DIFF. better 3,07 or 2,88 for 2+2?

[ggg1102]

Hi, I need an opinion about change differential (with a xjs 3,07:1 or 2,88:1).
I have a 2+2 first serie with original 3,31:1.
In my opinion the 3,31 is too short and when you go fast engine revs are to high.
So I'm orienting to buy a different ratio differential.
Two choices: 3,07 or 2,88.
I think 2,88 is more long ratio for a 2+2 that is normally heavier specially with for 4 people on board.

Does someone have experience?
What' your opinions?
Thanks
Giovanni

[Gfhug]

Giovanni, if you search through the forum you’ll find most will recommend 3.07. When I had my 3.54 diff changed I was advised by a very respected overhaul engineer that he recommended the 3.07 as the most appropriate and he had people who had insisted on 2.88 regret it and revert to 3.07.
There are others who prefer the 2.88, but you must consider what sort of driving you’ll be doing. Mostly cruising at high speed or lots of gear changes going up and down hill.

Make sure whoever does the work has a good reputation.

Good luck

Geoff

[abowie]

It's down to personal taste.

2.88 will give you slow acceleration from start but low revs at high speed.

3.07 will start faster and generally be a bit sportier but will have higher revs at high speed.

If you spend the majority of your time driving over 100kph go the 2.88.

If you do a lot of driving on windy roads and in town at slow speed, go the 3.07.

[gtjoey]

Go 2;88 , Ive switch many to 307 but by todays standard the LOWER the revs the better all round.
Who are you drag racing in a 55 year old car.
Go 288 I think youll be happy.
gtjoey1314

[Heuer]

I have a 2.88 diff and a 5 speed box with stock Jaguar ratios in my OTS but I would never put a 2.88 in again! My car has a very powerful engine (280 bhp, 340 lb/ft) and it can cope but it is a pain to drive in towns. First is too low, second too high for a comfortable 30mph so I am constantly hunting between those gears to the annoyance of my wife because of noise and jerkiness. Alpine passes are also a pain as the hairpins mean going into first and slipping the clutch to avoid stalling.

Good combo for touring Europe if you stick to the motorways but we favour the deserted and winding D roads because they are not policed. To give you an idea at 2,800 rpm in fifth we are doing an easy 100mph. Here in the UK with traffic levels and drivers travelling well below the limit I never get out of third gear, which is good for 80mph.

People jumped on the 2.88 because they are readily available from the three gear 2+2 auto cars but totally compromise the joy of the manual car. Avoid, avoid, avoid The 3.07 rules

[gtjoey]

I understand the 307 but your car is unique
Net 285 hp plus a 5 speed plus 288
You created the first Jaguar SUV
With the stock box and 288 with a real 190 hp
I think he will be ok
Imho
Gtjoey1314
What 5th gear are you running?
My new hemi pick up does 90 at 2,000 rpm
And that’s with a huge v8

[christopher storey]

Heuer's advice is sound, to the point, and even more importantly, correct. The 2.88 was only ever fitted by the factory to automatic 2+2 cars, where the torque converter can handle difficult i.e. uphill starts. Even with a 3.07 , I find on both my cars that repeated hill starts can make that nastiest of smells, that of an overheated clutch plate . Avoid the 2.88 with a manual gearbox

[Heuer]

What 5th gear are you running?

It is a T5 with 0.8 fifth gear.

With the stock box and 288 with a real 190 hp
I think he will be ok

That is my point a stock engine will struggle with the high ratio diff especially off the line or with hill starts. My car has a lot of torque (by design) and driving it is fun. I engage the clutch gently at tickover and progressively add throttle to get rolling. At this point other drivers smirk thinking I am an old git driving an old car When the engine hits 1,500 rpm the car is off like a scalded cat and once the peak of the torque curve is reached at 2,250 the acceleration becomes logarithmic; at 3,000rpm I grab second and a couple of blinks later I am over the national speed limit and still going

The Mangoletsi cable throttle helps enormously as it has twice the travel of the stock system so I can balance clutch and accelerator finely. I also have EDIS/Megajolt ignition with two dash switched maps - one nice and easy, the other letting loose the dogs of war. Those two upgrades make the 2.88 easier to drive in traffic but it is a 'game of consequences' - change one thing, add more things to overcome the deficiency.

[gtjoey]

I agree but by todays standards getting off the line with an extra 2 seconds on an old crate the average guy won’t care.
Yes it’s slower but in this case the guy just wants a NICE leisurely pace?
I think
Bang for the buck just dropping the rear going to a 288 is an easy way
I’m in my 2004 575 F1 and after 6 gears and 500 go at the wheels I’m looking for 7!and 8!

