[Mgs] Determine build date for an O/D transmission?

Max Heim mvheim at sonic.net
Mon Nov 11 14:15:19 MST 2019


My old 66 MGB had an extra hole in the dash next to the OD switch hole. So (after the experiment with the lighted switch) I used a red “jewel” generator warning lamp in this hole as an OD “on” lamp. I would have used the blue high beam warning jewel but it cost twice as much for some reason.

I didn’t want to drill any extra holes in the dash of my new car, so I am doing without a lamp. I did add the official OD escutcheon label to the switch, which draws attention to the switch and makes it a little more obvious.

The plastic steering column cowl seems like a good place for a warning lamp, if you pick a spot in line of sight from your driving position. These are readily available used for very little money, so drilling a hole into one would not be much of a sacrilege.

One problem I had with my lamp was that I wanted it bright enough to see in bright daylight with the top down, but I didn’t want it to blind me at night. I am not sure that there is a good solution to this other than a dedicated rheostat, which is way beyond the amount of fussing I was willing to put into the project.

--
Max Heim
'66 MGB

> On Nov 11, 2019, at 12:48 PM, Robert's New iPad <mgbobh at gmail.com> wrote:
> 
>    The indicator light is handy, I think, to avoid that unanticipated shift into OD during acceleration when one forgets to shut off the OD.
>    I used a “grain of wheat” 12v lightbulb in short piece of brass tubing, this assembly pushed into the small gap between the fascia panel and the steering column plastic housing. Wired to the hot lead from the switch, it shows whenever the switch would activate the OD, or OD would activate itself.  An LED would be even better, but this was done 20 years ago.
> Bob  
> 
> On Nov 11, 2019, at 2:44 PM, Andrew Lundgren via Mgs <mgs at autox.team.net <mailto:mgs at autox.team.net>> wrote:
> 
>> The '78 dash has an "Accessory Switch" that can be added.  I have a factory blanking plate over that switch right now. If I go with the dash switch, that is where it will go. I would like a light as well, but I prefer the correct look. 
>> 
>> I will probably pull the lever off of my non-O/D and use it, at least initially.  I will need to run the wires. If the wiring wasn't already a mess on this car from the PO, I would be more concerned about it being correct and using the shifter switch
>> 
>> (That and it is a CBB '78, so I am not that concerned apparently)
>> 
>> --
>> Andrew
>> 
>> On Mon, Nov 11, 2019 at 12:06 PM Max Heim via Mgs <mgs at autox.team.net <mailto:mgs at autox.team.net>> wrote:
>> It just occurred to me that this may not be as easy on a later car. A metal-dash car already has the hole in the dash for the toggle switch. There is probably not a handy hole in the 78 dash, and the “vintage-style” chrome-bezel toggle switch would look out of place.
>> 
>> For a while I had a Radio Shack “glowing blue” toggle switch installed (to remind me to switch off the OD), which might look more in keeping with the plastic dash. I was a little dubious about it handling the load, but it held up fine. The solenoid doesn’t draw much. I don’t really think there is any reason to run a relay, or the vacuum switch — a simple ON/OFF in series with the lock-out switch on the transmission works fine.
>> 
>> I don’t understand how a momentary push button switch (Bert’s suggestion) would even work...
>> 
>> 
>> --
>> Max Heim
>> '66 MGB
>> 
>> 
>> 
>>> On Nov 11, 2019, at 9:32 AM, Max Heim via Mgs <mgs at autox.team.net <mailto:mgs at autox.team.net>> wrote:
>>> 
>>> Exactly. I have a 1977 vintage blue label OD transmission in my 66. I have a dash-mounted switch to the left of the steering column. The wiring couldn’t be simpler. No weird expensive parts. The straight (as opposed to crookneck) dash OD switch is cheap.
>>> 
>>> You might not think the dash switch is as convenient as the gear lever switch, but it is really pretty ergonomic. You can flick it with the side of your hand while it is still in contact with the wheel — you don't have to go groping for it.
>>> 
>>> --
>>> Max Heim
