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Triumph TR6 - Overdrive overuse

I have heard a couple of different thoughts about the OD. The previous owner of my '70 TR6 told me to always take it out of OD before changing gears, than another person said don't worry about it - just leave it on all the time.
I liked the conservative approach, but sometimes I forget to switch the OD off, and then when starting out I hit 2nd gear, and it kicks on (after ~2 sec delay). At that point I curse my bad memory and then pull a OD off/ 2-4th gear shift.

Any thoughts regarding leaving on the OD? Is it really okay to leave the OD on all the time? What am I going to be replacing, due to my bad memory?

Tom H.

The overdrive should only work in 3rd & 4th, unless I am mistaken. The only thing to really avoid is reversing while the o/d is engaged, as this kills overdrives. It breaks up the one way clutch.
I always used the overdrive as another gear change, or as a quick downshift to pass or get up a hill. Do whats comfortable for you....just don't engage reverse in overdrive, and you may want to check the operation of the switch that is supposed to limit operation only in the 3rd and 4th shift gate.
Rod Nichols

Tom, Your overdrive will work in 2nd, 3rd and 4th. TR6's through 72 still used the "A" type overdrive which operated in 3 gears where 73 and later used "J" type overdrives in 3rd. and 4th only. There may be a mix on some of the 72's but not being a 6 expert in any means, I am not positive. The "A" type supposidly could handle the extra torque of 2nd gear. I personally (on my TR4A) have disconnected the enablement switch for 2nd. gear and only use it on 3rd and 4th. I will not hurt the overdrive to run it all of the time and in the worst case you have a ver quick gear change from 2nd to 3rd-overdrive! Don't worry about running it in reverse because if it is working and wired correctly it will not engage in reverse. The lock-out switches control which gears are enabled. But beware, as Rod stated, if it should stay engaged (usually because of a clogged operating valve or stuck solonoid) and you attempt to run in reverse.... BANG goes the roller clutch! You will actually feel the rear end of the car raise up just for an instant before this happens because the output shaft will refuse to turn, then it breaks. Ask me why I know!!!!!! Steve Yott
Steve Yott

I only use OD when I hit highway speeds. I never use the OD in 2nd or 3rd. It is to easy to lug the engine if you use it in 2 and 3 at the speed you are usually traveling at for those gears. I guess my problem is I do not do a lot of traveling at 50 KPH (30 MPH). ROD..FYI the A type overdrive can be used in 2,3,and 4th gears. Also has on the gear box a "prevention" switch as u mentioned. I do not think you are doing any damage leaving it in OD...other than the remember thing which I would constantly forget to do and then all of a sudden as I go into 2nd it would drop into OD.
IMHO I think the OD selection should be used only in top gear and as you down shift the first gear to down shift is OD....then no worries about lower gears and is OD on or off. Besides if you look at a modern day car the OD only kicks in after the highest gear has been reached. Now the controversy begins " to clutch or not to clutch?... that is the question." (sorry) I like to clutch when going in or out of OD if for no other reason than it makes me think I have a real 5 speed tranny. In reality the clutching on going into OD allows the engine RPM time to drop to match the new gear selection...going out of OD I clutch, give the throttle a blip and as clutch comes out the engine is a correct RPM for 4th gear. There are others that do not clutch at all.( this conversation has already been delt with in a past thread). If you leave the OD on all the time and you have a failure (melt down) of the OD in the energizer bunny state then you BETTER park so that you do not have to use reverse gear ( the reverse gear limit switch is not going to help you). This statement alone would scare me into not leaving it on all the time.
So Tom If you only use it after 4th gear then you will not have to remember or worry about a thing.
Rick C
Rick Crawford

Gentlemen - When you "switch into Overdrive" what happens is this. The switch energises a relay which socks 30 amps to the solenoid to pull it up the plunger in the solenoid (the "pulling" coil). Once the plunger in the solenoid has been pulled up, an internal switch in the solenoid automatically switches to a "holding" coil which draws only about an amp to "hold" it in overdrive. Internally, the accumulated oil pressure (about 325 to 400 psi) is released via an opened ball valve (opened by the solenoid, a shaft, 2 levers another rod, then the ball valve) and the cone clutch becomes pressurized. This moves the cone clutch to stop the planetary gears and that assembly from rotating. Now you are "in overdrive".

The overdrive gears are always in mesh, or in other words always engaged. All that happens to switch into or out of overdrive is to stop the 3 orbiting gears from rotating or to allow them to start turning again. There is never a drop to a new gear selection. The planetary gear assembly is rotating - or it is stopped. That's all. Thus endeth the ....

Don Elliott, 1958 TR3A with Overdrive
Don Elliott

Sheesh! Glad I finished that first sentence with "unless I am mistaken".....Sorry, I keep reverting to MGB experiences. Thanks for keepin' me straight!

Rod Nichols

Sorry to pick nits, but the closing coil of the sol. draws 15 amps, according to the manual. If you leave the od engaged all of the time, you are going from 1st to 2nd od, almost the same as 3rd gear,which is a fairly big jump. Each time you shift with the od engaged, the od is momentarily disengaged, because the sol. is only activated when the isolator switches are closed, since the switchs don't close until the shift is completed. This causes more wear on the sol. contacts and maybe the cone clutch. The bottom line is leaving the od engaged all the time results in unecessary wear and sluggish acceleration.

Ok then it looks like I have my answer - it's not going to break anything right away, but it will cause extra wear. Thanks for all the great advice.
Here's a funny related story. When I first got this car I had a heck of a time getting the OD to work properly, darned thing wouldn't disengage, and seemed to come on in reverse! I also had no backup lights. Never thought the two problems could be related... When I got to taking it apart I found the last person to work on it had miswired the reverse and 2nd gear switches. 2nd gear was turning on the backup lights, and reverse was enabling the OD. Two bugs with 2 wires, that's a good day.
Tom H.

You guys got way to much time on your hands.
Don K.

This thread was discussed between 08/10/2002 and 09/10/2002

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