Between 110 and 120 km/h (65 - 70mph) I get a whine out of either the transfer case or the transmission. I've had the truck since new and it's always been there, just more noticeable now that I have 70,000k on it. I've tried the Lucas in the transfer case to no avail - anyone have ideas? Thanks!

 

Most likely a diff or the t/case. How often do you change the gear oil? Consider going to a synthetic 85W/140 oil instead of the regular, this can make a big difference.

 

I agree with Mike, change the fluid in both differentials and the transfer case, I also use 85w-140 in full synthetic.
Some driveline whine is normal just because of the type of drivetrain it is.
Also change the fluid and filter in your transmission.

 

I had a whine coming from the rear of my 99DII with 95k at the time. It was barely audible at lower speeds, but got loud at around 70mph. It turned out to be the bearings surrounding the rear diff.'s output shaft i think it's called. Was told they are unservicable. Got a used diff for $300 US with 40k on it. Whine disappeared.

I have another one coming out of the front of the vehicle though. Anticipating putting a new (to me) front diff in it soon next year.


2 Qs (not to hijack your thread, I think they may actually help you)

Are the diff third members output shaft bearings truely unserviceable?
Can a front differential failure be dangerous?

 

Yes the bearings on the out put shaft are serviceable.

If your front diff explodes at best the gears strip and you keep driving with chunks of metal laying in the bottom and it is very noisy.

At the worst your front wheels lock up and you skid uncontrollably off a cliff into the ocean and burst into flames as you sink to the bottom of the Antartic Ocean.

Keep the diff full of fluid and you will be fine until you can get it fixed.

 

Spike, are you sure about that with the DII? I've never seen a service kit for it. Seen them for DI though.