The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
It is currently Thu Mar 28, 2024 5:34 pm

All times are UTC




Post new topic  Reply to topic  [ 15 posts ] 
Author Message
 Post subject: Overdrive disengaging
PostPosted: Sun Mar 03, 2019 1:21 pm 
Offline
Future Club member hopefully!
Future Club member hopefully!
User avatar

Joined: Mon Jan 05, 2015 12:42 pm
Posts: 309
Location: Ashington, West Sussex
Hiya everyone!

Just a bit of advice please - I've got my wonderful new overdrive gearbox in which is working wonderfully - except sometimes the overdrive disengages, usually after about 10 minutes of running. I can usually get it back in by switching the switch back and forth.

Also, does overdrive usually engage a few seconds after you flick the switch?

Thanks!

_________________
HQentity (Kyle)

1975 TRIUMPH DOLOMITE 1850 in Honeysuckle (Nina) 2015-2020
Image

"The harder the conflict, the more glorious the Triumph." - Thomas Paine


Top
   
PostPosted: Sun Mar 03, 2019 2:12 pm 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
In my experience of overdrives on Triumph and MG cars there is always a slight delay when you switch the O/D on. But it is slight - just a moment's hesitation. I think the delay is longer the more torque there is, and that backing off the throttle slightly will allow it to come on quicker. When switching off, the ones I have had switch out instantly.

If your O/D is switching out by itself, I would suspect the electrical connections first. The switch on the gear lever and the inhibitor switch in the gearbox. If either of these breaks contact momentarily the O/D will switch out.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Sun Mar 03, 2019 2:40 pm 
Offline
Future Club member hopefully!
Future Club member hopefully!
User avatar

Joined: Mon Jan 05, 2015 12:42 pm
Posts: 309
Location: Ashington, West Sussex
Amazing, thank you for your help! :) I'll have a look at the connections and see how I get on. :)

_________________
HQentity (Kyle)

1975 TRIUMPH DOLOMITE 1850 in Honeysuckle (Nina) 2015-2020
Image

"The harder the conflict, the more glorious the Triumph." - Thomas Paine


Top
   
PostPosted: Sun Mar 03, 2019 4:07 pm 
Offline
TDC Member
User avatar

Joined: Wed Nov 15, 2017 3:35 pm
Posts: 956
Location: Filey, North Yorkshire
After checking the wiring, double check the gearbox oil level. If it's a little low you might get issues.

_________________
Image


Top
   
PostPosted: Sun Mar 03, 2019 5:15 pm 
Offline
TDC Member

Joined: Thu Sep 28, 2006 10:06 pm
Posts: 1164
Location: Bristol
I once had the problem where the O/D would drop out after a few miles and it turned out to be the inhibit switch was going open circuit when it warmed up. The switch was changed and the problem was solved.


Top
   
PostPosted: Sun Mar 03, 2019 6:47 pm 
Offline
TDC Member

Joined: Mon Feb 02, 2009 7:39 pm
Posts: 241
If it helps, I converted my 1500 to overdrive and found that the switch operates the O/D unit within a split second. When it once stopped working altogether it was a plug and socket near the gearbox providing the electrical feed that was to blame. Unclipping it and cleaning the round pins and sockets as best I could has sorted it ever since - which was 2 years ago
Alan


Top
   
PostPosted: Sun Mar 03, 2019 7:40 pm 
Offline
TDC Member
User avatar

Joined: Fri Apr 15, 2016 11:08 am
Posts: 691
Location: Ayrshire, Scotland
The gearbox inhibitor switch is basically a push button that is operated when the selector moves into the 3-4 plane. Next time it turns itself off, try holding the lever over to the right and see if it comes back on. If it does the switch might need replacing or it might just need a washer removing from under it so it goes a fraction further into the gearbox.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)


Top
   
PostPosted: Mon Mar 04, 2019 6:33 pm 
Offline
Future Club member hopefully!
Future Club member hopefully!
User avatar

Joined: Mon Jan 05, 2015 12:42 pm
Posts: 309
Location: Ashington, West Sussex
So, although I haven't had the time to look at the problem directly, I've got more information from my work commute today haha! Pushing the gearstick over to the right doesn't change back into overdrive, making me lean more towards the dodgy wiring. 3rd overdrive is much harder to find than 4th, and today it only disengaged a couple of times in 20-ish miles of being used. As soon as I off/onn'ed the switch, it re-engaged without a hitch, so not a big problem. I'll clean up the connections and see where I end up :)

