Gearbox mounts for R8

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bgbiteme

Member
Fellow Frogger
Joined
Jun 23, 2004
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Location
Adelaide
One of the new gearbox mounts on my R8G has let go after just 500km - it's one of the sh*tty after-market (Chinese-made?) ones that I bought from France. So I'm thinking of upgrading to the reinforced mounts of the type sold by Mecaparts. This was recommended to me by GBS Alpine:
https://www.mecaparts.com/product/full-kit-of-gear-box-brackets-efficient-system/

The translation in the photo is:
"This kit allows the replacement of the original gearbox supports (which often come loose). The silent blocks of this kit work in line and without deformation of the rubber. Assembly is easy and durable. They have been used in competition on the Alpine A110, French champion of the 2010 VHC Rallies without any problem for more than 10 years. The photo shows the kit on this car (gearbox removed)."

Has anyone used these? Does anyone want to piggy back off my order from France because I'm thinking of getting 2 sets - one for my R8G and one for my R8.
 
I have had many posts and issues about mountings on here. I think the French engineers had a blackout in their design. My commonsense tells me that the gearbox and engine mounts are useless. Especially in competitive situations. No engine mount should carry any weight in a shearing position. And they all do. I will search for my post and then you can see what I did 10% of the cost.

That side mountings is actually for the sideways thrust when going around a corner and not to carry the gearbox. It is obvious that they will shear.

Frans.
 
Thanks Frans. I assume a professional rally driver putting a 110 sideways through a French forest is a pretty good testimony that these strengthened supports sold by Meca work well? Or are you saying you engineered a different solution? Whatever you can share would be much appreciated, because there's no way I'm going to put cheap Chinese supports back in the G.
 
I too sheared the first new set I installed after a short time, but I appear to have overcome this issue on my R8 by installing the 12mm spacers that are used on the A110 competition cars.
GBS has a diagram that shows how they are fitted. I made my own from some 20mm x 12mm thk aluminium.
I regularly have mine on a track and have not ever had an issue. I think the spacers help set up the mounts without any pre-stress.
You also get a bit of camber at the rear wheels which helps with the handling.
 

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I agree with Frans, the mounts are a very poor design and my experience with them is that they are subject to failure.
 
Gee that's a beautiful clean set up, thanks for sharing the info re the spacers - are you saying you are still using the standard aftermarket mounts that the likes of Arnaud Ventoux and Ichard sell?
 
I have a set of those spacers made up by a fitter and turner mate that I no longer require if you’re interested bgbiteme?

If we agree a modest price, I could possibly post together with the mirror surround unless you need them earlier.
 

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renault8&10 said:
I have a set of those spacers made up by a fitter and turner mate that I no longer require if you’re interested bgbiteme?

If we agree a modest price, I could possibly post together with the mirror surround unless you need them earlier.
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Woo hoo, yes please! Just let me know how much extra I owe you.
 
Yes and not had a problem for at least 5 years.
I would give it a try and see how it goes, I think it's a cheap option to try.
Besides, I believe if it's good enough for the A110, its good enough for my humble R8.

PS: the x 4 short spacers fix onto the rear cross beam, the long x 2 ones mount on the top of the gearbox (see GBS diagram).
 
i recall that those side mounts make a big difference to the handeling and feel in the rear end, when they let go ,agreed poor design .seems that those mounts restrict the movement of the g/box housing when accelerating and backing off ,pulling in on one side and out the other, playing havoke with the contact pach of the tyres .
 
And I now wonder whether the poor handling I experienced, that I had attributed to the Nankang tyres, might actually have been due to the delaminated gearbox mount. Time will tell...
 
The Mecaparts uprated mounts are much better than the originals. I am currently running these on the Dauph. It would be better to use bushings, which is what I used in the 8G and may well do with the Dauph when I can be bothered to make them..
 
A few things Mr Bgbiteme!

1. I did wonder about your handling comments. :)
2. I have heard from more than one source that the remanufactured gearbox side mounts fail - the rubber to steel bonding is poorer than the originals. I replaced mine 35 years ago with genuine ones and they are still attached, although peeling a wee bit. Peeling reduces the shear forces a bit as they deform!! It isn't only Renault side mounts, or specifically Renault for that matter, there's a litany of remanufactured rubber components of not particularly good quality
3. I have a set of those spacers, which reduce the amount of shear on the mounts, and was/am planning to use them next time I replace the mounts - I have another set of genuine ones in the cupboard.
4. If I were to buy new ones now, I'd buy the extra strength ones that are now available (AVP #4305). Still with rubber, not solid mind you.

AVP recommends the reinforced ones "for reasons of reliability and ease of assembly". Maybe that means they are not pulled strongly into shear when the bolts are done up?

