Am I using the overdrive properly or abusing it!

[MRG1965]

HI All, just been reading some threads during my lunch break and have seen a few posts on logic units for the overdrive and what it does.

 

I have a TR4 with an A type O/D and the standard 2nd, 3rd and 4th gear inhibitor switches, and no logic unit. All works perfectly well, for somebody who does not race, rally or thrash his toy (although I'm not saying that its a bad think, just expensive and annoying to have to fix things I've broken), but I will admit to a bit of enthusiastic driving on occasion.

 

Now to my question/point of confusion on the proper use of the O/D.

I'm not looking to fit a logic box, but from the other posts I understand that I'm supposed to disengage the over drive when I change up/down using the column switch and than re-engage the O/D after or am I just misreading the other post?

 

I can hear the solenoid disengage and re-engage with a click as I change gear as the isolator switches do their work. And thankfully stops it from engaging when in reverse as I'm prone to forgetting it's on, man of a certain age thing, I think or more likely just used to modern 6 speed boxes.

I use the O/D more as a 5th gear in top rather than to provide a 7 speed close ratio gearbox (see Sunday driver comment above ).

 

Any advise on the correct use of the overdrive in normal operation is much appreciated. And to possibly save me from a big repair bill.

 

 

Mark

[peejay4A]

There's not much you can do to break an overdrive in a standard car. It's designed to be switched in under hard acceleration. You can make things a little easier on the driveline and your passenger by easing off or even declutching when engaging and disengaging overdrive but don't get paranoid about it. If you forget you have it engaged it can get a bit interesting when pulling away at a junction for example. You go from first to overdrive second, to overdrive 3rd to overdrive top. You won't go very quickly though but nothing will break. That's where a logic box comes in handy, or my simple version which disengages overdrive when the gear lever passes through neutral but doesn't engage it again until you deselect and reselect overdrive. Once you get used to it, it's quite fun really.

[RogerH]

Hi Mark,

much the same as Pete except you can break the OD if deselecting with the engine revs not matched.

 

Moving up down the gears whilst still in OD dampens everything so you will be OK.

 

However if you decide to change down and allow the engine revs to fall to idle there could/will be a mighty clunk as the back wheels try to jiffy the engine along via the OD.

To overcome this simply raise the revs slightly immediately before deselecting.

 

This could happen with or without the logic box.

 

Roger

[Rob Salisbury]

Hi Mark, some simple rules for overdrive use:-,

carefully bend the column lever so that it is within easy reach of your outstretched right-hand middle finger when holding the wheel in the classic 10 to 2 position,

then plenty of power when engaging O/D,

a slight amount of power when diss-engaging,

never on a trailing throttle,

and don't ever,ever try to reverse with O/D engaged (stuck mechanically, or through an electrical fault), you will break the unidirectional clutch.

If your brain is engaged with your car, and your middle finger then you really don't need a logic box, using an overdrive properly is right at the heart of the TR driving experience, enjoy!!

Cheers Rob

[MRG1965]

Thanks all, sounds like I was not treating the O/D very well, but sounds like it will be ok.

 

Rob, I turned the column switch upside down when first got the car (rotated 180 degrees in the cowl) as it kept digging in to my right knee every time I got in and thought I'd either snap it off or ram it under my knee cap. Turns out that moved it to a much easier position for the index finger of my right hand ( just need the brain to connect) similar to the bending the lever idea, also now works in the direction my brain seems to expect it to work, maybe the PO installed it wrong in the first place or maybe I'm just odd.

 

Although I do like the idea of the switch on gear knob, but thats not a cheap change unless I can find a cheap knob(ow er misses) also not standard.

 

Thanks all.

 

Mark

[Alfrom]

Rob

 

Noticed that you said 'never on a trailing throttle' - why should that be? Is that advice applicable to the J-type OD?

 

(Just a question based on my ignorance - not questioning the advice per se.)

 

Thanks.

[peejay4A]

I have a J-type and have had an A-type and I have frequently engaged and disengaged on a trailing throttle with no ill effects.

[Cew]

 

 

 

 

I can hear the solenoid disengage and re-engage with a click as I change gear as the isolator switches do their work. And thankfully stops it from engaging when in reverse as I'm prone to forgetting it's on, man of a certain age thing, I think or more likely just used to modern 6 speed boxes.

I use the O/D more as a 5th gear in top rather than to provide a 7 speed close ratio gearbox (see Sunday driver comment above ).

