X308 or XJ40 differential in x300?

The differential in my 3.2l manual x300 started whining and is rapidly getting worse. I had a look inside and found metal chips, so I think it might be best if I get a replacement as I think the gears might have suffered in addition to the failed bearing.
So what I am wondering now is, are there alternatives I can look for, or do I have to find an x300 differential? Will the XJ40 or x308 units fit? I read something about an offset input shaft, but I am not sure wich differential has one and why some people seem to think it is OK to interchange the diffs anyway.

Regards,
Harald

I don’t think the X308’s will work, as their design changed to have the driveshaft in the center, whereas the earlier had an offset driveshaft angle.
Rob

Hi Robert,
Thanks for confirming the offset driveshaft.
The x308 diffs are cheaper, but I think none of the x308s had a gear ratio that would work anyway. The 3.2l manual has a 3.77:1 ratio and I need something that is not too far away from that. 3.54 will probably work and shouldn’t be too hard to find.

Cheers,
Harald

The XJ40 and X300 are physically identical. A few of the bolts/studs are different but I interchange them all the time.

3.58:1 is the common ratio for the 4.0 cars.

Thanks Motorcarman!
3.58 is even closer to the 3.77 I currently have.
I might have found a diff from a 3.6l XJ40. Would you happen to know if that is also 3.58?

Cheers,
Harald

The problem is that many, if not ALL the 3.6 cars have something like a 2.88:1 diff ratio.

There should be a ‘colored-tag’ on the rear diff cover that will designate the ratio and limited slip or not.

Oh, 2.88 won’t work at all. I’ll have to find something else then.

Hi Motorcarman,

I found 3.58 for the 4l cars, but can’t find any reference to 2.88 for any of the XJ40s.
Are you sure the 3.6l cars have different ratio from the 4l?

There seem to be two different input shaft flanges. One for cars with Jurid coupling at the input shaft and one for cars without. Can I just swap the flange from my old differential to a new one, or does that not fit?

Cheers,
Harald

The ‘flat-flange’ (4 bolt) is the 3.6 and most are 2.88:1 here in North America.

The JURID type diff has a pinion shaft with a centering extension.

I have cut the extension on the JURID shaft to fit sedan diff in an X100 (XK8 4 bolt flange) but I have never tried to fit a diff ‘the other way around’.

The fibre JURID coupler would not have the center support but I guess you could try it?

Thanks again! Since I need to buy a differential, it is probably best if I spend a bit more to get one with the correct Jurid coupling.

Cheers,
Harald

I picked up a differential today. It is a 3.58 out of a 4l XJ40 with the correct flange for the Jurid coupler. As a bonus it is a power lock!
I will probably replace it over the winter and will report in spring how much of a difference the 3.58 makes over the 3.77.

Cheers,
Harald

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Color code Orange/Yellow with a Black X?

It felt like a power lock so I went looking for a sticker.
It was really dirty and fell off, but I managed to clean it to look like this:

What is the easiest way to swap the differential? Drop the whole rear suspension and do it on the ground? Our can I get the differential out by just unbolting it?

The entire suspension unit needs to be ‘dropped’ on the floor and disassembled.

Just note where the washers/spacers are fitted for re-assembly.

Change the fluid while your are at it.

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Thats what I thought by looking at it. I am not really looking forward to tackling the job without a lift. But it has to be done…

It is really only held to the body at 4 points. Two upper horizontal bolts and two forward vertical bolts.
Just hang the calipers out of the way and disconnect the dampers and propshaft.

Ok, thanks for the heads up! It will have to wait until the garage is clear, but I will post how it went or, more likely, ask silly questions while I am at it.