Overdrive virgin

[Bwhitmee]

Ok, you are going to roll your eyes at me but I’m new to owning a GT6 Mark II and trying to understand the overdrive. Do I use it like a 5th gear? I keep forgetting to disengage. What Damage am I causing if do the following:

1. Forget to disengage when I come to a halt and then switch it off before pulling away in 1st gear?

2. Forget to disengage as I drop down through the gears?

3. Pull away in 1st with overdrive still engaged?

4. Use reverse gear while Having overdrive engaged?

Thanks!

 

[glang]

Hi, if your OD is wired correctly it should have an inhibitor switch that cuts it out in any gear selection except 3rd and 4th. This means that you cant do any damage whatever you do.

Most people use OD to reduce engine revs when cruising at higher speeds and also as an aid to overtaking where the car can be kept in 3rd +OD and then dropped out of OD when the opportunity to overtake arises....  

[Bwhitmee]

Thanks for that. So theoretically I could keep it in OD most of the time and only drop out of it when needing the revs to pull away or overtake...?

[glang]

The OD is cutting in and out depending on the inhibitor switch but you wouldnt notice as you change, for example, from third to second. However its bad practice to use it like this because its not recommended to accelerate hard with the OD engaged and this is more likely to happen if not controlling it with the manual switch.

[nang]

I have O/D in my 2500.. Personally, I use it as a 5th gear. i.e. disconnect it with the switch when changing down and only engage it when I 'm going fast enough to need "5th gear" . But that's me , others have their own methods. As long as the inhibitor switch is working and you can't engage it in reverse you should be fine.

Tony.

[PeteStupps]

Quoted from Bwhitmee-

Thanks for that. So theoretically I could keep it in OD most of the time and only drop out of it when needing the revs to pull away or overtake...?

Agree with Glang on this - it would be bad practice to leave it on all the time and rely on the inhibitor switch to disengage! If the inhibitor ever failed you wouldn't notice and would swiftly destroy the OD. Apart from that you'd have a massive gap between 2nd and 3rd, as the OD would kick in when you changed up. 

There is a logic box available - I think from Revington.TR - which automatically disengages the OD whenever you change gear. I know that's popular with people who do hill-climbs and whatnot. 

[RobPearce]

Quoted from PeteStupps-

There is a logic box available - I think from Revington.TR - which automatically disengages the OD whenever you change gear.

For some value of "change gear", anyway.

On the TR box, and big saloon, Stag, Sprint, the inhibitor switch works in such a way that it disengages momentarily when shifting from 3rd to 4th. This allows the logic box to go 3OD->4 automatically, so you can then re-engage the overdrive. On the small gearbox, this is not the case, so the logic box doesn't know you've gone from 3OD->4OD. With GT6 ratios, that's probably for the best as 3OD == 4 to all intents.

[PeteStupps]

Ah thanks Rob, I did not realise that. Wondered how it could detect changing between 3rd and 4th, with my limited knowledge of gearboxes!

 

[Pete Lewis]

and not mentioned but you will find on most triumph ratios that 3rd OD is the same as direct 4th 

its  not the best use of ratios you cant use it as a split shift  you only get 5   not 6 

Pete

[Dave Clasper]

Hi. My J Type failed recently (sorted now, when cleaned out the solonoid) was not disengaging. First, noticed when I stopped in M Way traffic and car was shuddering and a bit of a screeching noise in 1st/2nd gear.

It did disengage by it's own accord and Didn't switch it on again.

Changed the G.B oil when I sorted the solonoid. The magnetic filler plug had a few very, very, tiny bits of very,very shiny metal (Chrome of layshaft?) underneath the usual spikey, though softer stuff. Haven't got a magnetic drain plug.

Maybe it can cause some harm if disengaged in the low, forward gears, aside from the, "in reverse", bad problem?.

Cheers, Dave

[RobPearce]

2 hours ago, Dave Clasper said:

Maybe it can cause some harm if disengaged in the low, forward gears, aside from the, "in reverse", bad problem?

I don't think so. The issue with engaging in reverse is that it absolutely forces the unidirectional clutch to fight with the gearing, and one of them has to give way. That's not the case in any forward gear. The only problem with having OD engaged in first is that, if you put your foot down, there's much more torque available to be put through the gears. I think the J-type is pretty tough, though, so unless you really do boot it in first you're probably OK on a Spitfire, or even a Vitesse.

The screeching noise you got, and the shuddering, was probably down to the oil pressure not being high enough at low road speed, so the conical clutch was only partly engaged.

[Dave Clasper]

Thanks Rob. It's a Vitesse, though wasn't booted through the gears.

[yorkshire_spam]

I concur with @RobPearce unless it was thrashed in 1st then there shouldn't be any damage. 

