GT6 Noisy Gearbox

[Kevin Atkins]

Hello to all on the forum,

I have very recently bought a GT6 Mk. 3 (non-rotoflex, non-overdrive). The car is in very fair shape but it has been off the road for the last 14 years or so I believe, so I'm recommissioning it now. I haven't owned a Triumph before, but have had other older classics before.. various Minis, a very ropey Rover P6 and a few Alfa Romeos.

Anyway, the gearbox on the GT6 does seem very noisy in the indirect gears; fourth gear is OK. I have dropped the oil and replenished with the correct grade - it was a little low before, maybe 75% full, and since the oil change it's a little quieter but still seems much noisier than I think is ideal. I removed the gearbox cover to get at the oil filler, and it's one of the fibreglass aftermarket types and there is no sound-deadening material around it, and for now I've got the carpets out anyway.. So I'm sure that's not helping, but the noise in first, second and third gear does sound very harsh and unpleasant, which I'm sure isn't quite right.. I'm not expecting a whisper quiet modern gearbox, but this one sounds like it's in pain..

So, I think a replacement box is on the cards - I'm going to have to go the reconditioned route as a quick flip of gearbox will be necessary to keep me on the road, rather than doing a rebuild. What is the spares situation like with regard to gearboxes, and would any of you have recommendations?

Thanks in anticipation!

[Josef]

Mike Papworth (mike.papworth1@btopenworld.com) is the person to talk to for all things Triumph gearbox. He’s based in the Coventryish area if I remember correctly. Other than input shafts and some gears, especially for the earlier models, the majority of parts are easily available. 

[Clive]

Nicechoice of car.

Your gearbox issue is likely to be layshaft pin worn. Very common. 

Bad news, I am uncertain if anybody sells "exchange" gearboxes, most recondition your unit.

Mike papworth has a good reputation, but a long lead time. Pete Cox gearboxes is another good company.

[Pete Lewis]

TD Fitchet does  advertise  g boxes in the courier    

M Papworth gets a +1 from me 

how competent do you feel about looking at the box yorself    

pleanty of help on here if needed 

 

Pete

 

[Josef]

I have seen eBay listings for exchange small chassis Triumph gearboxes @clive, but know nothing about the companies there. (Hadn’t seen Fitchett’s ads that Pete mentions - they might even have NOS full boxes kicking about though  )

[dougbgt6]

Kevin,

Non Rotoflex makes it a very late one, after February 73.  I have the same and 1,2 & 3 are getting a little noisy, I try to get to 4 ASAP! A common problem, however the box can go on for a long time before it needs attention.  You would do well to line the inside of the cover with Silent Coat insulation which will cut the noise and heat down.

Doug

[johny]

Yes it can be a fine line between using the gearbox as is and repairing it before a bearing breaks up and damages gears in which case the box would never be accepted for exchange☹️

[Peter Truman]

3 hours ago, clive said:

 

Your gearbox issue is likely to be layshaft pin worn. 

 

Just to qualify by pin do you mean the actual Layshaft itself or the multiple needle bearings in each end?

 

[Clive]

3 minutes ago, Peter Truman said:

Just to qualify by pin do you mean the actual Layshaft itself or the multiple needle bearings in each end?

 

The metal "rod" that goes through through the layshaft. They seem to get very scored up. Especially in teh 2L cars.

A mate does a lot of gearboxes (OK, 10 or so a year) and the pin is the bit which most often is an issue. OD boxes seem to suffer more too.

[johny]

I dare say the mainshaft tip bearing surface will have some wear as well and that would also generate noise in all gears except 4th🙁

[Kevin Atkins]

Thanks so much for all of the replies, which are really helpful!

@clive I'll give Mike Papworth a call in the week, thanks for the heads-up

@Pete Lewis Thanks for the recommendation for TD Fitchet - I'll have a look at them too. I might also have a think about having a go at it myself - I've never done a gearbox before but if it comes down to it I'll have a go. The box itself changes gear fine, doesn't pop out of gear and all the synchros work perfectly.. it's just a bit noisy..

@dougbgt6 Thanks for that idea - Silent Coat was something I'd seen and then couldn't remember what it was, so you've reminded me - cheers! Yes, I'll definitely be adding some sound deadening around the gearbox cover / tunnel / floor wells etc. And also heartening to know that in spite of the noise, the gearbox may be OK for the time being (I do a very small annual mileage, < 2k / year, which was part of the reason for going the 'classic' route.. I had a 'modern' car that was just sat on the drive depreciating..)

@johny@clive I'm hoping that if it's the layshaft pin and / or needle roller bearings, they're less likely to break up as opposed to the mainshaft bearings or tip bearing? Either way, I'm driving it very gently at the moment (well, virtually not at all at the moment whilst I get it fully recommissioned / roadworthy 😉 )

 

[johny]

Theres lots of threads on here, some even with photos of the wear youre likely to find, if you search the gearbox section of the forum. The original Triumph workshop manual is also available online for free download and that has a very good chapter on rebuilding them...

[Josef]

If you are thinking of rebuilding yourself, I would recommend a set of YouTube videos starting here. Being able to see the internals before taking apart my own was really handy. On top of that the guy talks about how to do certain things when the factory WSM assumes you know, references a Churchill tool, etc. 

[68vitesse]

Have had several gearboxes apart including the one currently in the Vitesse in which I had to replace third gear and the cluster, no special tools needed except a length of rod to hold the cluster needles in place. Do not use grease to hold bits in place on reassembly, petroleum jelly, Vasolene, is the stuff to use.

Told some restorers grind down the main shaft tip and fit sleeve or fit oversized input shaft bearing weakening an already weak part, maybe just a tale.

