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tony barnhill
Great Pumpkin - R.I.P
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Mine all work in 3rd & 4th & automatically cut off when speed drops below OD range & kick back in when speed increases...so, I only turn it off when I'm going below 3rd
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OD Conversion?
- Thread starter Bret
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Tom Rynne
Senior Member
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Bret, if the OD is energized then shifting from forth OD to OD third on one equiped this way is no problem. Disengaging OD is a bit of a jump down in either 4th or 3rd and lots of folks will clutch to avoid this but the purists say the drivetrain was built to take it. Strictly personal choice.
Here in hilly western PA the third OD to third is great as it allows the downshift to accelerate to climb hills then a reasonable cruising speed back in OD third once cresting the hill.
The biggest step you might notice is regular third and then upshift and engage OD to 4th. Sorta like going from 3rd to 5th on a 5 speed. I will only do this on a 5 speed after wringing out third entering an interstate which is fairly level and go directly to 5th. Same would apply the the MG.
Here in hilly western PA the third OD to third is great as it allows the downshift to accelerate to climb hills then a reasonable cruising speed back in OD third once cresting the hill.
The biggest step you might notice is regular third and then upshift and engage OD to 4th. Sorta like going from 3rd to 5th on a 5 speed. I will only do this on a 5 speed after wringing out third entering an interstate which is fairly level and go directly to 5th. Same would apply the the MG.
Steve_S
Yoda
Offline
You can shift normally. The lockout switch will automatically disengage OD when you are in a gear that doesn't use it, which on later cars is all but 4th. When you shift back up to 4th, it will re-engage. If you downshift to 3rd and don't want it back in OD the next time you shift up, just flip the switch and it will remain in standard gearing. No clutch is needed and you can flip the switch at any time.
Personally I would find a way to fit a lockout switch to allow 3rd OD. I can't imagine life without it! I only use 4th OD for highway cruising as it basically robs what little horsepower you may have left at those speeds anyway, so using it for performance is futile. 3rd OD however can give you a big boost in performance climbing hills where 3rd is too low and 4th is too high.
Personally I would find a way to fit a lockout switch to allow 3rd OD. I can't imagine life without it! I only use 4th OD for highway cruising as it basically robs what little horsepower you may have left at those speeds anyway, so using it for performance is futile. 3rd OD however can give you a big boost in performance climbing hills where 3rd is too low and 4th is too high.
OP
Bret
Yoda
Offline
Well I’m having a hard time locating a shifter knob w/switch. Moss & VB sell the switch & cover but not the knob. So I was thinking about incorporating a knob that comes with one of those momentary switch on the shifter. This would mean having to use a relay to hold the OD circuit closed and have it deactivated whenever I shift out of fourth gear. Problem is there isn’t any way to down shift from OD into fourth gear should I need to do so. Oh well I’ll have to keep searching I guess or maybe make something up myself.
OP
Bret
Yoda
Offline
Rigging up a relay to act as a switch using a momentary switch isn’t that big a deal.
Most relays have double poles NO, NC and the swinger that toggles between them. So all you need to is use the one pole to activate the OD solenoid and the second poll to hold the relay in the activated position once the momentary switch is released.
Looking over the schematic you could use the fourth gear vacuum advance circuit as the voltage source for the circuit. Thus removing the voltage to the OD activation circuit when you shift “out” of fourth gear.
Perhaps this sounds complicated – but trust me it’s actually pretty simple & it shouldn’t require anymore than the switch and a relay to make it work. I bet I could make the whole think small enough to fit under the center console with the one wire to the fourth gear circuit and whatever connects to the OD solenoid.
But again I might be getting a bit ahead of myself as I haven’t even decided to buy the OD trans yet.
Most relays have double poles NO, NC and the swinger that toggles between them. So all you need to is use the one pole to activate the OD solenoid and the second poll to hold the relay in the activated position once the momentary switch is released.
Looking over the schematic you could use the fourth gear vacuum advance circuit as the voltage source for the circuit. Thus removing the voltage to the OD activation circuit when you shift “out” of fourth gear.
Perhaps this sounds complicated – but trust me it’s actually pretty simple & it shouldn’t require anymore than the switch and a relay to make it work. I bet I could make the whole think small enough to fit under the center console with the one wire to the fourth gear circuit and whatever connects to the OD solenoid.
But again I might be getting a bit ahead of myself as I haven’t even decided to buy the OD trans yet.
tony barnhill
Great Pumpkin - R.I.P
Offline
The switch & cover just snap on your original knob...look at your knob & you'l see where it comes apart.
tony barnhill
Great Pumpkin - R.I.P
Offline
Oh, I have them