Gear selection problems - GT6 Mk3

[Qu1ckn1ck]

I appear to have selector problems which started without warning last night.  Second gear could not be selected on the move and fourth and third gear selection became clunky and imprecise.  All gears can be selected when stationary but on the move gear lever movement appears odd and second cannot be engaged.

 

Initially I thought that the clutch was not disengaging properly but now I think it is the gear selector.

 

Any ideas or suggestions, please.

 

Nick

 

[Waynebaby]

Hi Nick,

 

It sounds very much like a bush has failed in the gear selector remote. The kits can be obtained from the usual suppliers but in my experience none of them are particularly good quality (although my latest from Canleys seems to have lasted the longest) Once you've wrestled the gearbox tunnel out, the job of removing the gear selector remote extension and changing the various bushes is simple enough. I find it is easier to relocate the gear selector back onto the box if you put the gearbox into 3rd gear before removing the selector extension.

 

From your symptoms I expect that you'll find the hemispherical nylon "cap" at the bottom of the gear lever has worn out. The spring beneath can sometimes push it's way up through the plastic and this is often due to the cir-clip which holds it in place on the gear lever not being correctly seated in it's groove. A ring spanner just big enough to push down the lever will help to locate the clip correctly. Put plenty of grease on the nylon cap when you re-assemble things and check the underside of the metal cap holding it in place for sharp edges which can wear away at the nylon component.

 

Whilst you're at it, check the tightness off the bolts holding on the top of the gearbox. These seem to work loose and can be the cause of oil leakage. 

 

Wayne

[Qu1ckn1ck]

Thanks Wayne, will take a look at that.

 

Have ordered the Canley rebush kit 519770 and hope that will fix the problem without having to remove major components.

 

Nick

[Pete Lewis]

The kit contains a selection to suit the evolution

the cup washers are often cropped with sharp edges which mince the spherical cups.

 

there are two 0 rings these seal the remote rod in the ally hsg, best to never try to use these

you need tomremove the square head dowel bolt , often fitted by a gorilla, the 0 rings sit inside the rod bore and you chop them on rebuild...leave alone .

 

There are two types of bush, plastic top hat and spacer tube and a rubber with flat washers

you need to check the bushes below the gear stick and one mid way along the remote rod

Check the pivot bolt if its too long or wrong way round it will foul the casting in 3/4th

amd change becomes |-) not |-|

 

Pete

[Qu1ckn1ck]

Thanks Pete.

[Pete Lewis]

afraid its H frame and tunnel out and remove the remote assi from the top of the gearbox

 

ive found a few where for reasons that bug me the square headed tapered dowel bolt on the front selector rod .

the selector is loosish  on the rod ,in as much as you can see the lever is moving on the rod.  but the dowel is screwed/rammed  home and is as tight as tight can be

undoing the thing can reduce you to tears and a wrecked dowel bolt

 

is a small point but this can add to any already slack in the section.

 

i now have an avid hate of dowel bolts 

 

pete

[Qu1ckn1ck]

Dismantled the gear selector remote and, despite it looking fine and tight, replaced all the bushes.  Also tightened up all the selector forks. This has not cured the fault - the gearbox still will not downshift into second whilst car is moving.

 

Starting to look expensive now.

 

Has anyone any ideas as to where to look next to diagnose and fix the fault ?

 

Thanks

 

Nick

[Pete Lewis]

does it baulk or crash during a change down

 

 Nick , a clutch that clears properly is first choice of problem

 

when synchro tries to synchronise the drive is from the mainshaft rotation and to engage a gear without crashing or baulking it has to whiz the clutch disc up to a synchronised speed in the blink of an eye  any drag will cause the change to baulk.

 

after that is box out and check the condition on the syncro rings and dog teeth  and  hub sleeve chamfers , balls and springs

 

or a trip with box to sunny luton 

 

Pete

[Qu1ckn1ck]

Thanks Pete.

 

It definitely baulks - just will not go into second gear while the car is travelling.

 

Nick

[Pete Lewis]

Well that can be synchro or clutch related

 

Does reverse engage without any nashing of teeth ??? First indication of clutch spin.

