Diff swap or 5 speed?

And it looks lovely too. :+1:

Do you know what the engine output is?

Hello Clive, sorry, I am up a mountain in France with limited internet.

Its about 280 hp, cant remember the torque, but plenty of it low down.

It feels like about as much pep as you would want without substantially changing the character of the thing by fitting suspension and braking “upgrades”.

I sure don’t know the ins and outs of E-type production, but I thought the early E’s (3.8) came with the 3:31 standard except North America - that’s YOU too, Canadians. Not much help, as getting an outlander to part with a rear end and getting it shipped, etc. is harder than other options - but… for some it may be an option. As I have posted, our current car, a solid lifter '65 Corvette with a 3:70 (the STOCK ratio with the solid lifter motors), can spin that on the x-way - not that it’s ideal, but it sounds like it can “take it”. When we took the Jag to a cars/coffee on I94 we were passed by a Superperformance GT40 and no way we could chase him with the 3:54 as he was a spec on the horizon.

We "caught " him, eventually…

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Understood and agreed, it’s all about balance. Personally I go for the suspension and braking upgrades, as support and balance for powertrain changes. I understand others look negatively on that, there is room for all our viewpoints. It’s only a car. (I can’t believe I said that…)


Your car your dream do what you want is my motto ….I may not agree ( I don’t really care in this case) but I do really appreciate the work that goes into these projects…… in the same way a hot rod der won’t like classics restored to original….but they sure as hell appreciate what it takes to achieve that ….horses for courses

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It’s a matter of perception. I lived all my life in countries where the speed limit is anything from 75 mph to unlimited. By the nature of that (speed limit) people drive with higher revs. We get used to it.

Hardly anybody got 2.50 gears or a 6-speed. If you get what I mean.
Of course, if you can’t bear your revs at cruising speed, go for 5-speed.

Or change diff, if it is a matter of originality. But, if you ever changed a diff (yourself), I doubt you would to it again.

Good news and maybe more good news. My airplane buddies recommended a shop that will redo the gearing in my old pumpkin. This shop has done it before quite a few times but not in the last 20 years. They asked me to do the research on part numbers so I’ll be searching here and maybe asking more questions.

The other good news is that I’ve found an XJS diff from a decent car. It’s a 2.88 and they want $600 for it. I imagine they’ll take less. So assuming the used diff is good, what’s the best path forward?

I’m thinking getting the old one rebuilt is the way to go. I’ll have a part that I know is good.
I’m not worried about cost.

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Assuming I did the math right.

Assume you are driving at whatever speed 3,000 RPM gets you with 3.54 gears. To achieve that same speed with 3.07 gears your engine will run at 2,600 RPM and will run at 2,440 rpm with 2.88 gears. Not much difference between 3.07s and 2.88s.

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Funny. I paid a little less than that for my new 1962 OTS. My, my, money is becoming worthless.

Use the 2.88 ….if you like long relaxed motoring at quite revs ….I love mine