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Gear oil smell

started smelling gear oil. so i have changed gear oil;front diff., manual tranny,transfercase and the rear diff. i still smell gear oil though. it is only when i shift it into 4th gear though. please help

Check to see if the thick rubber shift boot mounted to the floorboard is cracked. This is under the nice-looking shift boot tucked into the carpet.

The smell of gear oil motivated you to change the various oils? It would have motivated me to find the leak.

Did you check to see if the breathers are clogged?

If gear oil is leaking under the truck, as speed increases the odor is pulled forward in the vacuum over the bed. If you have a sliding back glass or tip-out windows on an extended cab the odor will be more noticeable.

On two occasions the cause of an oil smell in my cars turned out to be a leaking oil sending unit. It’s worth checking.

Ed B.

i checked there is no crack thank you