Results 1 to 15 of 15

Thread: Reversing w/. OD engaged - symptoms?

Discussions of Triumph motor cars

  1. #1
    Member
    Join Date
    Jun 2011
    Location
    Orange County, CA
    Posts
    47
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Reversing w/. OD engaged - symptoms?

    Hi guys - so the thought occurred to me that while it is known that reversing with the OD engaged is a big no-no I don't know what the immediate symptoms/reaction of the car would be if you did that?

    How would you know if you actually did that? My question comes from some short test drives up/down the hanger last night where I manually operated the OD engagement lever and all seemed well, but it occurred to be that if there was an internal fault in the OD that left it engaged somehow I wouldn't know what to look/listen for.

    Thanks!

  2. #2
    Great Pumpkin TR3driver's Avatar
    Join Date
    Aug 2003
    Location
    Sunny So California
    Posts
    19,256
    Thanks Thanks Given 
    7
    Thanks Thanks Received 
    104
    Thanked in
    99 Posts

    Re: Reversing w/. OD engaged - symptoms?

    When you start to back up with the OD engaged, it should resist somewhat; kind of like backing over a curb. As long as you don't force it "over the curb", it shouldn't harm anything. But the more insidious problem comes when there isn't enough pressure to engage the OD clutch at a standstill, and the pressure builds after you are already moving. In that case, you can listen for the big bang as the sprag clutch breaks.

    Proper adjustment of the solenoid is rather critical to an A-type, so I wouldn't bother doing too much testing before installing a solenoid. If it builds pressure as it should (a very important test IMO), and shifts at all, it will be strong enough to pull the car. In other words, IMO what you are doing is dangerous and not useful.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

  3. #3
    Member
    Join Date
    Jun 2011
    Location
    Orange County, CA
    Posts
    47
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Thanks Randall - seemed important to ask since I haven't seen this covered recently and didn't readily turn up in searching past posts.

    Good news if that she seems to built pressure quickly and shifts. That was the only test I did. Once I confirmed it built pressure I called it a day since I was also worried about the potential of causing issues. And of course I made sure the lever was in the correct (non-engaged) position before starting/moving the car.

    I didn't have any history on this OD so before starting to button everything up I wanted to quickly check that she was OK.

    Anyway, great info as usual. Thanks Randall.

    (sending a PM about stopping by)

  4. #4
    Senior Member
    Join Date
    May 2010
    Location
    Rosemont, PA
    Posts
    51
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Great information, considering I now have a 61 TR3 with overdrive that works. I've never had an overdrive car and didnt know, for instance, not to back up with it engated. Are there other things to know/do to operate it correctly and so that it continues to work right? What should I look out for and how do I best maintain it. Many, many thanks for any info. Tom
    TR3A, MGTF, 911SC, Z3

  5. #5
    Great Pumpkin TR3driver's Avatar
    Join Date
    Aug 2003
    Location
    Sunny So California
    Posts
    19,256
    Thanks Thanks Given 
    7
    Thanks Thanks Received 
    104
    Thanked in
    99 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Just to clarify, TomG, a normal installation includes lockout switches that prevent the OD from engaging in first or reverse. It won't blow the unit up if you accidentally leave the dash switch on (which is a Good Thing since I forget it all the time). Tom Lynch was asking about a test he was doing, without the lockout switches.

    There has been a lot of debate on the "proper" method of shifting the overdrive. Clearly the OD manufacturer's intention was that it could be shifted under full power (somewhere I've got an ad that talks about it "kicking like a mule"). But it's also likely to be somewhat hard on the unit, and I dislike the "bang" when shifting under part throttle, so I generally use the clutch when shifting into OD. Shifting out under power is much smoother though, so I generally don't bother with the clutch for that.

    Not really too much else to do, other than keep it full of oil and the oil changed per schedule. Again there is lots of debate over the "best" oil to use; with the factory recommending motor oil in earlier units and then changing to recommending 90 weight GL4 around 1960 or so (without any apparent change in the overdrive itself). I've been using Redline MT-90 for a few years now, and so far it gets my vote for "best". Both the overdrive and main gearbox seem to work better with it than anything else I've tried (and it is a GL4 oil as recommended by Triumph). However it's not cheap; and I haven't taken a look at the thrust washers in the main box (a known weak spot) to see how they fare with it.

    IMO, an economical "almost as good" alternative is 20W50 Valvoline VR1 (conventional not synthetic) Racing Motor Oil. British Frame and Engine did a long term test some years ago using that oil, and reported that after 5 years of normal use, the gearbox and OD looked "like new" inside. I used it myself for many years and it worked well enough. The Redline just gives smoother, more positive shifts, IMO.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

  6. #6
    Jedi Warrior
    Join Date
    Dec 2008
    Location
    Northern Cal
    Posts
    457
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Once again I find myself in the tracks of Randall.
    Have had very good luck with the Redline...and always use the clutch when shifting up or down...feels so much better. Have to admit I always worry about forgetting to have the overdrive off when parking the car. What a difference a good working overdrive made for me. Gil NoCal

  7. #7
    Jedi Trainee
    Join Date
    May 2010
    Location
    Marco Island, FL. 34145
    Posts
    339
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Things go snap crackle pop very quickly. I have an A-type from a TR6 that did just this. I can take pictures if you really want to see what it does.

