2nd Gen Non-Engine/Transmission Wierd Front Axle Issue - Any Ideas??

[LFalconer]

All, The 97 in sig has been pushing gear oil out of the overflow tube. Checked both sides by jacking up and turning wheels, no wobble or noise. Pinion shaft seems OK by turning the front driveshaft. Level is ok. After running say 10 miles in 2WD and 4WD the front axle housing is cool.



AT 50 mph there is a whump-whump sound seeming to be from front axle - but is speed specific.



Have not pulled front cover yet -



Thanks!



Luke

 

[ThrottleJockey]

The Overflow tube?



You mean the vent tube? I think you found your problem. That tube ain't for oil. How much gear oil did you put in? Maybe I'm all wet but I thought that was an air vent tube. Check the vacuum lines on the 4wd actuator.

 

[Dave M]

If I understand you right... the front diff is puking oil out the vent tube. Pull the vent tube and blow thru it to be sure its not plugged... not likely since it is flowing out it. Make sure the diff fluid level is 3/4 inch below the fill hole. I have heard if you overfill the fluid it will get past the oil seal in the diff carrier housing and flow out the axle housing onto the wheels.



I used a tie wrapped bent at 90 degree angle with a mark 3/4 inch below the bend to get the fluid 3/4 below the fill hole.



Dave

 

[LFalconer]

Guys - Thanks - yep poor use of term overflow tube, meant to say vent tube. THe level has been the same for 20k mile since I changed it 2 years ago - just started the puking last week. Good advice on the Central axle disconnect, however I believe it is vacuum only, as there is a transducer switch on the T-case that opens when you go to 4WD position that allows the vacuum to go the the actuator to pull the collar over the quill shaft to lock up the right side for 4wd operation. I replaced this transducer in Jan 08.



Thanks, Luke

 

[SRath]

If your front axle oil level is somehow increasing to the point it blows the excess out the vent, then either you are sucking/pumping oil from the vacuum source through your CAD, or you have just solved the oil shortage problem and your truck is worth as much as any other oil well.

 

[Dave M]

If your front axle oil level is somehow increasing to the point it blows the excess out the vent, then either you are sucking/pumping oil from the vacuum source through your CAD, or you have just solved the oil shortage problem and your truck is worth as much as any other oil well.

HA. . HA. . Ha... HA... thats funny!



sorry for asking a stupid question here but I'm not sure how oil from a vacumm source would get into diff?..... but sounds like something is pressurizing the diff. Wouldn't vacumm suck it out not push it in? Oh well... the CAD is a likely spot in the system to cause a problem since its in the axle housing.



Also, the vent tube on my 97 ends way up on the passenger wheel well. Tha's a long way up to puck fluid!

 

[SRath]

If your pumpkin is full, or overfull, and you haven't added any oil; something very strange is going on and that oil is coming from somewhere...



It could be that you have something intermittently clogging your vent tube until the pressure reaches a certain point, and then BLOWING out all at once.



If oil is not somehow getting in the CAD lines, is it possible for the lines to somehow be pressurizing your differential?



You could try disconnecting and plugging your CAD lines to see what happens. . ?



Disconnect your vent tube at the pumpkin, too, to see if it still blows out. The only reason the end of the vent hose is high up is to prevent water from a creek or similar from entering.



If none of the above point you to the problem, I'd go on TDR and ask the real experts...



Seriously, this is very interesting...

 

[LFalconer]

SRath - I like the Oil Well option - would be a rare time I actually made any money from the truck



Good idea on disconnecting the vent tube at the pumpkin - could be an odd clog I suppose. The tube terminates on the passenger side fenderwell inner side high up, so it is pushing it quite a bit.



How the CAD would pressurize the diff is beyond me as it should be all vacuum ??



Will post once I try a couple items



Thanks for the replies!!!!



Luke

 

[Dave M]

Just thinking here about a possible bad vacuum pump problem that could cause it to suck oil... are all your heater/ac controls working properly? They use the vacumm to control the vents etc. Might get on a vacuum line and disconnect it are feel for vacumm/oil in the vacuum line.

 

[ata]

The tube is held by a clip on the frame rail at the axle bump stop. Look at the clip and I'll bet it's got the vent line pinched shut. When the housing heats up the pressure pushes oil into the upper part of the hose and after awhile it will puke-it. Also as said before make sure your oil level is at least 1/2 to 3/4 inch below the fill plug hole.

 

[n7gxz]

Luke,



Have you been running through any axle deep water recently? If so you may have an axle shaft seal leak that let in water.



Kevin

 

[2broke2smoke]

pop the cover

 

[LFalconer]

Guys, Thanks for the suggestions, although I am with 2broke2smoke - given the noise the cover is coming off. All other items check out ok - although the pinched clip at the frame stop is a good one to remember!



Thanks, Luke

 

[Bob V]

If your vent tube has a low spot in it the fumes from the diff can accumulate and form back to a liquid. Over time there will be enough liquid to close off the vent, then presure will build and blow out that oil, and a little oil makes a big mess.

 

[LFalconer]

All, great comments - Quick update;



Took it to a buddy who is a mechanic with his own shop, used to be a Dodge mechanic for years.



Vent tube not clogged or pinched - he found some grass in the pinion seal area, and pinion seal is leaking. He felt the noise was tire runout as the Mud Terrains are close to replacement. He is replacing the pinion seal today.



Will update as whether this actually fixes the issue.



Thanks! Luke

 

[LFalconer]

All, A followup to this thread.



Buddy blew out the vent tube, no obstruction. Changed the pinion seal and cleaned out the grass that had accumulated in this seal area due to field use.



So far - no vent tube leakage, noise does appear to be the worn BFG Mud Terrains.



Luke

 

[EDankievitch]

Check and make sure the oil is from the rearend. Alot of rearends have been resealed because the engine crankcase vent tube driping on the axel