Grade of front Diff fluid
 

The 01 service manual says that the front diff fluid is 75W-140 and the rear is 80W-90 or 75W-140. I got a D60 at both ends, any reason I couldn't use 80W-90 in the front also?

Nope.

like zman, nope. i use a synthetic 80-90 in both my d60s, Royal Purple to be specific. it sounds hard to beleive, but my computer showed a 2mpg increase after the change. I think your truck has front CAD, so you probobly wont see such drastic improvements as i have.

you have it backwards, its 80w90 in the front and 80w90 or 75w140 in the rear. i was told 80w90 is fine but if you tow occasionally to put the 75w140 in it.

it really doesn't matter. any GL5 gear lube is fine. i use 80w90 or 85w90 non-synthetic in both.

I thought it seemed a bit strange as well thats why I asked. I guess the editors make mistakes too. Here is a cut and paste from the service manual for an 01.

FRONT AXLE
² The lubricant should have MIL-L-2105C and
API GL 5 quality specifications.
² Lubricant is SAE 75W-140 SYNTHETIC gear
lubricant.
REAR AXLE
² The lubricant should have MIL-L-2105C and
API GL 5 quality specifications.
² Lubricant is a thermally stable SAE 80W-90
gear lubricant.
² Lubricant for axles intended for heavy-duty or
trailer tow use is SAE 75W-140 SYNTHETIC gear
lubricant

One more thing to add. I have drained them both now and it appeared that neither diff had been changed before. Just an observation, but the rear fluid was much darker than the front. The front looked like new oil, could it be chrysler is sticking synthetic in the front only. I guess the rear darker color could be heat related simply caused by the driveline in 2H.

Unless you drive in 4wd constantly, the front will always be cleaner than the back, as the front free wheels.

You shoulda seen the crap that came out of my tranny and X-fer case from my jeep, it looked like mud, it was prolly the first time is about 10 years or so it was ever changed, if not longer.

OMG really i had all of my stuff changed in june of last yr. Diffs tranny and x-fer case. How often do they need to be changed? I wheel a lot so I know the front will look like the rear.

If you wheels alot in sloppy stuff you need to change it fairly often, prolly once or twice a year, other than that as needed or directed by owners manual.