 

the baulking is made by the baulk ring rocking 1/2 tooth oit of line while rotation speeds are differing

 

The baulk continues till the speeds are 'synchronised' dog teeth angles play a big part of the operation

 

if they are chimbled away you can crash durring a change or depending on the tooth chamfer baulk for ever

 

May be the box been rebuilt and some muppet has used a ring with the wrong chamfer angle

 

if you are sure the clutch is clearing ok then its box off and strip it down

 

of you need any help or part let me know

pete

[Qu1ckn1ck]

The original thought was clutch so that will be the next area to look at.  Clutch, gearbox and overdrive were all working perfectly smoothly until the very end of a drive home from Pirton when second gear baulked as I turned into my own road.

 

Nick

[Pete Lewis]

I take it 1 3 4 and rev are all ok ???

 

there also a likely culprit in the selector shaft inhibitor there are balls and rods between the shafts that interlock the selector forks to only engage one gear at a time

there could be a snag with these in that its not baulking , just unable to shift the 2nd fork

if its baulks you normally get the whine from the ring

 

if the selection goes hard , the interlocks in the top cover are worth investigating

[Qu1ckn1ck]

No strange noises at all, no gear teeth crunching or whining - gearbox is totally silent but just refuses to drop down into second gear.

[Pete Lewis]

That sounds more like selector rod problems

 

take top cover off, will it let you select 2nd on a bench

 

after thought you say when running so can you select 2nd engine off ???

 

if you can select 1st then 2nd is on the same fork and shaft but different selector interlock

 

but running or not running changes the fault thats contradictive to selectors

 

pete

[Qu1ckn1ck]

I have a very nasty feeling that a circlip on the gearbox mainshaft has failed, allowing the gears to move, just as happened repeatedly in the 1970's to the Triumph gearbox fitted to my then new Morris Marina 1.8 Coupe. 

[Pete Lewis]

the bearing circlip and the on on 3rd often give up,  but the  excess end float normally gets the stick to shift when on /off load 

 

Pete

[Qu1ckn1ck]

Just realised that this is basically the same gearbox design that I had sooooo  much trouble with in the 1970's.  It is now with the gearbox rebuilder who also does a very neat line in Ford Type 9 conversions for Triumphs and MG's.

 

From the various manuals it appears that the gearbox removal can be done by withdrawal into the car.  Is this correct for a gearbox with overdrive ?  The tunnel cut out is too short to allow that on mine so the engine had to come out to release the gearbox. 

 

Nick

[Pete Lewis]

box has to come out inside the car if OD has been retro  fitted they should cut the prop tunnel back around 6" and make a cover plate form sheet or from the removed section.

its std operation  to do this if you convert to adding a OD to a non OD car

engine out is a bit extreme   ,

 

pete

[Qu1ckn1ck]

So if the overdrive was factory fitted as standard to a GT6 Mk3 should the car have left the factory with a tunnel cut out long enough to remove gearbox and overdrive through the cabin ?  

 

The tunnel cut out is definitely too short to allow the gearbox to be withdrawn backwards - could a previous owner have added the overdrive gearbox during a rebuild but not cut back the tunnel ?

 

Nick

[Pete Lewis]

  yes Nick    it sounds  about the right story,

 

many are retro fitted and you have to cut the prop tunnel  across the whole model range

 

the commission plate number will  generally have an O at the end if factory fitted    

 

Pete

[thescrapman]

Any cut out more than about an inch says an overdrive was factory fitted.

 

Think long and hard before going type 9

[dougbgt6]

Type 9?

[Pete Lewis]

Its was popular bullet proof 5spd ford sierra gearbox , used to upgrade the 3 rails.

 

but often needs serious shortening of the remote if you want the stick in front of the handbrake

 

a number of companies do or did a conversion kit

Pete

[Qu1ckn1ck]

This guy's Type 9 conversions have bespoke cut and weld modifications to shorten the remote extension and bring the gearlever out in the correct position.  

 

He showed me one awaiting collection by a MG Midget owner and it looked very professional.. 

[Qu1ckn1ck]

Collected the GT6 from my friendly mechanic today.  

Started with gear selection problems and ended up with rebuilt gearbox, rebuilt prop-shaft, new clutch, new engine rear main seal, new engine mounts and a couple of other jobs.  Well,  it seems silly not to fettle the entire transmission once you have taken the engine and gearbox out.