My 1997 Ford F-150, 4.6L with automatic, is suffering from the slip join "clunk" at stops/starts.

My research has found this is a common problem when the output shaft splines get dried out. It causes the slip joint to bind and "thump" or "clunk" when it releases.

Most of the posts I have seen say the grease used for lubing the slip joint is Motorcraft PTFE type. enter image description here Others have said to just use standard high temp grease.

Can anyone provide reference to why the PTFE is recommended vs.using standard high temp grease? Would using the high temp grease cause issues/damage?

  • Every joint I saw had black molybdenum disulfide grease in – Martin May 9 '17 at 14:10
  • That's the stuff you need! – Inlandsmog May 11 '17 at 22:03
  • Sounds like an application for EP ( extreme pressure) grease . Usually they contain moly sulfide or graphite . – blacksmith37 Oct 6 '17 at 20:15

For F150 slip join Ford recommends to use 5L3Z-19A506-A grease which has a Calcium Carbonate thickener (it's written in the service manual) (5 USD for a single use pack). For some other vehicles Ford recommends XG-8 with a lithium based thickener with PTFE (Teflon) which is much cheaper.

As far as I know Calcium Carbonate more durable, more stable, less run-out and sustain better in high temp environment. But it's more expensive.

Btw I would check rubbers, maybe they're damaged.

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If the grease is exposed to the elements, consider using marine grease instead. It will not wash away as quickly.

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