Limited Slip Diff backlash/slack

[O.G.]

New as I am to Caterham driving, I have just put my home built kit 360R SV with a Limited Slip Diff on the road. Currently only 200 miles use since new.

When driving, there is a fair sized "clonk" between accelerating and overrun. This is backed up when by jacking up the back end and hand turning the prop shaft or a drive shaft. There is what I consider, as an engineer, a fair amount of play. Is this just a part of Caterham's "basic ness" or do I have a problem?

Is there some Tech data for backlash figures?

 

[elie boone]

The diff is BMW so there you can find Back lash data. be aware that in a caterham mechanical noises are not damped by insulation and you sit almost "in between" the mechanical components.

[Jonathan Kay]

This has come up a few times before but I can't remember the outcomes. Edited: Previous discussions, NB some of those are returned by the search not because it was a BMW diff that was the problem but because it was considered as a solution.

Any chance of comparing it with some others? Where are you?

Doesn't sound too likely from your post but are you sure it's in the final drive and not the prop shaft joint?

Jonathan

 

[ScottR400D]

In my experience there is a lot of free play in the BMW diff used. I'm at a loss to know why but when I built my car I was surprised by how much there is. Compared with the diff in my 5 series, which of course may be nothing like the Caterham one, the Caterham has a much larger angular movement of a rear wheel when taking up the backlash. Maybe 3 or 4 times the movement. 

Extra noise might be expected because of the location etc but the large amount of free play is just that, a large amount of free play, imo. 

[O.G.]

Thanks to those who have replied so far.

Jonathan, thanks but the prop shaft is fine, I did check that. I live in the Heathrow area and plan to attend the "AWSOM" meets of my local area at which I will see if I can find someone with the same Diff.

Elie & Scott, Yes your right the Diff is right by you left Buttock, not much chance of any noises being damped out.

I am also concerned that this contributes to the quite severe Kangarooing I get especially in 2nd as I coast slowing down (at low engine revs).

Anyway I will continue seeing if i can get the data.

Thanks

[elie boone]

kangarooing is almost always down to a light flywheel. For the back lash give Phil of Road & race a call at 01959525105

[John Vine]

kangarooing is almost always down to a light flywheel.

Although I guess it could also be a problem with the map or TPS setting? 

Can you (the OP, that is) move off smoothly from rest without touching the accelerator?

JV

[arty]

I hace similar sounds and prone to jumping. Muy friend just found some loose bolts when car was jacked up and on blocks and i ran it changing gear. I have only done 1200 miles since buying it from garage. 

[Shaky]

I have this also. As an engineer I was always taught mechanical noise equals wear. I had Nick Potter (Mr. Caterham) look at it. Seems to be some do it and others don't but all was tight. One of those "characteristics". I have a lightened flywheel and that seems to be the source of kanga when dawdling in traffic. It can be an art keeping it smooth but there is the fun....

[robjjones]

Hi Gordon,

I'm 200 miles into my fresh-build 360S SV, and can report a similar experience with the open diff to your LSD. Clunking, sounds like a bag of nails in 2nd and 3rd on the overrun. Kangarooing in slow traffic. Oh, and the lovely anti-social popping and banging on the overrun too. Had to mention that.

I don't think anything is wrong, and the kangarooing It's nothing to do with the light flywheel in my opinion (as I don't have one), I just haven't mastered the clutch sensitivity needed yet.

Best bet is to go to that local meet and compare notes in person. But don't worry in the meantime.

Rob.

[Rattie]

I say this every time this backlash thing crops up, but certainly on our R300D, with both the original Sierra and the current BMW diffs, we have had backlash significantly worse in the tripod-type universal joints than in the diff.

You can check this by putting the car into gear, engine off, then watch from below, e.g. with a mirror on a stick as someone rolls the car back and forth. The play I'm talking about can be seen as the wheel side tripod cup (with the toothed speedo ring), rotating before the diff side cup moves. I find there's more rotation between these two than there is "inside" the diff (and indeed through the gearbox.

Obviously YMMV

[O.G.]

Sorry, haven't been on about this recently, been out the country and other commitments. I Know - There is no more important commitment than "Your Caterham".

Simple answer first, John,  yes I can pull away without throttle, idle speed shows as 950.

I am in the process of comparing this Backlash with other LSD cars. It would be nice to find the official "workshop" figures though. Elie I will try Phil.

It's not so much clutch control. You just have to disconnect the drive when the revs drop below between about 2000 & 1700 as you slow down.

Rob, long live "popping & banging".

Gordon

 

[arty]

I contacted Ian at PT sports cars as he sold me my car. He says that the diff bolts often come loose and should be checked regularly.