Manual Box with 2.88 Rear Axle

[Retroman]

Hi,
Has anyone out there run an auto to manual conversion using the UK spec 2.88 axle with or without OD?

The standard 4 speed box would appear to give same engine / road speed ratio in top (OD maybe too much given !)but Is the first gear ratio ok for initial take off given that the engine has plenty of torque OK in practice or is too much for the standard clutch.

Appreciate there are theoretical disadvantages but has anybody actual ran one to establish if it actually a problem?

Thanks
Nigel

[christopher storey]

It slightly depends which box you are going to put in. The 2+2 box , and the S2 OTS/FHC boxes, which have KE KJ or KJS serial numbers are slightly wider ratios than either the Moss box or the early close ratio 4.2 EJ series boxes, and as a result have lower 1st gears which are satisfactory for the 2.88 . The engine will have no trouble pulling either the wide ratio or the close ratio , but the close ratio boxes will punish the clutch if you get into a situation where you have to make a number of successive hill starts, so the wide ratio boxes are better if you are sticking with the 2.88

[64etype]

My '64 3.8 FHC is retrofitted with an EJ close ratio gearbox and a 3.07 final drive. While launches from stand still are reasonable, I definitely would not want a 2.88 with the first gear ratio in the EJ. That said, the EJ transmission is a delight on a curvy road.

[Tom W]

I swapped from the 3.54 to a 2.88. I have the standard series 2 manual gearbox. No problems with the clutch, but I don’t live in a particularly hilly part of the world.

[tinworm]

3.31 for me - I find even the favoured 3.07 is too tall a ratio.

Barrie

[politeperson]

Here is me driving a 4.2 with standard 4sp. synchro and a 2.88 rear end.

No worries! Been all over Europe.

"Slightly" ungraded engine, but low speed torque same as a standard SU 4.2.

Not too much clutch slipping.

[Retroman]

Gentlemen,

I will give its a go with the 2.88 axle and see how it goes.

Politeperson's video has given me the motivation I need.
Great video and even better sound.

Now on the lookout for a decent gearbox!!
Thanks for all the good advice.
What a great forum.

Nigel.

[max-it-out]

I`m currently in the process of changing from 3.54 and wondering whether to go for 3.07 or 2.88 . I have 205 / 70 tyres , so they are actually a bit smaller than the original spec ( c. 3 % ). I just looked at the data for the early 3.8 cars , and the revs at 70 mph are quite similar to my car with a 2.88 fitted ( perhaps the tyres on earlier cars were bigger ? ).
It would be interesting to know the ideal gearing for the usual 60-70 mph cruising speed . Obviously there comes a point when the car is too high geared for the power available . Is there an optimal rpm where the engine works more efficiently , or doesn`t it matter ?

[Heuer]

Go with the 3.07. I have a 2.88 diff in my OTS and whilst it is good for hurtling through France at 100mph (3,000rpm) it is a pain on UK roads and certainly around town. I spend my life in 3rd gear as most traffic on main roads travels at 50mph or less. Around town I am constantly shifting between 1st and 2nd.

If you want to play with ratio's use this interactive tool:

RPM to MPH calculator: https://wahiduddin.net/calc/calc_speed_rpm.htm

[Polse7317]

David ... You risk a French police fine if you drive at 100 mph ...! keep your money for a good restaurant and elegant wine... Speed control radars are everywhere ....

[Heuer]

We stick to the C and D roads but I agree times have changed. Obviously the French Police no longer follow the -10% discount rule? Only time I was caught on the Autoroute they clocked me at 154kph which was discounted to 141kph which turned into a 45 euro fine - bargain after three weeks of 'pressing on'. It now makes the 2.88 diff even more pointless!

