Stiff gearshift when hot

[zcacogp]

Chaps,

Quickie. I went on a (sadly quite rare) decent-length run yesterday and noticed that the gearshift became quite stiff over time. The run was about 60 miles, by which time it was quite noticeable. The shift was stiff in both planes (fore/aft and left/right) and felt quite linkage-ish; it was evenly stiff, not rubbery, and had lost much of the 'feel'. Gears still selected fine and there was nothing unusual other than this, but it made me a smidge worried.

I then parked the car for about four hours, and when I came back to it, it was fine! As crisp and precise as usual. All was great, so I drove it home (another 60 miles), by which time it had become stiff again.

Predictably, it was fine again this morning for a few short runs.

I have rebuilt the gearshift mechanism of late so am quite familiar with the way it works, and this hasn't happened before. (It has been similarly hot with the rebuilt mechanism before). Given that it only happens when everything is quite hot I am slightly doubtful it is the shifter mechanism, although it is just about possible there is something that expands when it gets hot which causes a binding somewhere. The gearbox oil is probably about three or so years old, and will be changed as part of a big service in the coming few days. However has anyone come across these symptoms before? There will be more to tell when there is some fresh oil in the 'box, but if anyone else has some light to shed as to the cause of it I'd be keen to know.

Thanks,


Oli.

 

[Cater_Racer]

I'd think its gotta be one of those bearings on the change mech Oli.

I can't think 60 miles road work would get the gear oil out of sorts.

G

 

[zcacogp]

Gerry,

Hmmm, thanks. The modifications are a rose-jointed stabiliser bar, replacing the standard-fit thing that looks like it owes it's parentage to a baked bean tin or two. Do rose-joints get stiff when they get hot? (And they wouldn't be that hot anyway - how much heat is there on top of the gearbox?)

I'm not dismissing your theory - it's something I thought of, but didn't think that such joints got stiff when hot.


Oli.

 

[Cater_Racer]

Oli, is the exhaust running close to anything it shouldn't?
G

 

[zcacogp]

Gerry,

No closer than it did last time I drove it! []

It is all a bit close to the exhaust, but not that close. And the stabiliser bar runs on the off-side of the 'box; the other side to that of the exhaust. (Not that that makes a fat lot of difference.)

The stiff-linkage theory could be accurate if the rose joints have simply become dry or crudded-up over time, and the heat from the exhaust is exacerbating the problem. I know I fitted them without any kind of gaiter, thinking that they were fairly nestled into their home on top of the 'box and wouldn't get too dirty. Maybe this was a mistake. I'll take them off and clean them and re-lube them as part of the service, along with the 'box oil change. While changing two variables won't allow me to pinpoint the problem, it should solve it (fingers crossed.)

Thanks for your input - it's useful.


Oli.

 

[zcacogp]

Minor update: I dropped the 'box and removed the stabiliser bar yesterday and one of the rose joints was a bit stiff, with no obvious explanation. I put some PTFE lube onto it and wiggled it as much as I could with my fingers, which freed it up slightly. I suspect this is a premature failure of the joint, which is annoying as I will have to replace it.

I didn't have a spare so reassembled it and it works much as it did before when cold - i.e. perfectly well. Whether this slightly stiff rose joint is the cause of the problem or a red herring will remain to be seen, but I'll keep this thread updated.


Oli.

 

[Cater_Racer]

Sounds plausible, let's hope that's it.

 

[tref]

Maybe things have changed, but I always knew rose joints as the ultimate racer's toy - very good for as long as they last... and they last as long as they need to for that race. I kind of get the impression they give "kudos" to a road-car's racer pretentions, when really they're not suitable for road use. (But then I think the same about making everything in the suspension system as rigid as possible)

 

[zcacogp]

I wonder if you are right there Tref. Although I don't know what fails about rose joints; they should be more sturdy than the plastic-and-tin thing that they replaced. I contacted the people who sold them to me and asked whether they would change them under warranty but they have politely declined. I guess they aren't expensive so changing them every now and again isn't the end of the world - just a bit of a hassle.


Oli.

 

[zcacogp]

Tony update (not that anyone will be that interested!) - the people who supplied the original rose joints are sending me some replacement ones of higher quality with seals in them, which should be with me soon. However I drove the car for a reasonable distance again yesterday and the gearshift didn't stiffen up at all, so maybe the lubrication I put on earlier worked after all.


Oli.

 

[Hairyarse]

Sounds like you cracked it Oli []

I'm surprised that you had issue with it in the first place, I thought those joints would have been pretty bomb-proof

 

[zcacogp]

Well that's what I would have thought too Andy, but Tref thinks otherwise (and he's worth listening to as he knows a thing or two about cars.)

Thinking about it, rose joints are sold very commonly, leading me to wonder if they need to be changed often as consumables. For instance, the part I made the gearshift stabiliser bar out of is a go-kart steering tie rod, and they seem to be sold in quite large quantities, suggesting that karters get through them a lot. This could be because they get damaged in racing, or could be that they wear out frequently ...


Oli.

 

[Hairyarse]

Yep that sounds plausible and I'm always happy to listen to someone with more knowledge than me! []

Look forward to seeing the outcome of the MK2 version

 

[zcacogp]

Thanks ... it currently drives well, although it's off on another long(ish) run next weekend so we'll see what that brings.


Oli.