2nd Gen Non-Engine/Transmission Front axle has Synchomesh?

[RanchHand]

I am a bit concerned finding a light grade yellow oil in the front axle. The vehicle has 305k on the ticker, though I bought it in August 2016. I've been reading, googling, and going through oils, capacities, best practices, potential problems. In all that I read, unless I am missing specifics for my 2002 3500, the front axle should have 80-90 or similar. Question: is there a reason the axle has been filled recently with light grade oil, I am guessing Synchomesh,? I don't have the option of unlocking the front hubs, as some have mentioned when speaking of the heavy grade oil being used. Haven't checked front axle LS or non-LS, but rear D80 is non-LS. The oil level is about 1/2 inch below plug. I am ready to take action, hopefully I hear why I have this situation. Thanks.

 

[JR]

Should absolutely not be Synchromesh. Mineral 80w90 was originally spec'd for the front axle. Gear lube is cheap, if you suspect anything else it is best to change it out. Collect the used oil in a clean container so you can inspect for any possible wear metals in the oil.

 

[Killer223]

i've seen fresh 80-90 oil be kinda yellowish.

 

[KATOOM]

What exactly are you seeing? Maybe post a picture if you can.

You should be running regular 80-90 in there as nothing fancy or heavier is necessary. That said, if someone put a considerably lighter weight fluid in there, as long as they didn't use the 4wd in strenuous situations like snow plowing, it would still be fine.

 

[Wayne M.]

Synchromesh is not a hypoid, extreme pressure lube. Don't use it for a drive axle.
I think you might have a synthetic in there. The odor should be a dead giveaway.
Ever compare Dino vs. synthetic gear oil? It's pretty dramatic regarding the room temp thickness.
Not quite sure what your concern is? If you're not happy with what's in the compartment, dump it and put in synthetic 90. Can't go wrong with that. I understand mineral/ Dino 90 is the spec, but I don't think there's any bad side to upgrading to synthetic.

 

[SAndreasen]

I'm running full synthetic in the front and rear diff and it's yellow

 

[RanchHand]

Both local advise, and, thanks for the responses, I am fairly certain it is Synthetic in the front axle. If I tossed the contents in favor of a replacement oil, I would want to put Synthetic in. I will take a picture to post soon. I haven't seen signs of neglect in this used CTD purchase yet; all lube, filters, trackbar upgrades, tendency keeping to stock, point to good maintenance practices, thanks for teaching me that Synthetic was used, that it's a lighter grade than the normal axle lube.

 

[JR]

Good to hear!

When you specifically mentioned Synchromesh I assumed you were familiar with the fluid. It is far from resembling gear oil in any form (synthetic or conventional).

 

[Wayne M.]

Yes, Synchromesh is a 5/30 type oil that's rated for use in the NV transmissions. It says manual transmission fluid right on the bottle.