[malcolm]

I think the point being made is that the 2.88 makes life difficult on hill starts, and isn't great for the clutch, rather than being about how relaxed it is at higher speeds.
A very good Jaguar tester (one Norman!) spent a long while deciding that the 3.07 was right for the standard manual E Type with a 4 speed box, so that's what I'd stick with.

[christopher storey]

I'm obviously just wasting my breath on the question of hill starts . This bulletin board ( not , be it noted, someone's private blog ) is beginning to depress me, which after nearly 15 years of enjoying it , saddens me

[bitsobrits]

A very good Jaguar tester (one Norman!) spent a long while deciding that the 3.07 was right for the standard manual E Type with a 4 speed box, so that's what I'd stick with.

Norman was doing his testing on the rather tall bias ply tires of the time. With a somewhat shorter modern radial the 2.88 is likely nigh on the same overall ratio as the bias ply with 3.07.

And I would further observe there is only a bit over 6% difference between the two subject ratios to begin with. I'd wager that the majority of those who thinks there is a practical difference between them couldn't discern the difference in a blind test.

[christopher storey]

Norman was doing his testing on the rather tall bias ply tires of the time. With a somewhat shorter modern radial the 2.88 is likely nigh on the same overall ratio as the bias ply with 3.07.

Not so I'm afraid with the correct 80 ( or even 82 ) profile tyres for series 1 and 2 cars , nor indeed with 205/70s as used on S3 cars . Your proposition might be correct with 65 or lower profiles , but then you will run into severe ground clearance problems

[gtjoey]

Old jag guys are funny….
You guys find tragedy at every corner.
Run 205/70/15s on 6 inch wheels
Cut out the bump stops
Put in the 288 ring gear and
Ez steering and it will feel
Like a early 1990s xjs
Ahhhhhh so quite so smooth
And watch the Toyota Camry blow you away in second gear!
Go that route and you will enjoy the car for years to come
Or sell the damn old crate and buy a new Camry for half the price Haaaaaaaa
Love
Gtjoey1314

[Gfhug]

This bulletin board ( not , be it noted, someone's private blog ) is beginning to depress me, which after nearly 15 years of enjoying it , saddens me

Only eight years for me but I’m tending to agree with you Christopher. People can and should be allowed to give their thoughts but not to shout down others. What must the topic author think?
Let him decide what’s most appropriate for his car from reasoned discussion.
I’m very happy with 3.07 for a nice combination of performance when wanted and cruising without unnecessary high revs.

Geoff

[abowie]

This bulletin board ( not , be it noted, someone's private blog ) is beginning to depress me, which after nearly 15 years of enjoying it , saddens me

Only eight years for me but I’m tending to agree with you Christopher.
Geoff

That's what the ignore button is for.

[Series1 Stu]

It's the old story. Ask 12 experts a question and you'll probably get 13 different opinions, especially on an internet forum.

I can't remember what ratio I put in my car, I will have to check. I think it was 3.31 and it was suggested to me that it would be great with the T5 gearbox. When I finally get to drive the car I may regret it, but I do have the original 3.07 final drive assembly sitting under the bench, with its red paint still visible.

I don't feel entitled to an opinion here but, if I had asked the question, my 40 years of engineering experience suggests that I would follow David's advice and fit the 3.07. Unfortunately, the 5 speed option is a whole different ball game and wasn't part of the original question.

Regards

[malcolm]

Put in the 288 ring gear and
Ez steering and it will feel
Like a early 1990s xjs
Ahhhhhh so quite so smooth

Gtjoey1314

If I wanted a car that felt like a 1990's car, I wouldn't have bought a 1969 E Type. And if you want all the other bits you list on an E Type, you might as well buy a kit car for half the price. But in an effort to help the poor old OP who must be totally confused by now, don't listen to people like me who aren't experts, listen to people like David and Christopher who are, and go with the kit it was originally designed with, the 3.07

[max-it-out]

A very good Jaguar tester (one Norman!) spent a long while deciding that the 3.07 was right for the standard manual E Type with a 4 speed box, so that's what I'd stick with.

Norman was doing his testing on the rather tall bias ply tires of the time. With a somewhat shorter modern radial the 2.88 is likely nigh on the same overall ratio as the bias ply with 3.07.

And I would further observe there is only a bit over 6% difference between the two subject ratios to begin with. I'd wager that the majority of those who thinks there is a practical difference between them couldn't discern the difference in a blind test.

Yes , I think this is correct . If you look at the figures for mph and rpm in the original handbook ( 150 mph @ 5500 rpm ) . On mine with 2.88 diff and 205/70 s , 70 is 2700 rpm , 150 would be 5785 . So the early cars had even higher gearing .

[malcolm]

In the original handbook for my S2 2+2, 150 would be just over 6000 rpm!