Overdrive in all 4 gears?
Discussion
wheels1 said:
cheers Chard.
it only happens in first and second when the switch is on and the revs. reach 3500, very strange, i think i will just use in third and forth from what you say then.
cheers
Grant
Other than the switch itself which passes the current to the solenoid which activates the overdrive, there are two other controls between those elements of the system. it only happens in first and second when the switch is on and the revs. reach 3500, very strange, i think i will just use in third and forth from what you say then.
cheers
Grant
There may, depending on the type of overdrive, be a vacuum activated switch; this was included in the circuit to prevent "snatching" of the drivetrain on engagement/disengagement of the overdrive; it was certainly there on pre-68 cars, but it may not be present on LEs, as post-68 cars had the LH type overdrive, where I do not think that this was fitted as the operation of the overdrive unit itself cushioned the operation of the unit.
In all cases though, as well as the dashboard switch, there is another in-line electrical switch; this is screwed into the left side of the gearbox remote housing, which itself bolts onto the top of the gearbox; the remote housing contains the gear selector rod from the gear lever, and the switch is designed to prevent overdrive engagement in all but 3rd and 4th gears; the switch is activated mechanically and works by a plunger pressing against the selector rod, such that it only allows the current to pass through the switch to the solenoid when 3rd or 4th gears are engaged. If that switch fails and shorts out (as they do), it will allow the current to pass, and thus allow operation in all gears. The switch location is shown here http://www.moss-europe.co.uk/Shop/ViewProducts.asp... - part number 11 is the one!
From the sound of your symptoms, it is probably this switch that is allowing the overdrive to engage in first and second. You probably won't create untold damage if you simply ensure that you only use the overdrive in 3rd and 4th, but you must ensure that not only do you flick the dashboard switch to normal, but that it actually comes out of overdrive; as mentioned in the earlier post, if still engaged when reverse is used, it has the very real potential to wreck the overdrive unit. A replacement switch is about a tenner.....
MG Mark
SB - Nigel said:
I thought the later Bs had the overdrive switch in the gear knob ???
They are - causes a few snags as the wiring can break through wear and tear and it's not the easiest job to re-wire. Switch replacement is a doddle though and I think the gear knob is the same as they used in other BL overdrive cars e.g. dollys, triumph 2000sSB - Nigel said:
I thought the later Bs had the overdrive switch in the gear knob ???
Indeed they did, from '75 onward with the advent of the rubber bumpoer cars - I just put "dashboard" out of habit! Otherwise the systems from 68 onwards were the same, just the switch location that is different.MG Mark
Thanks for the advise guys, i went to collect a switch from the MGOC as they said they had over 50 in stock and its not far away, but when i got there they could not find them, it turned out they where all faulty and had been sent back!
Still my son was impresed with 8 forward gears. I will just use it in 3/4 for now, until i get a switch.
Grant
Still my son was impresed with 8 forward gears. I will just use it in 3/4 for now, until i get a switch.
Grant
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