New End Ratio for 1954 XK120 FHC

Dear list,

Following recent threads and after our first “serious” trip with the XK, in which it behaved faultlessly, it became apparent that I will change the rear end for a longer ratio.

I contacted a supplier of diff parts, that can stock a 4HA 2.88 end ratio, that would give me ca. 2300 rpm at 100Km/h instead of the present close to 3000 rpm. I assume that a Salisbury for a 1954 XK is not black magic?

  • Would anyone confirm that this is an “old gears out, new gears in job”?
  • Is there any further machining needed?
  • Other than getting the half-shafts out and getting a proper pre-load, is there anything else to be taken care off?

Many thanks,


2.88 is brave!
what motor are you running
what gearbox do you have
what wheels are you running
I had an XK140 original 140 motor but probably overbored with pair 2 inch carbs and xJ overdive box running 3.07 and in OD top it was doing 1600 at 100km but sufficient power when dropped from OD top back into 4th and sufficient power of the line

Terry, thanks for the reply, yes 1600 at 100 is steam boat… but the 120 has no overdrive, a 2.88 gives 2350 rpm at 100km/h in top gear, which is ideal.

I have the stock 3.4 with an 8S head and the Moss direct drive 4th. 3.57 is overkill…


My XK 140 FHC had the standard 4.09 rear axle of the overdrive version, but I got the advice to take a lower gear ratio and installed a DANA 3.72 version. The end result is that in overdrive mode the ratio is about 2.9 (28% reduction due to overdrive, if my calculation is OK).
If I had to overtake in the overdrive mode, I had to switch off the overdrive otherwise it would take too long.
If you have a similar end ratio (you say 2.88), I guess you will have to go back to third gear when overtaking, as the top gear will be only suitable for “touring”.

Disassembly of the rear axle is far from “old gears out, new gears in". If you have all the required tools and if you can get the rear hubs off and the half-shafts out, then you’ve accomplished a “hell of a job”. This was about the only thing I asked a specialist to do on my cars.

Bob K.

Thanks, yes, 3rd would be like a third and a half, so seems good to me. I also live in The Netherlands, and “cruuuzing” is 80% of my driving.

On some cars it is a simple in and out job, but on these it certainly isn’t.
I managed to do mine, having not done one before, but it is a very tedious job.
First you will need the following tools and equipment and know how to use them.
Electric welder.
Oxy Acetalyene welding kit.
Long breaker bar.
Large 3/4 drive socket wrench.
Sledge hammer and 2lb hammer.
50 ton press.
Dial gauge.
Marking blue.
Various lengths of tube, round bar, angle iron, threaded rod
and plate.
Trolley jack.
Torque wrench.
Vernier caliper.
Workshop manual.
A couple of weeks off work to do it!

In short: the hubs pressure-weld to the shaft and it’s a pain to remove them?

I guess you mean it boils down to that?

So let me reformulate: provided you manage to undo the shafts with a lorry-like shaft puller and suitable cursing, is it a “usual” diff job or will it need machining to the inside of the casing? You mention a lathe? Is that what you mean?


The lathe, electric welder and scrap metal are needed to make up the necessary tools, such as distance pieces, drifts, spacers etc. and the case spreader, which should be used especially on reassembly.
The oxy/ acet for heating up the hubs in order to attempt to get them off using an industrial type puller. The 50 ton press for when this method fails, and you have to bash out the whole bearing assembly complete with half shafts, with the afore mentioned sledge hammer.

Hi LLuis,
I replaced the 3.54 gear set in a 4HA 120 FHC rear axle a year ago and followed the instructions found in the factory Jag repair manual. The job was not trivial, but doable by anyone with decent mechanical ability and experience. Here is what is involved:

1, Removal of the hubs from the axles. This can be a challenge and has been discussed on this forum many times in detail.
2. Removal of the axle shafts from the rear axle housing. I used a slide hammer with jaws located under a washer and the axle nut. The axle end bearing comes out with the axle shaft. It can then be removed and replaced using a hydraulic press.
3. Removal of the differential carrier using levers, or a case spreader if you have access to one. I found it not necessary. The carrier is preloaded slightly and the Jag manual covers how that is achieved.
4. Replacement of the ring gear to the carrier housing. Dana supplies new high stress bolts to replace the old style that required bent tang keepers. The new ones are torqued to 80 ft-lbs and I also used thread locker. The old style was prone to breaking and destroying the crown and pinion gears.
5. Replacement of the pinion and bearings. This is very finicky and requires measurement and shimming to set the proper cone depth, which is key to proper engagement with the crown wheel. I made up a set of “set-up” bearings that could be slid on and off the pinion for shim selection.
6. Replacement of the carrier bearings. I also made a set of “set-up” bearings for the shimming operation that is requires to set proper crown wheel engagement and preload. This is the most time consuming part of the job and very frustrating, using yellow marking grease to see the gear engagement in forward and reverse. The carrier came out many times to get this right.
7. Replacement of the axle seals. New lip seals are available that are far superior to the old leather seals. In many case the old seals wore grooves in the axles. New axles may be required, I was lucky enuff to locate a good original pair.
8. Set-up of the end play of the axles. This requires a dial indicator and several iterations to get the shims right.

