Does anyone know if the center section of a xj6 will fit into the center section of the xk8. I want to do a gear swap and have found the right gears . Seems like both center sections are the same , it would be easy to just drop the xks differential , remove the center section an replace it with the xjs . IF anyone knows anything i would love to have that info. Its part two of increaseing performance in my 4.0 xk. Part 1 is camshaft upgrade and part 2 is rear gear ratio change. So if you have some info please send it my way. Just pm a guy who has done this swap, so im grasping for any info i can get.

 

You might want to look at a limited slip differential. With the higher rear axle ratio and additional horsepower I expect you'll get more wheel slip and may loose some of what you're hoping to gain. This is what I did.

What rear axle ratio are you looking at? Also, remember you need a TCM to go with your rear axle ratio.

Mark

 

Had a quick look into the DTCs for the transmission, and couldn't see one that is related to verify the gear via a wheel speed check. This does exist for the MB box and the later 6HP26 version where you then need to tune the TCM, so it looks promising to say the least.

You might want to check first BMW forums for instance as some models also use the same 5HP24 box as yours to see if they were able to change the gear ratio.

 

Spoke to phil at eurteck designs he is the programer and owner, The xk8 4.0 without supercharger does not need to be programed. Yes this is great news . Im looking at putting 3.58 gears to replace the 3.06 dogs that are in there. Thats why im trying to see whats interchangable. Hopefully the center sections are the same

 

Looks like a good swap. It will drop your 0-60 times without killing your gas mileage, or really effecting your top end. Best of both worlds..

 

You wrote

"I want to do a gear swap and have found the right gears . Seems like both center sections are the same , it would be easy to just drop the xks differential , remove the center section an replace it with the xjs."




I guess you want to install the 3.58 ratio but you are all over the place with xks and xjs as well as XK8 and XJ6!!

Here are some observations I have had on the subject.

The centerline diff in the XK is different from the offset diff of the XJ40/X300 limited slip diffs.
Most of the suspension components are interchangeable and the 'center section' as you call it will need to be replaced to match the offset pinion shaft diff.

I don't know if there is enough 'side' room in the propshaft tunnel to install the diff????

The X308 seems to have enough room but the X100 looks to have a narrow tunnel.

I don't know anyone that has done this and I have wondered if it would fit.

I might try this in my X308 someday if I get ambitious as I have 5 XJ40/X300 diffs and some are limited slip units. They are all 3.58:1 ratios.

The rear suspension mount or 'tie' studs are different from the XJ40/X300 to the X308 or X100. They bolt to the case on the rear cover and need to be swapped.

The propshaft will also need to be modified to use the JURID flange instead of the 4 bolt flat flange unless you find a NON-JURID diff from an early XJ40.

The ratios for the early diffs are 2.88, 3.54, 3.77 and 4.09 but I don't know if the 4 bolt flange has the same bolt pattern as the X100??

If you try this and are successful I would be interested to know how it worked out.

 

You wont be able to drop the internals of a XJ diff into a XK they are totally different, I know, I looked once myself as they are almost identicle in look except for the offset nose, however a complete XJ diff will go in but you will have to reroute the power cable from the battery as it get very close or fit a 2 piece XKR prop.

You will also need to change the front upright section of the rear carrier to allow for the offset nose