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o/d tranny

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artpart

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My new a-type o/d tranny arrived today and I have a question about it.... As I understand it, A-type overdrives are supposed to have 3 interrupter switches on the cover. Looking at the 3 interrupter switches from the top, 1)the most forward one (nearest the engine) is the 3rd/4th gear o/d switch; 2) the middle one is the reverse switch (so your reverse lamps will light with the gearshift lever in reverse); 3) and the rearward one is the 2d gear o/d switch.

My new gearbox has two switches: 1) one on the top of the cover; 2) and one on the side of the cover, just above the solenoid.

My assumption is that the switch on top is the 3rd/4th gear o/d switch and the switch on the side of the cover is the reverse switch. How can I confirm?

Chris
 
Hook up an ohm meter to each switch and see how it reacts when shifting into the various gears.
 
But remember that the switch on the top (which is probably 3rd/4th as you suspect) is not an interuptor... the switch completes a circuit (and OD is enabled) when 3rd or 4th is selected.

Sounds like you will have no OD in 2nd with this set-up. Thay may or may not be a big deal depending on how you drive.

Can't comment on the side switch as mine's a 4 which has no reverse lamps.
 
My J-type overdrive only engages in either 3rd or 4th gear. I have yet to figure out why anyone would want to engage overdrive in 2nd or even 3rd gear. I use my overdrive for exactly that, overdrive. Never could figure out how to utilize that overdrive to play with the gears. But then again, I sometimes have trouble walking and chewing gum at the same time.
 
Bill,

You know the dangers of chewing gum, so let's leave that alone. I love using of O/D in third gear when doing the back road runs. You can shift in and out with the flip of a switch and never have to clutch it.
 
Hey Bill, using overdrive in gears other than fourth are for places that have those big lumps in the ground some people call 'hills'. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif The long rolling type that make it easier to flick a switch up and down rather than shifting gears. /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
My TR3 OD is overhauled and reinstalled. It gives a good kick in the pants when going into OD, but smooth as silk coming out of OD. Did I do something wrong on the inside?
 
If it's an A-type, it has a tendency to slam a bit. Back off the gas a bit when you engage.


And, there are no hills here, unless you consider a highway overpass as a hill.
 
When I bought my A-Type at Carlisle years ago, we switched out the 4A case to a 6. We had to drill and tap the shifter to accomodate the third switch.
It has worked perfectly for 12-13 years.
 
Bill, having O/D in second gear is really great on tight, twisty canyon roads.

Fogdot, you can always use the clutch to lesen the harsh engagement.

Bob
 
I use the OD in 3rd for climbing our mountain... it's a slope where 4th is too tall & 3rd is more than I need so the OD fills the gap between the two.

I have been using the clutch when engaging... I know that kick-in-pants engagement is normal but just seems to me that if the OD clutch has to overcome the rotating mass of the engine it will have some long-term effect that can be lessened if it only has to overcome the rotating mass of the gearbox innards.
 
George, I too generally use the clutch unless the driving (meaning really tight, twisty stuff) is particularly quick and spirited. It seems that using the clutch has to have a beneficial affect on the drive train.
Bob
 
TR6BILL said:
And, there are no hills here, unless you consider a highway overpass as a hill.
Click to expand...

Just what I was implying. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

I guess you could count that bridge on I-10 coming into Baton Rouge a hill. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
Don't remember the name but I remember it being a big sucker... /bcforum/images/%%GRAEMLIN_URL%%/eek.gif
 
Shawn, when my engine was stock, I would often have to downshift from overdrive to 4th just to keep up when climbing a steep overpass. Since all the performance mods, I can now accelerate up any overpass whilst in overdrive. Cool.
 
A related question

A PO un-hooked all of the switches on the OD except the one for the back up lights. Do the other switches prevent the OD from being engaged except when the car is in 3rd or 4th gear?

If so, I would like to get them working. I would like to eleminate the possibility of leaving the OD engaged and trying to back up. I understand that this could cause fatal damage to the OD.

Hey, If I wuz smart I would be rich, Pete
 
TR6BILL said:
Since all the performance mods, I can now accelerate up any overpass whilst in overdrive. Cool.
Click to expand...

I can relate, isn't it cool! /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
69tr said:
...Do the other switches prevent the OD from being engaged except when the car is in 3rd or 4th gear?
Click to expand...

On the cover of a Type-A OD there are 2 switches. One allows OD to be selected in 3rd & 4th. The other (rearward) allow OD in 2nd.

If the switches are simply disconnected the OD will not engage at all unless the PO has also hardwired the relay ground... in which case OD can be engaged in any gear (including 1st & reverse) with nasty results.

OD-Cover.JPG
 
I use my overdrive in 3rd all the time. No clutch when I go up hills on the back roads. In and out, great fun.

Michael Scoggins
 
69tr said:
A related question

A PO un-hooked all of the switches on the OD except the one for the back up lights. Do the other switches prevent the OD from being engaged except when the car is in 3rd or 4th gear?

If so, I would like to get them working. I would like to eleminate the possibility of leaving the OD engaged and trying to back up. I understand that this could cause fatal damage to the OD.

Hey, If I wuz smart I would be rich, Pete
Click to expand...

It's easy enough to check - turn on your ign, and flip your o/d switch back and forth. You should hear the relay clicking, but only when you have the shifter in one of the gears that should be allowing overdrive. If it clicks regardless of the position of the shifter, your interrupt isn't working and I personally would disable the o/d completely until rectified... Pete (too)
 
Thanks everyone. I have the interior out of my car now while it is getting ready for paint. It will be a perfect time to undo (yet another) wiring mess.

One thing I will have to say about the PO. He was very inventive.

Pete
 
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