De rating Diffs?

[Grease Monkey]

Finally got fed up with the clonk coming from the back axle and have dropped the diff and carted it up to Russ to give it the once over.

(Why did AB put a chassis cross member directly under the Prop flange)

The question is, (it's a 3.54PL), do i get him to tweak the clutch on the PL or just leave as is?

I've done a few thousand miles and have no big problem going round corners but i've heard it said you should derate them for lighter cars (than the 3.6 XJS it came out of)

[Andy S]

Russ knows more about jag diffs on our cars than probably anyone else, why not just let him do his thing and set it all up for you.

[Happy Jim]

Why would you NOT want to do it would be a better question?

PS as I've just got hold of a 3.54 PL diff I'll be doing the same as you at some stage. Did you whip the body off in the obligatory hour or have you just struggled through?

Rgds

Jim

[russell_ram]

'why not just let him do his thing and set it all up for you?'

Becasue I gave him a choice - do it as would for most road applications or have it set up for a bit more aggresive operation.

Adrian is allowed to canvas opinion other than mine!

Russ

[Andy S]

Originally Posted by russell_ram

'why not just let him do his thing and set it all up for you?'

Becasue I gave him a choice - do it as would for most road applications or have it set up for a bit more aggresive operation.

Adrian is allowed to canvas opinion other than mine!

Russ

Russ I wasnt knocking mate, just that from all I have heard from people like Tinka etc I would have total faith in your recommendations.
Fair point if he has a choice to make, the purpose of which didnt really come across in the original post, as you have put it.

[wilf]

Depends on the major use for your car - mostly road use, then derate. Track or drag, leave tighter. But be ready for it to bite one cold, damp winter morning.

If you are not noticing any corruption of turn in, chances are it is shagged anyway. When Russ rebuilds it, it will come back into original specification.

[Grease Monkey]

Not going to be dragged or used on the track, but i do like to push hard around corners.

(Removing took around 3 hours with the body left firmly on)

[mylesdw]

Originally Posted by Grease Monkey

Not going to be dragged or used on the track, but i do like to push hard around corners.

(Removing took around 3 hours with the body left firmly on)

My understanding is that the preload only really effects the diff's behaviour when one wheel has VERY low traction, for example on ice or with very little weight on it. Pushing hard round corners is not really in this realm. The side effect of having a high preload is, however, understeer on light throttle. You really have nothing to lose in de-rating the diff.

[Grease Monkey]

Would sound like what Myles is saying matches up with what Russ said in that, even if it's derated, it only affects the slip at low power / revs. Once you give it some wellie the whole thing locks up anyhow.

What about if you're hooning round a large roundabout and one rear wheel lifts. With a std diff, that one wheel would end up spinning and it would be like taking your foot off the power and you go sideway. (which is quite fun if you're expecting it) Would this happen with a derated clutch, or would it still push with both wheels?

Sounds like if i'm not going to be using it in ice, heavy rain, drag strips or competition there's no downside to derating to 50%? of what it's set to in the Jag.

Up side is more responsive turning and easier turning sharp corners.

Russ, that sound about right?

[Grease Monkey]

Originally Posted by Happy Jim

Did you whip the body off in the obligatory hour or have you just struggled through?

Rgds

Jim

Before i replaced the body last time, i put an access panel above the diff bolts for access. What i should have done was cut a hole next to the propshaft bolt. Next time!