 

 

 

 

Mark

I use the overdrive in a similar way,but I ease off the throttle when engaging and blip the same when disengaging much like changing a gear.

 

You could always incorporate a warning light on the dash somewhere to let you know it's engaged,I'm sure someone on here has done this already,my old Jaguars had this built into the switch and I seem to remember the Sunbeam Rapier and Humber Sceptre having a light as well.

[Tom Fremont]

Coordinating the throttle with O/D changes can be an art form; my own version of it with over 20 years uninterrupted experience has room to improve still, but when I get it right there's nothing quite like it .

 

An uprated layshaft / cluster gear bearing arrangement ( that is, three needle bearings vs. two ) is about all I could recommend for a road car's O/D box to ensure its durability against, er, enthusiastic usage along with a beefed-up diff mounting kit. I think mine also have increased pressure settings in their accumulators. These factors were to enable them to contend with 150-170 BHP and up to 180 lb-ft.

 

Cheers,

Tom

[Rob Salisbury]

Rob

 

Noticed that you said 'never on a trailing throttle' - why should that be? Is that advice applicable to the J-type OD?

 

(Just a question based on my ignorance - not questioning the advice per se.)

 

Thanks.

It's as Roger says, you need to match the engine revs with what the back axle is doing to the OD via road speed, otherwise there will be a big shock sent through the drive chain, the U/Js just don't like it!!, as for the diff mounts on an IRS chassis??!!, call it mechanical sympathy, give everything a bit of a hand

...as far as the J type ODs go I've never had one so I can't be sure, but the engineer in me says keep it smooth, you wouldn't change down a gear with the engine at idle revs, so why do it to the OD?

If for any reason you need come out of OD at idle revs then just dip the clutch.

 

MGR1965, the OD switch(on or off) shouldn't be anywhere near your knee!!, unless you're steering with your feet!!, the wand should point upwards at about 45degrees when off and towards horizontal when on.

 

As Tom says, throttle/OD coordination when done right is brilliant, especially during full throttle upward changes with revs in the 4.5 to 5K region!!

cheers Rob

[peejay4A]

Disagree, sorry. No need to mollycoddle it.

Edited April 7, 2015 by peejay4A

[littlejim]

Mine gives a clunk if I ease off the throttle. Doesn't mind a bit of throttle going either way and no clunk.

[MRG1965]

It's as Roger says, you need to match the engine revs with what the back axle is doing to the OD via road speed, otherwise there will be a big shock sent through the drive chain, the U/Js just don't like it!!, as for the diff mounts on an IRS chassis??!!, call it mechanical sympathy, give everything a bit of a hand

...as far as the J type ODs go I've never had one so I can't be sure, but the engineer in me says keep it smooth, you wouldn't change down a gear with the engine at idle revs, so why do it to the OD?

If for any reason you need come out of OD at idle revs then just dip the clutch.

 

MGR1965, the OD switch(on or off) shouldn't be anywhere near your knee!!, unless you're steering with your feet!!, the wand should point upwards at about 45degrees when off and towards horizontal when on.

 

As Tom says, throttle/OD coordination when done right is brilliant, especially during full throttle upward changes with revs in the 4.5 to 5K region!!

cheers Rob

HI Rob, yes that's why I moved it, it seemed to be in the most awkward position possible. The PO had it low down for some reason or other, or maybe that's the way it was when he got it, but either way sounds like its now in the right position.

 

Clive, I've seen on other posts about a warning light, might fit one in the next couple of weeks, I've got some wiring to do when I fit a RetroSound Zuma radio (Birthday present).

 

Mark

Edited April 8, 2015 by MRG1965

[RogerH]

Hi Mark,

there aren't many places to fit a warning light without making holes etc.

If you have to look at a warning light to see that you are in OD then surely a quick glance at the rev counter would do the same.

In 4th gear the speedo and tacho needles point in the same direction.

In 4th OD the tacho needle is slightly anticlockwise.

 

Roger

Edited April 8, 2015 by RogerH

[McMuttley]

Roger, sounds like your speedo is not working as designed, it should be waving about erratically - generally between 20 and 60 (or more) mph.

 

Interesting advice from all on how to drive with an o/d.

 

I think I need to adjust my pedals as there is a cavernous gap between brake and throttle which means that blipping on downshifts is nigh impossible.

 

(unless of course I have very small feet !)

[littlejim]

Hi Mark,

there aren't many places to fit a warning light without making holes etc.

If you have to look at a warning light to see that you are in OD then surely a quick glance at the rev counter would do the same.

In 4th gear the speedo and tacho needles point in the same direction.

In 4th OD the tacho needle is slightly anticlockwise.

 

Roger

I had a spare hole in the lowest part of the 'H' near the heater controls. I put a blue light there wired into the 'overdrive on' circuit.

I find it handy despite what Roger says about the rev counter. (I'm older than him.)

[monty]

Hi Mark,

there aren't many places to fit a warning light without making holes etc.

If you have to look at a warning light to see that you are in OD then surely a quick glance at the rev counter would do the same.

In 4th gear the speedo and tacho needles point in the same direction.

In 4th OD the tacho needle is slightly anticlockwise.

 

Roger

As I don't smoke I have put a warning light (as well as one for the fan) in the ashtray! A friend carefully drilled the holes into the Bakelite & all the wiring is concealed by the ashtray. All neat, tidy & useful!

Cheers,

Monty.

[Tom Fremont]

Indicator light for O/D has never appealed to me ( not that I always know where mine is, but almost ). If I wanted its mode more apparent I might put a thin strip of white tape on the front of the switch handle.

[McMuttley]

I had green/yellow tape on the gear knob, it reminded me when selecting reverse that there was also green/yellow tape on the o/d switch. I took it off and kept forgetting i had parked with o/d on.

[ianc]

McMuttley:

I have small (size 6) feet an in order to be able to 'heel and toe', an extension on the accelerator pedal makes all the difference. Mine is a 'Paddy Hopkirk' model, but, in the early 1960s, I made a similar device for my TR2 from a piece of aluminium sheet, which I clamped to the accelerator pedal. The bottom edge of the device inclines to the left, so bringing the accelerator towards one's heel.

Ian Cornish

[McMuttley]

Ian, you are a proper old fashioned heel and toe'r. All the kids these days roll their foot sideways, which c'est impossible for me in a 3

[Motorsport Mickey]

You get more feel if you can roll across on the ball of your foot, the modification Ian suggests is well worthwhile and works on TR3s also.

Make up a plate about the same size of the accelerator secure it to the pedal between the brake and accelerator where it fits nicely and brings control of the accelerator to the outside of your foot whilst allowing the inside to use the brake pedal. You soon get used to making sure your foot clears the appropriate pedal.

 

Mick Richards

[Stag powered]

In thirty years of driving overdrive Triumphs I have never bothered treating the overdrive in any particular way, and certainly have always disengaged on a trailing throttle without any problems.

I must admit to having knackered an A type in my hard driven tuned 2.5PI saloon years ago, but that was probably due to using overdrive in second, something I stopped doing after that.

I tend to use the overdrive as a 5th gear now in the TR, as quite honestly it is struggling to hold on to the 200lbft of torque from my Stag engine when in third, but it is a Dolomite Sprint J type unit that has covered about 150,000 miles. I believe the overdrives for lesser powered models work at a lower operating pressure than those aimed at the higher performance models, but I had this one in the shed and it has lasted 22 years and about 70,000 miles in the TR so I can't complain.

 

Neil

[TR5tar]

Hi Mark,

 

Good topic.

 

I'd never used overdrive until I got my TR, so like you I was a bit unsure about the best way to use it. I did a bit of research on the forum and elsewhere when I first got the car and gleaned that many people advise coming out of overdrive before changing gear, which is what I've being doing. I've also just really used it as a 5th gear, like you. However, since reading this thread, I've tried coming out of overdrive before lifting off the throttle (as Rob and Roger advise), and it certainly seems a smoother change to me, so I think I'll continue doing that.

 

Darren

[MRG1965]

Cheers Darren, yes I'm like you this is the first car I've ever had with an O/D and other than having a good technical understanding of how they worked, I had no experience of actually using one.

There do seem to be accepted practices, but others find that showing it no special treatment works too.

During the spring/summer, I'll be trying various things no doubt to improve my skills in this area.

My real concern is not having to spend many hundreds of pounds in the future to exchange my box of bits for a recon unit.

But there have been no real tales of doom and disaster, so I'm assuming that as long as I don't drop out of O/D at 5000 rpm (and bugger the engine) or reverse with it stuck in (and mangle the O/D innards) it should have a long and happy life. But I'll still try various suggestions from the forum to see if we can improve the experience.

 

Mark