Replacing Overdrive Mounting Plate

[Martin V]

GT6 MK3 D Type OD

(continuation of past post about crack in mounting plate) 

I had the enthusiasm to look at replacing the mounting plate today. I’d read or been told on here somewhere that once the bolts are removed the gearbox can be jacked enough at the rear ( in situ) to slide the plate out forwards.

Well, several hours gone this afternoon into strip done of the tunnel, removal of mounting bolts ( 4 plate and 2 mounting block) and partial exhaust removal ( not needed), I’m stuck with the plate not seeming to have room to slide forward even when able to move fully forward free of the mounting bracket and drain plug. 
 

Can anyone advise? Seems whomever said it was possible wasn’t speaking about same GT6 mk3 chassis rails and gearbox with D overdrive?

To me it seems that gearbox needs to come out?

That might be too much for me and I’ll end up part reassembling for local expert to resolve unless you think if I could do something like removing the bell housing bolts (support rear of sump) lift the OD and bell housing in unison enough to get the plate out. Like a lift of Gearbox without pulling it out fully?

[dannyb]

What if you take the propshaft off and jack it higher. 

Danny

[Martin V]

Thanks Danny, I think that’s the next step, but the limiting space is where the gradient of gearbox comes down and chassis rails go up. 
 

[Colin Lindsay]

I may be reading this wrong but are you removing the entire rear mounting, or just the plate it attaches to? I'd be inclined to remove the entire thing ie remove the y-shaped mount off the gearbox, if it's stopping the plate from moving under it (unless as Danny says you're not jacking high enough?) Apologies if I'm way off track, long time since I needed to remove one on anything but Heralds, but can you access the rear mounting bolts as they currently sit and so slide the entire assembly off?

[Martin V]

15 minutes ago, Colin Lindsay said:

I may be reading this wrong but are you removing the entire rear mounting, or just the plate it attaches to? I'd be inclined to remove the entire thing ie remove the y-shaped mount off the gearbox, if it's stopping the plate from moving under it (unless as Danny says you're not jacking high enough?) Apologies if I'm way off track, long time since I needed to remove one on anything but Heralds, but can you access the rear mounting bolts as they currently sit and so slide the entire assembly off?

Hi Colin, 

actually I did the mount bolts from beneath so the plate is free to move. When I jack the gearbox at the back for the Overdrive unit next to drive shaft the plate slides forwards but then stops at the point that the shape of gearbox comes down and chassis goes upwards. At that point there isn’t room to jiggle the plate out.

 

[Colin Lindsay]

I understand, the GT6 chassis layout is a dim memory for me these days. In that case, can you remove and replace the mount with the plate in situ, just slid out of the way a bit?

[Martin V]

Thanks guys. With two minds in the task this morning rather than myself plus ‘er indoors chipping in, we managed to proceed as originally hoped.

We slackened off the front engine mount bolts a little and then tried jacking agin with my custom made block of wood onto the back end of the overdrive. With this jacked just that little bit further it gave us scope to wiggle the plate enough to get it forward and rotated. Doing this plate jiggling from above in the passenger well gave better opportunity to extricate the offending plate backwards up into the passenger well.

A quick repeat in reverse (Haynes style) got the new plate into position. Bolts dropped into place, nuts tightened a little but not all the way and after a short drive I’ll nip them up properly.

I’m glad I did the job as the plate has a clear longer crack mid way down from one side as well as the crack I could see (when beneath) from the rear edge. 
 

The last task of course is to put tunnel back in, great 😒my favourite

[Graham C]

As normal if you walk away from the job and go back the next day things always go well.

Found that after numerous years of working on triumphs.

If a problem walk away and think, ideal when it is a hobby car not your daily runner. 

Remember chasing around on a Sunday morning for an odd item before shop shuts as at 12:00 in the 80's to get the car back on the road for Monday.

Graham

[Josef]

How far north are you in North Yorks? If you're close enough to me and want the old plate welded up I'd be happy to do it. Better than binning it as they're a desirable part!

