More driveshaft woes

[AG2728]

At a track day at Brands last year, early in the day I ran over some debris from an incident in front of me, so came straight back in to the pits. There were scuff marks all along the floorpan where the chunk of fibreglass had gone straight under the N/S of my car, front to back but otherwise all seemed ok so I went out again and carried on as normal.

It was torrential rain for most of the day and by the end of the session, a knocking noise had developed from the rear. Initially I thought it was the diff. When I got the car home I found that the retaining clip was missing from my N/S outer driveshaft boot, the boot was ripped to pieces, adrift from the tri-lobe and all the grease had been washed out of the CV joint due to the biblical weather conditions. The bearings were trashed and I had to stump up for a complete shaft, as that is how they come.

I had just assumed the debris from the morning had dislodged the clip and eventually the boot came away. Fair enough, s**t happens, so onwards and upwards. Fitted my new driveshaft and everything seemed ok.

Following a full day at Curborough last week, I was convinced that during my last couple of laps of the day I could hear another knocking noise. I put it down to paranoia.

Got my car up on the ramp today for an oil change and spanner check and, lo and behold, my outer N/S driveshaft boot clip is again, missing from my shiny new driveshaft, with grease splattered all over the underside. So my previous debris theory was probably incorrect.

I can now see that the blade of the ARB and the joint of the drop link have been impacting the tri-lobe under full compression.

The ARB blade has been gouged away.

And the drop link is bent and the joint shows signs of heavy impact.

So, mystery solved. I had previously checked the possibility of ARB and driveshaft clashing but they did not appear to be moving in the same plane. I checked the drop links and ARB after Brands and they were both unmarked.

What I failed to take into consideration was the massive amount of sideways endfloat and lateral flex in the ARB which at full movement to the left, puts it straight under the CV boot retaining clip.

It would seem that at Brands, the driveshaft had probably just kissed the ARB mechanism, shedding the clip but not hard enough to leave witness marks whereas at Curborough, the much more brutal rough concrete variegated rumble strips had them smashing into each other. Not ideal but I am glad to have got to the bottom of it and can now see exactly what has gone on. Expensive way to learn though.

As it was dry at Curborough, there is still some grease left in the CV and the boot is intact. I probably wont even remove the driveshaft but will back-fill it with grease in situ. I will just have to replace the clip, the trashed rose joint and link.

My drop links were set quite short and I am hoping that by adjusting the drop links as long as I can get them will hopefully keep all these parts clear of each other. Otherwise will be in the same position again.

Has anyone else had this issue?

Andy

 

 

[Jonathan Kay]

Private Message sent.

[7 wonders of the world]

Make sure you don't use normal moly 'CV grease', the Tripode joints require this

https://www.demon-tweeks.com/gkn-tripode-joint-grease-320g-tube-gknms9u025/?istCompanyId=a2904180-3a7d-4e56-b876-cf81c9512180&istFeedId=0f6db192-3a9a-4369-b1f8-79615c622f96&istItemId=wptppxlxr&istBid=t&utm_source=bybuybye&utm_medium=css&utm_campaign=nmpi&utm_term=generic&utm_content=generic&gclsrc=aw.ds&&gclid=EAIaIQobChMI7qX0yZzX6gIVTe7tCh0-yQBOEAQYASABEgJ9gfD_BwE&gclid=EAIaIQobChMI7qX0yZzX6gIVTe7tCh0-yQBOEAQYASABEgJ9gfD_BwE&gclsrc=aw.ds&source=aw&awc=6538_1595089812_5d5edaa81ae35c0e9703627fd9d66b0c

[AG2728]

Yes. I have the grease.

Edited to add it's a 420R and I have been running the rear bar on full soft.

[7 wonders of the world]

[Geoff Brown]

But the CC recommendation is that the drop links are adjusted with the ball joints as close together as possible. I presume any other adjustment will alter the handling?

Surely there is something else fundamentally wrong under the back end?

[AG2728]

JK has kindly directed me to this post from last year.

It is a reply from CC to Ctr Mint

-----------

 Having re-read your email, I read that you are running the ARB on its softest setting.  Try it one up from that and/or lengthen the link rod.  Something along the way has changed which means that in the race application, in the softest setting (rarely used) it can touch the driveshaft.  See if that’s the case.

-----------

I didn't really want to go any stiffer at the back but looks like I will have to.

Or maybe just stock up on spare driveshafts and drop links at £400 a pop.

[7 wonders of the world]

So CC are clearly aware of the potential conflict between the drop link and the boot clip....... what have they done to make owners aware of this problem and have the items being modified so the softtest position on the RARB either clears or no longer exsits...?

This is probably very good for driveshaft sales but poor for owners who are expected to pick up the tab every time through no fault of their own....

 

[DJ.]

If you don't want to go stiffer at the back, how about removing the rear anti-roll bar completely and see how you like it? A friend with an R400 removed his and found it a big improvement, but that was for road use.

Duncan

[SM25T]

My car much nicer without rear ARB on the road. Previously, with the ARB, if you hit bumps on corners, it transferred the bump to the opposite wheel too.

[ChrisC]

Or you could reverse the drop link and fit it with the old spacer, if you want to use the softest setting.

https://caterhamparts.co.uk/fixings/435-mounting-boss-rear-anti-roll-bar.html 

[Geoff Brown]

 I remember CTRMINTS problem, the advice was to position the drop link one hole in from the rear. My R400 has had the link in that position since build so I would not be aware of any potential problem. But obviously CC is ?

The back end is not that stiff in that position - try it fully to the front hole then you will know it is stiff !

[AG2728]

My car much nicer without rear ARB on the road

This one is predominantly a track car.

Or you could reverse the drop link and fit it with the old spacer, if you want to use the softest setting

I've seen that set up but it wouldn't help here as it won't change the position of the ARB blade, which is also contacting the driveshaft

 I remember CTRMINTS problem, the advice was to position the drop link one hole in from the rear

Yes. It seems the way forward is to go one step stiffer by doing this or to go one step softer by removing the bar altogether. I will have to give it a go

Andy