Hi, I have converted my 66FHC from 3:54 to 3:06… my 65OTS still has 3:54 diff. The 3:06 is a slight slip of the clutch to take off. The 3:54 is simply dump the clutch. I have driven a customers car with a 5 speed conversion. Yes, it does cost more,but it definitely is the way to go if you can afford it. At a lecture I attended by Norman Dewis, Jaguar`s development man for the E type, I asked him what was his favorite diff ratio. He said the 3:31 was the best of both worlds, however it is a rare find today and 5 speed conversion were not done back then.
Me too. I went with one that did not have an LSD and it was much less expensive (<$900 including shipping though that was 7 years ago). A plus is that the 3.058 is a stronger unit that the original (I forget the teeth/fraction involved but Dick M will have details).
The swap was just a lot of basic wrenching.
I was fortunate enough to find an NOS 3.07 speedo for not much money (Norman Motors in my case).
If you tell me your tire size and the final gear ratio you install, I can calculate the speedometer TPM with high precision for you. The Smith’s speedometers of this generation had interchangeable innards, so if you can find a speedometer with the correct TPM, it’s easy to swap.
I puta 2.88 in my 4.2 FHC ….fabulous 60 mph 2100 rpm …. Ok so it doesn’t have the same off the line as a 3.54 but it’s still quick… and I don’t keep looking for 5th gear…… I’m about to start on a 2+2 which will have the od gearbox taking it all down to 2.24 if I use a 2.88 diff ….but even a 3.54 goes down to 2.76 with od …. So may stick with that …still summing up the options
The Driven Man gearbox I got has a 0.73 OD.
When calculating this up against a standart 4 speed gearbox, it will act a a final drive with a ratio of 2.58
Not bad at all.
3.8, 8:1 comp, 3.07 diff. Got off the line just fine, could shift from 1st to 4th at 20mph and pull away cleanly. 24mpg reliably. If I had another one, I’d leave it as it is.
I’m not sure …. I just had my mechanic do it he used a xj12 diff and brakes… works perfectly …… I know the autos used a 2.88 in Europe and US I believe so must fit the diff……. Someone else will know for sure
I have a 64 S1 with a 2.88 as well and a 65 S1 with a 3.07.
I really like the 2.88 as the car gobbles up the road.
As long as you get the Salisbury Diff you can use the whole lot in an E-type I just changed the seals and the bearings on them. Try to avoid the Dana or your brakes wont fit.
I have S2 brakes on S1s, as I got a bit of fade with the smaller S1 pads.
I think the first 2.88 conversion I did cost me £400 which was the cost of a V12 Salisbury locking diff from an XJS.
Dave, you’ve gotten a lot of good advice here and I wanted to share my experience as well. My '62 had the Moss box and needed a new clutch so I took the opportunity to upgrade the gearbox while the engine was out. I really agonized over whether to go for a all synchro 4 speed or a 5 speed. Ultimately I went with a Broadsport 5 speed in October 2019. All in, the kit (gearbox, mounts, propshaft) cost $6000. If you choose a 5 speed I think this is the only reasonable option on the market right now. It transformed the car for me, likely in large part because I didn’t have the Moss anymore which made it a lot more fun to drive. I also now get 23-24mpg on the highway.
I have heard that Driven Man has input shaft problems (ie they have a tendency to break). In fact, the shop who did my swap will no long install those due to that problem. I will add that at the time I heard rumors that Paul C. was going to start making the JT5 again so I tried to hold out for that. My understanding is that he never did make it again because he can’t get good quality input shafts.
I have been very happy with the 5 speed. As of today I have put about 13,000 miles on it without issue. An important point with the Broadsport is the possibility that the cross member may need to be cut and welded to make it fit. My car did not require this but I’m sure others do. The result in my car is that the output flange of the gearbox clears the cross member by a very small distance. After about 10,000 miles my rear engine mounts settled a bit which cause this to contact the cross member. I shimmed it up with a few large washers under the mount bushings to solve that problem. Took me less than an hour for that project.
Would I do it again instead of a 4 speed with 3.07 rear gear (my diff is 3.31)? Hard to say. As others have mentioned, when you get a 5 speed for these cars what you are getting is a bespoke gearbox made by a company that might not be around forever. I’m not sure if that is truly a problem but I suppose it could be. With the 4 speed you get to have all Jaguar parts which I think is a positive.
I’m restoring a 1971 V12 right now and am putting a 4 speed with OD in that one so I have on of each!
I think you will be satisfied either way. Since you already have an all synchro 4 speed I’d probably be tempted to just change the rear axle ratio. Its probably worth just having the entire differential professionally rebuilt at the same time so you never have to worry about it again. This runs $2000-2500. A local shop in PA rebuilt mine last year for $2300 and when I called Coventry West to get a ball park price it was about the same.
Agan this depends on what you have and what you want. I would never go for a 5-speed, but then again I have never owned a SWB personally.
I was happy with the MOD conversion and a 3.31 final drive in my ex S1 4.2L 2+2 and am currently happy wth the 3.54 final drive and a 4-speed in the V12 OTS as it happily revs into 6.000+ rpm in top gear. YMMV.
I switched to a 3.07 in my 70 ots years ago ($700). I am very satisfied with it. A 5 peed is fine but the cost is significant and I woried that parts may not be be available down the road.
Most of, if not all of them, are based on existing, proven transmission platforms. Despite what some vendors try to claim, they did not engineer their own transmission and internals. They at most re-cased the internal mechanisms from existing ones. (i.e. T-5, MT75, Supra, etc.)
So if one studies the gearbox details, it may be possible to see how many bespoke parts they really need. It sounds like the input shaft is one of them for the T-5 based units.
But for others, like the “billet case” transmissions, it might only be the case that is custom. The most common wear parts like synchronizers, bearings and even gears are readily available. (though I remember reading that one of the common boxes used overseas - was it a Getrag or the Supra box? - was hard to get parts for now.)