[christopher storey]

I agree with David ( Heuer ) . The 2.88 was only ever fitted to automatics where hill starts were no problem . Even with the 3.07, the EJ box 1st gear is too high for comfort if and when , as happened to me, I was put in a position where a hill start was needed evey few yards, and after about the 3rd occasion the clutch started to smell unpleasantly

[Keith G]

Although a lifelong Jag fan and previous owner of 3 XJ's back in the 90's, I only recently bought an E-type, a 1968 S1.5 OTS which I bought from a guy in Toronto and shipped back. It was exported to New York from the factory, and the tab on the diff is hard to make out, but appears to show 46/13, and the speedo has 1312 printed on the face. So, obviously a 3.54 diff, standard fit on a US spec car. Also, it has 205/70 R15 tyres fitted. But on the road, the car is very low-geared, feels like it needs at least one more gear, maybe two! It redlines at 78mph in top! I have checked the speedo, and it's about 8-10% optimistic, about normal for a 60's car. Even allowing for the 3.54 diff, and the modern tyres, that doesn't add up, does it? I am planning to get the diff changed for a 3.07 this winter, but want to be sure before embarking on that cost. I would be grateful for any advice.

[mgcjag]

Have a look here....viewtopic.php?t=120

[Gfhug]

Welcome to the forum.
What revs do you class as red line? As 78mph at redline seems very strange. Rev counters can be unreliable so it might pay to have that checked by e.g. Speedograph Richfield.
Mine suggested a 3.54 diff but was over reading the correct 3.07 figures.

Geoff

[Keith G]

Thanks Steve for the link, that thread was apparently too old for my searches to pick up, but very interesting.

Thanks Geoff for the welcome, the car reaches an indicated 78 mph at 5500rpm. I have to change up at about 60 in third when overtaking, and the engine howls between 4000-5000rpm in third when accelerating hard, so the tacho appears to be about right! I will get it checked as you suggest, all the same. The 1312 printed on the speedo, and the 46/13 tab on the diff both seem to confirm that the car has a 3.54:1 ratio, which is what you would expect for a car shipped new to the US, which I know to be the case. Everything points to that, except the performance on the road. According to the link Steve gave me, an E-type with a 3.54 diff should do 65mph at 3000 revs, so 119mph at 5500revs. My car only does 78, which means the gearing is too low by about 35%. I even wondered if it had been modifed in then past for competition in hillclimbs, or something like that. I'm baffled, and hoping someone on the forum can shed some light!

[mgcjag]

Hi Keith....you really need to check what ratio your diff is....jack up the reat end......turn the propshaft by hand and measure the turns of the rear wheel...you cant just rely on a diff tag....Steve

[Keith G]

Hi Steve

Thanks, yes, that makes sense, it will prove the absolute truth beyond doubt. I just bought a low-profile trolley jack, so this will be its first task! I'll try it at the weekend!

Cheers!

[lestere]

I converted my 66 2+2 from the 3.54:1 diff to 2.88:1 a few years ago. This conversion transformed the car from a buzzy noisy drive on faster roads to a relaxed drive still with plenty of torque. Third is now a fantastic overtaking gear. Previously 3000revs in 4th gear was around 64mph and now 3000rpm is almost 80mph. Being a 2+2 with the wider ration gearbox the car has no problems with hill starts.
Just one point, be carful not to rely on the speedo and revcounter. They can be very inaccurate. A satnav or app-based speedometer can help here and there are calculators on line to give you a true ides of RPM when you input ratios and tyre sizes. You will need to recalibrate your speedo after a axle ratio change.
We all have our own preferences on the way we like our cars to drive. I am very glad I went for the 2.88 ratio.

[Keith G]

Hi Lester

Thanks very much for that, it's very interesting to hear different owners' perspectives. Do you find you are often changing down into first around town, as another member mentioned? I like the idea of being able to cruise fast at modest revs, so I am tempted by a 2.88. My car has a non-standard stainless exhaust fitted with four tailpipes, it sounds great ticking over but makes a hell of a noise when accelerating hard, so all the more reason for low revs when cruising. I'll need to check whether my roadster has the wide-ratio box, but at the moment it pulls away happily from barely moving in second, so I can't imagine it will be a problem. Having said that, I live near Macclesfield, so hill starts do arise!

Cheers!