>>> '66 MGB
>>> 
>>>> On Nov 11, 2019, at 8:08 AM, Charley Robinson via Mgs <mgs at autox.team.net <mailto:mgs at autox.team.net>> wrote:
>>>> 
>>>> I've swapped OD gearboxes into two CBBs.  In both cases I used the gear levers from the original non-OD transmissions.  I don't see any reason that you can't use the gear lever you already have for the OD box.  
>>>> 
>>>> As to the OD switch, I'd put it on the dash if I had an open spot for it that was handy to my right hand.  In the CB cars the wiring and switch are already installed but there's no reason you can't find the white circuit that Paul mentioned and run a wire from it to your switch and from the switch to the lockout switch on the OD box.  Looks like there are a couple of switches in the Moss catalog that would look OK on the dash.  The switch is just a SPST that can handle the solenoid current.
>>>> 
>>>> My $ .02,
>>>> 
>>>> CR
>>>> 
>>>> On 11/11/2019 7:35 AM, Andrew Lundgren via Mgs wrote:
>>>>> I have a '78. The transmission is a blue label, but the seller doesn't have the shift lever.
>>>>> 
>>>>> A lever for a '78 is not a cheap thing, and my son who is driving it a lot right now likes the Walnut MG logo shifter it has.  So I'm looking at options for how to install the O/D switch. 
>>>>> 
>>>>> From the moss catalog, it looks like the '76 switch won't work with the '78. So I might have to buy the parts to put together the shifter switch or put it in the blank accessory switch above the fan on the dash.  
>>>>> 
>>>>> 
>>>>> 
>>>>> On Mon, Nov 11, 2019, 1:45 AM PaulHunt73 <paulhunt73 at virginmedia.com <mailto:paulhunt73 at virginmedia.com>> wrote:
>>>>> None of that is to do with the OD itself.
>>>>>  
>>>>> Which gears it operated on is a function of the linkages on top of the gearbox, and you can have it on 3 and 4 or 4 only as you wish.  When the TCSA was introduced in late 76 to control 'surging' a third switch was added to the top of the gearbox that operated in 2nd and 4th, and this was wired in series with the OD switch operating in 3rd and 4th to produce a 4th gear only output controlling the TCSA and vacuum advance.  I suspect that was not very reliable as it was an external micro-switch so it was deleted and the gearbox components changed so the switch operated in 4th only, as done to the V8 several years previously.  The gearbox switch now controlled both OD and TCSA. 
>>>>>  
>>>>> The gear lever itself changed for the 77 model year to incorporate the OD manual switch, but that can also be fitted to any year, or the 77 converted back to some other switch, as you wish.
>>>>>  
>>>>> The wiring prior to 77 was from the manual switch on the dash or the column, to the gearbox switch on a yellow and a yellow red, then from there to the solenoid.  For 77 on it was from the ignition supply on a white to the gearbox switch, then from there to the manual switch on the gear lever, and from there to the solenoid.
>>>>>  
>>>>> Black label or blue label determines which speedo is compatible - black label was used on CB cars and used a 1280tpm speedo.  Blue label was used on RB cars and used a 1000tpm speedo.  But speedos can be recalibrated if you end up with the wrong combination. 
>>>>>  
>>>>> So as a 78 it should have a blue label OD and the manual switch on the gear lever, as the column switch - which together with the plastic dash was new for the 77 model year - won't have that function.  But if the car has the earlier RB dash and column switches you don't need the gear lever switch, which is prone to shorting out and causing harness damage.
>>>>>  
>>>>> PaulH.
>>>>>  
>>>>> ----- Original Message -----
>>>>> Not so much. It will be a a bit still until the transmission arrives. (Freight from NY to UT) I'm just trying to figure out which shifter it should have had as well as which gears it should work on.  
>>>>> 
>>>>> I'm going to be putting it into a 78, but the current owner is still trying to track down the shifter from his friend, the previous owner. He doesn't know if it was a late shifter or an early one.
>>>>> 
>>>>> I'm trying to determine how to wire it in.
>>>>> 
>>>>> 
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