Fixing The GT6 Overdrive Fault | HenRefurb

This episode, I'm having a look at the GT6's Overdrive Gearbox which has had an annoying fault for months whereby it only works in 4th gear and barely ever in 3rd. It also engages very slowly.
This video is action packed, lots of driving shots and a chance to hear the old beast roar and a bit of a strip down and repair job to get the old girl up and running properly once again!
This is a 1971 Triumph GT6 MK3 with a Laycock D-Type Overdrive fitted.
If you have any queries about this video, the tools I have or anything else, just ask in the comments section and I will do my best to answer then.
Thanks for watching.
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[@MickGrout]

This Video was so helpful, particularly the switch info. I didn't have a clue, after watching I cured my intermittent Overdrive for the princely sum of £11. Thanks - Mick

[@HenRefurb]

Glad it helped! Mine is still working fine years later too.

[@WalterReynolds-hh6mw]

A late viewing, but I'm glad that I stopped by. I'm glad that you found the cause; I would have started underneath the car at where the wiring goes into the O/D box. But, I'm not a GT6 owner, and have only viewed one other video on curing an intermittent O/D cutting out problem. Well done.

[@HenRefurb]

Thanks. It's still going strong all these years later too!

[@domweaver3488]

Hey!!! Just bought a spit after a 16 year hiatus. Overdrive suddenly decided to stop working - so though I’d KZbin for some answers…… my EAE588K! I can’t believe it! You’re the guy I chased into the Forest a few years back and you invited me in for tea. Nice to see the old girl again!!

[@HenRefurb]

Well hello there! Long time no see, I hope you're well. I was out in the old girl today in fact!

[@user-vh6vo2tf9v]

Thank you. Having the same problem on 72' GT6. Goes in and out of OD 1:40 in fourth! Great video. Chris

[@HenRefurb]

Let me know if you have any joy sorting it!

[@ChrisEdgcombeBetterOnVinyl]

Hi, thank you for looking at my comment about GT6 over drive. I have tried your suggestion of adjusting the bracket and took the car for a drive, all working fine until about 40 miles and the OD dropped out, and didn't come back until a cold start the next day! Pretty much what it always does. Also the previous owner had the overdrive stripped down and restored but probably didn't drive the car any distance. Just to add a little variety, my TR4a has just lost the overdrive, thinking it is electrical as it has simply stopped working, and my son's MGB GT has developed a fault where the OD has to be left on after switching it on when in reverse gear, when you use the OD on the road it drops out, until you switch it on and reverse a little before driving off, how is that for bizarre! cheers Chris

[@HenRefurb]

@@ChrisEdgcombeBetterOnVinyl there's quite a bit going on in those gearboxes. Electrical faults should be easy to spot, one of the most useful tricks is attaching a lamp to the solenoid connectors. This way you'll see if the lamp goes out when it shouldn't then you have a power supply fault. Intermittent faults like yours sound like a build up of debris inside the control valves that eventually blocks the flow to the point the gearbox gives up. on a D type overdrive, this can be accessed without removing the gearbox. Just one plug on the top to take off and then a small screwdriver to pull the tube out. Clean and put back in. I have a D type in my garage that I can send photos of if you are interested. Message me on facebook if you like.

[@njaahkbackyardbodyworks1807]

Nice car with a nice sound. Thanks for sharing your troubles with us. My GT6 has overdrive and was having similar problems before I stored it. Now I have it in the shop and doing a full restore on it. This info will come in very handy when I get to the mechanics of it....keep it shinny....cheers!!!

[@HenRefurb]

That’s great! I’m glad you enjoyed the video. Good luck with your restoration!

[@frankmgallo]

Great video I just bought a 70GT6 with that type of overdrive. Still waiting for delivery but I will test it and hopefully it will operate as yours does. Great kept the GT6 maintenance videos coming 👍🏻

[@HenRefurb]

That setup with the overdrive is superb and so much fun to drive too! I hope you enjoy yours as much as I have mine!

[@jeffj4870]

Brings back memories for me,had a MK 111 back in the 70's(K Reg, Sapphire Blue),but it did rot sadly. I' m in my 70's now!☺️. One other problem I had,a valve spring broke & the valve fell into combustion chamber,bent the stem into a perfect right angle. Head off,piston just ok,recut the seat,new valve & springs...off we go.

[@HenRefurb]

Haha, love to hear the memories! They are super cars to drive. Love mine, but it has been a while since I drove her now due to some body issues that I don't want getting wet. Had my fair share of failures over the years too, too much hard driving!

[@buckwheatINtheCity]

The poor man's Ferrari sounds very convincing.

[@manumores]

Hello, I think you have a very nice style of filming/editing. It's a really enjoyable video to watch and i'm looking forward to new posts. Very neat! The more videos that are published about the car, the more people will be helped by them. My car's a 1967 Mk1 with OD and at the time i searched the web for every possible picture or video to get as much info as possible before buying it, and to get me along with decision-taking during the restoration (which,sadly, i'm not doing myself...). My own are just what they are but i published them just so people may find something in them that helps them. The issue in this video is stored in the back of my mind, so that if ever i get a similar problem, i will recognise and identify it immediately. So, potentially this video will help me in the future. Keep 'em coming!

[@HenRefurb]

Thank you very much for your kind words! I'm really glad you enjoyed the video, I'll aim to do more as and when I get time to do so. I was toying with the idea of doing an Overdrive rebuild video to show people how to completely dismantle and reassemble one as I have a spare one in need of some work.