[Pete Lewis]

and  even add a bit of a stiffener

pete

[johny]

Yes the metal in those corners has had a hard life having been bent in 3 directions during the stamping process. I think the original design was stronger but of course cost more due to the welding involved☹️

 

 

[Martin V]

On 17/09/2024 at 21:28, Josef said:

How far north are you in North Yorks? If you're close enough to me and want the old plate welded up I'd be happy to do it. Better than binning it as they're a desirable part!

Thanks Josef ! I'm near Knaresborough.

I'll ask if one of my mates will weld it up as at the moment it is hung on my garage wall as a trophy ! 

I might even ask my local classic guys to do the same and add a stiffener plate so that I can use it if I ever need to do the same again.

Edited September 22 by Martin V

[Martin V]

I've now driven the car a couple of times. After a nice 50 mile cafe drive into North Yorkshire the other day I did put the car back on the ramps to inspect the source of a new knocking noise.

Whilst I've got rid of some very metallic knocks where I guess the plate was flexing and something knocked on the odd bumpy road (plenty). The new knock sounded (and felt) like upper bracket/gear selector top part of gear box is knocking on odd bumps and seemed to be knocking my side. I looked beneath and there's about a cm or so gap, same or a little bit more where the clutch mounting bracket passes the inner tunnel.

I decided to fully slacken off the 4 plate nuts, take the car gently along through the village and back home onto the ramps to see if it settled better position wise. I then tightened them up again. I also checked the nuts on the engine mounts that they were tightened. I actually recall that these mounting nuts probably weren't that tight prior to this recent job and wondered if that could have been causing extra stress on that rear mount plate.

Today, off to Sport Cars in the Park just close to where we are, the knocking was perhaps even more pronounced especially when the engine was cold and again on some bumpy bits. No noises on a lovely road at good cruise speed. Incidentally SCITP was mainly high end performance cars, big shouty exhaust pipe cars and revving cars with tinted windows brigade but there were about a dozen of what I'd consider to be classic sports / performance cars. I parked next to a couple of Maserati sports cars to show them up for being fat and lardy.

So I'm now thinking, do I loosen the nuts again and do the same procedure and expect a different result, maybe leverage gearbox over a little? Or do I try perhaps putting some front valance rubber edging strip around the fibreglass tunnel aperture to at least see if that changes the sound of the noise thus confirming the origin. At least with the latter I could then consider trying to trim out the aperture next time I can be bothered to get under the carpet (probably H support out I reckon to get enough room for the job). OR do I check install new engine mounts which is I guess a bigger job by far!

Any ideas, similar thoughts or other directions to check?

 

...of course in the picture the nearer article in the image usually is made to look bigger than it really is & yes the tail ends were in line at the back - GT6 of course had the prettier rear end 😉

Edited September 22 by Martin V

[johny]

Can you try moving the engine/gearbox yourself Martin or perhaps get a beefy assistant to do it? Rock the engine vigorously and see how much movement you get and if the knocking is produced and then do the same from underneath on the gearbox perhaps with a lever of some kind... Do you notice the gear lever moving around much when driving as it should be pretty steady?

Bit of money in the photo but agree on the best looking one😁

[Colin Lindsay]

18 hours ago, Martin V said:

...of course in the picture the nearer article in the image usually is made to look bigger than it really is & yes the tail ends were in line at the back - GT6 of course had the prettier rear end 😉

That's the sort of situation where I'll arrive in a Herald and ask the stewards: "Where are the Classic Cars at?" or "Do I just park beside the modern ones here?"

[Pete Lewis]

dont ignore the exhaust making contact somewhere ,  very common knocking  thats cheap to fix    just have to find it 

Pete

[Martin V]

5 hours ago, johny said:

Can you try moving the engine/gearbox yourself Martin or perhaps get a beefy assistant to do it? Rock the engine vigorously and see how much movement you get and if the knocking is produced and then do the same from underneath on the gearbox perhaps with a lever of some kind... Do you notice the gear lever moving around much when driving as it should be pretty steady?

Bit of money in the photo but agree on the best looking one😁

The knock noise do coincide with the gear lever moving but the gear lever is normally pretty stationary, just a slight bigger movement when it knocks. I'll look further into it Johny, TR3 is on my ramps just now awaiting a new speedo cable so I'll not be under the GT6 until later this week. I'll do a visual engine bay check on the mounts and give it a shove!