_________________
HQentity (Kyle)

1975 TRIUMPH DOLOMITE 1850 in Honeysuckle (Nina) 2015-2020
Image

"The harder the conflict, the more glorious the Triumph." - Thomas Paine


Top
   
PostPosted: Wed Mar 06, 2019 7:47 am 
Offline
TDC Member
User avatar

Joined: Sat Oct 07, 2006 8:23 pm
Posts: 1173
Location: East Staffordshire
Check the wiring that goes down the gear stick shaft. The cable enters lower down and is a known trouble spot for shorting as the wire chafes and wears away.

_________________
Mike

1980 Vermillion Sprint - 174bhp


Top
   
PostPosted: Wed Mar 06, 2019 8:40 am 
Offline
Future Club member hopefully!
Future Club member hopefully!
User avatar

Joined: Mon Jan 05, 2015 12:42 pm
Posts: 309
Location: Ashington, West Sussex
I did wonder about this actually!! I was going to attach a piece of nylon to the top of the cable before I pulled it through, as I can imagine its a nightmare to push it back up?!

_________________
HQentity (Kyle)

1975 TRIUMPH DOLOMITE 1850 in Honeysuckle (Nina) 2015-2020
Image

"The harder the conflict, the more glorious the Triumph." - Thomas Paine


Top
   
PostPosted: Wed Mar 06, 2019 9:10 am 
Offline
TDC Member

Joined: Thu Sep 28, 2006 10:06 pm
Posts: 1164
Location: Bristol
I think it unlikely to be the wires up through the gear stick shorting being damaged as normally when this happens you get a shock in your hand when you switch the overdrive out caused by the normal very high voltage that is induced in the wiring by the magnetic field associated with the operating solenoid valve collapsing. If you are replacing that bit of wiring my recommendation is replace it with a length of heat resistant ceiling light pendant wire as the two cores are contained in an outer covering which provides protection and make certain that this covering just comes through into the knob.

It could be the contacts inside the Overdrive switch in the gear stick. A spray with WD 40 might help.


Top
   
PostPosted: Wed Mar 06, 2019 9:20 am 
Offline
TDC Member

Joined: Sun Oct 26, 2008 7:26 am
Posts: 2473
Worth remembering that overdrive loom was just pulled off another old gearbox and untested. It may well be worth using new wires up the gearstick and checking the connections carefully.... Virtually all overdrive issues are electrical. (or low oil, or blocked filters which can be ruled out here)

_________________
Clive Senior
Brighton


Top
   
PostPosted: Wed Mar 06, 2019 12:18 pm 
Offline
Future Club member hopefully!
Future Club member hopefully!
User avatar

Joined: Mon Jan 05, 2015 12:42 pm
Posts: 309
Location: Ashington, West Sussex
Yes, very good point there Clive! Do I just use standard wire?! & wrap it all up? Do I need a higher resistance wire for the overdrive? I don't mind replacing it all, just need to know what to use haha! :')

_________________
HQentity (Kyle)

1975 TRIUMPH DOLOMITE 1850 in Honeysuckle (Nina) 2015-2020
Image

"The harder the conflict, the more glorious the Triumph." - Thomas Paine


Top
   
PostPosted: Wed Mar 06, 2019 3:30 pm 
Offline
TDC Member

Joined: Thu Jul 28, 2016 9:55 am
Posts: 5
Mine dropped in and out and was due to fatigued wiring around the base of the gearlever. If not that, the inhibit switch is probably the next item to check.


Top
   
PostPosted: Wed Mar 06, 2019 7:24 pm 
Offline
TDC Member

Joined: Thu Sep 28, 2006 10:06 pm
Posts: 1164
Location: Bristol
Just visit B &Q and purchase a ceiling pendant light fitting and use the twin cable or purchase some pendant lighting cable which will be heat resistant ( A plus I made some connectors for the switch by cutting down a couple of standard connectors if you do not have the special connectors.

See photo's

Image

Image

Image


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 15 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 25 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited