5 speed options

[Tom W]

Thanks. My gearbox number starts KE, so I assume it falls under the K* range of ratios.

With the 12.5in rolling radius, that would give the following spread of speeds in each gear for my gearbox. This is based on 1100rpm being the minimum rpm, 2250rpm the point below which you’ve dropped off the maximum torque curve, 3500rpm being a reasonable change up point for driving steadily, and 5000rpm being the maximum for a 4.2.

1st at 1100rpm. 8.8mph
1st at 2250rpm. 19.8mph
1st at 3500rpm. 30.8mph
1st at 5000rpm. 44.1mph

2nd at 1100rpm. 15mph
2nd at 2250rpm. 30.6mph
2nd at 3500rpm. 47.6mph
2nd at 5000rpm. 68mph

3rd at 1100rpm. 20.4mph
3rd at 2250rpm. 41.8mph
3rd at 3500rpm. 65mph
3rd at 5000rpm. 92.9mph

4th at 1100rpm. 28.4mph
4th at 2250rpm. 58.1mph
4th at 3500rpm. 90.4mph
4th at 5000rpm. 129.1mph

Changing up at 3500rpm will still leave the engine in the torque band for the next gear. Below 1100rpm, trundling round town, then drop down a gear, or if I’m already in 1st, then I’ll dip the clutch and wait for a bit more space between me and the car in front. All this correlates with the real world driving experience, I really don’t feel the 2.88 is unsuitable for the car.

[64etype]

A 2.88 might be OK for a 4.2 engine and KE gearbox, but I would not want a 2.88 with a 3.8 engine and an EJ gearbox. The overall first gear ratio for launching from standstill is just OK with a 3.07.

[chrisfell]

My 2d.

My car has a 43/14 axle (3.07). I never rev my engine over 3500 rpm. There is no need through the lower gears in order to make “good progress”, and 90mph is licence threatening territory. and very noisy.

I once drove from Prescott Hill to Salisbury in top gear. (Its a long story involving a PO who should have known better.) That’s 90 miles without changing gear, all the way. Including through towns and villages, roundabouts and junctions. No strain on the clutch, the engine is torquey enough to cope and will pull from below 1000rpm with no bother.

In my view a 2.88 axle will be just fine. Just make sure it is a LSD.

[politeperson]

Yes.

I have a spare Jaguar XJS Dana 2.88 you can have for £400 if you want.

You will have to pick it up or I will pallet it for £80 ish

It seems OK but will need XJS rear calipers.

If you dont want it I will list it in Wanted/For Sale.

James

[Barry]

To answer your question, David, my V12 develops 400bhp, and 375lbs ft Torque. I think with 500 horses it may be a bit too much power!! As I said, standard Jag 4 speed with 16” wheels and 225 60 VR16 Continentals, and the 2.88 dif, it’s 88mph at 3500rpm.