911

Hill climbing today in full competition. After a full-on climb at 10/10ths the front tyres are warm, and the rears are cold! This is not normal. the car drives as though it is a front driver, not at all normally.
I have an early RA box and 4.11 diff fitted and the bloody AP clutch.
Has anyone lost the rear drive due to:

1 Viscous diff 'telling' the abs to dissconnect the diff during the hard braking?
2 Failure of the centre diff to drive to the rear?

I really need your help on this on, John Banks, Andy F and Pavlo to name just a few of the respected experts!

911.

mark@wrx

Sounds like centre diff failure to me. Were there no noises or vibrations?

greasemonkey

What was the surface temperature, and what tyres were you using?

That's not possible. The VC diff can't disconnect/change its behaviour like that. It's a dumb component, doesn't have any way of responding to external conditions or inputs.

It's extremely unlikely that this has happened. If you'd suffered a serious centre diff problem the likeliest mode of failure would probably be a total loss of drive than simply losing one axle or t'other.

Even if it had "gone" in a manner that only affected the rear output, or if indeed you'd had a rear driveshaft failure or something else that'd taken the drive out of the rear axle, you'd have felt the centre diff slipping as the viscous coupling tried to direct some torque to the front axle (would have felt a bit like your clutch was slipping). You would almost certainly have heard some very unpleasant sounding noises from the transmission too.

In short, you wouldn't be asking us whether the diff had failed, it would have been very obvious that something was wrong.

Suspect the explanation for this is more likely to be in the tyre and/or weather department than anything else. Take it you checked the tyre pressures? Assuming you have the standard viscous coupled centre diff, what do you have in the front and back?

911

Thanks for the advice guys!
Cool dry track. Soft racing moulded slicks @ usual 34 psi all round.
Trans is silent, smooth, no vibrations etc.
I just don't nkow why the car is doing this.
Last year running on my Stiv3 box and Kumho road tyres, the tyres were all very warm, and the fronts much more so, usual stuff.
Please keep thinking!
Graham.

911

Sorry missed a bit.
The RA trans in the car is a 4.11, none DCCD with matching diff from the same doner car, about 1994 vintage (?) The trans is bog standard and has never been messed with. It/they have Sikolene synthetic oil in them. The box is just over the dipstick max level.
The tyres are remould tramack moulded slicks, softest compound, moulded on radial carcases, made by Maxsport (same as the more famous Colway tyres).

The AP clutch is the one i am having so much trouble with, pedal stays half way down.
911

colin c

I had this problem a couple of times after replacing my clutch with a Helix organic clutch, the clutch was not at fault ! First time it was caused due to not enough free play in the clutch master cylinder, someone must of adjusted it to get the clutch to bite lower before I bought my Scooby. The second time was caused by the return spring on the clutch slave cylinder, I replaced it with a new spring which is stronger than the old worn spring and now my clutch is excellent

Colin.

T-uk

you definitely have the bearing in the centre of the flywheel for the clutch issue?

are you sure the box and rear diff came out the same car?, I thought they would have been 3.9diffs.

AlanG

Is the clutch master cylinder needing bled?

Best way to do it is undo the two bolts retaining it to the gearbox and keep the bleed nipple to the top so there is no air trapped.

While your at it, take the plunger part out and "stretch" the spring inside as well, these have a habit of losing their tension. (Well on mine it does... )

911

Thank you as ever to everyone's reply!
Just got home from the weekend's races.....1st in class, lots of crunched 2nd to 3rd changes, and lots telling me I DO have a 4 wheel drive Scooby.
The car will now come apart, box/diff out (they are both 4.11 ratio), get that bloody clutch out (probably the reason for the crunches) and have a GOOD look at what is in there.
Done all the spring things etc, but a new one on me is the input shaft/flywheel bearing!
The thrust bearing is still moving about when you blast the car through the gears, and i doubt that the clutch is getting enough travel to clear the clutch engagement.

The (perfect) Sti box/diff will go back in (nice job eh?) and I will start all over again!

Anyone want an RA trans? (I'm serious!)

If I find the AP clutch is duff, then what to fit instead?

I'm knackered now, thanks again for all the replies guys.....
911

Mark A

iTrader: (1)

Well done, much competition in your class ?

Mark A

911

Mark, I wish I could bragg, the class started with only 5, then on race day was down to 2! A tweeked Cossie and me.
I clocked a miserable 61.9 secs, my best was 60.01 in August last year, so a very shallow 'victory', but 6 points nevertheless!
This is why I'm so pi**ed off with the clutch/box thing. So frustrating!
Graham.

Mark A

iTrader: (1)

When's the next race? May
This is when my season starts, due to various delays in sorting the car.

Mark A

911

Yes, May it is at Prescott. Non championship race, not sure if I'm in yet.
Must get the car done for then!
Seen my other thread and Andy F's thoughts?
Graham.