did the first sprint in the indy today at teeside, and luckily apart from it being bloody cold and a drop of rain this morning the sun came out this afternoon and dried the track out

Anyway, big problems out on track and i think it might be the diff.
I can get away from the line wheelspin or not no problem and accelerate away fine. Knock it into second and floor it, the car keeps accelerating forward then all of a sudden BANG, something engages in the diff (LSD plate?) and the car surges forward. into third in a straight line good traction same again engine revs round and it is sort of like the clutch is slipping but then BANG diff clanks and the car picks up speed again.

I definatley dont have a slipping clutch from a standing start and once up to speed 4, 5 and 6th no problem.

I tried a different approach on a couple of laps and feathered the throttle in and the car accelerated fine until it reached around 9K - 10K BIIIG slip then BANG diff again. I took the car for a quick pootle round the pacddock and the diff seemed a little noisier than i remember.
Any advice before i rip the diff out. I am sure the diff is an Xr4x4 LSD but i will check.

The only other option it could be is that because i overfill the engine (R1) the clutch may be too wet??!!! and causing it to slip when pushed, full throttle or peak power 9-10K

thanks in advance
Paul

BTW i cam e 3rd out of 4 runners.. not what i was expecting but at least i wasnt last..........i blame the car

[Edited on 9/4/06 by skydivepaul]

The sierra diff is viscous so no clutch plates in there. If it wears out then it stops being an LSD and acts like an open diff again.

I have experienced similar on mine - although not quite so much of a bang as you seem to be getting.

It seems that in order for the viscous coupling to kick in, one wheel must start spinning, then the 'magic' viscous fluid heats up and thickens which locks up the diff - this is probably when you get your bang. I can feel mine coming in and out on a long corner when I am close to the limit - it goes spin, grip, spin, grip etc - wierd really.

What it really means is that the sierra LSD is not really up to serious motorsport applications. the way forward seems to be a quaife ATB diff which is the way I am going as soon as I can rake enough cash together.

HTH

Mark

Paul, are you coming to Harewood next week? I'll be there if you want a natter

Cheers

Mark

I might have a ride up there but only as a spectator. is it on saturday or sunday?

p.s. i will post a video of incar footage later and you will see what i mean. i only videod the lap i took it easy on the acceleration though. how much is a quaife lsd??

I may be barking up the wrong tree entirely but........
as the diff starts to do the LSD thing, it will put extra berries on the whole drive train. I'm assuming you have a BEC so do you have a torque tube fitted? Or is it the prop bearing? Or movement in the engine mounts? Have you tried it without the bonnet on to see if the engine is trying to jump around?
Just my tuppence worth....

quote:

---

Originally posted by owelly
I may be barking up the wrong tree entirely but........
as the diff starts to do the LSD thing, it will put extra berries on the whole drive train. I'm assuming you have a BEC so do you have a torque tube fitted? Or is it the prop bearing? Or movement in the engine mounts? Have you tried it without the bonnet on to see if the engine is trying to jump around?

dont have a torque tube (what do they do?? and i am sure the centre bearing is o.k. Engine is a 99 R1. I have overfilled the oil as i normally do with the exception now that i have a sump baffle in place.

Assuming the diff is o.k.? could the problem be..
start .o.k
run up the power..one wheel spins.....lsd kicks in....puts strain on engine and clutch slip?

it may be possible, i am going to study the in car video again
cheers
Paul
Just my tuppence worth....

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The torque tube used in BEC's are not really torque tubes. They are a sort of built-in-to-the-prop cush drive to take the shock out of the drivetrain, instead of having a rubber donut.

Harewood is on Sunday 16th, ATB diff is from £5-600 quid plus a few bits of fettling

Hope to see you there

Cheers

Mark

Sorry to be the bearer of bad news but it doesn't sound anything like your diff to me, it sounds like your gearbox.

Is it only whilst in second and third gear that this happens??

Phil

And having reread you initial posting, the clutch should be immersed in oil so overfilling shouldn't cause any probs.
If the problem is specific to particuler gears, then look at the 'box but as I read your post, I was thinking of when you would be changing gear and whereabouts on the track you would be. This was to try and work out what conditions made your fault occur, and to see if it was speed, decelleration, accelleration, cornering, wheelspin, etc.
The more info, the better.....

quote:

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Originally posted by Hellfire
Sorry to be the bearer of bad news but it doesn't sound anything like your diff to me, it sounds like your gearbox.

Is it only whilst in second and third gear that this happens??

Phil

---

problem occurs during straight line acceleration and at about peak power 9-10K, i think its only in 2nd gear so maybe that could be it.

i had a look on an R1 forum and they say you can get clutch slip at higher revs if you have overfilled the oil too much especially in BEC and sidecar applications.
I think I'll drain a bit of oil out and have another go before i dismantle anything