Regards

Paul

 

[johny]

Yes reducing tip from 0.5" to 12mm to fit sleeve is done so as you say some risk. New mainshafts now available though....

[Clive]

36 minutes ago, 68vitesse said:

Have had several gearboxes apart including the one currently in the Vitesse in which I had to replace third gear and the cluster, no special tools needed except a length of rod to hold the cluster needles in place. Do not use grease to hold bits in place on reassembly, petroleum jelly, Vasolene, is the stuff to use.

Told some restorers grind down the main shaft tip and fit sleeve or fit oversized input shaft bearing weakening an already weak part, maybe just a tale.

Regards

Paul

 

My friend has a GT6 box in his spitfire. Apart from doing a cut and shut on the input shafts (to get correct ends and length) he also machined the mainshaft and made a brass bearing to replace the tip bearing. 

125K miles later all is well, no noises, leaks or anything. However, it is a mk3 spitfire and he goes not drive it hard. 

For the vast majority of owners who do not drive their cars hard and/or long distances, machining the tip will give many years of service. I expect not very different to a new mainshaft? It is the old question, if DIYing is the extra outlay worthwhile? If so, and the car will be "used" it would be worth spending a bit more and going to an 18mm tip setup. 

The other issue is that teh rest of the internals are now largely shagged to a greater or lesser degree, and new stuff is not easy to find. Unless you have a stack of used boxes to strip for parts until you find a set of very good internals.

[Pete Lewis]

and you dont need any special tools   , vice  hammer  punch and a couple of spanners 

apart from circlip pliers and a dummy layshaft spindle and you can make that from wood or a  bit of hose the right size 

steves on line wsm   Triumph Car Service manuals - Vitessesteve

pete

 

[Kevin Atkins]

Thanks for all of the replies. I have done some study and looked at the YouTube videos you recommended and I've decided I'm going to have a go at rebuilding the gearbox myself. I was going to have to pull the gearbox anyway, and that bit looks like it might be awkward but the box build itself doesn't look too bad (famous last words..) What's the consensus on getting the box out? Where I live we have a shared parking lot, and pulling the engine and box out may get in the way of my neighbours, so pulling the box out from inside the car would be preferable if it's not ridiculously difficult?

[Clive]

47 minutes ago, Kevin Atkins said:

Thanks for all of the replies. I have done some study and looked at the YouTube videos you recommended and I've decided I'm going to have a go at rebuilding the gearbox myself. I was going to have to pull the gearbox anyway, and that bit looks like it might be awkward but the box build itself doesn't look too bad (famous last words..) What's the consensus on getting the box out? Where I live we have a shared parking lot, and pulling the engine and box out may get in the way of my neighbours, so pulling the box out from inside the car would be preferable if it's not ridiculously difficult?

From inside is OK. Passenger seat out, H frame, tunnel out. Undo the prop (will need at least one rear wheel off the ground). The rest is rear mount, speedo cable, slave cylinder, starter motor. Then jack under the rear of the sump and lift so the tail is above the prop tunnel, bellhousing bolts and then it should slide right off.

[Kevin Atkins]

Thanks @clive that's good to know - I remember trying to wrestle a (very heavy) Leyland LT77 box onto a Rover V8 from underneath and it was a pig of a job lining it back up on reassembly, but from above and working inside the car is hopefully better. And I'd hope the Triumph box is a (little bit) lighter than the Rover.

Looks like I know what I'll be doing over Christmas now.. just ordered the rebuild kit..

[Josef]

Getting it back in is more awkward than getting it out as the weight becomes hard to get any lift on as it gets closer to the engine. One trick I read about too late to help me is to put much longer studs (or threaded rod, or bolts with the heads removed) into some of the top three studs that hold the box to the engine, this’ll help get the alignment right. You can then swap the studs back for normal size ones when the box is in place. 

[NonMember]

Yes, getting it out through the inside is OK but it's a two man job because of the awkward lifting and manoeuvring. As Josef say, putting it back in is more awkward but with the long studs trick and a helper it's not too bad.

[Clive]

40 minutes ago, NonMember said:

Yes, getting it out through the inside is OK but it's a two man job because of the awkward lifting and manoeuvring. As Josef say, putting it back in is more awkward but with the long studs trick and a helper it's not too bad.

I have done it loads of times alone. Even the T9, which is hefty with the iron bellhousing. That is when I started using teh long stud sliders. I had the gearboix in and out 5 times in a couple of weeks as some clutch release stuff I bought was faulty. And I didn't suspect the new stuff until I applied some Sherlock logic.

If the GT6 box is non OD, they are a doddle, quite light.

[Pete Lewis]

and a decent length of timber can help use as a lever between floor and undeside of the box  to wiggle the box and take some weight on refit 

keep hands away from the sharp end of the prop tunnel 

use a bit of timber or anything  to act as a rough visual gauge for the gap clutch hsg to back plate  what looks aligned never is  very often is |\  not | |

as well as seat /seats out  might help with steering wheel off to aid space and cover the carpets with something 

Pete

 

[Kevin Atkins]

Really helpful replies everyone. So the rebuild kit is on its way, and then that's got me thinking.. I might see if I can locate another box suitable for rebuild and fix that, then flip that in.. otherwise, never having done this before, if I run into trouble I've got a car with no gearbox. I've never tried a gearbox build before, so it'll be a learning experience and all part of the fun, but I don't want the added pressure of having to have it done in short order.

And then there's a big list of other things to sort on the car, but she runs and drives, Rome wasn't built in a day..

I'll post back when I've got stuck in to the gearbox build..

Hope everyone has a cracking Christmas!