Crack in Overdrive Mounting Plate

[Martin V]

Hi All,

May be a simple question here for you guys just to put my mind at rest a little in short term regarding my GT6 1973 MK3 with OD.

I noticed a while back a small crack in the Overdrive mounting plate (I'll attach a photo asap to this thread). I assumed when it went to a well know garage near to Leeds that they would have flagged it to me when they had the Gearbox and OD out of the car if it would be a problem and worth replacing at that time. As they didn't mention it I assumed no issue and stupidly I forgot to ask them about it as the experience overall was not straight forward.

I looked again yesterday when checking on my small oil drip origins. Seems still odd drops down onto exhaust from Gearbox (poss top gasket) and from OD itself (who knows where - seems to me that this box of tricks is the worst thing invented if you want to not drop oil).

Anyway, I digress, the crack seems to have grown and I have only done a couple of 50 milers and couple of short 10 mile trips to shops. I've now put some paint on the end of the crack so that I can base my judgement on something specific over next weeks.

Having finally got the car into "going to" show state I'm loathed to start stripping out the tunnel again until towards end of the year.

I just read an old post where someone asked if possible to replace without Gearbox/OD removal and I was pleased to read that consensus was YES. But with Tunnel removed.

I guess I'm hoping to confirm that this is very common (by the design of all the weight being on an extended tab it seems it is bad design anyway) and not urgent to fix?

Another interim fix might be that a mate of mine can weld on a small brace across the plate /split to tied me over.

What do you guys advise?

 

Edited April 28 by Martin V
Missed photo

[68vitesse]

Drilling a hole at end of the crack will often stop it.

Regards

Paul.

[Nigel Clark]

I would suggest carefully drilling a small hole at the end of the crack.

Haha,  Paul beat me by seconds! 

Nigel

[Colin Lindsay]

Might be a common occurrence; I had (might still have, haven't seen it in ages) one of those plates on the shelf, and it was cracked in the same place - top right curve of this old photo, you can just make out the horizontal line of the crack going out to the very edge. 

[johny]

I wonder if its to do with the torque twist of the engine/gearbox and its certainly not very nice. Could almost be welded in situ couldnt it?

[Graham C]

Drill a hole at the end of the crack and weld the crack upto the hole.

Next winter take the plate out and elongate the chassis and od holes, as it seems to me that the plate is stressed and this may help we told the plate better.

Graham

[Martin V]

52 minutes ago, johny said:

I wonder if its to do with the torque twist of the engine/gearbox and its certainly not very nice. Could almost be welded in situ couldnt it?

Thanks Johny, I’ll discuss with my pal to see if he’ll have a go with me.

 

Thanks Graham , yes I think any new plate needs some extra bracing before fitting.

[johny]

Strange as my vitesse OD mounting plate is a different design and seems to have reinforcing in that area🤔

[micklewis]

vee the crack and weld it . 

your rear mount is under lateral stress  slacken mounting bolts on the plate and drive it around the block to settle ,then tighten 

 

 

mick 

[chrishawley]

Not completely sure but there is seems to be a witness that the crack has already propogated well beyond the point indicated by the red marker: as per purple arrows in modified image. And possibly, with the eye of faith, propagtion another inch beyond that. I'd find myself thinking that a comprehensive repair is needed, more than can be achieved with the plate in situ.

[Martin V]

Thanks again guys.

If I can get access beneath, I’ll try slackening the bolts mounting the plate or the OD bracket to allow self positioning.

 I’ve had a close look at the other marks and it seems clear that those are spanner marks just on the paint top surface. I don’t think anything more sinister but time may tell.

I’ll have a chat with my pal about temporary weld solution as per Mick and others advice.

Many thanks.

Edited April 29 by Martin V
Update

[Martin V]

Hole drilled & 4 mounting nuts slackened off (although they didn't seem tight anyway).

I'll let you know how it goes and whether I need to take action to replace sooner than end of the season !

 

Thanks for your support.

[wimpus]

This remembers me to check mine.

As i had seen a crack on my mounting plate to.. (Spit 1500 with OD and +236.000miles..)

[Martin V]

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 undo 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?

Edited September 16 by Martin V