309 Drive Shaft Too Long With Adjustable Top Mount And -Ve Camber

[SweetBadger 94]

Hi all, I had my first race on Saturday at Cadwell Park. Amazing track and amazing day, can't wait till the next one.

 

However it wasn't all smooth sailing - on the test day the car was suffering from really bad vibrations on any right hand corners (more cornering force = more vibrations). This wasn't apparent on the road and was not affected by steering angle. The vibrations were consistent with wheel speed.

 

At first I thought there was a problem with the 3J plate diff, but about 15mins into the second test session the near side drive shaft let go big time! CV joint overheated and spat metal through the CV boot.

 

So 4 hr round trip to pick up a brand new 309 shaft, and we were back in business... Not quite... The next day in qualifying, the new shaft gave exactly the same issues, and then the CV boot split and spat all the grease out when it was being power tested on the hub dyno!

 

We managed to get a stretch boot from a local motor-factors which we vented with a WD40 straw and it got us through the race; the shaft held out but right hand bends (most of them at cadwell!) were a bit rattly!

 

 

I'm running 309 wishbones, but I think that the increased -ve camber from top mounts moving the suspension strut inwards and the lower ride height, led to the shaft being compressed so that it had very little play left, then on the right handers the engine was shifting enough so that the shaft ran out of travel.

 

Has anyone else experienced this?

 

I'm going to try a 205 shaft and see if the 10mm shorter shaft sorts out the issue, if it doesn't I'm at a bit of a loss as to what was causing the vibrations...

[welshpug 1,656]

try adding a third buffer to prevent the sideways movement, you can also shift the engine to the left ont he transmission mounting as the two 13's in the cradle are in slots in the bush.

 

probably wise to check how much flat you have, through the damper travel, remove the spring or lower the spring pan and jack the wheel up, with the driveshaft nut loosened check how much the CV will move inwards.

[SweetBadger 94]

I have a third buffer, but it was right handers causing the issue in the left hand shaft (compressing it too much), so in effect moving the engine away from the third buffer.

 

We moved the engine over as far towards the drivers side as possible on the gearbox mount and trimmed some rubber from the third buffer, which helped matters but didn't alleviate the issue completely. I've ordered an uprated gearbox mount from BBM which might help (was the only standard engine mount left on the car).

 

Good call on checking how much flat/travel the shaft has left through the damper travel, should be easy enough by adjusting the coilovers, and jacking up the wishbone.

[Tom Fenton 1,541]

The vibration is the tripod joint bottoming out in the inner CV cup. Ideally you need to measure your right height and then dummy assemble it all preferebly by removing the spring from the damper. You want the tripod to end up in the middle of the inner cup at ride height, then check it in bump and droop. There isn't much free movement to play with. If you were bottoming with a 309 shaft then try a 205 shaft.

I found the better solution was to make some rose jointed bottom arms to sort the camber, then position the top mounts in the fully rearward position for maximum caster. You can then use the 309 shafts without issue.

[cheesegrater 43 1 Cars]

Im running 205 shafts with 309 arms and no issues to report so that maybe the best fix as like Tom said it sounds like the shafts are bunching up.

[SweetBadger 94]

 

I've run 205 shafts on it with the 309 bottom arms previously with no issues (1.6 shafts too; were fine even after 10+ track days), and that was without the eccentric top mounts, so I've ordered a 205 shaft and will give that a go.

 

Annoying to have probably wasted £90 on a brand new 309 shaft, guess it'll do for an emergency spare.

 

Funny how it's only the n/s shaft that suffered though...

[SweetBadger 94]

So I checked how much the drive shaft plunge I had with the suspension taking the weight of the car by jacking the wishbone up and loosening the drive shaft nut off then pushing the drive shaft towards the diff until it bottomed out - only had about 3mm to play with, so I think I've found the issue!

 

205 shaft fitted and there's about 10mm more plunge, so hopefully that'll sort the issue.

[Goliath 94]

Thanks this thread has given me an idea, as I too am experiencing a vibration on right hand bends so I will take the hub nut off and check for movement. I never used to have a problem though, so I can only assume it has been brought on by my engine mounts wearing out leading to the engine moving more on right hand bends.

[Henry 1.9GTi 36]

Had same issue with shafts bottoming when running ball joint spacers. Luckily was only testing on a trackday so short stints and have very hard engine / box mounts so all it did was casue the CV boot clip to come loose and a bit of grease escaped. I got away lightly! Good to know that a 205 shaft can go back in without causing problems though.

 

I'm doubly keen for Brands GP now, getting the bug! Shame i'll have to pay registration and dyno fee for one race :|

[SweetBadger 94]

 

To follow up on this, after measuring the driveshaft plunge on both sides with 205 shafts fitted, I now think that this issue was not due to the extra -be camber, as in theory both sides should have been affected.

 

I think that the 3j diff (or at least the one I have) doesn't allow the near side shaft to go into the gear box far enough, leaving the shaft compressed by approx 8mm extra...

 

See here: http://forum.205gtidrivers.com/index.php?showtopic=164242&hl=