All in all it is a very finicky job, especially if it is your first time doing it. Setting the zero cone depth requires a special measurement tool, or some imagination. In my case I used a flat bar across the main carrier journal lands, with a depth micrometer set to the pinion face and adjusted for the thickness of the bar.

The last advice I will offer is to check the spline count of the new DANA 44 pinion input shaft. Crown wheels and pinions are supplied as a matched set and you are advised not to reuse your old one. In my case the new pinion had a higher count of the pinion splines and I had to obtain a matching pinion input flange. It did not slide on properly and I spent hours hand filing the splines to fit. The input flange needs to be removed several times to get the bearing preload correct, so it is important to worry this detail at purchase rather than after the fact.

A professional shop will have all the necessary measurement tools and set-up bearings. A local shop (in CT) charges around $2500 to do this job, including a new DANA 44 gears set. Also be aware that there is a split point on the gear sets offered by DANA that requires a different carrier housing. I don’t recall what that was but you may fall into that.

Tom Brady

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Thank you so much. Very clear.

Differential Carrier Breaks | West Coast Differentials

here is the split ratio (3.73 / 3.92), so according to this, the OP should be ok, in that he does not require to buy a new carrier, but I have an inking 2.88 might be an issue, so triple check with the supplier, or a suitably experienced professional gear shop.

I think the Dana and Jag ring gearset have different size holes too, one is 3/8" the other 7/16, so you either need to drill & tap or fit sleeves, I cant remember which way it is

Google can answer that for you

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Not sure where you are in the world, but if there are shops nearby that specialize in off-road Jeep drivetrains they will be extremely familiar with the Salisbury 4HA rear axle. The contemporary Dana-Spicer model 44 was widely used in American light trucks throughout the mid 50s through the early 1980’s and internally is virtually identical to the 4HA. Since the off road and rock climbing crowd is almost always interested in gear ratios 4.88 and lower (higher numerically) they almost always have used gear sets laying around (though it’s doubtful you will find a 2.88 there). The contemporaneous Dana 44 used the same size axle shaft and spline count as the Salisbury. The Salisbury 3/8" bolts are a well known weakness, so if you can find a Dana carrier with the 7/16“ bolts it would be a worthwhile upgrade.


The Salisbury uses 3/8" bolts which are extremely marginal for sporting use. I can’t count the number of broken 4HA ring gear bolts I’ve seen with the threads stretched or the heads broken off. The Dana 44, which was usually found in trucks, use 7/16" bolts. There’s no reason you can’t put the course spline Dana 44 carrier in the Salisbury housing.

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I think that (at least) some US spec S3 XJ and XJS had 2.88 Dana diffs in them , probably have LSD too, less sure about Euro spec. Listers on those forums will probably know

You can use a home made spreader made from angle iron and threaded rod with nuts
Spreads the case just enough to make things much easier, but not risk overstretching

The trick here is that the 1950’s to 1970’s Dana 44 differential used the same size axle splines as the 4HA, so it was a straight swap. When you get into the later IRS varieties the splines are different and things are not as straight-forward. I have never needed a spreader to service one of these. The bearing preloads are just not that high.

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Hi again all,

Now time to look into buying a crown and pinion.

I wondered, thre are new DANA 44 carried and pinion units at 35 splines? Will these fit the XK120 4HA shafts?

Settling for 2.72 or 2.88 with the original Moss and looking forward to it.

Many thanks,


XK120-140-150 Salisbury rear axles all use coarse spine axles and pinion gears. The axles are 19 spline and the pinion gears 10 spline. This is also true for other 1950’s-60’s vehicles that used the Dana 44, including Jeep, Ford trucks, Studebaker trucks, International Harvester trucks and Lincoln and Ford station wagons. The newer Dana/Spicer stuff uses fine spline axles and pinions.

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I thought the 120s were all using 2HA, not 4 HA. I recently changed my ring & pinion in the 140 to 3.07 from 3.54. I used the Dana parts and had to change the pinion to the kind with U bolts and that meant a new drive shaft for about $275.

Nope. Very early, 49-50, was ENV, then 2HA through 52 or so, 4HA after that. 2HA and 4HA used the same half shafts.

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In fact, the ENV was used up until at least late 1951. I have noted a LHD fhc from March 1952 #679486, although the SPC states the first 2HA was fitted to #679222. Perhaps the ENV was used intermittently for a while after the change to Salisbury…?

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