overdrive issues

[Felix]

Hi, my overdrive on a mk2 gt6 has stopped working. It had been running perfectly for a while, but has suddenly stopped, and with no burning smell. The switch is the stick type on the steering column. I've tried testing it in 3rd with ignition on and there is definitely a clunk coming from the left side of the tunnel in the passenger footwell. Originally I thought this was just the relay on the bulkhead clicking, but oddly, there's no overdrive relay beside the battery, just the horn relay. Does this sound like it is more likely to be a J Type overdrive with no relay and the solenoid on the LHS of the overdrive unit? What's the next logical step? Tunnel off?

Thanks!

Felix

[Jason]

If you can hear the solenoid clicking and everything else is working OK (no slipping whilst under power) then my first thought would be gearbox oil level.

There's are some useful on-line resources you can read through to decide on a battle plan

http://www.canleyclassics.com/?xhtml=xhtml/infodatabase/overdrives.html&xsl=infodatabase.xsl
http://www.buckeyetriumphs.org/technical/jod/JOD1/JOD1.htm

Although the TR6 references are for a different box, the overdrive and it's troubles/solutions are very similar.

[Felix]

that last link is an incredibly useful blog, thank you for that. My next step is to check the oil and hope that it is the possible cause of my problem.

I'll update the thread with the results.

Felix

[Felix]

the reverse light isn't working either. Hmm, makes me think the two are connected? Could this be an electrical fault after all?

[rotoflex]

If there's no additional overdrive relay, the OD installation may have been post-factory with possibly non-standard wiring going straight through the switch with no relay.  If that's the case, it would be a good idea to straighten it out & wire it as the factory did overdrives (with the relay), and the sooner the better.

I agree with Jason:  if you can hear the solenoid go clunk under the transmission cover, then suspect insufficient gear oil in the transmission (which shares its oil with the overdrive).

Loss of reverse lights is strange if the OD solenoid is working.  There are a number of possibilities involving the reverse light switch & the Overdrive inhibitor switch, but nothing that seems to add up to these symptoms.  I'd really recommend first filling the transmission oil as soon as possible, & then on the first free day possible removing the transmission cover to see what's going on with the OD & reverse light wiring.  It could be just a coincidence that your reverse light switch has gone out at the same time, but regardless, you'll have to remove the transmission cover to get to it anyway.

[Pete Lewis]

if unsure about what OD is fitted  Dtype has solenoid on OS and needs a relay due to initial hi current on pull in

J type  has operating solenoid on  N/S  and due to much lower current dosnt generally need a relay.

if the covers off and its a D type take off the square side cover and watch the solenoid pull a lever , in the lever is a 3 mm hole which needs to align with a similar hole in the case ( use a drill as a guide) if it doesnt line up adjust the rod nut.

on top of the tower is two switches on does reverse the other cuts the OD feed when in 1st 2nd.  you may have a linked problem here. depends how ts all wired in.

wires up the gearstick are notorious for chafed and shorted out,  if a re wire is needed get some silicone sleeved wire which takes the heat and flexing much better that std wires.

Pete

[bob dunn]

http://www.tcoc.ie/wiki/item/367891

[bob dunn]

I hope the above helps

[Felix]

thanks for all of the advice.

I stripped the tunnel off and topped up the gearbox oil. It was fairly low, but took about half a litre to fill it up. However, the overdrive was still not working... at least now I could double check all of the electrical cables and actually see the solenoid move when overdrive was switched on in 3rd and 4th. I was still scratching my head, wondering what to do next. J Type overdrives are supposed to be more reliable, aren't they?

Finally, with further friendly advise, I took it for a spin and hit the side of the overdrive casing with a hammer when I was out for a short drive. Well, well, well, the overdrive was stuck on, and a little tap released it. I'm not sure what the technical term is for "hit it with a hammer" but it worked first time! I'll leave the tunnel off for a bit longer just to make sure it doesn't get stuck.

Thanks again for the help,

Felix

[mikew]

If it does stick on again DO NOT put the car into reverse - this can easily destroy overdrives - its all to do with the one way clutch

[rotoflex]

What Mike said, although I can see how it would be hard for someone to tell who wasn't extremely familiar with the car's speed vs. rpms.

It's interesting that it's a J-type overdrive.  GT6's all came with D-type OD's, & fitting a J-type isn't a drop-in project.

[Phwoar]

I believe "gentle persuasion" is the technical term. Well done!

[Nick Jones]

A bit of "percussive maintenance" can work wonders......

Nick

[Phwoar]

Walk softly and carry a big hammer! Drilled into by my dad who was no mechanic!

[Felix]

I was expecting to find a D type overdrive, but the lack of a relay and the clunk coming from the passenger side of the tunnel made me suspicious. And with the tunnel off, it confirmed my suspicions. I'm guessing the overdrive was fitted to the car at some stage in its history, since the j-type can't be original for a J Reg facelift mk2.

I'm going to make a note of revs at certain speeds with overdrive on and off so I can look out for it if it happens again. If only the speedo was accurate, but that's a separate thread (it is about 10mph higher than the speed on a satnav).

[RedRooster]

If only the speedo was accurate, but that's a separate thread (it is about 10mph higher than the speed on a satnav).

Your satnav is wrong GT6's are fast even when they are parked )
RR

[Pete Lewis]

old speedo tolerances were to read  upto  +10%     +/- 4 Mph    and  must not read slow.
          so at a true 60 it can read 70  which meets the rules of the day .
     Pete

[BrendanD]

Mine reads 80 when I'm doing 90.....
I must get it out and re calibrate it!

[Saltddirk]

BrendanD wrote:

Mine reads 80 when I'm doing 90.....
I must get it out and re calibrate it!

are you running different tyres or Diff?
I did not think you can recalibrate the speedo, not unless you change the gears inside.
There should be a printed figure on the speedo indicating the number of revs it takes per mile.
I can not help you with the spit figures, but attached is a picture of the Roadster speedo, it is the top figure.

[BrendanD]

This explains how. doesn't look to difficult.
http://www.szott.com/lotusinfo/Smith-jaeger_speedo_repair.pdf

It's on the GT6. It's just out without a reason as I've got standard diff, OD and equivalent diameter tyres (175/70 rather than 155/80).

[Felix]

well that didn't last long. I took the car out twice today. The overdrive worked fine on my first trip, but by the second journey (10min later) it stopped working again. Now where did I put my hammer?

[BrendanD]

Can't recall have you stripped apart the filters and cleaned them thoroughly?
Probably the only thing you can do with an OD before taking it out and sending it off for repair...

[Saltddirk]

BrendanD wrote:

This explains how. doesn't look to difficult.
http://www.szott.com/lotusinfo/Smith-jaeger_speedo_repair.pdf

It's on the GT6. It's just out without a reason as I've got standard diff, OD and equivalent diameter tyres (175/70 rather than 155/80).

Mmmmm,
Actually without reading the whole document, that is not calibrating that they are doing but setting the zero. Still it can solve what is wrong with your speedo.
I might have expressed myself a bit wrongly in the first post.
Dirk

[Felix]

BrendanD wrote:

Can't recall have you stripped apart the filters and cleaned them thoroughly?
Probably the only thing you can do with an OD before taking it out and sending it off for repair...

I thought the filters on a j-type overdrive are better than d-type and there's not much to gain from going  the huge effort of cleaning them out? I haven't tried, but I'm running out of options.

felix

[BrendanD]

I cleaned mine out before I fitted it ( as a conversion) a few years ago. FULL of gunk. Yes the filters are good, but that doesn't mean they don't get full up with stuff and that may be restricting your flow.