Thornton 'Powrlok' Limited Slip Differential

Saloons
1

Hello again,

I’m sure that it has been posted numerous times but in case there is more recent information, I’m wanting to fit one of the ‘Powrlok’ differentials to my 3.4 MK2 MOD. Do they just fit right in or do I need a new housing? I know that these were standard issue on 3.8’s and options on 3.4’s. What are the benefits or pitfalls and where would I acquire one in good order?

Cheers,

Tim

2

They fit straight in. Essentially you need the “guts”, inside the housing.
You can retain the crown and pinion, and won’t need to remove the pinion. You can also retain the crown wheel carrier. (I think).
Good time for a change of ratio though.
They are not exactly rare secondhand, and probably still available new from Dana.

3

Thank you, very helpful. What gear ratio would you suggest?
Cheers,
Tim

4

Gear ratio depends on what you want from the car. Standard ratio for the O/d box was 3,77 if you want acceleration then stay with that ratio, if you are looking for a long legged cruiser then you can go to a 3.54 or 3.33 and lose out on the acceleration.
Just be aware that I believe there are constraints as to which gear set will fit into the pumpkins.
I had a 3.8’S’ with 4sp O/d from a S1 or S11 XJ6 with a 3.07 diff, was a bit sluggish off the line but 1800 rpm @60mph

5

Hello Robin,

I think that I will retain the standard ratio.

I have made contact with Dana in Australia and will wait to hear what they have to say. If they can’t supply new then I’m sure that I can find a good one elsewhere.

Cheers,

Tim

6

I would be surprised if a new one was available via Dana, as the MK2 has a Salsbury diff
(even though a Dana unit may be able to be fitted)

Probably your best bet is a used one, most inexpensively via a local Jaguar Club member,
if not, I expect JagDaim in Melbourne would be able to sell you one off the shelf

7

Okay, thank you very much Tony. I’ll ask members of the Jag Club here in Victoria as well as JagDaim. I’m happy to know that they are not a scarce item! It will be good to fit one as I restore the car.
Cheers,
Tim

8

Dana were very prompt and helpful getting back to me which was a most welcome surprise. Unfortunately, they no longer carry them for a MK2 which isn’t surprising. However, I have traced a good unit already and will fit that in due course.
Cheers,
Tim