I just changed out the rear differential fluid in my truck for the first time. I only have 40,000 miles on the truck right now. Fluid looked fairly black & dirty, but didn't have much metal on the magnet on front cover.

I had planned on changing out the front fluid also, but after I checked it it still looks really clean...not even black at all.

I have hardly used the four wheel drive very much on the truck. Probably only a handful of times for an extended period.....

I just had a couple of questions.....

On the 2002 models do the front axles & differential move at all unless the 4 wheel drive is engaged?

Also, even if the fluid looks clean & the truck has 40,000 miles on it & it's the first time ever changing it should I go ahead and change it anyway to inspect the gears & put fresh fluid in?

Thanks for the help.


Mike

 

a lot of gear oil is normally black

 

IMO when to change is up to you. pending how much driving towing etc. on the rear. I change my rear 80 every year due to the ammount of driving I do. but I do check the level throughout the year. if I do a heavy tow or alot of 4 wheeling usually in winter hunting snow etc. I will usually change my front prior and usually change it after in feb-march. I do light 4 wheel driving in the spring and summer. to me if you have never changed it. change the front its cheap insurance because now you know its been done. and done by you. as far as the oil and what to use I think you already have went down that road. good luck.

 

Remember not to fill it to the bottom of the fill hole...

 

On a 02.5 everything is turning up front all the time . I would change it out with your rear , before 02.5 I wouldn't change the front out as much.

 

Thanks,

I guess I was just curious about weather or not the differential turns at all up front when 4wd isn't engaged because it would explain why the fluid still looks so clean. I bought my 02' in May of 2002 so I'm pretty sure it wouldn't be considered 02.5 model. I'll probably still go ahead and change it soon though just to make sure there's no junk in there.....

I did make sure not to fill to bottom of fill hole on mine on the rear diff. I think the fluid probably about 1/2" or so below bottom of fill hole. Haven't had any problems with leaks. Although the service manual on the 02' says to fill fluid to the bottom of the fill hole so I'm not certain what's correct on that part.

 

Unless you have unlocking hubs on the front and I don't mean the axle disconnect, some part or all of the front differential will be moving. It's a shame the factory stopped offering unlocking hubs.

 

They finally wised up and moved the fill hole lower in '98 so you can fill to the bottom of the hole both in the front and rear.

 

I believe the spiders will turn on one side but not your ring and pinion if the truck has a CAD. Nor will the front driveshaft turn with a CAD. The ring and pinion and pinion bearing does the most shearing dammage to the oil and deterorates it. If they aren't turning the front oil is not really being used ,hense it looks new for a long time. I could be wrong with this statement , it has happened once before

 

Agreed the ring and pinon and drive shaft will not be turning with a cad but without the cad all will be turning. The spiders can chew up easier as the teeth are smaller. I like to clean my diffs out regularly as who knows what you'll find.

 

why not? i've always filled mine to the bottom of the fill hole ......250 thousand miles w/ no leaks

 

There are some spec's that advise against this in the owners manual. Overfilling could cause leaks in these cases. Both of my trucks advise lower then the fill hole spec's in the owner's manuals. I have no knowledge of what's called for in your owners manual for your model year. I guess the better advice would have been to check the owner's manual.

 

D80 for my 01.5 calls for 1/2"-3/4" below fill hole per owners and shop manuals. D60, no CAD, up front 1/2" below fill hole. My front fluid looked opaque and used at 50K when I got my truck, the royal purple in it is still clear and purple at 91K in September. I use 4 wheel drive about 500 miles a year.

Kurt

 

As mentioned, early 02's have the CAD (axle disconnect). Easy to check. Have someone watch front drive shaft as you pull forward in 2wd.
With CAD, only axle turns in 2wd. So good idea to engage 4x4 occasionally for lubrication (coating). Fluid lasts longer if you have the CAD.

02 Service Manual calls for filling up to bottom of hole.

RJ

 

Sorry for walking on this one, didn't read sig!

Kurt