[@matthewwylie4551]

Another great video! Keep it up! As a fellow GT6 owner I was wondering what central locking system you have installed?

[@HenRefurb]

Thank you! It is a Hawk HA280 Pro alarm system. I wired it all in myself. The door actuators are just off the shelf two wire actuators I got on eBay or something. Yet to find a way of popping the boot lid!

[@tjm3900]

I like to fit a small idiot light to tell me when the O/D is powered. In a case like this it also serves as a diagnostic tool. A while back, the O/D relay on my car stuck in the on possition, so O/D was on all the time. The light warned me of the problem before damage was done.

[@HenRefurb]

I'm very tempted to try the same thing. Answers a lot of unknowns with the switches etc. Got some slight issues with my gearstick switch now.

[@beetjeklooien585]

Awesome! Love the GT6

[@That_AMC_Guy]

If it's engaging slowly, one of the first places you check is inside the OD units "sump". There is a small oil pan on the bottom, cast aluminum held on by 10 or so bolts. Remove it and the filter. Clean the filter and the little pan. There's usually a magnet glued to the bottom of the pan that attracts all the worn clutch material (from the OD engagement band). Clean everything, top up the oil if necessary and test. If it's still engaging slowly after that, it may be time to invest in a good quality pressure gauge to check the PSI the pump is putting out because it may be time for a pump rebuild. Though, if I'm being honest, I'm more familiar with the J-type overdrive.... not the D-type. So, your mileage may vary.

[@HenRefurb]

I hadn't too long stripped down and rebuilt the OD at the time of this video. As mentioned, it ended up being the inhibitor switch bracket which had moved away from the cam. Banged it back into position and it has been great ever since! It is however, about time I gave the overdrive and gearbox a service so I will give the sump a clean out as you've suggested!

[@jontg429]

Man that car sounds good! I keep pestering the wife to let me get a Spitfire, but so far she is not letting me do it lol!

[@HenRefurb]

You should definitely do that! They are great fun, I used to have a few Spitfires, miss having the roof down with the noise behind!

[@HenRefurb]

Also, remind her just how cool she'd look in the passenger seat of one!

[@tam_ryan1036]

Excellent and a great fix! But 😂 .... those dice!! 🤦‍♂️ ;-)

[@HenRefurb]

I’m amazed it took so long for someone to mention them!! My girlfriend got them for me when I put the car on the road 5 years ago and they’ve just been there ever since! Been all round Europe like that too!

[@tam_ryan1036]

@@HenRefurb Ooops..... girlfriend got them for you = not another word from me! - Love em! ;-)

[@HenRefurb]

Hahaha spot on!!

[@user-dx6pt9oo6h]

Hi bro 👋👋👋 good project 👍👍

[@HenRefurb]

Thanks mate!

[@lowey53]

Great to see the GT6 finally mate just out of interest how old were you when you got the car as im tackling mine at 22 and just starting uni

[@HenRefurb]

I bought The GT6 when I was 21 back in 2012. 5 years ago I got it back on the road after doing a full ground up restoration that took 2 years! I’ve had a few Spitfires, first was when I was 10 but that one was a junkyard car, I had a road legal one when I was 17!

[@Robert-ts2ef]

Why do you need overdrive in third gear as opposed to just moving into fourth gear and then use overdrive as a fifth gear?

[@HenRefurb]

Sorry for the slow reply. The answer is you don't. However it's a lot of fun when on the rev limiter in 3rd gear engaging overdrive. It's a very quick gear change and gives you an edge if you are racing someone!

[@DavidPlass]

That's a beautiful GT6. I'm curious about the binnacle (escutcheon?) for the ignition switch. Is it from a later Spitfire?

[@HenRefurb]

Thank you! It wasn’t a few years back. Yes the steering column is from a Spitfire 1500. It makes it easier with the controls etc. And getting the key in the ignition too.

[@DavidPlass]

@@HenRefurb thanks for the information. I'm going to look into getting one for my 72 GT6!

[@HenRefurb]

I would highly recommend it! You also get a fancy wiper control stick with an electric washer button and a one wipe option. I turned my old wiper control knob on the dash into an intermittent automatic wiper controller. The main/dip beam controls are better and you get a horn button on the stick too which is really easy to use which means I can have he solid moto-lita steering wheel centre fitted too!

[@DavidPlass]

@@HenRefurb Eeven though it won't be needed for a few years, I just found a 1500 steering set for my GT6. Thanks for the inspiration.

[@HenRefurb]

David Plass excellent news! It’ll be worth it in the long run!

[@logankirk995]

Hi- what exhaust system do u have on the gt6?

[@HenRefurb]

The manifold is the standard cast one, down pipe is standard, the centre section and Y-piece is from the Phoenix exhaust system and the two rear pipes are custom made to replace the silencers with pipe. It’s very very loud when you put your foot down!

[@logankirk995]

HenRefurb - awesome I’m starting my gt6 project soon👌

[@HenRefurb]

Good luck with it, they are awesome cars!

[@zach4384]

How tall are you?

[@HenRefurb]

6' 2" and I find the car extremely comfortable. Longest drive I've done in her in one go was 12 hours and I got out at the other end and felt absolutely fine unlike in any modern car I've been in with all the adjustments in the world on the seat. I reckon I'd be in trouble if I was any taller though!