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Viscous Coupler bad


New Member
May 1, 2019
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Year, Model & Trim Level
2004 Mercury Mountaineer
A simple question i think. My viscous coupler is bad is binding up on sharp turns. Before I spend the money for a new one or used transfer case, does anyone know if adding a friction modifier to the fluid or replacing the existing fluid with the Ford transfer case fluid would free up the coupler? Figured it was worth asking.

Thanks in advance.

Assume that you have the AWD Mercury. Have you ever changed the t-case fluid before. Quite easy to do. Would defiantly do that before swapping out a new t-case.

Try changing the fluid first if you haven't yet. I went through that last year with my 98 AWD. It was dark fluid for two years from buying it, and then I began to feel binding while turning the wheel sharp.

If you have serious binding now, be cautious how much more you drive it before fixing it. Mine ate the front differential, right before I was sure the issue was the viscous clutch. I had a spare front diff, but most people don't, and rebuilding a diff, and a transfer case is not fun. I've got the parts to repair mine now, when I get time to dig into it.

If you have serious binding now, I'd pull the front drive shaft, to save the front diff. My 98 as people know will roll while in park, slowly yes, but slowly creeping is still not good. I use the parking brake often now.

No fluid will fix a binding viscous coupling. They have a silicon fluid that’s sealed internal to the coupling itself, and can’t be serviced or replaced.