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MG MGA - Gearbox rear mount

I need to replace the rear flexible bush. My local mechanics reckon the only way to do it is to remove the motor/gearbox. Is it possible to replace the bush by removing the floorboards and gearbox cover. Has anyone done it? Are there other ways to get to it without removing the power plant?
N Blackwell

I have just searched the archive and the news is not looking so good. Looks like they're right. Any helpful hints at this stage might make me feel better.
N Blackwell

Hi. Replacing that bushing with the tranny on the workbench is a substantial challenge. Replacing it on the vehicle would be next to impossible. I dont know if it is even possible. However, if you wanted to try, here are my thoughts. The tranny tunnel and floorboards would need to be removed. The tranny would need to be raised at the rear, meaning that motor would have to drop at the front. Therefore the rad, motor mounts, fan blades, etc, would likely need to come off. The engine would need to be supported by a chain hoist or hydraulic jack, and would need to be lowered as the back of the tranny was raised. Assuming that the tranny bushing could be raised enough to adequately clear the two frame mounting ears, the bushing could then (perhaps) be removed. See Barney Gaylord's website for removal tips) The challenge would then be to install the new bushing. To do this, one would need to rig up some sort of threaded puller arrangement, to essentially "pull" the new bushing into the transmission case. A suitably sized socket could be used to push the bushing, and a tube slightly larger than the bushing could be used to "accept" the bushing,(on the opposite sode of the tranny) and would ride on the aluminum tranny dogear. This aluminum dogear is fragile, so hammering the bushing into place would NOT be acceptable! Some sort of puller would HAVE to be used! Personally with all the hassles, poor probability of success, and potential damage to the transmission and vehicle, I would think that it would be much better (and considerably less work) to just pull the transmission from the car! Additionally, you need to be aware that somne of the tranny bushings are improperly sized! They have been machined oversize and are too large to fit the transmission casing!!!! I had to chuck my bushing in a lathe and remove considerable material, so it would fit propery. My improperly sized bushing was purchased from Moss Motors about 2 years ago. Hopefully the problem has been resolved by now. Cheers, Glenn
Glenn

Agree with Glenn that replacing the bushing with the gearbox in situ would be damned near impossible. Best to get the 'box out and on the workbench, and then follow Barney's well-documented how to, found here:

http://www.mgaguru.com/mgtech/gearbox/gt105.htm

Good luck, and let us know how you make out.
James Wolff

Is it possible to remove the transmission ,from the car without removing the interior or removing the engine??????
Gordon Harrison

No. You either need to take out the engine first or remove the floorboards, tunnel, and toe board.
John H

If you do decide to try it insitu make sure you measure the OD of the new bushing and the ID of the hole to make sure that they are sized correctly. There are many repro bushings out there that are too large in diameter. You risk breaking the dog if it is too tight.

Speaking from the voice of experience. I purchased my replacement from Moss in Jan04. Hopefully they have them sized a bit better by now!
Ken

Echo what Ken says. Recently I got a replacement transmission mount and found it about.030" oversize. Send it back and got antother one with the same problem. Ended up turning it down on the lathe to a light interference fit.
Steve Mc

To get the gearbox out, you have to remove the engine. It will only come out forwards, as chassis bits get in the way to prevent removal backwards and upwards.

Taking toeboards, firewall, floorboards, seats, tunnel, handbrake etc out is a much bigger job, and is totally unnecessary. It still leaves you having to take the engine out, unless someone has done a mod job on the chassis member that passes under the gearbox.

In addition to removing the engine (only a 2 hour job) You do need to remove the gear shift tower, by removing carpeting from the tunnel, taking off the cover plate around the gearchange (the one the rubber gearleaver bellows fixes into)(2BA screws I think) and then undo 4 bolts securing tower to extension. That's ALL that you need to do inside the car to get the gearbox out, everything else has to be done at the dirty end!
dominic clancy

I replaced mine after I had removed and completely stripped the gearbox and even then it wasn't easy! It is vital to check the bush OD. I bought one from Moss last December 2005 and the OD was 25 thou oversize plus the central tube was too short and asymmetric. I returned it to Moss and got one from Brown & Gammons: almost certainly from the same source as this one was identical in appearance to the Moss item, i.e. steel colour and finish the same, central tube too short and asymmetric but it was oval on the OD varying from exact size to 10 thou oversize.
I think the reason MG designed an interference fit was because the bush was factory fitted cold and they didn't want a loose fit at the higher running temperature: as aluminium expands more than steel I calculated that the bush should be between 3 and 5 thou larger diam. than the casing hole. So I decided to go with the B&G bush and put it in the deep freeze for an hour. Just before fitting I put the gearbox casing in a bucket of boiling water for 15 minutes. Even with all this fuss it wasn't an easy fit. Good luck Mike
m.j. moore

Guys
Thanks for all your comments. Guess I'll have to take the power unit out and I will certainly be checking the OD of the bush I have. Upon installation I am also going to fit a radiator shroud to aid low speed cooling. Has anyone tried one? Do they work?
Cheers
Neale
N Blackwell

I have heard mixed reviews on the shroud but one often overlooked item for cooling is the replacement of the thick felt pad that mounts to the hood where it closes on the radiator. Really increases air flow through the radiator where it belongs.
Ken

Neale

I tried the LBC Co version of fan shroud and I could not detect the difference. It also makes it a right pig to adjust or replace the belt or remove and replace the radiator.

Ensure a good quality clean radiator (horizontal fins - not zig-zag type between tubes. It should also have a 2" thick matrix), the felt pad mentioned above is fitted, carefully twist the grille louvres to allow max air flow, ensure carbie settings correct and timing just short of 'pinking', water wetter added to coolant; and I also use distilled water, from the de-humidifier, with the anti-freeze to prevent scale deposits. Check thermostat and temp gauge accuracy too. I even fitted a new water pump which did nothing either!

If all this fails there is a very nice Kenlow electric fan which does do the job. I retained engine driven fan too.

I had awful over-heating problems in hot weather, only the Kenlow sorted me, however on my recent engine rebuild I found my cylinder head was from an MGB with its bigger combustion chamber and valve sizes and the pistons were still the low compression concave topped type. This means a very low compression ratio, probably less than 8:1. With a "B" head the "A" engine needs high compression flat top pistons to bring the compression ratio back up to somewhere about right. I reckon that was my trouble. Am still running-in and a hot summer's a way off yet. Wonder how many other "A's" have got "B" heads with this low compression ratio causing overheating...? It's a thought.

Pete
Pete Tipping

I doubt there are any Pete because I would expect the opposite to be true and that this arrangement would cause the engine to run a lot cooler. It would be creating less power so that is what to expect. I have none of the items you mentioned above except for the electric fan and a spotlessly internally clean radiator. The electric fan helps me when I am in the Middle of France during an extrodinarily hot Summer in a town driving at 10 MPH. It does not help at speed although the car does NOT overheat in those circumstances.
Bob (robert) I am coming out!! yes I once owned an MGB!!

Bob

Mine would overheat at below 40 mph or over 50 mph on a hot day. Traffic lights - forget it! It also boiled over getting into Le Mans for the Tour de Pilots on the Friday night before the 24 hour race and dumped a lot of water out of the overflow all over the cathedral square! The temperature was reading 100 psi on the Oil Gauge!!! Had to top-up with bottled drinking water...

Love that car...

Pete
Pete Tipping

This thread was discussed between 12/03/2006 and 25/03/2006

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