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View Full Version : Hmmm - not quite the same. What to do?



tdskip
07-24-2012, 07:36 PM
Hi guys - got the seals on the A-type (read that as I had Chris my British car specialist do it) and am about to put it back in.

I thought the transmission mount was looking a little beat up and I had a new one on the shelf from TRF but boy of boy are they different in height.

I'm sure the older on compressed a bit but this much - I don't think so. There is at least a 1/4 inch height difference between them.

https://i207.photobucket.com/albums/bb73/tdskip_photos/1966%20TR4A%20Solid%20Axle/transmount.jpg

TR3driver
07-24-2012, 07:48 PM
The new one from TRF seems to work fine for me. I think it was a later design, for better vibration isolation.

tdskip
07-24-2012, 08:23 PM
OK - was worried about the angle of the geabox.

Thanks Randall.

Brosky
07-24-2012, 08:27 PM
That's why you have u-joints in the drive shaft Tom.....but I can see your concern in the height. It must be a design change, as the threads look to be the same height on both.

tdskip
07-24-2012, 10:57 PM
Hi Paul - hope you are having a good summer. Thanks for the confirmation.

JerryVV
07-25-2012, 05:23 AM
Engine and Transmission mounts are mostly made of Natural rubber which has the best vibration dampening characteristics. The down side is that Natural rubber compounds don't have very good resistance to oils. I suspect that the old mount has collapsed due to oil contamination.

tdskip
07-25-2012, 06:59 AM
Hi Jerry, agreed, and it collapsed some but not the fully difference between them.

But this had me thinking, should we coat the rubber bits in something to help the fight off oil etc better before installing them?

With how short of a life rubber bushings have these days is there a rubber treatment that would help prolong them?

CJD
07-25-2012, 07:56 AM
Hi Jerry, agreed, and it collapsed some but not the fully difference between them.

But this had me thinking, should we coat the rubber bits in something to help the fight off oil etc better before installing them?

With how short of a life rubber bushings have these days is there a rubber treatment that would help prolong them?


I don't know of any. When they get oil soaked they soften. When they get old they harden. So it should average out in the end...LOL.

John

Marvin Gruber
07-25-2012, 09:26 AM
Just a thought here. Motor mounts do the same, shrink down some so they would help with the angle. New mounts all around will help keep the angle as it should be. Still not that crucial.

Marv

JerryVV
07-25-2012, 12:00 PM
The best protection would be a shield of some sort that would deflect the oil and not permit it to get in contact with the rubber. But as another says the heat would eventually make it harder.

Rubber is a compound that includes many ingredients to give it certain properties. It also uses a curing agent and for Natural rubber it is often a sulfur compound. When mixed it begins a chemical reaction called cross linking. In a press heat and pressure accelerate the curing. Some of the ingredients are oils which give the rubber it's ability to flex and absorb vibration in the case of dynamic mounts. So adding additional oils will tend to soften the rubber over time.

If you want an idea of what oils can do to natural rubber try placing a thin boot of some sort into some gasoline (which is an oil of sorts)and watch it swell over a period of a few days. A friend once placed the rubber boot from an OD solenoid in gasoline to remove the grease and clean it. When he came back to it a few days later it had grown to 3x it's size and wondered what was wrong with the boot. Nothing was wrong other than his mistake.

tdskip
07-25-2012, 07:27 PM
Hi guys - thanks for this thread. Got everything installed today after a VERY annoying couple hour stint struggling with mounting the gearbox (which I'll detail on another thread).

Height on the taller mount looks OK - haven"t driven her yet but I suspenct it will be OK.

Thanks again.