In the process of swapping my xjs 3.31 diff head for an series 3 e type 3.54 diff head

This was all going fine until I tried to swap on the brake xjs calipers

The bolt hole tabs were too big and I had to take a grinder to them to allow the bolt holes to line up. This worked on one side but now i've run into the issue that the xjs caliper bolts are too long by a few mm on the other side and ill need to get a slightly shorter bolt or grind the xjs bolt head down to allow it to fit between the diff housing body and caliper mount.

I can do this and it will solve the immediate problem - but it got me to thinking are these diff heads the same and can they be swapped at all. Clearly there are some differences in the housing appearance - but more importantly, are there any major setup differences in the overall width of the unit that will effect alingmnet etc?

I always understood that these units were the same between the models - but clearly they aren't

Has anyone else discovered this?

 

The XJS had 2 different diff's, don't know about the eType. I do know the internals are interchangeable. I swapped XJ40 3.58 into my XJS diff housing. I had to marry the XJS and XJ40 hemisphere's as my car has the speedo in the diff.

From pics I have seen the e Type has different calipers, grinding the tabs will weaken the mounts, you DO NOT want the rear brake calipers to break off (even if the rear brakes on an XJS do almost nothing).

If I were you I'd swap the e Type hemisphere and gears into the your XJS housing, is the e Type an LSD?

 

In terms of the material I need to remove to get the calipers to fit, we're only talking a couple of mm from the calipers to get them to fit so I'm not stressed about that. Could easily be removed from the main diff body as well if required

My main concern is about the alignment/fitment of the new diff in relation to the existing axles etc

Does anyone know if there is any real differences in the measurement of the housing itself?

 

I agree with Warrjon that swapping the internals into the original XJS diff casing is best. In order to compare the two casings/diffs, the crucial suspension dimensions that need to be identical are:

• Width between the output flanges
• The dimensions of those flanges and their fixings
• Height of the diff top above the output flange centres
• Depth of the lower wishbone fulcrum centreline below the output flange centres
• Total width of the lower wishbone fulcrum castings (ie the bracket bolted to the side of the diff on which the lower wishbone fulcrum is mounted) being identical
• Distance between the two lower wishbone fulcrums across the bottom of the diff being identical.
• All fixings threads and hole sizes being identical

Greg

 

Thanks for responses - and apologies for the delay in replying, as I haven't had a chance to follow up on the critical measurements Greg mentioned.
I have now just compared/measured (somewhat crudely) the differences in the diff heads. The overall critical measurements appear to be the same i.e. output flange overall width/height, diff height etc

Despite the fact the diff heads look a little physically different - the only real difference appears to be the caliper mount position which is the exact opposite to the e type mount i.e. on the other side of the mounting flange

I ended up making minor 'adjustments' with grinder to get the xjs calipers to fit the e type diff head - but it now all appears to be together as it should. Was really only 2-3mm in places that had to be removed and the majority of that was from the diff head itself to allow for the long xjs caliper bolts to fit between the flange and the diff head itself.

Once I've got this all bolted back into the car - will post an update