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| Problems with the gearbox extension mount on a 1970 Mini K https://www.ausmini.com/forums/viewtopic.php?f=2&t=88412 |
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| Author: | gilow [ Sat Jan 24, 2015 6:52 am ] |
| Post subject: | Problems with the gearbox extension mount on a 1970 Mini K |
Hello Ausmini members, My first post, so I do hope I am asking this in the right place. I have just finished a 4 and half year rebuild of our 1970 Mini K. This was a bare-metal rebuild, and though it took longer than I planned, it was fun and we love the result. We have had the car back on the road now for about 3 months. It is totally stock standard, no modifications, as close to "factory" condition as we could go. But last week I noticed a lot of up and down movement in the gear stick when accelerating and decelerating. I assumed it was a loose gearbox extension mount (there have been two big bolt tightening sessions since we put the car back on the road as things settled in.) I got the car up on the ramps last night and had a look, and the gearbox extension mount appears to have failed, in that there is movement within the mount itself. The circular steel plate with the single stud that faces to the rear of the car is moving in relation to rubber block itself. Now the mount is brand new, so before I go and replace it again, I am trying to work out if I did something wrong. There is no apparent pulling or compression strain on the mount, I would say the only force it was exposed to would be the up and down of the engine torque. The engine is a stock standard 1100cc with absolutely no modifications, but it does have new pistons, rings etc so it is probably putting out close to factory specification. So, any suggestions? Is this a common failure, or is it a sign that I did something wrong? Matt |
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| Author: | drmini in aust [ Sat Jan 24, 2015 7:28 am ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
You need to ensure the tunnel bracket is pushed hard up against the mount. If not, torque tears the plate off the rubber. This is true with either Australian (Mackay Rubber) mounts or the imported ones. I have broken both in the past. If you cannot get the slotted bracket forward enough, put a big flat washer on the stud. Mine has been fine (with ~125crank HP) since I did this. |
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| Author: | gilow [ Sat Jan 24, 2015 8:31 am ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
Thanks DrMini, I did not realise that rear bracket could be adjusted. I will go and have a look and see if there is movement available, if not I will try as you suggested and pack the mount with a washer. Matt |
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| Author: | Phil 850 [ Sat Jan 24, 2015 9:54 am ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
The rubber mount needs to be compressed, so force the mounting bracket as hard as possible against the mount and then tighten in position. As the engine torque moves the mount, the movement is taken as a shear force (vertically across the mount) and if the rubber is not pre-compressed, the rubber will go into tension and tear away from the plate that it is moulded to. Rubber is great in compression and shear but fails easily in tension ! |
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| Author: | TheMiniMan [ Sat Jan 24, 2015 11:33 am ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
also helps to have a passengers side engine steady bar assembly fitted too |
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| Author: | TK [ Sat Jan 24, 2015 12:04 pm ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
Check all other mounts to ensure they are in perfect condition, especially the engine tie bar bushes. |
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| Author: | drmini in aust [ Sat Jan 24, 2015 12:06 pm ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
TheMiniMan wrote: also helps to have a passengers side engine steady bar assembly fitted too This is essential for a rodchange box, but IMO is not with a remote, for road use anyway. Cooper S never got it. These brackets are not too robustly mounted to the bulkhead either, on many (rodchange) cars the stock setup rips a big hole there. I've not torn a remote mount in 15 years, since I ensured the tunnel bracket is pushed hard up tight against the mount. 
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| Author: | TheMiniMan [ Sat Jan 24, 2015 3:35 pm ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
yeah the ext housing rear mount certainly needs to be squeezd up hard & tight & often we have packed them with washers too... but in regards to the pass side engine steady bracket ripping holes in the panel,,, well that`s due to the rubber sealing slab under the bracket/plate affair allowing excess movement & cracking & eventually tearing bits out with the (obviously already excessive engine movement , "Usually" from lack of maintenance &/or ignorance to the fact that these thin rubber strips need to be taken out & thrown away,,, & then the blanking plate needs to be fitted under that panel (inside the car) to ensure a sandwich plate solidity,,, once this is done & all other engine mounts, engine steadys & gearshift mounts are all in good nic & fitted correctly without any undue twist or strain,,, then happy motoring for many many years without any mounts busting... it`s just a simple thing but the extra engine steady supports all mini engines extremely well & also helps stop the diagonal twisting that a single steady creates. not meaning to create an argument but in my experience adding a pass side engine steady is pretty-much mandatory in all our engine fitments  regardless of shifter arrangement/design.however,,, in saying all that crap--> on a concourse Cooper "S" i`m happy to leave as should be factory without one
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| Author: | gilow [ Sat Jan 24, 2015 5:57 pm ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
TK wrote: Check all other mounts to ensure they are in perfect condition, especially the engine tie bar bushes. Thank you TK, I will double check them. They were all new but I wonder if I have wrecked any of them with my beginners mistake. We do have the stabiliser rod from the side of the block to the firewall... but I thought it was on the drivers side. Is there another type? Matt |
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| Author: | drmini in aust [ Sat Jan 24, 2015 6:09 pm ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
gilow wrote: TK wrote: Check all other mounts to ensure they are in perfect condition, especially the engine tie bar bushes. Thank you TK, I will double check them. They were all new but I wonder if I have wrecked any of them with my beginners mistake. We do have the stabiliser rod from the side of the block to the firewall... but I thought it was on the drivers side. Is there another type? Matt That is the standard one fitted to all Minis. Australian Clubman shaped Minis with rodchange boxes had an extra one, it went from the thermostat housing back to the firewall where the 2 heater hoses go through. As I said, remote shift boxes and 850s didn't get this. |
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| Author: | VulcanBB18 [ Sat Jan 24, 2015 9:12 pm ] |
| Post subject: | Re: Problems with the gearbox extension mount on a 1970 Mini |
Here you can see the passenger side engine steady Matty (Miniman) is talking about above. With a remote gearbox you get good stability but every bit helps it seems.  cheers, Jacob |
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