[Guppy916]

If your thinking of a Revington box , email Tim on,  tl_walker@tesco.net,  and tell him what you want and he will send you one, I think i got mine way back in January 2017 and it's worked great no problems at all, 

[Jason C]

I too am a OD virgin, this thread makes for great reading. In the future I would like to fit an OD to my Vitesse, namely for a fifth gear cruising on the open road. I like the idea of the OD with the stalk switch, but wonder “what if I leave OD engaged” – does the driver know it’s engaged by the feel, and or the rev counter? Thought a light on the dash may have been useful, but as I haven’t driven an OD before, what do I know, would be great to hear peoples thoughts...

Does an overdrive make for a more rewarding driving experience? I have heard people say the overdrive is better than a traditional 5 speed and great for winding roads.

[Rutty]

Hi Jason.

I can tell its engaged by the engine revs and the position of the leaver or switch if it on the gear stick unless its dark. But then just move the leaver and you will soon find out. I can't see a point of a light on the dash but its your car and if that's what you want to do then go for it.

O/D is great on winding roads as you can keep the power on while changing though there are some that say you shouldn't do this. I have a great blast up Hartside pass this year mainly leaving the car in 3rd and using the O/D. 

Mark

[RobPearce]

I've quite often forgotten to switch the overdrive out when slowing for a junction. It's not a problem - the inhibitor does it for you, and you only notice when you've pulled away and accelerated up to change into 3rd, when you get 3OD instead. At that point you either flick it back out to get acceleration or smile at the Vitesse's lovely wide torque curve that means your mistake doesn't matter.

Like Rutty, I also think OD is even better than 5th gear because you can keep your foot down while it engages.

[Hogie]

10 hours ago, Jason C said:

I too am a OD virgin, this thread makes for great reading. In the future I would like to fit an OD to my Vitesse, namely for a fifth gear cruising on the open road. I like the idea of the OD with the stalk switch, but wonder “what if I leave OD engaged” – does the driver know it’s engaged by the feel, and or the rev counter? Thought a light on the dash may have been useful, but as I haven’t driven an OD before, what do I know, would be great to hear peoples thoughts...

Does an overdrive make for a more rewarding driving experience? I have heard people say the overdrive is better than a traditional 5 speed and great for winding roads.

Hi Jason,

I have an 'A' type OD logic box on my TR4A and it makes the OD work a treat.

I use a press button to engage - which is almost effortless. It has a warning light as you can see the position of a press button.  

In the Black Forest a couple of years back I used 3rd gear to do the hair pin bends and the 3rdOD for the short straights. A couple of miles, no clutch use, a couple of dozen gear changes.

There are better options than the Revington item.

 

Roger

[Jason C]

Hi Roger,

Overdrive sounds fantastic, an exciting improvement to the driving experience. Driving through the forrest in a TR4A sounds magic!

best,

Jason

[tr250]

Overdrives are great especially here in the States. Loooong roads mean higher revs, lower fuel economy, and even quieter cabin wo Overdrive. 
 

As others have mentioned on twisties, going in/out of OD is wonderful, you don’t have to touch the clutch. 
 

I think a Mk2 GT6 will have a D-type overdrive. I believe the D-Types build and maintain hydraulic pressure so you have instant Overdrive. You may not notice it’s in OD because of it. The later J-Types build pressure when engaging with the switch so it takes a sec or two. Almost annoying when left on all the time. 
 

Have fun with your new toy!

 

Todd

[thescrapman]

A types have an accumulator, and a pump that's works one way, J type donhave an accumulator, and a pump that works up and down.

Don't think the D type has an accumulator, and has a one way pump.

[Bish]

I love the overdrive on my Sprint. As others have said cruising in third round the bends flicking in and out of overdrive is a joy. I also enjoy accelerating hard in forth and flicking the overdrive in which means you don’t lose revs like you would changing into fifth with a clutch. But I guess it’s not doing the overdrive any favours?

I converted my MK1 Vitesse to overdrive too. Best modification you can make in my book. Worth every penny. 

I too thought I was going to break it somehow, and was a bit forgetful with it at first, always leaving it in at roundabouts etc. My advice is to drive it don’t be scared of it. You will get used to it! It soon becomes second nature to flick it out of overdrive when necessary. 

The extra MPG is most welcome of course, especially with petrol prices as they are. Just under £1.60 per litre of super unleaded round these parts now! 

Edited November 29, 2021 by Bish

[Dannyb]

I fitted one of these to my 1500 Spit. It makes it dead easy to operate over the standard sliding switch especially when wearing gloves.. 

Danny

[Dannyb]

One thing I should point out with the above gear knob is you will have to drill and tap the to match the triumph leaver. 

Danny

[Dannyb]

1 minute ago, Dannyb said:

One thing I should point out with the above gear knob is you will have to drill and tap the to match the triumph leaver. 

Danny

tap it to match the triumph lever  😜

Danny