I am having a problem with leakage of synthetic gear lube, from the 9 inch bronco rear end that I put under my hot rod during the annual winter up grade and maintenance. I also rebuilt and installed a 4-71 gmc blower at the same time.the blower was rebuilt by me with a kit from ebay.new seals bearings etc. I put synthetic lube in the front cover and it appears to be leaking between the blower case and the cover.{new gasket} I have run my 6-71 blower for about 20 years,using regular gear lube,and it has leaked very little. Now back to the rear end.it is leaking between the housing and the carrier{chunk,punkin,hog head,or what ever they call it where you are from}Icleaned everything thoroughly,used a new gasket and new copper washers on the studs.I have retorqued the studs several times and they are not loose.When I removed the rear end from the bronco it showed no signs of leaking. I read an article in a harley mag.about this problem,{leaking synthetics} but I figured they leak just about everything! Have any of you guys had this problem,or heard about it.?

Before I started using synthetic oils, I spoke to an Amsoil rep at a trade show and he warned me that syn. lubes,due to their smaller molecular structure and lower surface tension,would find places to leak where conventional oils wouldn't.Some of the engines in various trucks and equiptment that were switched to syn. started leaking upon the changeover.
I've found that use of silicone sealants with all gaskets seems to be the answer.I still have a few motors that leak at shaft seals,even after seal replacement.It seems that anything less than a perfect, new gasket or seal will allow synthetics to find a way out.
Even new vehicles,which I change to synthetics after a 10000 mile break-in,
develope aleak or two,mostly inareas where oils puddle against gaskets or seals most of the time,like bottoms of valve covers,oil pans,etc.
It seems that some of the properties that make synthetics work so well also cause them to find their way out of where they belong.
Best answer sofar seems to be to seal up what you can and live with what you can't.
Good Luck,George

^^^^^^^
what he said.

I know my motor has leaks with synthetic that aren't there with a blend or regular oil. and it is fairly fresh.