as the V8 but the V8 has extra strengthening on the pinion housing. 2000 & 2200 are 3.54:1 with 2 planet gears, V8 are 3.08:1 with 4 planet gears.

*Early Dunlop braked diffs have different output shaft housings but they're all interchangeable.
 
4 cyl is 3.54:1
V8 is 3.08:1

The V8 has 4 planet gears and a deeper ring gear than the 4 cyl. Allegedly very late 2200s had this as well. Never seen one.

As I've found the V8 ratio is really too tall - it compensates for the fact there is no overdrive transmission. 1:1 top either auto or manual gives 24.7mph/1000rpm which is really a 5th gear.

What a P6 needs is better transmissions with more gears and keep the 4 cyl ratio.
 
Hi, Two good answers but for completeness. The spelling is differential and the correct word for 'translations' is 'ratio'.

Colin
 
guys, thanx for the answers!
I become two diffs (one from a 2200 and one from a 3500) with a collection of parts. How can I find out which ratio they have without open?

@ Peter: I have a 5-speed R380 installed. do you think that would harmonize better with a 2200 Diff?
 
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guys, thanx for the answers!
I become two diffs (one from a 2200 and one from a 3500) with a collection of parts. How can I find out which ratio they have without open?

@ Peter: I have a 5-speed R380 installed. do you think that would harmonize better with a 2200 Diff?


The LT77 with an 0.77:1 5th will give you 32.09mph/1000rpm in 5th. Thats 51.65kph/1000rpm. Now many people run this setup but it is higher than the SD1 which is both more aerodynamic and some 10% more powerful, so you might find it struggling a little uphill when cruising - the problem being at motorway speeds you drop below the torque peak and the effect of this is much more dramatic than a couple hundred rpm would suggest. You could drop it back a bit with 70 profile tyres but I doubt it'll make much difference. The real problem is with the ZF conversion as top is 0.73:1. Then you get 33.85mph which is just silly (54.48kph).

As I say Rover stretched the gears with the torque of the V8 but it comes at a price. A P6 is much slower in gear than the power and weight suggest because it doesn't have the right gearing.
 
guys, thanx for the answers!
I become two diffs (one from a 2200 and one from a 3500) with a collection of parts. How can I find out which ratio they have without open?

QUOTE]
Turn the input shaft to check the ratio. The one will take 3.54 turns for one revolution of the crown wheel the other 3.08. Its enough difference to be able to check easily
 
So is it possible to build a 3.54 ratio V8 diff ?
ie are the pinion gears the same ? or the crown wheels the same ? nothing the same ? can the 3.54 gearset be fitted to the V8 carrier ?

I ran my car around Snetterton with the tired 3.5 litre engine using the V8 diff and an LT77 and can confirm that it wouldn't pull the skin off a rice pudding - way over geared. I would like another crack at it with the 4.6 to see how that is before playing with rear gears as the car is so nice on the street as a tourer.
 
So is it possible to build a 3.54 ratio V8 diff ?
ie are the pinion gears the same ? or the crown wheels the same ? nothing the same ? can the 3.54 gearset be fitted to the V8 carrier ?

IIRC it can be done but it's not a straight swap. I think it needs a spacer made to fit between the crownwheel and the carrier and different bolts to attach it, but relatively simple to work out once you have all the bits in front of you.
 
Crikey. I'd imagine a potential 160mph gear in a P6 is probably not exactly what you want.... I reckon the original 4 cyl diff is about spot on for road use anyway with a 5 speed box. Still way too high for the track.

I've been talking to Colin Gould about getting such a hybrid diff built apparently possible based on the late 2200 diff with a bit of machining. I did this for my ZF conversion to illustrate the issue. The irony of course is many 4cyl cars in the past have been fitted with a V8 diff to get some motor legs. But we all know what it really needs is more cogs.

As you can see compared to similar vehicles direct drive (1:1) is between 10 and 20% too tall. That's because 4th on a 3500S and 3rd on the 3500 is trying to fulfill the role of both direct and overdrive.
Overdrive gear (5 manual, 4th ZF auo) is again about 10% too tall and of course all gears are proportionally out leading to slower acceleration in real world usage than you should be getting from a car of the power and weight.

gear.revised.jpg
 
Aye, but all show and no go makes for a dangerous combination at this time of year, idle musing and internet searching can be wallet busting :)
I want to make the Rover unit work and I think that the 3.54 with shot peened input, and output shafts with the stress rising step blended and peened may be the way to go.

Harvey I am going to PM you with a link to something, pls have a looky for me ta.
 
Hi Jorgen, good luck with the install. The snow has only just gone here, so no more testing just yet. I think for the road you will find the diff acceptable - it depends if you do traffic light Grand Prix or not, certainly for autobahn cruising it will be good. I would be interested to hear your induction plans and final out put. Regards Mark
 
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