(I don't disagree with Frans but it must have been deliberate. I presume the design was intended to provide resistance to rotation of of the transaxle in driving. They must have read the book about Alex Moulton and rubber suspension (published, by all places, by Rolls Royce Heritage Trust). Fabulous book.)
 
I have my own ideas regarding the engine mounts. Apart from being of a bad design, they at least have a rubber blob at the bottom so that when they break or sag the rubber blob rests in the mounting cradle and you won't lose the engine. When accelerating the engine's rotation to propel the car forward is pushing down on the mounts, ie the downwards force is equivalent to what is exerted to lift the front. To solve this problem I have made my mountings out of angle iron. In between is a rubber mount that will be compressed when accelerating and cannot shear. This is what they look like. Those mounts are dirt cheap general-purpose mounts at the rubber shop.

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The gearbox mounts are modified original brackets in which I have welded a length of 1" galvanised water pipe. Then I bought a packet of rubber mounts that fit in there. I think it is from a Holden front suspension rubbers. They are pressed in with a vice and a length of tube is inserted as well and fitting the mount is identical to the factory mounts. I reckon that if those rubbers can carry a Holden, they can carry a Renault gearbox as well. The side mounts are left as standard and do the side thrust work and prevent the rotational action exerted on the engine/gearbox unit when cornering very hard. The race car is still running the original side mounts which is ok with racing tyres and they haven't sagged because the top mount is carrying the weight as it should.

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I think that those side mounts that you buy at MecaParts are such an overkill and that they are trying to rectify the problem at the wrong place. Yes, it will last but with such a monstrosity of a mounting, you would expect it to last.

There you have my opinion and everybody is entitled to my opinion. ;););)
 
Frans said:
I have my own ideas regarding the engine mounts. Apart from being of a bad design, they at least have a rubber blob at the bottom so that when they break or sag the rubber blob rests in the mounting cradle and you won't lose the engine. When accelerating the engine's rotation to propel the car forward is pushing down on the mounts, ie the downwards force is equivalent to what is exerted to lift the front. To solve this problem I have made my mountings out of angle iron. In between is a rubber mount that will be compressed when accelerating and cannot shear. This is what they look like. Those mounts are dirt cheap general-purpose mounts at the rubber shop.

View attachment 236576

View attachment 236577

The gearbox mounts are modified original brackets in which I have welded a length of 1" galvanised water pipe. Then I bought a packet of rubber mounts that fit in there. I think it is from a Holden front suspension rubbers. They are pressed in with a vice and a length of tube is inserted as well and fitting the mount is identical to the factory mounts. I reckon that if those rubbers can carry a Holden, they can carry a Renault gearbox as well. The side mounts are left as standard and do the side thrust work and prevent the rotational action exerted on the engine/gearbox unit when cornering very hard. The race car is still running the original side mounts which is ok with racing tyres and they haven't sagged because the top mount is carrying the weight as it should.

View attachment 236578

View attachment 236579

I think that those side mounts that you buy at MecaParts are such an overkill and that they are trying to rectify the problem at the wrong place. Yes, it will last but with such a monstrosity of a mounting, you would expect it to last.

There you have my opinion and everybody is entitled to my opinion. ;););)
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You could sell a whole batch of those top mounts Frans! The original is a curious design... I've not yet touched mine, mind you. 370,000 km and 59 years. The early rubber might be best? Of course, it might be that it has failed and I haven't noticed!!

Best wishes for 2024 if I haven't already said so!
 
Wow Frans I am impressed with your engineering ingenuity. I have 3x R8's - I will use Kevin's spacers with a pair of NOS mounts on my G, but would love to try a set of your engineered mounts on my 'fake' G (an R8 with a G 4-shock rear, big box rebuilt by Rob Sealy and a hot 12 engine). I wonder if there is anyone in Australia who could make up a batch of Frans's custom mounts?
 
bgbiteme said:
Wow Frans I am impressed with your engineering ingenuity. I have 3x R8's - I will use Kevin's spacers with a pair of NOS mounts on my G, but would love to try a set of your engineered mounts on my 'fake' G (an R8 with a G 4-shock rear, big box rebuilt by Rob Sealy and a hot 12 engine). I wonder if there is anyone in Australia who could make up a batch of Frans's custom mounts?
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I imagine up in Clare it wouldn't be a problem at all if they had that photo, a cross member and a correct mount bracket and original bush to get the dimensions right.
 
From my dodgy memory.
Normally if the top gearbox mount fails you get noise from the bolt sitting on the cross member and wheels have a negative camber. It is not easy to change as mostly the bolt has been inserted from the engine side and cannot be withdrawn unless the gearbox is separated from the engine. I did most of a muster with the left side gearbox mount broken and the centre mount also hanging on the bolt. It was noisy and the wheel on the broken side had a heap of neg camber but we finished the event.
 
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