  8. #8
    Senior Member
    Join Date
    May 2010
    Location
    Rosemont, PA
    Posts
    51
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Thanks all for the information. Very helpful as always.
    TR3A, MGTF, 911SC, Z3

  9. #9
    Jedi Warrior
    Join Date
    Apr 2012
    Location
    Raleigh, NC, USA
    Posts
    616
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    2
    Thanked in
    2 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Is it ok to drive the car after reversing in over drive, and possibly causing damage, once the overdrive is no longer engaged? Or is it necessary to repair the overdrive before doing any driving? Thanks!
    Bob

  10. #10
    Jedi Warrior
    Join Date
    Oct 2012
    Location
    Albany, OR
    Posts
    407
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    1
    Thanked in
    1 Post

    Re: Reversing w/. OD engaged - symptoms?

    A quick and easy check to tell if the OD is engaged is to put the car in neutral (engine not running) and attempt to push it rearward. If it won't move, the OD is engaged. From my experience, if you catch the situation before something goes bang, there is no damage and you have dodged an expensive bullet.
    Berry

  11. #11
    Yoda CJD's Avatar
    Join Date
    Feb 2011
    Location
    Arlington, TX, USA
    Posts
    5,279
    Thanks Thanks Given 
    6
    Thanks Thanks Received 
    26
    Thanked in
    26 Posts

    Re: Reversing w/. OD engaged - symptoms?

    If your switches are rigged properly it is not possible to reverse in OD. If they are not, then you would have felt the resistance before the sprag clutch blew. Once the rollers in the clutch disintegrate, then you have metal flowing around in the OD unit. So...if it is truly damaged it is best to not drive it.
    John

    1955 TR2

  12. #12
    Jedi Warrior
    Join Date
    Oct 2012
    Location
    Albany, OR
    Posts
    407
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    1
    Thanked in
    1 Post

    Re: Reversing w/. OD engaged - symptoms?

    John-If the sliding member sticks to the brake ring, the OD will be engaged in all gears even if the isolator switches are functioning.
    Berry

  13. #13
    Yoda glemon's Avatar
    Join Date
    Jun 2007
    Location
    Nebraska, USA
    Posts
    3,351
    Thanks Thanks Given 
    13
    Thanks Thanks Received 
    10
    Thanked in
    10 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Agree with Berry, my overdrive, which I bought as rebuilt, used to stick when I first started driving the car. No electrical problems, just tight mechanicals somewhere. Lucky the issue sorted itself out after a few months of use (and seemed to only happen when hot, it would pop back out after sitting a while.

    I would also add that I have had a few cars with O/D and always felt the disengage was more of a jolt to the drivetrain than the engage (but I never pressure tested any of them, so maybe they were not operating at optimal pressure and didn't pop in sharply). The early Healey Hundreds had an ingenious, or some said diabolical overdrive system which only allowed the O/D to engage over certain speeds through the use of a centrifugal force actuated switch off the gearbox, and also had a throttle position switch that only allowed it to disengage if the gas pedal pushed down a bit. This was all to prevent shock to the system, but was dropped on later cars and never used on Triumphs so could have been over-engineering.

    I will back off the pedal when shifting into O/D and push it in when disengaging, this seems to lessen the shock. Never hada mechanical issue with overdrive internals, but have had plenty of electrical Gremlins.

  14. #14
    Yoda CJD's Avatar
    Join Date
    Feb 2011
    Location
    Arlington, TX, USA
    Posts
    5,279
    Thanks Thanks Given 
    6
    Thanks Thanks Received 
    26
    Thanked in
    26 Posts

    Re: Reversing w/. OD engaged - symptoms?

    Quote Originally Posted by titanic View Post
    John-If the sliding member sticks to the brake ring, the OD will be engaged in all gears even if the isolator switches are functioning.
    Berry
    Absolutely! Just trying to point out that it is not an issue with a properly working OD. Mine stuck after the rebuild until I switched to the MT90 oil.

    It's cool hitting the OD switch at full throttle to feel the auto style woosh...but I always engage and disengage with the clutch released. That reduces the hits on the OD to a minimum. Not necessary, but just me.
    John

    1955 TR2

  15. #15
    Jedi Hopeful
    Join Date
    Oct 2018
    Location
    Livermore, Ca
    Posts
    167
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    7
    Thanked in
    7 Posts

    Re: Reversing w/. OD engaged - symptoms?

    I used to drive my GT6+ from Northern Cal. to San Luis Obispo and invariable some one in a 240z or similar would pull up along side and want to race.
    I would quietly drop down into third gear, then floor it and engage the OD. That car could chirp the tires at 55 mph. Lots of fun and I never did blow the thing up.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •