• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Overdrive indicator

Share this page

Looks to me like you have no switches, probably due to the fact that the od was added to a non od trans. Easiest cure is to replace the top cover with one already drilled for and with lockout switches installed, otherwise you will have to remove this one, drill and tap, find switches-relay- wiring.
 
What if I just add a switch to the one that is drilled for second gear?

I just ordered 2 switches from Moss, so they're coming. I'll check to see if they have the top plate and relay also.

Is the OD relay I have no good for this if I add the other 2 switches?

Tab
 
Could be that's a later cover; I think some of the very late ones had a 3-4 switch somewhere else, rather than on top. Check the diagrams on TRF's web site (I can't right now, have to go).

The relay should be fine.

One of Nelson's articles talks about adding the holes for the early style interruptor switches. Not terribly difficult, but you'll need to strip the cover and locate the hole fairly exactly, plus buy a tap in the proper metric thread. (Don't recall the thread offhand, but it's not a common one; not in any of the sets I own or found online. Might be M16x2.)
 
TR3driver said:
However, my preference would be for a warning light that only warns of an unusual condition.
Click to expand...
Aircraft generally use the lights out philosophy. Lights off ("all is right with the world"), amber light on ("this could get worse") or red ("this is not good at all"); a gearbox about to go into reverse with the OD engaged falls into the red category. If you do that, then you can make the light very bright and obvious as you want it to be a big distraction.
 
Tab,

The top plate is cast and contains the shift handle interface with and the shifter rods. I didn't see any switches in the bosses in your pix.

Do you already have a switch for 3/4?

If there is already a 3/4 switch, then pull the shift cover (top plate), drill and tap, and install an additional switch where shown in previous post in this thread. Refer to Moss (page 34) or service manual exploded view of trans.

You will probably need to remove at least one shifter rod in order to drill and tap for switch. ISTR that you remove the shift handle (1 bolt (13) through the stamped metal cap (12) plus anti rattle spring and ball (10 $ 11), remove the bolt holding the shift fork on the affected shift rod (28), and slide the shift rod (25) out of the cover. There are some springs and balls for the shift rod detents that you need to catch when the rod comes out (30 & 31). DON'T LOOSE THEM! Reverse for reassembly.

All who are familiar with OD's are invited to chime in and correct me if I'm wrong about any of this. Haven't worked with any of this stuff for 40+ years.

I think one relay is good for all. Check wiring diagram to be sure. Wiring is my weak point (or one them).
 
Wrote the above without seeing Tr3drivers post. I was not aware of the switches positioned elsewhere. OD's weren't very common where I am and I last twisted wrenches for a living in 68. Ignore my post and get advice from someone more familiar with your setup.

Jim
 
TRDejaVu said:
a gearbox about to go into reverse with the OD engaged falls into the red category.
Click to expand...
Fortunately, that particular disaster should be impossible, if everything is working and wired properly. That's the whole concept of the lockout switches, to disable the OD in reverse & first (and second on some cars). The warning light is just to alert the operator when he does something stupid, like pull up to a stop sign/light with the OD switch left on. Think of it as a stall warning
grin.gif


But the consequences aren't all that dire, it just tends to lug the engine in 2nd gear (when the OD kicks in), and probably adds to OD clutch wear (since the pressure is so low that it tends to slip for awhile).
 
bgbassplyr said:
All who are familiar with OD's are invited to chime in and correct me if I'm wrong about any of this. Haven't worked with any of this stuff for 40+ years.
Click to expand...
That's reasonably close, although I wouldn't want to go that far without removing all 3 shafts and replacing the seals for them. Depending on the vintage of the cover, there may be some stop pins to remove as well. The balls and pin for the shift interlock are another thing that you have to watch for and remove, as they have a tendency to get lost inside the casting. They are also a bit tricky to get back in place properly when reassembling.
 
Randall,
Thanks for reminding me. As I said, 40+ years and a case of 'sometimers' will cause the details to disapear, at least until you get your hands on/in it.

By the time I moved on from wrenching, TR4's were still new enough and OD's rare enough, that I didn't encounter any.

Jim
 
Forgot to mention : I've never tried taking the shift detent balls & springs out through the shaft bores, but I don't think it will work very well. On earlier covers, they are held into their bores by threaded plugs, which can simply be unscrewed to remove the spring and ball (or plunger in some cases) through it's bore.

On later covers (sometime after 1970), they were retained by plain push-in plugs, somewhat similar to cup-type 'freeze' plugs. I remove those with a tap, a nut and a short length of pipe (a stack of flat washers would work just as well). Sorry I don't recall the tap size offhand, it's whatever will bite into the 'cup' of the plug. Spin the nut up the tap, then add the spacer and turn the tap into the plug until it starts to turn the plug. Then use the nut as a puller, to lift the plug into the spacer. Takes longer to type this than to do it, once you've got the tools sorted out.

This is easier and quicker IMO than the method Nelson gave
https://www.buckeyetriumphs.org/technical/Gearbox/GearboxCover/GearboxCover.htm

Since I had some threaded plugs on hand, I tapped the holes and installed the earlier type threaded plugs as Nelson shows. But the plain plugs I removed could have been used again. They are trapped in place once the cover is installed anyway, so it doesn't matter if they are a little bit loose (provided they hold long enough to check the tension and install the cover).
 
Randall,
Thanks for the correction. As I said, 40+ years and a case of 'sometimers' will cause the details to disapear, at least until you get your hands back on/in it.

Thsnks, Jim
 
Interesting tidbit on this situation.

I checked the reciepts in the voluminous and very well organized, with Excel spread sheets to boot, restoration records kept by the fellow that restored the car and found a receipt for the overdrive. It seems that he sent his old transmission as a core for a completely rebuilt one from an outfit by the name of Quantum Mechanics in CT. I called there today and spoke with John, the owner and same guy who rebuilt it. John couldn't figure out why there were no switches located on the top of the housing either, so I sent him the same photo I posted here.

He said he would take a look at it and get back with me.

Very nice guy and he seems to know a good bit about Triumph tranny's. He seems to think that a couple of the wires may be crossed causing the OD to engage in reverse. I guess I'll just have to wait and see.

Tab
 
Let us all know. I know that I'm curious, and I think others may be too.

Jim
 
John Espisito also did my overdrive -- it is the one pictured in a prior post (this thread) with the switches clearly labelled with marker on the top cover.

John was so thorough with mine it is hard to imagine he would send out something without the needed switches. He also stands behind his work so you should be able to sort this out.
 
UPDATE!

I was going through the photos of the restoration and came across one that shows the location of the 3-4th gear overdrive switch. As John suspected, it is located rear of the 3 bosses more forward on the housing.

He thinks that somehow the reverse light wire may have been wired to the switch improperly. Since my car does not have a reverse light, it will take a little investigation to solve this problem.

Anyway, I've posted an image of the transmission that clearly shows the switches location.

Overdrive Switch

John also told me, that per his recommendation to the previous owner, the 2nd gear switch was left off. He said using overdrive is second gear is not a good thing to do for some reason. No big deal since I would never use it in 2nd anyway.

Tab
 
Tab --
The switch you marked in yellow, on top of the tranny is the 3 - 4 gear indicator switch. The one on the left side of the top cover, right next to the other switch, is the reverse light switch. If you have the standard wiring harness, with fittings for two switches (2nd gear and 3 - 4 gear), and it got attached to the reverse light switch, that would explain your ability two engage OD when shifting to reverse. When re-installing, ENSURE that the OD wiring attaches ONLY to the switch on top of the cover and NOT to the one off to the left side. That switch can be used if you wish to wire up a reverse light. It is regarded as VERY IMPORTANT not to engage OD while in reverse. This breaks the OD unit in an expensive manner.
 
:iagree:

However, it's a shame you won't be using OD in 2nd. 2nd OD is a wonderful split between 2nd direct and 3rd direct; plus I love that kick in the pants when you flip the switch with the throttle on the floor. Also a joy when working hard through the twisties in the mountains, as you can cover from about 30 mph all the way to 60 mph without taking your hands off the wheel (or your foot off the gas).
 
Is that an A-type OD in the picture. Looks a little different to me. If it is a J-Type or something similar that may explain why it is not set up to work in 2nd.

Certainly my A-Type from John E has the 2nd gear switch and gets used in second quite regularly (not counting when I forget it is engaged and leave a stop sign shifting from 1st to 2nd OD).
 
I think its an A-type, but it looks like the solenoid hadn't been installed yet. Just a guess, but I'd say the top cover, and possibly the whole trans setup is from a TR6. Nothing wrong with that, though.

The reverse switch can be useful, you can always install a reverse light like a Lucas L661 lamp, which would be 'period correct' and a pretty quick install with the switch already there.

Randy
 
Back
Top