 

[Martin V]

21 minutes ago, Pete Lewis said:

dont ignore the exhaust making contact somewhere ,  very common knocking  thats cheap to fix    just have to find it 

Pete

I'll check again Pete. The exhaust is not clamped anywhere between manifold and the rear mounting rubber mountings that hang from the underside at rear. If engine moves then the whole thing does move for sure.

[Pete Lewis]

it surprising hw much the engine cants under torque so whats clear static is in rattle mode when on the move

there should be a steady  bracket and  clamp onto the gearbox 

Pete

[Graham C]

I concur with the comments, check;

1) engine mounting have they torn with moving the engine around, Jack the engine up - wood under the sump.

2a) overdrive mounting damaged torn

2b) movement of the chassis overdrive plate, overdrive mounting moving on plate

3) exhaust hitting chassis.

4) prop shaft at wrong angle so hits floor due to engine moving.

You will get engine movement as you change gear.

Graham

[Martin V]

Seems that all is mechanically OK on mounts and position. My thinking is that when it was put together by PO there wasn’t much room on the hole in the tunnel but it was all together and easiest fix could have been to slacken all the mountings and leverage gearbox across to near side a small amount to centre the selector better. Lazy but true very possibly and could well explain the rear mounting plate cracking as it did on the near side at the rear with gearbox wanting to be a tad towards drivers side.

Gap around tunnel was finger thick on near side and 3 or 4 mm on drivers side. I should have noticed when I put tunnel back in last week. 

1 hour all out of car and marked up area for 15-20mm clearances. 10 mins with angle grinder. 1 and a half hours to get back together (typically centre arch bolts to floor were being tricky). Cover back on car before lunch!

 

 

 

Edited September 24 by Martin V

[Martin V]

On 23/09/2024 at 14:45, Pete Lewis said:

it surprising hw much the engine cants under torque so whats clear static is in rattle mode when on the move

there should be a steady  bracket and  clamp onto the gearbox 

Pete

Hi,

Further to this thread I had a check this weekend under the car. All good regarding the plate.

I went under to take apart and refit with compound the exhaust joint that I’d undone to complete the above job.

I looked how I might add a support bracket to the exhaust. My stainless Bell system just hangs from two exhaust straps beneath the bumper. These seem to allow some front /back directional movement more than any side to side.
 

There is no obvious place to add a support. First joint 2-1 is beneath bell housing and no point supporting there in my view. The next joint sits right at back of overdrive and in the small gap after the mounting plate. There is no suitable fastening to overdrive unit itself.

The only option I see would be to use a 4” approx piece of the rubber exhaust hanging rubber but fastened to either chassis or mounting plate bolt. Any advice on whether this compromise support to chassis would be helpful /worthwhile. 

I’ve touched up the chassis rails around the exhaust so that I can see if there are touch points in the future.

[johny]

Perhaps the drawing from the free to download workshop manual would be useful Martin as it shows fixings 6 (gearbox) and 9 (diff). The first was definitely solid as all part of engine and looks like the second is as well, I suppose to keep it all tucked up as high as possible....

[Colin Lindsay]

Part 6 of the diagram to rear gearbox bolt as shown below is a good start. This seems to be the standard fitting point for an exhaust hanger on the Herald model. (that bolt isn't tightened fully in, by the way) It's just a right-angled twisted metal strap so that one end sits against the gearbox and the other sits sideways for the exhaust clamp bolt. I've used it on all three of my Heralds, one O/D and the other two not.

[Martin V]

1 hour ago, johny said:

Perhaps the drawing from the free to download workshop manual would be useful Martin as it shows fixings 6 (gearbox) and 9 (diff). The first was definitely solid as all part of engine and looks like the second is as well, I suppose to keep it all tucked up as high as possible....

I’d looked at the same. The first (5) is the one I’d considered as my twin cans each have a strap already. 

I see Colin’s picture below and that makes sense with fixing to gearbox rigidly which still allows engine /exhaust gearbox to wiggle a bit together as one.