Uneven driveshaft length

[buzzer]

I am in the process of setting up the suspension after putting in new radius arm bushes. In measuring up prior to adjusting I notice that the distance from the upright to the gearbox centreline is 3mm different from one side to the other. I suspect this due to setting the backlash in the gearbox. So the diff is not actually central in the casing.
I have adjustable bottom links so I can get the camber set correctly.  But to get the car tracking parallel I will need to pack one radius arm bush more than the other as I see it.
Any views on this? Has anyone else come across this?

[jbcollier]

Hmm, not sure.  I would remove the driveshafts and measure the protrusion of the output shafts.  Check the output shafts for play as well, there should be effectively none.  Perhaps there is an issue inside the diff itself.  Is this a stock transaxle?  Or, a NG3?

[jbcollier]

Also, of course, check the usual suspects: wheel bearings and u-joints.

[buzzer]

I have had the box off to  redo the gearbox seals, so confident all that is ok, but I will check how far in the splined uj’s are in out from the gearbox and do some further investigation to determine where the difference is.

[4129R]

If the gearbox mounting plate, where the two 1/2" bolts secure that to the rear chassis hoop, were misaligned for any reason, this would put the measurement out.

Is the gearbox loose at the rear, or bolted in position?

Your chassis could be out of true at the back.

[buzzer]

Just been measuring everything. Fortunately it’s up on a drive on ramp.  One adjustable lower link is longer than the other. I’ve checked the driveshafts the offset from the gearbox and to the brake backplate and they all check out out to the centre line of the gearbox. The camber is set correctly at 1 degree negative and toe in currently at 1 degree. I then looked at the upright....hmm it looks like the bottom hole position is different on both units in relation to the top driveshaft mounting.  So the wheel alignment is ok it’s just that the lower link is longer in one side to accommodate the discrepancy in the upright.  Lotus quality control hey?

[4129R]

If your car was the spare race car, maybe it was involved in an accident and rebuilt with non-production line parts, and they checked the geometry, and compensated accordingly.

Competition cars have strange things done to them. I owned the car which won the Group N Rally Championship for a well known Japanese manufacturer, and no way was that Group N legal.

[buzzer]

I think I have this sorted. Have laser checked alignment and it’s good enough until I get it on a professional set up to check. I’m pretty sure it’s was the upright that was causing the issue.  What was interesting though was that the radius arm mount was rose jointed and for what I wanted (and to meet regs) I needed to change these. Also the ride over bumps shocked the whole chassis. On a track that is smooth it’s ok but on our roads it’s terrible.
Anyhow the radius arm had been clearly modified as the bolt size was 14mm not 12mm or equiv unf.  So to sort this I had to sleeve this.  The old rose joints mounted on the outside of the chassis and I had 30’ of toe in originally (3mm). The new bushes I mounted on the outside with the larger part of the polybush into the chassis. I then packed between the arm and the bush to sort out the toe in which I have increased slightly. It needed 2 thick washers

[BDA]

It's interesting that the rose joints seem to cause such a bad ride. I have Richard's twin link rear suspension. The lower arms use rod ends (rose joints) exclusively. The upper arms only have rod ends on the outboard but the inner bush does not offer much compliance. The radius arm pivot as well as the entire front suspension use the stock bushings and my ride is comfortable but very firm on the road. The thing that makes my ride so firm are my shocks and springs. My springs are 250# front/ 130# rear. Of course uneven country roads are less comfortable. I wonder if your springs/shocks is really causing your ride problems...

[BobW]

I have RD's adjustable radius arms with rose joints at both ends. Installing them improved the drive (alignment) and had no effect on ride harshness. I'd suspect spring/shock settings. I'm running stock springs and adjustable shocks front and rear set one click off full soft, on the premise that the car was designed around body lean and a 'soft' suspension.

[BDA]

I'm surprised that one click off full soft would make that big a difference but it's impossible to relate your one click to anything because one brand may have, for example, 12 clicks and another might have 24. Even if the two brands have the same number of clicks, the change from click to click could easily vary by a lot. Lastly, one shock might be stiffer than another right out of the box.

I would dial your shocks back that click and see how it feels.

[buzzer]

Definite improvement in ride much much smoother.  Not only shocked from rough roads but a lot less hashness.  I changed nothing else.