I have a 97 xk8

My goal is a 4.0x gear but not LSD.

Is the only way to get there to use a custom XJ diff with the selected gear [i.e. dana 44 parts]?

Then subframe adapter from XJ to bolt up with minor mod?

Is there any link that details this change?

Neglect TCM programming as I'm using a different computer.

 

You can get a 4.? (cant remember which) standard for an XJ, this will bolt straight in but you will have to change the front plate to allow for the offset of the diff, you will also need to change your prop to an XKR 2 piece type, the UJ will allow for the off centre of the flange

 

Thanks xkracer,

Which XJ would be a likely candidate, the xj12? xjs?

How would I identify the proper ratio?

 

As for the mechanics, others will have to address those questions. I can however say that in my case, I wanted an LSD. It was during my research on this mod that forum member JgaXkr offered to sell me his 3.27 rear axial ratio with the corresponding TCM. The 3.27 axial ratio is an actual Jaguar XKR part and is provided on Mexican XK8/Rs.

Mark

 

Thanks for the comments.
I found a locations that says they have a 4.09 from a 91-97 xj6 available.
Would that be a candidate?

Can I modify my front plate to work [cut for the offset], or will i need the XJ front plate?

 

4.09 sounds like the one I was thinking of, it is what a friend of mine has fitted to his manual XKR. I would replace the plate with the XJ item, you may weaken the original by cutting it about, I am sure you will be able to get one easy enough from a breaker.

There is one you need to bare in mind, I was told by a diff builder the XJ item does not like more than 350bhp, depending on your output might depend on ther diffs life span

 

The higher the ratio the smaller the tooth of the gears and that could be a weaker spot (not sure if that is also the weak point XKRacer is referring to though). You might want to consider doing a shot peen treatment of the pinion/crown, as that could strengthen the tooth more.

 

I was hoping to avoid breaking it apart, but I'm right at 350 hp right now.
Maybe I'll take the risk.
Thanks for the info.

 

Mark, any word on the delivery of your Quaife diff?

 

It arrived a couple weeks ago and will be dropped off at a shop specializing in differentials this week. They will build a differential using the LSD abduction the 3.27 gears.

Mark

 

Glad to hear it, that's great news!

 

I bought a XJ6 differential from coventry west... with 4.09 gear.
BUT


I ran into a hurdle using XJ6 diff into the XK8. The XJ6 input flange is 3 finger, I suppose to accept a rotoflex or guibo style connection?


The original diff is 4 bolt style universal connection.


How to adapt 1 to the other?
I found an adapter that might work from thedriveshaftshop.
Is there a kit to replace input flanges?

 

You're going from the stock 3.06 to a 4.09? Wow! You must also be reprogramming the shift points for the transmission. How are you doing that? I'd be interested in how it works out.

Mark

 

Luckily, I don't have to worry about that.
I'm using a t56 6 speed manual transmission.

And the engine is no longer Jaguar.

But I'll give you some feedback regardless

 

Have you tried to fit the standard XK8 flange?

 

This seems like an obvious choice, but I'm hesitant to break the nut loose on the input flange unless I know that It'd work. I understand that there is a preload set for this nut, and breaking it free will void my warranty.

I will talk to Coventry to see.

 

Thats true. You could contact jgaxkr, he has done something similar.

 

The XJ6 uses a jurid (the same type flexjoint as a guibo except it's for the rear of the driveshaft) instead of a u-joint as on the XK8. Why didn't you get a used XK8 diff?

 

That's the pinion nut, very sensitive to adjustments. You could burn up the internal bearings with an incorrect adjustment.

 

I've never talked with him, I will try. Thanks.

That's what I was expecting. They don't come with a 4.09 gear.

Yeah, so I hear. Thanks. It seems like a bad idea to remove.

Here's what I was thinking of trying, since it's a standard 1350 spicer universal I believe:

The Driveshaft Shop | 2004-2011 GTO / G8 / Camaro / CTS-V conversion plate - Pontiac - Domestic Driveshafts